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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Antennae Booster
Hi Group, can someone help please, I have an antenna booster that requires a power supply of 6v 100ma, can i use a variable power supply 6v 300ma???
Thanks, |
#2
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Antennae Booster
Stu jaxon wrote:
Hi Group, can someone help please, I have an antenna booster that requires a power supply of 6v 100ma, can i use a variable power supply 6v 300ma??? Assuming that they're both DC supplies, and assuming that you get the polarity correct (positive-supply to positive-load, negative-supply to negative-load), and assuming that you're careful to not turn the variable power supply up to higher than 6 volts... yes, it should work. The 300 mA capacity of the variable supply is greater than the 100 mA which the booster will draw, and that's OK. However, turning up the supply to above 6 volts may damage the booster. I'd recommend checking the supply voltage with a voltmeter before you connect it to the booster. Do be aware that "antenna booster" amplifiers can cause more problems than they solve. In most cases you'll get better results by improving your antenna setup. |
#3
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Antennae Booster
On Tuesday, September 22, 2020 at 5:56:17 PM UTC-4, Dave Platt wrote:
Stu jaxon wrote: Hi Group, can someone help please, I have an antenna booster that requires a power supply of 6v 100ma, can i use a variable power supply 6v 300ma??? Assuming that they're both DC supplies, and assuming that you get the polarity correct (positive-supply to positive-load, negative-supply to negative-load), and assuming that you're careful to not turn the variable power supply up to higher than 6 volts... yes, it should work. The 300 mA capacity of the variable supply is greater than the 100 mA which the booster will draw, and that's OK. However, turning up the supply to above 6 volts may damage the booster. I'd recommend checking the supply voltage with a voltmeter before you connect it to the booster. Do be aware that "antenna booster" amplifiers can cause more problems than they solve. In most cases you'll get better results by improving your antenna setup. OK, very good. Thanks for that advice. |
#4
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Antennae Booster
Dave Platt wrote:
----------------------- Do be aware that "antenna booster" amplifiers can cause more problems than they solve. In most cases you'll get better results by improving your antenna setup. ** Unless you need to run multiple co-ax lines from your antenna, such boosters are a useless scam. I could only laugh at folk I saw buying them to *fix* the lousy pic that was coming from an indoor antenna in analogue days - and scowl at the ignorant pigs who supplied them for that purpose. This are not different now. ...... Phil |
#6
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Antennae Booster
On 9/23/2020 3:26 AM, Dave Platt wrote:
Stu jaxon wrote: Hi Group, can someone help please, I have an antenna booster that requires a power supply of 6v 100ma, can i use a variable power supply 6v 300ma??? Assuming that they're both DC supplies, and assuming that you get the polarity correct (positive-supply to positive-load, negative-supply to negative-load), and assuming that you're careful to not turn the variable power supply up to higher than 6 volts... yes, it should work. The 300 mA capacity of the variable supply is greater than the 100 mA which the booster will draw, and that's OK. However, turning up the supply to above 6 volts may damage the booster. I'd recommend checking the supply voltage with a voltmeter before you connect it to the booster. Do be aware that "antenna booster" amplifiers can cause more problems than they solve. In most cases you'll get better results by improving your antenna setup. Agreed on all points except that, in certain situations, using an antenna booster is the only way to get an acceptable reception. TV came to this remote corner of India in 1980 when some army people discovered that it was possible to receive stations in neighbouring Bangladesh. Due to the very hilly terrain, reception varied from fair to unusable within tens of meters, all with outdoor yagi antennas. Antenna boosters were a must. The boosters were all alike, made up of 4 or 5 bjt amplifier stages. Power was fed to the booster via twin 300-ohm cable from an indoor 12V AC supply and gain was adjusted by means of a series potentiometer. I was the local "expert" and I experimented with different antenna types, including yagi arrays and helical antennas with a 6-foot plane reflector. Some people claimed that reception was noticeably improved by hanging aluminium pans on their yagis. |
#7
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Antennae Booster
On 9/23/2020 1:02 PM, Pimpom wrote:
On 9/23/2020 3:26 AM, Dave Platt wrote: Stu jaxon wrote: Hi Group, can someone help please, I have an antenna booster that requires a power supply of 6v 100ma, can i use a variable power supply 6v 300ma??? Assuming that they're both DC supplies, and assuming that you get the polarity correct (positive-supply to positive-load, negative-supply to negative-load), and assuming that you're careful to not turn the variable power supply up to higher than 6 volts... yes, it should work. The 300 mA capacity of the variable supply is greater than the 100 mA which the booster will draw, and that's OK. However, turning up the supply to above 6 volts may damage the booster. I'd recommend checking the supply voltage with a voltmeter before you connect it to the booster. Do be aware that "antenna booster" amplifiers can cause more problems than they solve. In most cases you'll get better results by improving your antenna setup. Agreed on all points except that, in certain situations, using an antenna booster is the only way to get an acceptable reception. TV came to this remote corner of India in 1980 when some army people discovered that it was possible to receive stations in neighbouring Bangladesh. Due to the very hilly terrain, reception varied from fair to unusable within tens of meters, all with outdoor yagi antennas. Antenna boosters were a must. The boosters were all alike, made up of 4 or 5 bjt amplifier stages. Power was fed to the booster via twin 300-ohm cable from an indoor 12V AC supply and gain was adjusted by means of a series potentiometer. I was the local "expert" and I experimented with different antenna types, including yagi arrays and helical antennas with a 6-foot plane reflector. Some people claimed that reception was noticeably improved by hanging aluminium pans on their yagis. Once I even rigged up a passive re-radiator with a back-to-back pair of yagis on a hilltop for a client who had no reception at all in his house which was located on the blind side of the hill. It worked somewhat but was not really satisfactory. What I couldn't really explain was that reception slowly but steadily degraded in the decade from 1980 to 1990 (when cable TV arrived). In 1980, I could often get excellent reception in my house with literally an aluminium coat hanger plugged into the antenna socket. By contrast, I could watch the 1990 FIFA World Cup only with an array of four yagis *and* an antenna booster. |
#8
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Antennae Booster
Pimpom wrote:
-------------- Agreed on all points except that, in certain situations, using an antenna booster is the only way to get an acceptable reception. TV came to this remote corner of India in 1980 when some army people discovered that it was possible to receive stations in neighbouring Bangladesh. Due to the very hilly terrain, reception varied from fair to unusable within tens of meters, all with outdoor yagi antennas. Antenna boosters were a must. The boosters were all alike, made up of 4 or 5 bjt amplifier stages. Power was fed to the booster via twin 300-ohm cable from an indoor 12V AC supply and gain was adjusted by means of a series potentiometer. ** You are describing a dedicated "mast head amplifier" which do work well with weak signals. "Antenna boosters" are not the same thing, only meant for indoor use. ..... Phil |
#9
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Antennae Booster
On 9/23/2020 5:02 PM, Phil Allison wrote:
Pimpom wrote: -------------- Agreed on all points except that, in certain situations, using an antenna booster is the only way to get an acceptable reception. TV came to this remote corner of India in 1980 when some army people discovered that it was possible to receive stations in neighbouring Bangladesh. Due to the very hilly terrain, reception varied from fair to unusable within tens of meters, all with outdoor yagi antennas. Antenna boosters were a must. The boosters were all alike, made up of 4 or 5 bjt amplifier stages. Power was fed to the booster via twin 300-ohm cable from an indoor 12V AC supply and gain was adjusted by means of a series potentiometer. ** You are describing a dedicated "mast head amplifier" which do work well with weak signals. "Antenna boosters" are not the same thing, only meant for indoor use. I'm familiar with the term 'masthead amplifier' but they're all called 'antenna boosters' over here - in popular usage, on the package and sometimes on the unit itself. I didn't know that the latter term is reserved for indoor units elsewhere. |
#10
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Antennae Booster
Stu jaxon wrote:
---------------------- Hi Group, can someone help please, ** Did I hear someone say "antennae booster" ?? https://allyouneedisbiology.wordpres...ects-antennae/ ..... Phil |
#11
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Antennae Booster
masthead amplifiers generally need a power injector which might have coax in coax out and a port for power. The amp is on the mast.
