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Confused about Frequency Counters
Although I used someone's frequency counter back around the 1970s, I
never owned one. From what I recall, back then, there was a BNC connector on the unit, where test leads connected and were used to determine the frequency within a radio stage, or used to check the output from a signal generator. I'm looking on Ebay and seeing some costly ones selling for $100 and up, which have lots of buttons and connectors. -OR- seeing some that are listed to go from 1 CPS to 70 or 80 MHZ, which tells me that they can show audio frequencies, and up to the 70 or 80 MHZ limit, which means they will work for AM radio, many Ham bands, CB radio, but *NOT* FM radio. Then what caught my eye were these inexpensive handheld ones, such as: http://tinyurl.com/y84hun67 However, these do NOT have BNC connectors. Just an antenna. (No test lead connector), So, obviously, they can not read audio freqs, and can not be used to check the stage in a radio, but should probably pickup the output from a signal generator if the sig gen test leads are held near the antenna. However, this device (above URL) only covers 50 MHZ to 2.4 GHZ. That means it's worthless for AM radio, CB radio, and many lower Ham bands. (In my case, this would be pretty useless, since I mostly work on radios that are AM FM CB or SWR. Ideally, something that covered 1CPS to 110 MHZ would be best suited for my needs, but I cant find anything like that, at least not in the price range of $50 or less. (which is what I am willing to pay for something I wont get real much use from). My antique Eico 320 Signal Gen only goes a little over 100 MHZ, so once again, the example URL I posted would not be real helpful. So, I am pretty confused. What's better, an antenna or test leads? Do they actually make and sell LOW PRICED Freq Counters that go from 1 CPS to 110 MHZ or so? Then again, it almost appears that to get full coverage of all Frequencies, a person needs to buy TWO Freq counters, since UHF TV covers the 470 to 806 MHZ. But once again, what good is a Freq Counter with no test leads (just an antenna) for use on television? |
Confused about Frequency Counters
On 5/27/2017 9:55 AM, wrote:
Although I used someone's frequency counter back around the 1970s, I never owned one. From what I recall, back then, there was a BNC connector on the unit, where test leads connected and were used to determine the frequency within a radio stage, or used to check the output from a signal generator. I'm looking on Ebay and seeing some costly ones selling for $100 and up, which have lots of buttons and connectors. -OR- seeing some that are listed to go from 1 CPS to 70 or 80 MHZ, which tells me that they can show audio frequencies, and up to the 70 or 80 MHZ limit, which means they will work for AM radio, many Ham bands, CB radio, but *NOT* FM radio. Then what caught my eye were these inexpensive handheld ones, such as: http://tinyurl.com/y84hun67 However, these do NOT have BNC connectors. Just an antenna. (No test lead connector), So, obviously, they can not read audio freqs, and can not be used to check the stage in a radio, but should probably pickup the output from a signal generator if the sig gen test leads are held near the antenna. However, this device (above URL) only covers 50 MHZ to 2.4 GHZ. That means it's worthless for AM radio, CB radio, and many lower Ham bands. (In my case, this would be pretty useless, since I mostly work on radios that are AM FM CB or SWR. Ideally, something that covered 1CPS to 110 MHZ would be best suited for my needs, but I cant find anything like that, at least not in the price range of $50 or less. (which is what I am willing to pay for something I wont get real much use from). My antique Eico 320 Signal Gen only goes a little over 100 MHZ, so once again, the example URL I posted would not be real helpful. So, I am pretty confused. What's better, an antenna or test leads? Do they actually make and sell LOW PRICED Freq Counters that go from 1 CPS to 110 MHZ or so? Then again, it almost appears that to get full coverage of all Frequencies, a person needs to buy TWO Freq counters, since UHF TV covers the 470 to 806 MHZ. But once again, what good is a Freq Counter with no test leads (just an antenna) for use on television? What good is a frequency counter WITH test leads for television. Where are you gonna connect those leads and what's the signal level there? And how do you measure channel 40 when channel 42 is 10x stronger. You suffer from test equipment buyer's exaggeration. "I dunno what I want so gimme EVERYTHING, and then some, for cheap." Take a step back and decide what you need to measure that you didn't need for the last 50 years. I designed frequency counters for a living back in the day. I have more than a few. I haven't turned one on in more than a decade, and here's why... FOR CHEAP COUNTERS: They're inaccurate. If you're setting a radio frequency, you want an ACCURATE counter. Most other times, the accuracy is irrelevant. It's go/nogo. The accuracy and stability of the timebase may be the most important parameter. What do you want to do? They're insensitive. You typically can't go probing around in equipment and learn anything. A counter typically reads the biggest signal it hears. You might find that everything reads 120Hz. Probing around in a radio circuit may detune it. What do you want to do? I find an oscilloscope to be a more useful tool. You can read the frequency right off the screen with sufficient precision for most troubleshooting tasks. And you can do it in the presence of noise that might render a counter useless. Expensive counters have a few bucks worth of counting stuff. The majority of the expense is in the timebase and the front end that helps you trigger on what you want to observe. All those knobs are there for a reason. If you need more accuracy, you probably need a LOT more accuracy. Draw a frequency chart from 0 to 2.4 GHz. Put an arrow at every frequency where you ever needed to measure a frequency and the specs of the counter you'd have needed to do it. Let that be your guide. You might decide that you still don't need a counter that you can afford. ;-) You can do audio with a cellphone app. Just be careful what you plug into that microphone jack. This seems to be closer to what you want. EBAY ID 401196543325 If it has a removable antenna with signal and ground connections, you can make test leads. Just be careful with DC or too much signal breaking it. |
Confused about Frequency Counters
On 28/05/17 04:35, Jeff Liebermann wrote:
On Sat, 27 May 2017 12:55:02 -0400, wrote: Look for something that has a built in prescaler. Something like this: http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 The basic counter goes from 100KHz to 60MHz. The other ranges use a prescaler to divide down the input frequency so that it ends up at less than 60MHz and can be counted. I have two of those. I bought the second because I thought I'd broken the first, it performed so badly. They're as bad as each other. If you have a strong and stable signal, it can work ok, but the input design is poor. The HF and the pre-scaler both have dual-gate mosfets, but there's no gain control (automatic or otherwise) and the inputs are paralleled. I've disconnected the two inputs by cutting a track and soldered on a little bit of RG-158 to an SMA connector for the high range. I'd love it if Mike is willing to share some of his counter front-end wisdom. |
Confused about Frequency Counters
On Sat, 27 May 2017, Jeff Liebermann wrote:
On Sat, 27 May 2017 12:55:02 -0400, wrote: Look for something that has a built in prescaler. Something like this: http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 The basic counter goes from 100KHz to 60MHz. The other ranges use a prescaler to divide down the input frequency so that it ends up at less than 60MHz and can be counted. I"m assuming those really cheap portable counters are using prescalers, since they only start counting at 50MHz or something. INtended for two way radio checking I assume, so you don't need the lower frequencies, and a whip or rubber duckie antenna will pick up the output power fine. I've certainly thought about buying one of those cheap ones, hoping I could bypass the prescaler, though I suspect another issue, the prescaler isn't a decade counter. Back when Heathkit came out with a frequency counter, circa 1971, the prescalers were decade counters, and things got better as they improved, and the frequency counters had higher limits. But that sort of IC seems out of fashion now, so the prescalers are meant for other things, and offer a binary division, so bypassing it in the counter (and maybe adding an input stage) means the clock for the counter is "wrong". Michael |
Confused about Frequency Counters
mike wrote:
You suffer from test equipment buyer's exaggeration. "I dunno what I want so gimme EVERYTHING, and then some, for cheap." Take a step back and decide what you need to measure that you didn't need for the last 50 years. I designed frequency counters for a living back in the day. I have more than a few. I haven't turned one on in more than a decade, and here's why... FOR CHEAP COUNTERS: They're inaccurate. ** Anything using a crystal time base will have good accuracy. If you're setting a radio frequency, you want an ACCURATE counter. Most other times, the accuracy is irrelevant. It's go/nogo. The accuracy and stability of the timebase may be the most important parameter. What do you want to do? They're insensitive. You typically can't go probing around in equipment and learn anything. ** Yep, RF circuits are very load sensitive and you will need a FET probe to buffer the signal. But any counter will read the carrier frequency of a transmitter, long as it has a few milliwatts of output. Radio mics operating in the VHF and UHF bands can be read by placing them close to a short antenna attached to the BNC input. Analogue mobile phones (remember them) would read from 5 yards away. ...... Phil |
Confused about Frequency Counters
Michael Black wrote on 5/27/2017 7:24 PM:
On Sat, 27 May 2017, Jeff Liebermann wrote: On Sat, 27 May 2017 12:55:02 -0400, wrote: Look for something that has a built in prescaler. Something like this: http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 The basic counter goes from 100KHz to 60MHz. The other ranges use a prescaler to divide down the input frequency so that it ends up at less than 60MHz and can be counted. I"m assuming those really cheap portable counters are using prescalers, since they only start counting at 50MHz or something. INtended for two way radio checking I assume, so you don't need the lower frequencies, and a whip or rubber duckie antenna will pick up the output power fine. I've certainly thought about buying one of those cheap ones, hoping I could bypass the prescaler, though I suspect another issue, the prescaler isn't a decade counter. Back when Heathkit came out with a frequency counter, circa 1971, the prescalers were decade counters, and things got better as they improved, and the frequency counters had higher limits. But that sort of IC seems out of fashion now, so the prescalers are meant for other things, and offer a binary division, so bypassing it in the counter (and maybe adding an input stage) means the clock for the counter is "wrong". I don't think the prescaler is the problem is it? The problem is the inappropriate front end. If you design a decent front end and feed the prescaler with that signal it should work at lower frequencies ok. It may not have timing controls to let you measure below some 10s of Hz or so, but is that really a problem? Or do the prescalers work in some way I'm not familiar with so they just don't operate at lower frequencies? -- Rick C |
Confused about Frequency Counters
On 5/27/2017 6:25 PM, Phil Allison wrote:
** Anything using a crystal time base will have good accuracy. ..... Phil I don't expect anything I could say would change your mind. We'll just have to disagree on that. |
Confused about Frequency Counters
mike wrote:
--------------- Phil Allison wrote: ** Anything using a crystal time base will have good accuracy. I don't expect anything I could say would change your mind. ** Why I change my mind when what I posted is correct ?? We'll just have to disagree on that. ** You must enjoy being wrong. You have nothing that explains your strange opinion ? ..... Phil |
Confused about Frequency Counters
On Sun, 28 May 2017 08:09:04 +1000, Clifford Heath
wrote: On 28/05/17 04:35, Jeff Liebermann wrote: On Sat, 27 May 2017 12:55:02 -0400, wrote: Look for something that has a built in prescaler. Something like this: http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 The basic counter goes from 100KHz to 60MHz. The other ranges use a prescaler to divide down the input frequency so that it ends up at less than 60MHz and can be counted. I have two of those. I bought the second because I thought I'd broken the first, it performed so badly. They're as bad as each other. Thanks. I was thinking of buying some of those. I should have known as much of the low cost "modules" that I've purchased seem to have deficiencies as a result of crude design or cost cutting exercises. To clarify my my comments a little, I was not recommending the purchase of any of the devices I pointed to on eBay. I meant them as examples of devices that have prescalers, which was part of the OP's rant on requiring multiple counters to cover the frequency range. My comment "Something like this:" usually preceeds something that I haven't worked with. If you have a strong and stable signal, it can work ok, but the input design is poor. The HF and the pre-scaler both have dual-gate mosfets, but there's no gain control (automatic or otherwise) and the inputs are paralleled. I've disconnected the two inputs by cutting a track and soldered on a little bit of RG-158 to an SMA connector for the high range. I picked that particular example because it has a drawing of the PCB showing i/o and controls: http://i.ebayimg.com/images/g/hBYAAOSwAPVZGlOn/s-l1600.jpg It has two adjustments labelled "High channel sensitivity adjust" which I guess would help with the tiggering. Do these controls work, or were they deleted in yet another cost cutting exercise? I'd love it if Mike is willing to share some of his counter front-end wisdom. The OP has not disclosed how he plans to use the counter. If it's a bench instrument, that requires precision, I suggest any of the numerous used HP counters available on eBay. https://www.google.com/search?tbm=isch&q=hp+universal+counter Especially the HP 5300 series: https://www.google.com/search?q=hp+5300+counter&tbm=isch I have accumulated a fair collection of these and find that used counters are a far better deal than the eBay instruments, such as: http://www.ebay.com/itm/Victor-VC3165-Radio-Frequency-Counter-RF-Meter-0-01Hz-2-4GHz-K8M3/122448388056 Incidentally, since the OP is into tubes, my favorite counter is an HP 5248M with genuine Nixie tubes. Middle right above the spectrum analyzer: http://802.11junk.com/jeffl/pics/home/slides/lab.html The pile of 4 plugins under the Glad bag box are the various mixer type downconverters I previously mentioned. I also have an HP 5245L: https://www.eevblog.com/forum/repair/repair-of-hp-5245l-nixie-frequency-counter/?action=dlattach;attach=204375;image Cheap but scarce on eBay: http://www.ebay.com/itm/HP-Hewlett-Packard-5248L-Electronic-Counter-5254C-Frequency-Converter-15-3-0GHz-/182520538437 -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On 28/05/17 14:25, Jeff Liebermann wrote:
On Sun, 28 May 2017 08:09:04 +1000, Clifford Heath wrote: On 28/05/17 04:35, Jeff Liebermann wrote: On Sat, 27 May 2017 12:55:02 -0400, wrote: Look for something that has a built in prescaler. Something like this: http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 I have two of those. I bought the second because I thought I'd broken the first, it performed so badly. They're as bad as each other. Thanks. I was thinking of buying some of those. I should have known as much of the low cost "modules" that I've purchased seem to have deficiencies as a result of crude design or cost cutting exercises. It was developed by a good hobbyist who posted everything online. I think that full schematics of slightly earlier versions are available online. He uses a dual-gate MOSFET before the prescaler and before the main counter, with the inputs paralleled. I think that affects the sensitivity (though I don't have measurements) so for my 2nd module, I cut a track to separate the input paths. I might wind up adding an independent input amplifier with AGC, or even a pot to adjust the 2nd gate bias on the MOSFETs for a manual gain control. A little difficult though, as parts of the circuit are underneath the LED displays, so I'd need to remove those. The main counter is a PIC. |
Confused about Frequency Counters
The Prickman Liar wrote:
-------------------------- I don't think the prescaler is the problem is it? The problem is the inappropriate front end. If you design a decent front end and feed the prescaler with that signal it should work at lower frequencies ok. It may not have timing controls to let you measure below some 10s of Hz or so, but is that really a problem? Or do the prescalers work in some way I'm not familiar with so they just don't operate at lower frequencies? ** Wow !! Is it just dawning on this total moron that he is one ? ..... Phil |
Confused about Frequency Counters
On Sat, 27 May 2017 21:25:42 -0700, Jeff Liebermann
