|
Digital AM/FM Signal Generator
I have come into a small, but totally unexpected windfall. As is the way of these things, it will be split into thirds, one to savings, one to my wife for spending on the house - as is her habit, and one to play with.
I am looking for a *SIMPLE* AM/FM/SW signal generator - need not be stereo, but I would like it to be digital. And, cheap. I have two vintage devices that work just fine, but as I am gently approaching my "retirement" bench (still about 5 years out, but close enough) I am trying to reduce the clutter to fewer, but easier to use instruments. I see devices in the many thousands of dollars - no need for that. Nor will I fuss about Chinese-Origin equipment in this case, as long as it is reliable and simple. The number of radios I actually align in a year, or FM tuners may be counted on both hands, or fewer. And of those, few of them are so far off as to require much effort - well, maybe that last Hallicrafters. If this is too much to expect, what about a _REALLY_ good analog device, small, simple and solid-state? I am patient, and can wait as well. No rush whatsoever. My budget is at/around US$320. Along these lines - what about something like this? https://www.ebay.com/itm/Leader-LSG-...AOSwVuNbGAM L Thanks in advance! Peter Wieck Melrose Park, PA |
Digital AM/FM Signal Generator
wrote:
My budget is at/around US$320. Along these lines - what about something like this? https://www.ebay.com/itm/Leader-LSG-...AOSwVuNbGAM L ** That unit has a frequency range of 25MHz to 499MHz. Specs are hard to find so I am not sure if it does wide FM ( +/- 75 kHz ). Being "synthesised" makes it very stable, but so are all the broadcast stations. ...... Phil |
Digital AM/FM Signal Generator
On Tuesday, June 19, 2018 at 2:00:29 PM UTC-4, wrote:
I have come into a small, but totally unexpected windfall. As is the way of these things, it will be split into thirds, one to savings, one to my wife for spending on the house - as is her habit, and one to play with. I am looking for a *SIMPLE* AM/FM/SW signal generator - need not be stereo, but I would like it to be digital. And, cheap. I have two vintage devices that work just fine, but as I am gently approaching my "retirement" bench (still about 5 years out, but close enough) I am trying to reduce the clutter to fewer, but easier to use instruments. I see devices in the many thousands of dollars - no need for that. Nor will I fuss about Chinese-Origin equipment in this case, as long as it is reliable and simple. The number of radios I actually align in a year, or FM tuners may be counted on both hands, or fewer. And of those, few of them are so far off as to require much effort - well, maybe that last Hallicrafters.. If this is too much to expect, what about a _REALLY_ good analog device, small, simple and solid-state? I am patient, and can wait as well. No rush whatsoever. My budget is at/around US$320. Along these lines - what about something like this? https://www.ebay.com/itm/Leader-LSG-...AOSwVuNbGAM L Thanks in advance! Peter Wieck Melrose Park, PA I like my Rigol DG1022. But only goes to 25 MHz. https://www.rigolna.com/products/wav...rators/dg1000/ 100 MHz get's more expensive. George H. |
Digital AM/FM Signal Generator
What I am looking for is something that goes from Longwave through FM (US commercial band).