Other amplifiers may just need a power source and are not remotely mounted. I'm currently using a channel master CM-7777 at the mast with an 18db amp in the attic with an attenuator, so 0-18db. i think the CM-7777 is defective. For distribution to about 12 locations I was using a 30-45db amplifier until it went south. Currently distributing the signal to two locations. |
#12
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Antennae Booster
Pimpom wrote:
============= ** You are describing a dedicated "mast head amplifier" which do work well with weak signals. "Antenna boosters" are not the same thing, only meant for indoor use. I'm familiar with the term 'masthead amplifier' but they're all called 'antenna boosters' over here - in popular usage, on the package and sometimes on the unit itself. I didn't know that the latter term is reserved for indoor units elsewhere. ** I have Indian neighbours from Hyderabad - he's an IT expert and she a stay at home mom. I soon discovered "Indian English" differs from mine in numerous way - we regularly wind up speaking at cross purposes cos they apply different meanings to everyday words. She also spends hours each day staring at her I-phone so picks up lots of Americanisms. For instance - they had no idea what Styrofoam was cos their name for it is "Thermocol". It's hard for them to believe their English is actually a bit odd as they only socialise with other Indians. ..... Phil |
#13
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Antennae Booster
On 24/9/20 10:17 am, Phil Allison wrote:
Pimpom wrote: ============= ** You are describing a dedicated "mast head amplifier" which do work well with weak signals. "Antenna boosters" are not the same thing, only meant for indoor use. I'm familiar with the term 'masthead amplifier' but they're all called 'antenna boosters' over here - in popular usage, on the package and sometimes on the unit itself. I didn't know that the latter term is reserved for indoor units elsewhere. ** I have Indian neighbours from Hyderabad - he's an IT expert and she a stay at home mom. I soon discovered "Indian English" differs from mine in numerous way - we regularly wind up speaking at cross purposes cos they apply different meanings to everyday words. She also spends hours each day staring at her I-phone so picks up lots of Americanisms. For instance - they had no idea what Styrofoam was cos their name for it is "Thermocol". It's hard for them to believe their English is actually a bit odd as they only socialise with other Indians. Indian English is a recognised variety of English. Not even definitely a dialect, as it has its own grammar in some cases, which can be argued to make it a distinct language (as e.g. Schweizerdeutsch is a distinct language, not merely a dialect of German). https://en.wikipedia.org/wiki/Indian_English CH |
#14
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Antennae Booster
On Wed, 23 Sep 2020 17:56:57 +0530, Pimpom wrote:
On 9/23/2020 5:02 PM, Phil Allison wrote: Pimpom wrote: -------------- Agreed on all points except that, in certain situations, using an antenna booster is the only way to get an acceptable reception. TV came to this remote corner of India in 1980 when some army people discovered that it was possible to receive stations in neighbouring Bangladesh. Due to the very hilly terrain, reception varied from fair to unusable within tens of meters, all with outdoor yagi antennas. Antenna boosters were a must. The boosters were all alike, made up of 4 or 5 bjt amplifier stages. Power was fed to the booster via twin 300-ohm cable from an indoor 12V AC supply and gain was adjusted by means of a series potentiometer. ** You are describing a dedicated "mast head amplifier" which do work well with weak signals. "Antenna boosters" are not the same thing, only meant for indoor use. I'm familiar with the term 'masthead amplifier' but they're all called 'antenna boosters' over here - in popular usage, on the package and sometimes on the unit itself. I didn't know that the latter term is reserved for indoor units elsewhere. In cellular service, it's called a TMA (tower mounted amplifier): https://en.wikipedia.org/wiki/Tower_Mounted_Amplifier If the downlink is via RF instead of coaxial cable, it might be considered an "active repeater": https://encyclopedia2.thefreedictionary.com/Active+Repeater There is also a "passive repeater" which functions in the same manner using two antennas, but lacks a powered amplifier. If the downlink coax cable or RF path operates on a different channel than the receive signal, it's a "TV translator". -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#15
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Antennae Booster
On Wed, 23 Sep 2020 13:58:54 -0700 (PDT), "Ron D."