wrote: this: http://www.ebay.com/itm/Blue-RF-Sign...nter-Cymometer -Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 The basic counter goes from 100KHz to 60MHz. The other ranges use a prescaler to divide down the input frequency so that it ends up at less than 60MHz and can be counted. I have two of those. I bought the second because I thought I'd broken the first, it performed so badly. They're as bad as each other. Thanks. I was thinking of buying some of those. I should have known as much of the low cost "modules" that I've purchased seem to have deficiencies as a result of crude design or cost cutting exercises. To clarify my my comments a little, I was not recommending the purchase of any of the devices I pointed to on eBay. I meant them as examples of devices that have prescalers, which was part of the OP's rant on requiring multiple counters to cover the frequency range. My comment "Something like this:" usually preceeds something that I haven't worked with. If you have a strong and stable signal, it can work ok, but the input design is poor. The HF and the pre-scaler both have dual-gate mosfets, but there's no gain control (automatic or otherwise) and the inputs are paralleled. I've disconnected the two inputs by cutting a track and soldered on a little bit of RG-158 to an SMA connector for the high range. I picked that particular example because it has a drawing of the PCB showing i/o and controls: http://i.ebayimg.com/images/g/hBYAAOSwAPVZGlOn/s-l1600.jpg It has two adjustments labelled "High channel sensitivity adjust" which I guess would help with the tiggering. Do these controls work, or were they deleted in yet another cost cutting exercise? Although I am not willing to spend big money on this, I tend to avoid those super cheap boards with no cabinets. I dont know how they can even sell them that cheap, so obviously they are not quality. Not to mention it costs 5 times the price of the board to buy some sort of box to put those boards in, and for all the connectors and stuff. So, by that time I'd have $25 or $30 invested. I'd rather find a complete unit that is better quality and eliminate all the hours it takes to put them into some sort of box. Making boxes and drilling all the holes and that sort of thing has never been something I am real fond of anyhow. I am currently looking at a Hickok 380, several HP counters, and a C&C 150. That Hickok is a BID sale, which means I dont have much of a chance of getting it. (Being on dialup, I cant place a bid in the last 10 seconds). Normally I dont even bother with bid sales, and just do the "Buy It Now" items. The HPs are all over my price range, but I dont need to buy it today or even this week. I can wait till I find a better deal. That C&C 150 seems like a real good deal, (about $39 with shipping), but I have never heard of that brand so I am looking to see if I can find more reviews of it. It appears to be a rather high-end device, with lots of features and a very wide freq range. My main reason to get a counter is mostly just to check the frequency coming from my Signal Generator. Having one that also checks audio freqs would be kind of nice, since I have a tone generator that I'd like to be able to know the frequencies it's outputting, but that is not an absolute necessity. I probably got more use from the Freq counter I used in the 70s (which was borrowed). Back then I was doing a lot with CB radios and that counter would check the CB channel output for accuracy. But I dont do much with CBs anymore, since no one uses them now. |
Confused about Frequency Counters
On 28/05/2017 12:20 PM, mike wrote:
On 5/27/2017 6:25 PM, Phil Allison wrote: ** Anything using a crystal time base will have good accuracy. ..... Phil I don't expect anything I could say would change your mind. We'll just have to disagree on that. **Here is a crystal I specified for a project back in the 1990s (because it was cheap). I paid AUS$0.22 each for them in 1,000 quantity. It's cheap because it is typically used in clocks. http://au.element14.com/ael-crystals...mhz/dp/9509585 Here is the technical data: http://www.farnell.com/datasheets/31...801.1495964215 +/- 20PPM is very decent accuracy. Plenty good enough for regular domestic service. Certainly, for professional stuff, you'll need an oven for the crystal. -- Trevor Wilson www.rageaudio.com.au |
Confused about Frequency Counters
Trevor Wilson wrote:
------------------- mike wrote: Phil Allison wrote: ** Anything using a crystal time base will have good accuracy. I don't expect anything I could say would change your mind. We'll just have to disagree on that. **Here is a crystal I specified for a project back in the 1990s (because it was cheap). I paid AUS$0.22 each for them in 1,000 quantity. It's cheap because it is typically used in clocks. http://au.element14.com/ael-crystals...mhz/dp/9509585 Here is the technical data: http://www.farnell.com/datasheets/31...801.1495964215 +/- 20PPM is very decent accuracy. Plenty good enough for regular domestic service. Certainly, for professional stuff, you'll need an oven for the crystal. ** Please note that the tempco of 50ppm over the range of -10C to 60C. So well under 1ppm per degree C !!! The initial accuracy can easily be trimmed to under 1ppm match the usual operating temp - say 20 C. Put those simple facts together and it ain't difficult to get 5ppm accuracy in your workshop. Just don't put the X-tal next to a hot component on the PCB - like Jim Rowe of EA did with their 1GHz counter. ..... Phil |
Confused about Frequency Counters
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Confused about Frequency Counters
On 5/28/2017 8:57 AM, Ralph Mowery wrote:
You really need to buy one of the used service monitors. Like this for example: http://www.ebay.com/itm/272688535932 -- Jeff-1.0 wa6fwi http://www.foxsmercantile.com --- This email has been checked for viruses by AVG. http://www.avg.com |
Confused about Frequency Counters
On 5/28/2017 3:03 AM, wrote:
I am currently looking at a Hickok 380, several HP counters, and a C&C 150. That Hickok is a BID sale, which means I dont have much of a chance of getting it. (Being on dialup, I cant place a bid in the last 10 seconds). Normally I dont even bother with bid sales, and just do the "Buy It Now" items. Have you been living under a rock for the past 20 years? https://www.esnipe.com/ -- Jeff-1.0 wa6fwi http://www.foxsmercantile.com --- This email has been checked for viruses by AVG. http://www.avg.com |
Confused about Frequency Counters
wrote:
On Sat, 27 May 2017 21:25:42 -0700, Jeff Liebermann wrote: Although I am not willing to spend big money on this, I tend to avoid those super cheap boards with no cabinets. I dont know how they can even sell them that cheap, so obviously they are not quality. Not to mention it costs 5 times the price of the board to buy some sort of box to put those boards in, and for all the connectors and stuff. So, by that time I'd have $25 or $30 invested. I'd rather find a complete unit that is better quality and eliminate all the hours it takes to put them into some sort of box. Making boxes and drilling all the holes and that sort of thing has never been something I am real fond of anyhow. I am currently looking at a Hickok 380, several HP counters, and a C&C 150. That Hickok is a BID sale, which means I dont have much of a chance of getting it. (Being on dialup, I cant place a bid in the last 10 seconds). Normally I dont even bother with bid sales, and just do the "Buy It Now" items. The HPs are all over my price range, but I dont need to buy it today or even this week. I can wait till I find a better deal. That C&C 150 seems like a real good deal, (about $39 with shipping), but I have never heard of that brand so I am looking to see if I can find more reviews of it. It appears to be a rather high-end device, with lots of features and a very wide freq range. My main reason to get a counter is mostly just to check the frequency coming from my Signal Generator. Having one that also checks audio freqs would be kind of nice, since I have a tone generator that I'd like to be able to know the frequencies it's outputting, but that is not an absolute necessity. I probably got more use from the Freq counter I used in the 70s (which was borrowed). Back then I was doing a lot with CB radios and that counter would check the CB channel output for accuracy. But I dont do much with CBs anymore, since no one uses them now. Can't blame you a bit for not jumping on those "kits" mentioned previously. Often more trouble than they're worth when you consider all the other stuff you have to buy and then all the work to assemble and make work. The C&C 150 seems like a pretty good deal for you. Certainly in your price range, and appears to be a decent entry level counter. You can get a manual from the manufacturer' web site (http://www.cncinst.co.kr/english/bbs...ual&wr_id=13); (Registration required, but nothing out of reason, like credit card numbers, etc.) You'll probably find out, if you research "reciprocal counters" (of which, this is one) that they offer much better resolution than other "normal" counters, especially at low audio frequencies. This is a good thing, since you can select a shorter gate time for the measurement than normal counters. If you want to measure an audio tone of, say 123.4 Hz, you'd need to select a gate time of 10 seconds to get the last digit to display. With a reciprocal counter, you can select a gate time of 1 second, or even 0.1 second, and see all the digits the counter can display. It actually measures the period of a signal, and a microcomputer inside the counter does a bit of math to calculate and display the frequency with all the digits the counter is capable of displaying. Good luck with your choice, Dave M |
Confused about Frequency Counters
Or you can just buy something that works.