I would like it to be digital so that I could check it (once) with a proper counter, and the rely upon it until the next check. I am not calibrating NASA probes, but vintage AM/SW radios and (mostly) vintage FM tuners. I do have a FM-Stereo transmitter that will give me right/left only and Mono as well as fully frequency-agile, and vary from a few MW to about 50 MW, but if I have something that is really off, an independent SG would be helpful without requiring a lot of fuss. Thanks again! Peter Wieck Melrose Park, PA |
Digital AM/FM Signal Generator
|
Digital AM/FM Signal Generator
On Tue, 19 Jun 2018 11:00:26 -0700 (PDT), "
wrote: My budget is at/around US$320. Perhaps an HP 8640B generator. I have several and used to fix them. Looks like the selling price is about $300 (including shipping) on eBay: https://www.ebay.com/sch/i.html?_from=R40&_nkw=hp+8640b&_sacat=181992&Brand =HP&LH_Sold=1&LH_Complete=1&_sop=15 Hmmm... Might go slightly over your limit, but methinks is with it. Also, I've been able to find rather old service monitors, which I consider more useful. Wavetek or SSI 3000A. I think I paid about $300. Gotta run... -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Digital AM/FM Signal Generator
On Wednesday, June 20, 2018 at 12:14:41 PM UTC-4, Fox's Mercantile wrote:
Obviously, it will hand 10.7 MHz FM IFs. You can modulate it with an external generator. Um.... Um.... Meaning I will replace one (1) analog incumbent with two items. I am half-German, so I should find this appealing at some level, but it defeats the entire purpose of the exercise. Peter Wieck Melrose Park, PA |
Digital AM/FM Signal Generator
On Wednesday, June 20, 2018 at 12:16:27 PM UTC-4, Jeff Liebermann wrote:
file:///C:/Users/pwieck/Downloads/8640B-Signal-Generator-Operating-and-Service-Manual-08640-90017.pdf Give me the manual-seems to do about everything I want. There is one that would be $350 FOB 19027, and with a 30-day full guarantee. Looks very clean. Thoughts? Peter Wieck Melrose Park, PA |
Digital AM/FM Signal Generator
|
Digital AM/FM Signal Generator
On Wed, 20 Jun 2018 09:52:08 -0700 (PDT), "
wrote: On Wednesday, June 20, 2018 at 12:16:27 PM UTC-4, Jeff Liebermann wrote: file:///C:/Users/pwieck/Downloads/8640B-Signal-Generator-Operating-and-Service-Manual-08640-90017.pdf Ummm... that's the URL that points to your own c: drive. There are downloadable HP8640 manuals all over the internet. However, there are variations, packaging differences, options, and specialty variations such as avionics or military versions. I think I have most everything in PDF form and can snail mail a CD or arrange for you to download them. Give me the manual-seems to do about everything I want. There is one that would be $350 FOB 19027, and with a 30-day full guarantee. Looks very clean. Thoughts? My pitch line is that you can get some really nice used HP RF generators for little money. The danger is that it might be too old to get parts, or have some well hidden problem that you don't immediately notice. A 30 day guarantee is fine, but you pay shipping both ways. At 45.8 lbs (20.8 kg), that's not cheap. There are a few potential mechanical problems. The big one is that the bevel gears in the frequency range and modulation rotary switch mess are cracked. Someone makes replacement gears using 3D printing, but I haven't seen them. I would prefer brass. I'm tempted to make some but would need to buy an indexer for the mill that I'm sharing. Here's what it looks like: http://802.11junk.com/jeffl/pics/HP8640B/ I can explain how I fixed the gears later. The good news is that once the hole in the plastic gear is enlarged to fit the brass ring, and glued, it stays fixed. Here's a list of some other potential problems and fixes. Some of my stuff is mixed in there, somewhe http://www.ve7ca.net/TstH86.htm I have an HP8640b on the bench (or rather under the bench) that needs a new RF output amplifier. Check the options. Opt 1 and 2 involved the frequency ranges as explained in: http://electronicsrevisited.com/html/hp_8640b.html Opt 4 is for avionics. You definitely want Opt 3, which is reverse power protection. Without it, you run a good chance of accidentally burning out the output attenuator. There's a 0.1A fuse in the N connectors, but it's better to let Opt 3 protect the unit. They don't make them like this any mo http://802.11junk.com/jeffl/pics/HP8640B/slides/hp8640b-fix.html However, I'm wondering if an HP8640B is what you really need. The cavity oscillator is really low noise, which is what I need for SSB noise and IMD measurements, but not much else. Perhaps a synthesized generator might be better. I have an HP8656A generator: https://www.ebay.com/sch/i.html?_nkw=hp8656+-Philips Looks like the average selling price of $350 is over your limit: https://www.ebay.com/sch/i.html?_nkw=hp8656+-Philips&LH_Sold=1&LH_Complete=1 Maybe haggling with the seller will drop the price into your range. I have an HP8656A: http://802.11junk.com/jeffl/pics/home/slides/test-equip-mess.html Upper right, bottom of the pile on the shelf. Over the last 10(?) years I had a few problem. - The rear panel RF output connector is rather inconvenient. - Calibrating the RF output, deviation, and AM modulation, were needed after I screwed things up my not reading the instructions. - The push buttons on the front panel tend to hit the front panel bezel and stick. I'm sure I can fix it if I take it apart, but haven't had the desire or time. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Digital AM/FM Signal Generator