wrote: masthead amplifiers generally need a power injector which might have coax in coax out and a port for power. The amp is on the mast. Other amplifiers may just need a power source and are not remotely mounted. I'm currently using a channel master CM-7777 at the mast with an 18db amp in the attic with an attenuator, so 0-18db. i think the CM-7777 is defective. For distribution to about 12 locations I was using a 30-45db amplifier until it went south. Currently distributing the signal to two locations. Masthead amps make good targets for lightning hits. I've seen a few where every semiconductor in the amp was fried. The CM-7778 has 16dB gain: https://www.channelmaster.com/TV_Antenna_Preamplifier_p/cm-7778v3.htm while the CM-7777 has 26dB gain: https://www.channelmaster.com/TV_Antenna_Preamplifier_p/cm-7777v3.htm Also see the CM-7777HD (adjustable gain) and the CM-7778HD (distribution amp). This might help: "CM-7777, CM-7778 Titan 2 & CM-7778HD detailed troubleshooting." https://support.channelmaster.com/hc/en-us/articles/360002548994-CM-7777-CM-7778-Titan-2-CM-7778HD-detailed-troubleshooting-CM7777-CM7778- -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#16
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Antennae Booster
Clifford Heath wrote:
=================== Phil Allison wrote: ** I have Indian neighbours from Hyderabad - he's an IT expert and she a stay at home mom. I soon discovered "Indian English" differs from mine in numerous way - we regularly wind up speaking at cross purposes cos they apply different meanings to everyday words. She also spends hours each day staring at her I-phone so picks up lots of Americanisms. For instance - they had no idea what Styrofoam was cos their name for it is "Thermocol". It's hard for them to believe their English is actually a bit odd as they only socialise with other Indians. Indian English is a recognised variety of English. ** Sure - as typically spoken in India, you see it on TV, movies etc. But educated folk, living outside India for many years lose most of those idiosyncrasies. Tricks you into thinking they have left them behind. Conversations with them are fun but always fairly short. You soon run into a language /cultural dead end. Big shame. ...... Phil |
#17
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Antennae Booster
Two peoples separated by a common language.