https://www.amazon.com/Victor-Precision-Frequency-Counter-Digital/dp/B00MDVN4R0 -- Jeff-1.0 wa6fwi http://www.foxsmercantile.com --- This email has been checked for viruses by AVG. http://www.avg.com |
Confused about Frequency Counters
On Sat, 27 May 2017 19:24:00 -0400, Michael Black
wrote: I've certainly thought about buying one of those cheap ones, hoping I could bypass the prescaler, though I suspect another issue, the prescaler isn't a decade counter. Back when Heathkit came out with a frequency counter, circa 1971, the prescalers were decade counters, and things got better as they improved, and the frequency counters had higher limits. But that sort of IC seems out of fashion now, so the prescalers are meant for other things, and offer a binary division, so bypassing it in the counter (and maybe adding an input stage) means the clock for the counter is "wrong". Michael http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 To get from 2400 MHz to 60 MHz requires dividing by 40. However, that doesn't seem to be how this one works. Checking the prescaler chip from the photos, http://img.yunqudao.com/UploadFolder/4f2543ab-bfc8-48f0-9aff-c49e51612b75/Default/40_6.jpg I find a Fujitsu MB501L prescaler: http://pdf1.alldatasheet.com/datasheet-pdf/view/61659/FUJITSU/MB501L/+4155-UwSHHTTVdRhCtYT+/datasheet.pdf That's a 64/65 or 128/129 prescaler for a dual modulous synthesizer. I would guess(tm) that the eBay counter would use divide by 64 to get: 2400 / 64 = 37.5 MHz which is too low to utilize the full 60 MHz counter range. However, there's a problem. The MB501L prescaler is only rated to 1.1GHz. How they claim 2.4GHz will remain a mystery. If I had this counter (and a clean workbench), I would probe it to see what they're really doing. I couldn't find a schematic. There are some handheld counters that count to 60Mhz, and use a divide by 40 prescaler, which results in the proper frequency ranges: 2400 / 40 = 60 Mhz However, I can't find an example right now. The 40 is achieved with a divide by 4 followed by divide by 10, which I guess qualifies as a decade prescaler of sorts. As I recall, it was usually done with 2 ECL chips, which sucked plenty of power and were not cheap. Here's another way to use a prescaler: http://www.startek-usa.com/FREQ%20CTRS.htm The frequency ranges a 50MHz, 800MHz, and 2800MHz which correspond to: /1 /16 and possibly /64 Sorry, but no schematic or block diagram found. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On Sun, 28 May 2017 16:13:52 +1000, Clifford Heath
wrote: On 28/05/17 14:25, Jeff Liebermann wrote: On Sun, 28 May 2017 08:09:04 +1000, Clifford Heath wrote: On 28/05/17 04:35, Jeff Liebermann wrote: On Sat, 27 May 2017 12:55:02 -0400, wrote: Look for something that has a built in prescaler. Something like this: http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 I have two of those. I bought the second because I thought I'd broken the first, it performed so badly. They're as bad as each other. Thanks. I was thinking of buying some of those. I should have known as much of the low cost "modules" that I've purchased seem to have deficiencies as a result of crude design or cost cutting exercises. It was developed by a good hobbyist who posted everything online. I couldn't find any such project. I suspect that it might have gone the same way as the various M328 component test meters being sold online. The original project was open source. It was then commercialized by various vendors with wildly varying pricing. Much of the stuff I've found was early versions of the board and firmware. Meanwhile, the project has done on to add features and improve the firmware, but the online stuff seems stuck with early revisions. This link includes some history: http://www.instructables.com/id/AVR-Transistor-Tester/ I can't seem to find the original development site, which was in Germany. I think that full schematics of slightly earlier versions are available online. He uses a dual-gate MOSFET before the prescaler and before the main counter, with the inputs paralleled. I think that affects the sensitivity (though I don't have measurements) so for my 2nd module, I cut a track to separate the input paths. If the amplifier is used to simply produce a square wave out of whatever it fed into the input, low gain might be a big problem. So will noise around 0v which is why a "threshold" adjustment is usually supplied. Getting such a simple amplifier to work from 0.1MHz to 2.4GHz is unlikely, which might explain the lack of sensitivity. I might wind up adding an independent input amplifier with AGC, or even a pot to adjust the 2nd gate bias on the MOSFETs for a manual gain control. A little difficult though, as parts of the circuit are underneath the LED displays, so I'd need to remove those. May I suggest that you remove the input amp and setup something that give the prescaler a 50 ohm input. Then, design a broadband RF amplifier that has a chance of working over the frequency range. Something similar to a CATV or OTA TV/FM amplifier might be suitable. However, don't worry about getting a flat frequency response. Just take whatever you can get that produces enough drive to make the MB501L prescaler happy. A collection of communications freq range bandpass filters would be nice to prevent triggering on out of band junk. The main counter is a PIC. I'm not PICky. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On Sun, 28 May 2017 09:57:35 -0400, Ralph Mowery
wrote: YOu really need to buy one of the used service monitors. They can be had for around $ 1000. You get a counter signal generator and many more things. I'll pass..... I'd first have to rob a bank anyhow, in order to pay for it, and I think the bank clerks would just laugh when I pointed a soldering gun at them... (Or maybe a glue gun, or a caulking gun) :) |
Confused about Frequency Counters
On Sun, 28 May 2017 09:12:06 -0500, Foxs Mercantile
wrote: On 5/28/2017 8:57 AM, Ralph Mowery wrote: You really need to buy one of the used service monitors. Like this for example: http://www.ebay.com/itm/272688535932 Overpriced. Look at the prices of the sold listings: http://www.ebay.com/sch/i.html?_nkw=Motorola%20R2001&LH_Complete=1&LH_Sold =1 I have two R2001D boxes parked in my palatial office waiting for the mythical "spare time" needed to fix them. One has most of the red LED's on the right bashed in by someone dropping something heavy on the front panel. The other has a very weak CRT display, which is probably an HV power supply problem. Both have lock problems, which means it's time for a tantalum transplant. They've been sitting there for about 3 years. If I wait long enough, maybe the owner will forget I have them. I have a few other service monitors. There are three SSI/Wavetek 3000 series service monitors in this photo, plus one more I recently acquired. Typical cost was $300/ea: http://802.11junk.com/jeffl/pics/home/slides/BL-shop5.html In the middle left, is an IFR-1500 service monitor (with an intermittent power supply). I paid $1500: http://802.11junk.com/jeffl/pics/home/slides/test-equip-mess.html There are several cell phone specific service monitors hidden in various corners. Yep, service monitors are a good thing to have an use, especially in the field or on mountain top radio site. It has everything that you might need to work on radios including a counter. All have TCXO or OCXO reference oscillators for accuracy. At home, I have a home made GPSDO for even more accuracy. However, there's a catch. All the stuff in the photos is from the 1980's which means that components are starting to fail. It's a continuous battle to keep these things running and usable. If you decide to invest in an older service monitor, be prepared to occasionally dive in and do some repairs. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On Sun, 28 May 2017 10:19:43 -0500, "Dave M"