On Wed, 20 Jun 2018 16:42:08 -0500, Fox's Mercantile
wrote: About the HP8640, very nice piece, BUT the lower frequency limit is 500 KHz. The actual range is 450kHz to 550MHz. It will go to 1024Mhz with the Opt 2 frequency doubler. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Digital AM/FM Signal Generator
On Wed, 20 Jun 2018 09:52:08 -0700 (PDT), "
wrote: Thoughts? "Choosing an RF Signal Generator" http://www.ab4oj.com/test/sig_gen.html "HP-8640 Service: Hints & Kinks" http://www.ve7ca.net/TstH86.htm "The HP 8640B RF Signal Generator" https://www.ebay.co.uk/gds/The-HP-8640B-RF-Signal-Generator-/10000000010610658/g.html "Phase noise measurements microwave bricks compared to HP8640B, HP8662A, and HP8656A" http://www.ke5fx.com/brick/brick.htm "HP 8640B Repair" http://jvgavila.com/hp8640b.htm http://jvgavila.com/wb1.htm YouTube videos on HP8640B" https://www.youtube.com/results?search_query=hp8640B Gotta run (again)... -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
Digital AM/FM Signal Generator
seems to do about everything I want.
About the HP8640, very nice piece, BUT the lower frequency limit is 500 KHz. And, it's not really "digital" as the OP requested... it's an analog cavity oscillator. The commercial versions (but not the military OPT 323 variant) do have a frequency-lock capability which will lock to the crystal oscillator in the counter timebase, though... with this in use its stability is quite good and I'm told the phase noise level is excellent. It's not quite within the OP's stated budget, but... I recently picked up an 8648B for under $500, delivered. Very nice beast, covers 100 kHz up to 2 GHz, with AM and FM and phase modulation, and good enough GPIB control to be useful. Even without the high-stability oscillator option, it was within 1 PPM after a warmup, and it trimmed quite nicely to within their recommendations (10 PPB) using my rubidium standard as a reference. |
Digital AM/FM Signal Generator
In article ,
Jeff Liebermann wrote: There are a few potential mechanical problems. The big one is that the bevel gears in the frequency range and modulation rotary switch mess are cracked. Someone makes replacement gears using 3D printing, but I haven't seen them. I would prefer brass. There's a guy in India who has been making sets in brass... I'm in the middle of installing a set now. He posts on the HP test-equipment mailing list, and has some of the brass gears up on eBay. The other issue I've run into, with that switch assembly, is that the two white plastic parts (the shaft which holds the two small planetary bevel gears, and the rectangular piece which clamps onto this shaft and actuates the rear switch decks) are a bit dodgy. The tighten-it- down clamp head on the rectangular piece was cracked, and even after repair it isn't gripping the shaft well enough to prevent slipping. And, the new brass gear which _should_ rotate freely on this shaft, is rubbing and squeaking... either its hole is a bit under-sized, or the plastic shaft isn't dimensionally stable after all of these years. So, I have a bit of adjustment to do. I'd love to replace both of these plastic bits with something more stable (maybe a metal shaft with metal axles for the planetary bevel gears, and a composite or Delrin assembly in back) and might try fabricating something if I can't get the existing plastic parts back into service. |
Digital AM/FM Signal Generator
In article ,
Jeff Liebermann wrote: You should have taken my advice and glued the cracked gear back together with epoxy. I may well do that, to put my existing gears back in usable condition. I've done about 10 gears like this without experiencing any problems. Well, not quite. The last one I did, I either got the mixture wrong on the epoxy, or used some ancient tube of epoxy which refused to harden. I've made a lot of use of G-Flex epoxy for jobs like this - it works very well on most plastics, and also on metal. Incidentally, while you have the gearbox apart, bend the other non-broken gears a little to see if they are in any danger of breaking in half. Most will break at the set screw with very little pressure. Might as well have it break now, rather