George Bernard Shaw |
#18
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Antennae Booster
In article ,
Jeff Liebermann wrote: Masthead amps make good targets for lightning hits. I've seen a few where every semiconductor in the amp was fried. Yeah... probably need to consider them to be a potentially-sacrificial component. The really troublesome ones I've heard/read about, are the cheapies... sometimes using just a single broadband transistor as a gain element. Some of these have been known to break into oscillation, for some reason (or no reason) and blast broadband noise all over the place. https://www.gpsworld.com/the-hunt-rf...nce%20in%20fog. talks about one such case, in which several on-shipboard "active TV antenna" systems were emitting enough RF crud to blank out GPS reception in the harbor in Moss Landing, CA. Not a good thing to lose your GPS when you're trying to come into a foggy harbor at night. This is one reason why which buying a well-tested, professional-grade mast-head amplifier would probably be a better idea than buying a generic cheapie. |
#20
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Antennae Booster
On Tuesday, September 22, 2020 at 4:54:39 PM UTC-4, Stu jaxon wrote:
Hi Group, can someone help please, I have an antenna booster that requires a power supply of 6v 100ma, can i use a variable power supply 6v 300ma??? Thanks, ____________ My idea of a "booster" or "signal amp" is a bigger/higher gain antenna. As far as language differences are concerned, England and India are forever bound by their use of English. Compared to them, what is spoken in the States is called AMERICAN: a rebellious corruption and *******isation of what is spoken/written in the two aforementioned nations. Where else do you hear "nucular" routinely substitute for nuclear? Or plural's of item's succeeded with an apostrphe s? LOL! |
#21
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Antennae Booster
On Fri, 25 Sep 2020 01:15:02 -0700 (PDT), Chris K-Man
wrote: My idea of a "booster" or "signal amp" is a bigger/higher gain antenna. Do you mean that a "bigger" box is your idea of a better TV antenna amplifier? This looks plenty big: http://www.ambery.com/rfmp-w50.html Dimension: 498mm (W) x 360mm (D) x 280mm (H) Or, perhaps you mean't something other than size? Higher gain does not buy you much in the way of a performance improvment. At best, all you need for gain is a bit more than the coax cable loss between the amp and the TV (or distribution amp). Too much gain just generates intermodulation products, AGC overload, and other receiver problems caused by too much signal. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#22
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Antennae Booster
On 9/25/2020 10:50 AM, Jeff Liebermann wrote:
On Fri, 25 Sep 2020 01:15:02 -0700 (PDT), Chris K-Man wrote: My idea of a "booster" or "signal amp" is a bigger/higher gain antenna. Do you mean that a "bigger" box is your idea of a better TV antenna amplifier? This looks plenty big: http://www.ambery.com/rfmp-w50.html Dimension: 498mm (W) x 360mm (D) x 280mm (H) Or, perhaps you mean't something other than size? Â*I stored a rack mount Wingard distribution amplifier for years before I tossed it. I was about 19" x 6" x 3". I always thought it would be good for something, but never ran across that something. Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*Â* Mikek Higher gain does not buy you much in the way of a performance improvment. At best, all you need for gain is a bit more than the coax cable loss between the amp and the TV (or distribution amp). Too much gain just generates intermodulation products, AGC overload, and other receiver problems caused by too much signal. -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#23
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Antennae Booster
jeff:
Antenna is pretty big, A Winegard HD-8200U and the CM-7777 antenna mounted amp. The reason why I don;t TRUST is I did gain measurements using a Sencore 8VSB tester. My gain measurements were not consistant, but they were not done at the same time. I measures the signal at the antenna and the NEXT day the signal after the power injector (about 30') Gain varied from 15.6 (physical channel 3) and 27.1 for channel 21. I'm at least 30 miles outside of Philly and aimed toward Philly stations. The rotor also has a bypass braid around it which many people forget. A large tree is going to hit by lightning first. |
#24
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Antennae Booster
On Fri, 25 Sep 2020 12:36:44 -0700 (PDT), "Ron D."