wrote: I probably got more use from the Freq counter I used in the 70s (which was borrowed). Back then I was doing a lot with CB radios and that counter would check the CB channel output for accuracy. But I dont do much with CBs anymore, since no one uses them now. Can't blame you a bit for not jumping on those "kits" mentioned previously. Often more trouble than they're worth when you consider all the other stuff you have to buy and then all the work to assemble and make work. The C&C 150 seems like a pretty good deal for you. Certainly in your price range, and appears to be a decent entry level counter. You can get a manual from the manufacturer' web site (http://www.cncinst.co.kr/english/bbs...ual&wr_id=13); (Registration required, but nothing out of reason, like credit card numbers, etc.) You'll probably find out, if you research "reciprocal counters" (of which, this is one) that they offer much better resolution than other "normal" counters, especially at low audio frequencies. This is a good thing, since you can select a shorter gate time for the measurement than normal counters. If you want to measure an audio tone of, say 123.4 Hz, you'd need to select a gate time of 10 seconds to get the last digit to display. With a reciprocal counter, you can select a gate time of 1 second, or even 0.1 second, and see all the digits the counter can display. It actually measures the period of a signal, and a microcomputer inside the counter does a bit of math to calculate and display the frequency with all the digits the counter is capable of displaying. Good luck with your choice, Dave M I am now the owner of a C&C 150. For the price, and considering the specifications, I just took a chance in the dark (literally), since I drove to a local WIFI at midnight and from my car, I bought it. I had a feeling it would be sold if I waited until today. I did find one of those discussion groups on the web, in which they were discussing it. Some guy bought one (on ebay) for around the same price I paid, and he was pleased with it, but did not know how to use a lot of the features and controls. Someone in that discussion posted a URL for the manual. (Not the same one you posted). This one: http://clayphillipsracecars.com/other/150-166.pdf (I bookmarked the URL). This is the manual that's upside down, which I posted about.... (Apparently, others like this have been sold on Ebay recently). The discussion occured about a month ago). (There actually was another one being sold on Ebay, but for about $20 more, with shipping). All I got to do now, is wait for it to arrive.... Till then, I'll read the manual. (and wont have to stand on my head to do it). Thanks for the help! |
Confused about Frequency Counters
On Sun, 28 May 2017 13:43:26 -0400, wrote:
http://clayphillipsracecars.com/other/150-166.pdf This is the manual that's upside down, which I posted about.... Congrats on getting the counter. I downloaded the manual and found that *ALL* of the pages were inverted. No problem. Fire up PDF-Xchange and click on the "Rotate CW" button at the top of the screen. That should fix all the pages. Then do a: File - Save As to replace the original with something readable. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On 29/05/17 02:43, Jeff Liebermann wrote:
On Sun, 28 May 2017 16:13:52 +1000, Clifford Heath wrote: On 28/05/17 14:25, Jeff Liebermann wrote: On Sun, 28 May 2017 08:09:04 +1000, Clifford Heath wrote: On 28/05/17 04:35, Jeff Liebermann wrote: On Sat, 27 May 2017 12:55:02 -0400, wrote: Look for something that has a built in prescaler. Something like this: http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 I have two of those. I bought the second because I thought I'd broken the first, it performed so badly. They're as bad as each other. Thanks. I was thinking of buying some of those. I should have known as much of the low cost "modules" that I've purchased seem to have deficiencies as a result of crude design or cost cutting exercises. It was developed by a good hobbyist who posted everything online. I couldn't find any such project. I suspect that it might have gone the same way as the various M328 component test meters being sold online. The original project was open source. It was then commercialized by various vendors with wildly varying pricing. Yes, that seems to describe it. Google for Sanjian Studio (which is on the PCB) and you'll find an English translation of the manual. That had assorted URLs to www.hellocq.net where the many stages of this project's development was discussed. You have to log in to see the schematics. I subscribed, but my account seems to have now expired (I didn't get the spam that I expected from this subscription). So I only have the assorted files I downloaded, see he https://www.dropbox.com/sh/z91pqvcpg470tuy/AAAIRnVfRDqrbrJwA3yBVQVPa?dl=0 I think that full schematics of slightly earlier versions are available online. He uses a dual-gate MOSFET before the prescaler and before the main counter, with the inputs paralleled. I think that affects the sensitivity (though I don't have measurements) so for my 2nd module, I cut a track to separate the input paths. If the amplifier is used to simply produce a square wave out of whatever it fed into the input, low gain might be a big problem. So will noise around 0v which is why a "threshold" adjustment is usually supplied. Yes. High gain is a problem too, causing spurious transitions. Something similar to a CATV or OTA TV/FM amplifier might be suitable. However, don't worry about getting a flat frequency response. Just take whatever you can get that produces enough drive to make the MB501L prescaler happy. Yes, except it's meant to be (and mine are) and MB506. A collection of communications freq range bandpass filters would be nice to prevent triggering on out of band junk. Good idea. The main counter is a PIC. Earlier schematics show two 4-bit counters before the PIC, which by itself does not have a 60MHz counter. Clifford Heath. |
Confused about Frequency Counters
On 29/05/17 02:16, Jeff Liebermann wrote:
On Sat, 27 May 2017 19:24:00 -0400, Michael Black wrote: I've certainly thought about buying one of those cheap ones, hoping I could bypass the prescaler, though I suspect another issue, the prescaler isn't a decade counter. Back when Heathkit came out with a frequency counter, circa 1971, the prescalers were decade counters, and things got better as they improved, and the frequency counters had higher limits. But that sort of IC seems out of fashion now, so the prescalers are meant for other things, and offer a binary division, so bypassing it in the counter (and maybe adding an input stage) means the clock for the counter is "wrong". Michael http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620 To get from 2400 MHz to 60 MHz requires dividing by 40. However, that doesn't seem to be how this one works. Checking the prescaler chip from the photos, http://img.yunqudao.com/UploadFolder/4f2543ab-bfc8-48f0-9aff-c49e51612b75/Default/40_6.jpg I find a Fujitsu MB501L prescaler: http://pdf1.alldatasheet.com/datasheet-pdf/view/61659/FUJITSU/MB501L/+4155-UwSHHTTVdRhCtYT+/datasheet.pdf That's a 64/65 or 128/129 prescaler for a dual modulous synthesizer. I would guess(tm) that the eBay counter would use divide by 64 to get: 2400 / 64 = 37.5 MHz which is too low to utilize the full 60 MHz counter range. However, there's a problem. The MB501L prescaler is only rated to 1.1GHz. How they claim 2.4GHz will remain a mystery. I assume the MB501 was 2c cheaper than the MB506 that the project was designed with. Find one of the many versions that actually use the MB506 instead. |
Confused about Frequency Counters
wrote on 5/28/2017 1:43 PM:
On Sun, 28 May 2017 10:19:43 -0500, "Dave M" wrote: I probably got more use from the Freq counter I used in the 70s (which was borrowed). Back then I was doing a lot with CB radios and that counter would check the CB channel output for accuracy. But I dont do much with CBs anymore, since no one uses them now. Can't blame you a bit for not jumping on those "kits" mentioned previously. Often more trouble than they're worth when you consider all the other stuff you have to buy and then all the work to assemble and make work. The C&C 150 seems like a pretty good deal for you. Certainly in your price range, and appears to be a decent entry level counter. You can get a manual from the manufacturer' web site (http://www.cncinst.co.kr/english/bbs...ual&wr_id=13); (Registration required, but nothing out of reason, like credit card numbers, etc.) You'll probably find out, if you research "reciprocal counters" (of which, this is one) that they offer much better resolution than other "normal" counters, especially at low audio frequencies. This is a good thing, since you can select a shorter gate time for the measurement than normal counters. If you want to measure an audio tone of, say 123.4 Hz, you'd need to select a gate time of 10 seconds to get the last digit to display. With a reciprocal counter, you can select a gate time of 1 second, or even 0.1 second, and see all the digits the counter can display. It actually measures the period of a signal, and a microcomputer