than while you're using the generator. Both of the larger gears with set-screws are cracked, and will need repair. The third large gear (the one which normally free-wheels on the shaft) isn't cracked, and I don't think it has a set-screw hole, but I suspect the nylon has probably shrunk and is putting the plastic under tension/compression. Might be worth it to deliberately split it between teeth, and give it the same file-and-epoxy treatment. The other issue I've run into, with that switch assembly, is that the two white plastic parts (the shaft which holds the two small planetary bevel gears, and the rectangular piece which clamps onto this shaft and actuates the rear switch decks) are a bit dodgy. The tighten-it- down clamp head on the rectangular piece was cracked, and even after repair it isn't gripping the shaft well enough to prevent slipping. I haven't seen that yet. I'll take a look at the two I have when the bench is clear. That might explain some backlash in the shaft. Looking at pictures on the net, I suspect that at least part of this problem exists only on the "old" switch-and-gear assemblies - the ones made with real wafer switches. The "new" switch-and-gear assemblies that use the PC-board-style switches with the plastic-disc-and-finger contactors, may use a different type of shaft for the planetary gears; the photos I've seen show the use of a metal tube with metal axles, rather than plastic. It's quite possible that the rear plastic part (the coupler) simply doesn't exist at all in the "new" assembly, since the rear switch section seems to be another of the PC-board type rather than a stack of three wafers. So, the whole "bad plastic tube and coupler" problem may not exist at all on a lot of the 8640Bs. I'm not thrilled with the machining quality shown in the photos. It's adequate, but not great. If anything, the plastic shaft has SHRUNK making a loose fit more likely than a tight fit. I can measure mine if you need a comparison. I'd appreciate that - thanks@ I would bet the hole has burrs, shavings, or is undersized. I think it may be both... that is, some burrs, possibly undersized (although the other two did fit OK onto the metal shafts of the switches), and maybe some changes in the plastic. Here's what I got when I measured everything with a Miyutoyo digital caliper: Central rod .1120-.1125 Shaft ID .129 Shaft OD .2470 at the tail, as much as .2505 next to the axles. Gear ID .2490 to .2500 Axles .124-.125 Planetary gear center .125 So, the shaft does seem to be a bit over-size where the gear is supposed to rotate on it - possibly some damage there - I should be able to smooth it down. I've already burnished the inside of the gear to get rid of any burrs that might have been there. I suspect that the two plastic planetary gears may have shrunk a bit with age, just as the plastic parts of the three big gears did - I need to open the holes up a bit to get them to rotate easily on the axles. I'd love to replace both of these plastic bits with something more stable (maybe a metal shaft with metal axles for the planetary bevel gears, and a composite or Delrin assembly in back) and might try fabricating something if I can't get the existing plastic parts back into service. It looks as if I'd be able to use some fairly "stock" metal parts to make the shaft... 1/4" OD fairly-thick-wall brass tube, and 1/8" brass rod. The trickiest part would be mounting the 1/8" axle rods... I'd probably have to drill slightly-undersized holes in the sides of the tube, press-fit the axle rods into place, and then maybe silver-solder them. Gotta talk to my machinist friend about this. Can you generate the G code needed to make the part? Maybe after six months teaching myself how to use a CAD program :-) I'm helping setup a CNC mill that can possibly make it. http://802.11junk.com/jeffl/pics/CNC-conversion/ The catch is that we don't have a rotary indexer or gear cutter, so all the teeth will need to be shaped with a small end mill. That's slow and not fun. It would almost be easier to make a silicone rubber mold and cast the gears from resin. I _think_ the gears I have will work out - either the plastic ones (repaired) or the new brass ones I bought (maybe after some burnishing or other tweaking). It's the center tube and planetary-gear drive that I'd need, and I'm not sure CNC milling would be the way to go. I did find a supplier who sells Delrin rod with a slightly-oversized 1/4" diameter and a slightly-undersized 1/8" central opening. This might work, if I drilled out the inside to a bit more than 1/8", and then machined down the OD to .125". Unfortunately I haven't found anybody who sells this particular variant in small quantities. |
Digital AM/FM Signal Generator
|
| All times are GMT +1. The time now is 09:52 PM. |
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 DIYbanter