wrote: Antenna is pretty big, A Winegard HD-8200U and the CM-7777 antenna mounted amp. https://winegard.com/products/hdtv-digital-antennas/hdtv-antenna-amplifiers/boost/hd8200u-platinum-hd-series-antenna https://www.channelmaster.com/TV_Antenna_Preamplifier_p/cm-7777v3.htm Unless you're dealing with weak signals and fringe coverage, a high gain (26dB in this case) amp is an invitation to overload problems. Quoting the Channelmaster data sheet: The Titan 2 High Gain Preamplifier is recommended for professional installers only. Due to the high gain output of this product, it can result in over amplification if not used in the appropriate scenario. Over amplification can cause issues with the television tuner’s ability to receive and display some or all channels. Note that there were 3 radically different versions of the CM-7777 amplifier. Which version do you have? https://photos.imageevent.com/holl_ands/files/ota//CM7777%20Ckt%20Brd%20Rear%20Photo%20-%20damaged%20rlongfield.jpg The original Titan 2 amp had a phenolic PCB. V2 had separate VHF and UHF outputs, while V3 has them combined into one output. Therefore, my guess is that it's a V2. The reason why I don't TRUST is I did gain measurements using a Sencore 8VSB tester. My gain measurements were not consistant, but they were not done at the same time. I measures the signal at the antenna and the NEXT day the signal after the power injector (about 30') Are you trying to measure amplifier gain using an OTA (over the air) signal? The amplifier gain is not the same for the VHF and UHF sections. It's also has some intentional "tilt" in the frequency response intended to compensate for the higher coax cable losses at the higher UHF channels. Gain varied from 15.6 (physical channel 3) and 27.1 for channel 21. I'm at least 30 miles outside of Philly and aimed toward Philly stations. Due to intentional "tilt" in the frequency response, that's too much "tilt" for the amplifier. CH3 = 60 MHz, CH21 = 512 MHz. Cable loss for 100ft of RG-6/u is 1.6dB at 60 Mhz and 5.2dB at 512 MHz. Therefore, I would expect to see a corresponding: 5.2 - 1.6 = 3.6dB difference in gain between CH21 and CH3. Comparing with your measurement: 27.1 - 15.6 = 11.8dB Yep, way too much "tilt" in your measurement. Do it again, this time with a spectrum analyzer and an RF sweep generator. The rotor also has a bypass braid around it which many people forget. What is a bypass braid? I've never heard of the term. Neither has Google search. Do you mean something like quad shielded RG-6/u? A large tree is going to hit by lightning first. Large height or large girth? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#26
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Antennae Booster
What is a bypass braid? I've never heard of the term. It was a piece of heavy braid to connect the upper mast to the lower mast for grounding. It was supposed to prevent lightning or static discharges from damaging the ball bearings or their races. The grease wasn't conductive, and would harden into an insulating layer of varnish. That forced the downlead to carry the discharge current. |
#27
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Antennae Booster
On Sat, 26 Sep 2020 17:21:21 -0700 (PDT), Michael Terrell
wrote: What is a bypass braid? I've never heard of the term. It was a piece of heavy braid to connect the upper mast to the lower mast for grounding. It was supposed to prevent lightning or static discharges from damaging the ball bearings or their races. Thanks. Even with the magic buzzwords, I wasn't able to find any rotator or tower installation instructions that involved such a bypass braid. I don't think it will do much to prevent 20,000 Amps from turning a big antenna rotator into a metal recycling candidate. I double if it will do much to prevent arcing from pitting the bearings. The are a large number of bearings in the rotator and it only take a decent connection through one bearing to discharge a static electricity buildup. I've taken apart a few rotators and found plenty of rust, considerable loss of grease, but no pitting (except from the rust). The bypass wire might also protect against an unusual situation where a ham operator uses a tower or mast as both a monopole antenna and a rotator mount. In transmit, the RF current will go through the rotator bearings. That's not a problem if the rotator is not in