inside the counter does a bit of math to calculate and display the frequency with all the digits the counter is capable of displaying. Good luck with your choice, Dave M I am now the owner of a C&C 150. For the price, and considering the specifications, I just took a chance in the dark (literally), since I drove to a local WIFI at midnight and from my car, I bought it. I had a feeling it would be sold if I waited until today. I did find one of those discussion groups on the web, in which they were discussing it. Some guy bought one (on ebay) for around the same price I paid, and he was pleased with it, but did not know how to use a lot of the features and controls. Someone in that discussion posted a URL for the manual. (Not the same one you posted). This one: http://clayphillipsracecars.com/other/150-166.pdf (I bookmarked the URL). This is the manual that's upside down, which I posted about.... Just curious, is the manual a series of images of pages or is the text selectable? I received a PDF document of an old PDP-11 listing from someone who wanted help typing it in. I realized when I clicked my cursor over the text it would select even though it was clearly created from images. Seems some software in the path (possibly my reader) was doing optical character recognition on the document. Most of it came through ok, but once in a while the slightly out of adjustment printer characters would be misread like a 9 for a 0, or a 0 for an O. Still, it saved a lot of time. Anyone else see scanned documents showing selectable text? -- Rick C |
Confused about Frequency Counters
On Mon, 29 May 2017 08:45:50 +1000, Clifford Heath
wrote: I downloaded, see he https://www.dropbox.com/sh/z91pqvcpg470tuy/AAAIRnVfRDqrbrJwA3yBVQVPa?dl=0 Got it and thanks. Nice the way the download is packaged as a single ZIP file. The docs are in Chinese. I haven't tried Google translate on it yet. The new schematic is very difficult to read the text. I'm also having problems decoding the "forum description". It's readable imported into MS Word as Unicode-8. The photos of the PCB seem to be the old design, which lack the extra divider chips. This is going to be a challenge. Something similar to a CATV or OTA TV/FM amplifier might be suitable. However, don't worry about getting a flat frequency response. Just take whatever you can get that produces enough drive to make the MB501L prescaler happy. Yes, except it's meant to be (and mine are) and MB506. It also says MB506 on both the old and new schematics. http://www.qsl.net/n9zia/900/mb506.pdf That's odd because it's a divide by 128 or 256 that goes up to 1.6GHz. At 2400MHz, divide by 128 yields 18.75MHz. I originally thought that it would need to use all of the 60MHz counter frequency range, but now I'm not certain. The PIC used is apparently slow, and won't go that fast. 18.75MHz seems about right for the PIC16F628a where the data sheet says it quits at 20MHz. http://ww1.microchip.com/downloads/en/devicedoc/40044f.pdf The ForumDescription.txt file says that it's divide by 64 on the first page, but then claims that the low channel goes to 75MHz, and later claims that the prescaler is an MB501. Kinda looks like the ForumDescription.txt file is a mixture of the old and new designs. Looking at the new schematic, I see that one bipolar front end transistor was replaced by a dual gate mosfet. However, it doesn't look like the gates were tied together on the schematic. The original schematic is tiny, but after enlargement, I don't see a dot where the wires cross. Also, if you follow the signal path through the prescaler chip on both the old and new schematics, the higher frequency range input goes through the prescaler, into the DG MOSFET, and then to the PIC counter. If there is a sensitivity problem, it would only be on the lower frequency range input, which goes to the DG MOSFET directly. Earlier schematics show two 4-bit counters before the PIC, which by itself does not have a 60MHz counter. Probably correct, but I can't tell what those are. Also, I think you have it backwards. The older schematic shows no dividers, while the new schematic shows what I guess are dividers. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On Mon, 29 May 2017 00:08:29 -0400, rickman wrote:
I received a PDF document of an old PDP-11 listing from someone who wanted help typing it in. I realized when I clicked my cursor over the text it would select even though it was clearly created from images. Seems some software in the path (possibly my reader) was doing optical character recognition on the document. Most of it came through ok, but once in a while the slightly out of adjustment printer characters would be misread like a 9 for a 0, or a 0 for an O. Still, it saved a lot of time. Anyone else see scanned documents showing selectable text? Searchable text is a standard PDF feature, even with bitmapped text. PDF-Xchange has built in OCR (optical character recognition) that will read through the graphical text, do its best to convert it to ASCII text, and save the combined file. After that, you can use the search, select, edit, functions: https://www.youtube.com/watch?v=CWtHOsIKaKw https://www.tracker-software.com/knowledgebase/351-How-do-I-OCR-a-document The free version will do all that except edit and save the resulting text. For that, you need the registered version. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On Sun, 28 May 2017 21:22:33 -0700, Jeff Liebermann
wrote: On Mon, 29 May 2017 08:45:50 +1000, Clifford Heath wrote: I downloaded, see he https://www.dropbox.com/sh/z91pqvcpg470tuy/AAAIRnVfRDqrbrJwA3yBVQVPa?dl=0 I missed the translated user manual (in English). It shows a sensitivity graph for the high frequency range with the following comment from Pg 12: It is noted that the UHF channel allows measurements up to about 450 MHz. This path comprises a divide by 64 stage claimed to be able to operate to 2.4GHz according to the published specifications. It is therefore surprising that the sensitivity fell as quickly as it did. Looking at the schematic and layout, my never humble opinion is that the designer didn't know anything about RF design and layout. The schematic shown on Pg 13 is quite different from either the old or new versions of the design that I previously mentioned. Instead of the extra divide by 4 packages, it has a 2nd DG MOSFET in front of the PIC counter. It also lists the prescaler as an MB506 which is divide by 128/256, not 64. It also shows that the gates of the DG MOSFET are NOT tied together. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
Jeff Liebermann wrote on 5/29/2017 12:36 AM:
On Mon, 29 May 2017 00:08:29 -0400, rickman wrote: I received a PDF document of an old PDP-11 listing from someone who wanted help typing it in. I realized when I clicked my cursor over the text it would select even though it was clearly created from images. Seems some software in the path (possibly my reader) was doing optical character recognition on the document. Most of it came through ok, but once in a while the slightly out of adjustment printer characters would be misread like a 9 for a 0, or a 0 for an O. Still, it saved a lot of time. Anyone else see scanned documents showing selectable text? Searchable text is a standard PDF feature, even with bitmapped text. PDF-Xchange has built in OCR (optical character recognition) that will read through the graphical text, do its best to convert it to ASCII text, and save the combined file. After that, you can use the search, select, edit, functions: https://www.youtube.com/watch?v=CWtHOsIKaKw https://www.tracker-software.com/knowledgebase/351-How-do-I-OCR-a-document The free version will do all that except edit and save the resulting text. For that, you need the registered version. I'm not sure what "standard" means. I was viewing a document full of imaged text the other day and none of the permissions were set to preclude anything. Yet I couldn't select any text as it had not been OCR'd. I assume the OCR has to be done at capture time. Are you saying a reader will convert images to text? -- Rick C |
Confused about Frequency Counters
On 29/05/17 14:51, Jeff Liebermann wrote:
On Sun, 28 May 2017 21:22:33 -0700, Jeff Liebermann wrote: On Mon, 29 May 2017 08:45:50 +1000, Clifford Heath wrote: I downloaded, see he https://www.dropbox.com/sh/z91pqvcpg470tuy/AAAIRnVfRDqrbrJwA3yBVQVPa?dl=0 I missed the translated user manual (in English). It shows a sensitivity graph for the high frequency range with the following comment from Pg 12: It is noted that the UHF channel allows measurements up to about 450 MHz. This path comprises a divide by 64 stage claimed to be able to operate to 2.4GHz according to the published specifications. It is therefore surprising that the sensitivity fell as quickly as it did. Looking at the schematic and layout, my never humble opinion is that the designer didn't know anything about RF design and layout. That was my conclusion also, and that (plus the earlier published versions) is why I said "advanced hobbyist". Not even very advanced, certainly not RF-experienced :) I don't know what frequency the PIC counter input is capable of, but I know that the AVR counter is clocked; so you can only count at half the CPU clock frequency. Bah, humbug. The schematic shown on Pg 13 is quite different from either the old or new versions of the design that I previously mentioned. Instead of the extra divide by 4 packages, it has a 2nd DG MOSFET in front of the PIC counter. It also lists the prescaler as an MB506 which is divide by 128/256, not 64. Both my units have MB506. It also shows that the gates of the DG MOSFET are NOT tied together. The units I have have both pairs of protection diodes, and the inputs are joined only at the connector. I cut the trace and soldered a bit of co-ax onto the prescaler input capacitor. I don't have a good RF source (yet - currently building, see https://github.com/cjheath/AD9851LCD) so I can't evaluate the sensitivity. Clifford Heath. |
Confused about Frequency Counters
On Mon, 29 May 2017 17:29:44 +1000, Clifford Heath
wrote: I don't know what frequency the PIC counter input is capable of, but I know that the AVR counter is clocked; so you can only count at half the CPU clock frequency. Bah, humbug. The clock crystal is 4MHz on the old version. I can't read the numbers on the schematic of the new version. That doesn't look very promising for measuring 60MHz inputs or even with /4 at 15MHZ. It also shows that the gates of the DG MOSFET are NOT tied together. The units I have have both pairs of protection diodes, and the inputs are joined only at the connector. I cut the trace and soldered a bit of co-ax onto the prescaler input capacitor. Oh swell. So the PCB wiring might not follow the schematic. I suppose it doesn't matter since the DG MOSFET seems to be badly biased anyway. I was having nightmares last night from thinking about this counter. Maybe I should give up while I'm still sane? I don't have a good RF source (yet - currently building, see https://github.com/cjheath/AD9851LCD) so I can't evaluate the sensitivity. Before you reinvent the wheel, there are AD9851 based DDS generators available on eBay. http://www.ebay.com/sch/i.html?_nkw=dds+generator+ad9851 along with the associated LCD display: http://www.ebay.com/itm/PIC16f-Controller-for-the-AD9851-DDS-Signal-Generator-Module-/182593721953 However, those only go up to about 70MHz and the output looks distorted above 30MHz. If you're going to test the counter all the way to its rated maximum frequency (2.4GHz), you're going to need a better generator. DDS has benefits for a function generator and arbitrary waveform generator, but is limited to lower frequencies. This looks interesting (and tempting): http://www.ebay.com/itm/ADF4350-v4-0-137-5MHZ-4-4GHZ-OLED-display-Signal-generator-RF-signal-source-12v-/262688224985 137.5MHz to 4.4GHz signal generator in 10KHz steps. Looks ok to about 1GHz, but drops in output and increases in sidebands at higher frequencies. Looks like the same board, but in a shielded box: http://www.ebay.com/itm/137-5MHZ-to-4400MHZ-Signal-generator-frequency-generator-RF-signal-source-dc-12v-/271838837908 Or maybe this thing: http://www.ebay.com/itm/0-5Mhz-470Mhz-RF-Signal-Generator-Meter-Tester-For-FM-Radio-walkie-talkie-debug-/172598060649 Or maybe something computah controlled via USB: http://www.ebay.com/itm/RF-Signal-Generator-35MHz-to-4-4GHz-via-USB-16dBm-Plus-Features-2000-units-sold-/201929990411 Or maybe a real RF generator from HP, TEK, Fluke or others that can actually be calibrated and trusted. This is the cheapest HP I could find: http://www.ebay.com/itm/Hewlett-Packard-hp-8656A-Signal-Generator-1-990MHz-rf-signal-generator-04-/252950700229 I have an HP 8656A but prefer to use an HP 8540B. Top right: http://802.11junk.com/jeffl/pics/home/slides/test-equip-mess.html -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On Mon, 29 May 2017 02:04:11 -0400, rickman wrote:
Jeff Liebermann wrote on 5/29/2017 12:36 AM: On Mon, 29 May 2017 00:08:29 -0400, rickman wrote: I received a PDF document of an old PDP-11 listing from someone who wanted help typing it in. I realized when I clicked my cursor over the text it would select even though it was clearly created from images. Seems some software in the path (possibly my reader) was doing optical character recognition on the document. Most of it came through ok, but once in a while the slightly out of adjustment printer characters would be misread like a 9 for a 0, or a 0 for an O. Still, it saved a lot of time. Anyone else see scanned documents showing selectable text? Searchable text is a standard PDF feature, even with bitmapped text. PDF-Xchange has built in OCR (optical character recognition) that will read through the graphical text, do its best to convert it to ASCII text, and save the combined file. After that, you can use the search, select, edit, functions: https://www.youtube.com/watch?v=CWtHOsIKaKw https://www.tracker-software.com/knowledgebase/351-How-do-I-OCR-a-document The free version will do all that except edit and save the resulting text. For that, you need the registered version. I'm not sure what "standard" means. Bad choice of words. I meant that the PDF standard: https://en.wikipedia.org/wiki/PDF/A includes searchable text as part of the standard. I'm too lazy to look up the chapter and verse. I was viewing a document full of imaged text the other day and none of the permissions were set to preclude anything. Yet I couldn't select any text as it had not been OCR'd. Yep. If you scan text as a bit map image, and save it in PDF format, it cannot be text searched. You have to feed it to an OCR program, which is capable of attaching the OCR text to the PDF, save it, and then you can search. I assume the OCR has to be done at capture time. No. It can be done at any time with any reasonable document. I usually make some effort to realign the text and improve the contrast to make it easier (and faster) for the OCR program to do it's thing. Are you saying a reader will convert images to text? If the images look like readable ASCII characters, yes. I don't think size makes much difference, but I haven't done much experimentation into how badly I can butcher the text and the OCR will still work. I also haven't tried to edit the text after reading to correct OCR errors. Maybe a demo will help. Note that the initial scan and file saves were done in Irfanview, while the OCR and subsequent saves were done in PDF-Xchange: Original document scanned to JPG using Irfanview 4.44: http://802.11junk.com/jeffl/OCR%20Demo/JPG.jpg This is not searchable. Same document saved to PDF using Irfanview 4.44: http://802.11junk.com/jeffl/OCR%20Demo/PDF-no-OCR.pdf This is also NOT searchable. Same document in PDF-Xchange 6.0 build 322.4 after OCR: http://802.11junk.com/jeffl/OCR%20Demo/PDF-after-OCR.pdf This one can be searched. PDF-Xchange screen grab showing a typical search result: http://802.11junk.com/jeffl/OCR%20Demo/PDF-Xchange-screen.jpg -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On Mon, 29 May 2017 11:00:12 -0700, Jeff Liebermann
wrote: I also haven't tried to edit the text after reading to correct OCR errors. Here's how to edit OCR errors using Adobe Acrobat: http://blogs.adobe.com/acrolaw/?s=ocr+and+image+layer I'm still trying to figure it out using PDF-Xchange Editor. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Confused about Frequency Counters
On 30/05/17 03:16, Jeff Liebermann wrote:
On Mon, 29 May 2017 17:29:44 +1000, Clifford Heath wrote: I don't know what frequency the PIC counter input is capable of, but I know that the AVR counter is clocked; so you can only count at half the CPU clock frequency. Bah, humbug. The clock crystal is 4MHz on the old version. I can't read the numbers on the schematic of the new version. But I don't think the PIC has a clocked counter anyhow. I assume that the AVR does it to (sometimes) avoid the need for a low-pass filter. The xtal on mine is marked "SCK451C" and "TC,A.426", whatever that means. It was about 15ppm slow, but seemed quite stable, based on measurements taken with an HP5386A. Quite a few people have patched in a TCXO to these units. It also shows that the gates of the DG MOSFET are NOT tied together. I don't understand why they used a DG MOSFET, nor why, since they did use one, they didn't use the upper gate for gain control. It seems they're feeding the signal into the upper gate, so won't get the best bandwidth from the cascode behaviour. The units I have have both pairs of protection diodes, and the inputs are joined only at the connector. I cut the trace and soldered a bit of co-ax onto the prescaler input capacitor. Oh swell. So the PCB wiring might not follow the schematic. I haven't found the schematic of the current-manufacture. I was having nightmares last night from thinking about this counter. Maybe I should give up while I'm still sane? I think it's fixable, perhaps with an additional front-end. It would still be easier and cheaper than building from scratch. I don't have a good RF source (yet - currently building, see https://github.com/cjheath/AD9851LCD) so I can't evaluate the sensitivity. Before you reinvent the wheel, there are AD9851 based DDS generators available on eBay. Who do you think designed those? People like me :) I have a bit of that Jedi "build your own light sabre" thing going on. Plus there's no accessible used test equipment market here in Australia. Whenever nice gear comes up at bargain prices, merchants buy it up and slap a stupid price on it. http://www.ebay.com/sch/i.html?_nkw=dds+generator+ad9851 That's exactly what I'm using for development. They have all copied a flaw in the output filter design, leading to very low output at higher frequencies. Some impedance problem, it's not designed to drive 50ohms. I'll add a buffer. along with the associated LCD display: http://www.ebay.com/itm/PIC16f-Controller-for-the-AD9851-DDS-Signal-Generator-Module-/182593721953 I loathe and detest both PICs and those 16x2 displays. I'm building one with 320x240 colour touch screen. The Arduino also has TTL-level RS232, so add a $2 USB module and you have USB control. However, those only go up to about 70MHz and the output looks distorted above 30MHz. If you're going to test the counter all the way to its rated maximum frequency (2.4GHz), you're going to need a better generator. DDS has benefits for a function generator and arbitrary waveform generator, but is limited to lower frequencies. I expect to incorporate an ADF4351 also, and possibly two AD9851's, to give quadrature (but still cheaper than AD9854 or whatever the multi-channel DDS chip is). E.g. https://www.aliexpress.com/item/35Mhz-to-4-4GHz-4400mhz-PLL-RF-Signal-Source-Frequency-Synthesizer-ADF4351-Development-Board/32757566484.html The ADF351's have the same problem as most of those VCO synthesisers, that they won't sweep cleanly. Changing the frequency makes them jump wildly about until they stabilise again. This looks interesting (and tempting): http://www.ebay.com/itm/ADF4350-v4-0-137-5MHZ-4-4GHZ-OLED-display-Signal-generator-RF-signal-source-12v-/262688224985 137.5MHz to 4.4GHz signal generator in 10KHz steps. The Arduino clone and TFT Touchscreen LCD cost me $AU14 all up. https://www.aliexpress.com/item/2-4-SPI-Serial-TFT-LCD-Touch-Panel-240x320-Dots-5V-3-3V-Module-ILI9341-Driver/32665656357.html Add the $30 ADF4351, a $17 $AD9851, and USB and you have a nice bundle for half what the above costs. Or maybe a real RF generator from HP, TEK, Fluke or others that can actually be calibrated and trusted. This is the cheapest HP I could find: http://www.ebay.com/itm/Hewlett-Packard-hp-8656A-Signal-Generator-1-990MHz-rf-signal-generator-04-/252950700229 "Does not ship to Australia" I have an HP 8656A but prefer to use an HP 8540B. Top right: http://802.11junk.com/jeffl/pics/home/slides/test-equip-mess.html I have to give this HP5386A back, but not in a hurry - my friend also has mountains of test equipment. He worked in sat-comms, so has contacts who call him before dealers get there - but he loves to hoard it all :( Clifford Heath. |
Confused about Frequency Counters
On 29/05/17 03:43, wrote:
This one: http://clayphillipsracecars.com/other/150-166.pdf This is the manual that's upside down, which I posted about.... .... Till then, I'll read the manual. (and wont have to stand on my head to do it). Other people have also given you a method, but I thought it was worth mentioning that the standard OSX (Mac) Preview app does PDF natively, and it's trivial to invert, shuffle, delete, etc. Just show the page thumbnails on the left, click on one, type Command-A to select all pages, and hit Command-L twice to rotate. Command-S saves the rotated file. You can also select and delete individual pages, re-order pages, and even drag pages in from another document. It's nice, and it's standard. Clifford Heath. |
Confused about Frequency Counters
Jeff Liebermann wrote on 5/29/2017 2:00 PM:
On Mon, 29 May 2017 02:04:11 -0400, rickman wrote: Jeff Liebermann wrote on 5/29/2017 12:36 AM: On Mon, 29 May 2017 00:08:29 -0400, rickman wrote: I received a PDF document of an old PDP-11 listing from someone who wanted help typing it in. I realized when I clicked my cursor over the text it would select even though it was clearly created from images. Seems some software in the path (possibly my reader) was doing optical character recognition on the document. Most of it came through ok, but once in a while the slightly out of adjustment printer characters would be misread like a 9 for a 0, or a 0 for an O. Still, it saved a lot of time. Anyone else see scanned documents showing selectable text? Searchable text is a standard PDF feature, even with bitmapped text. PDF-Xchange has built in OCR (optical character recognition) that will read through the graphical text, do its best to convert it to ASCII text, and save the combined file. After that, you can use the search, select, edit, functions: https://www.youtube.com/watch?v=CWtHOsIKaKw https://www.tracker-software.com/knowledgebase/351-How-do-I-OCR-a-document The free version will do all that except edit and save the resulting text. For that, you need the registered version. I'm not sure what "standard" means. Bad choice of words. I meant that the PDF standard: https://en.wikipedia.org/wiki/PDF/A includes searchable text as part of the standard. I'm too lazy to look up the chapter and verse. I was viewing a document full of imaged text the other day and none of the permissions were set to preclude anything. Yet I couldn't select any text as it had not been OCR'd. Yep. If you scan text as a bit map image, and save it in PDF format, it cannot be text searched. You have to feed it to an OCR program, which is capable of attaching the OCR text to the PDF, save it, and then you can search. I assume the OCR has to be done at capture time. No. It can be done at any time with any reasonable document. I usually make some effort to realign the text and improve the contrast to make it easier (and faster) for the OCR program to do it's thing. It is so easy to be misunderstood. I'm talking about the text showing up in the PDF document. I receive d a document that was clearly a scanned image in a PDF file. But the text was selectable and copyable. The two options are the image was scanned and OCR when the PDF was made, or the PDF viewer had OCR scanning built in. Since I couldn't select the text in another scanned image PDF it must be the former. Are you saying a reader will convert images to text? If the images look like readable ASCII characters, yes. I don't think size makes much difference, but I haven't done much experimentation into how badly I can butcher the text and the OCR will still work. I also haven't tried to edit the text after reading to correct OCR errors. Maybe a demo will help. Note that the initial scan and file saves were done in Irfanview, while the OCR and subsequent saves were done in PDF-Xchange: Original document scanned to JPG using Irfanview 4.44: http://802.11junk.com/jeffl/OCR%20Demo/JPG.jpg This is not searchable. Same document saved to PDF using Irfanview 4.44: http://802.11junk.com/jeffl/OCR%20Demo/PDF-no-OCR.pdf This is also NOT searchable. Same document in PDF-Xchange 6.0 build 322.4 after OCR: http://802.11junk.com/jeffl/OCR%20Demo/PDF-after-OCR.pdf This one can be searched. PDF-Xchange screen grab showing a typical search result: http://802.11junk.com/jeffl/OCR%20Demo/PDF-Xchange-screen.jpg -- Rick C |
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