motion, but potentially a big problem if the bearings are moving, arcing merrily as they roll along. To be fair, I haven't proven that this is happening, but I'm fairly certain it could easily be tested. The grease wasn't conductive, and would harden into an insulating layer of varnish. That forced the downlead to carry the discharge current. I've seen grease turned to varnish, usually in salty marine atmospheres or after using the wrong type of grease to lubricate the rotator. I sometimes find some water in the bearing race. In my never humble opinion, what's happening is the grease is getting washed away by rain, fog and condensation. The idea grease would be something that can (in order of most important to least important): 1. Will not wash out (i.e. marine grade grease). 2. Inhibits galvanic corrosion and rust formation. 3. Does no "foam" or create abscesses that collect water. 4. Slightly conductive to discharge static electricity. 5. Tolerates high temperatures by NOT evaporating or dripping. 6. Handles a heavy load. What I've been using are various marine lithium based grease concoctions such as WD-40 Specialist Marine-Grade Grease: https://www.amazon.com/WD-40-Specialist-Marine-Grade-Resistant-Grease/dp/B071R943VS/ https://www.wd40.com/products/water-resistant-grease/ Note that this is lithium based and not white-lithium grease. Please note that very little of this has much to do with a receive only TV antenna, rotator, and mast/tower. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#28
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Antennae Booster
On Sat, 26 Sep 2020 20:13:15 -0400, Ralph Mowery
wrote: In article , says... h a spectrum analyzer and an RF sweep generator. The rotor also has a bypass braid around it which many people forget. What is a bypass braid? I've never heard of the term. Neither has Google search. Do you mean something like quad shielded RG-6/u? A large tree is going to hit by lightning first. Large height or large girth? Bypass braid for a rotator is for lightning protection. Methinks it has more to do with discharging a static electricity buildup (St Elmo's Fire) than protecting against a lightning hit or lightning induced current. You put a piece of wire to the mast above the rotator and then to the mast below the rotator. That is suppose to make a good connection from the top mast to the bottom mast. Well, I've never seen such a thing, never had anyone request it, and couldn't find with Google any installation instructions recommending such a practice. It is not so much the actual gain of the amplifiers, but the noise figure. If just feeding one or two tv sets all the gain needs to be is just to make up for the loss of the feedline if the amp is very near the antenna and a little more depending on the noise figure of the TV set. If the amp is near the TV, it needs very little gain (maybe 10 db) and better have a noise figure much lower than the TV tuner. Agreed. I think I mumbled something about too much gain causing intermod problems further up this thread. Another problem is loss of dynamic range when the added gain also raises the noise floor but not changing the overload point. Way back in the dark ages of TV, the receivers were stone deaf and any kind of RF preamplifier offered a performance improvement. These days, with GaAs low noise front ends, the best that a preamp can offer is to compensate for coax cable losses. Hopefully a tall tree will get hit first,but no guarentee. We don't get much lightning here on the left coast[1]. I live in a forest full of 100ft and higher trees. I know of three local trees (out of millions) that were hit by lightning in the past 40 odd years. Both were in rather odd locations, such as the bottom of a canyon or surrounded by taller trees. My best guess is the tree holding the most water has the highest conductivity and therefore gets hit first. [1] Mother nature delivered our accumulated savings (with interest) of lightning on Aug 15, 2020, with a really impressive display of flashing lights, and starting 500+ big fires that are currently trying to incinerate California, Oregon, and Washington states. 5 million acres burned and climbing. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#29
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Antennae Booster
Measurements: The CM-7777 has only one input. I used an OTA signal, not on the same day.
I measured before the pre-amp one day and after the power injector (about 30') on another day. Cable is copper clad RG6QS. Measured with a Sencore SLM1453i http://salestores.com/sencor01.html. These measurements were done before the re-assignment of channels. The measurement is problematic because of 1) Tilt and 2) different days. "Evaluation of a Winegard HD8200U Antenna with a Channel Master CM-7777 30 dB mast mounted Preamp" FM trap is enabled in the antenna pre-amp. May 2019 Voltages in Columns C and F are in dBuV Gain is just Column F minus Column C @antenna (N3) @In Attic (N4) Gain(N5) 2 53.6 73.5 19.9 3 42.4 58.0 15.6 4 47.5 67.5 20.0 5 29.9 54.1 24.2 6 59.5 80.6 21.1 7 Fail 37.4 Fail 8 16.1 Fail 41.6 Fail 9 22 Fail 38.1 Fail 10 * * 46.5 Fail 11 * 39.4 Fail 12 36.7 58.4 21.7 13 * * 35.0 Fail 14 * * 28.5 Fail 15 * * 29.2 Fail 16 * * 31.6 Fail 17 * * N5 49.2 18 * * 27.7 Fail 19 * * 39.5 Fail 20 * * 28.9 Fail 21 27.6 Fail 27.6 22 43.4 63.6 20.2 23 * * 25.9 Fail 24 * * 28.4 Fail 25 * * 34.3 Fail 26 32.2 55.2 23.0 27 * * 29.2 Fail 28 * * 27.6 Fail 29 * * 25.8 Fail 30 * * 26.8 Fail 31 21.2 48.7 27.5 32 32.3 56.7 24.4 33 * * 30.1 Fail 34 34.4 * 56.0 21.6 35 * * 27.4 36 * * 30.2 37 * * 30.7 38 * * 39.0 39 * * 28.7 40 * * 33.1 41 * * N1 31.2 42 U U N6 55.5 43 * * 31.3 44 U U N7 Missed a few here, "I think the reason for the * @antenna is that the Sencore didn't find anything Using 8VSB modulation. Not sure." TVFool data from Highest to lowest NF 6 (6.1) ABC NM: 42.6db Pwr -48.2dbm 2Edge, 28.8 miles .... 42 (29.1) Fox NM: 21.5 Pwr: -69.4 2Edge, 28.9 miles On one TV using a converter box, it shows 29/100 for signal strength on it's internal meter for 29.1 and 91 for channel 6.1. This includes another amp at 35 feet (unknown gain) from the 7777, then 65 feet to a 2-way splitter and about 35' to the TV. The "stupid" Samsung "Smart TV" only shows s/n ratio. I do have a "tuner" that will show both in real units. The system is/will be: Mast amp (currently CM-7777, plan to change to a Kitz lower NF amplifier) 30'; RG-6QS copper clad Power injector in attic Variable 0-18db gain amplifier using an attenuator 65'; RG-6QS copper clad to basement; About 40' to each TV location (some less, some more) Currently: A 2-way splitter to two TV's about 40' away. Planned: Blonder Tongue BIDA 75-43a (30-45 db Gain with tilt compensation cards and variable) that replaces a Tin Lee amplifier four 24 db 4-way taps to 12 locations (existing, but not currently used because of a broken amplifier) Locations are around 40' away. The gain is unknown because the AMP and attenuator WAS prior to the 2-way splitter and it was recently moved to the attic as is. performance is definitely better. My main distribution amp died and I'm planning to replace it with a Blonder-tongue BID 75a-43 for 12 locations fed by four 4-way 24 db taps. This has available various "tilt cards", but might consider a custom VHF attenuator. I think the CM-7777 might overload with cellular signals. Why copper clad? Friends that were in the satellite TV industry gave me 1000 feet. |
#31
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Antennae Booster
On Saturday, September 26, 2020 at 11:14:26 PM UTC-4, Jeff Liebermann wrote:
On Sat, 26 Sep 2020 17:21:21 -0700 (PDT), Michael Terrell wrote: What is a bypass braid? I've never heard of the term. It was a piece of heavy braid to connect the upper mast to the lower mast for grounding. It was supposed to prevent lightning or static discharges from damaging the ball bearings or their races. Thanks. Even with the magic buzzwords, I wasn't able to find any rotator or tower installation instructions that involved such a bypass braid. I don't think it will do much to prevent 20,000 Amps from turning a big antenna rotator into a metal recycling candidate. I double if it will do much to prevent arcing from pitting the bearings. The are a large number of bearings in the rotator and it only take a decent connection through one bearing to discharge a static electricity buildup. I've taken apart a few rotators and found plenty of rust, considerable loss of grease, but no pitting (except from the rust). The bypass wire might also protect against an unusual situation where a ham operator uses a tower or mast as both a monopole antenna and a rotator mount. In transmit, the RF current will go through the rotator bearings. That's not a problem if the rotator is not in motion, but potentially a big problem if the bearings are moving, arcing merrily as they roll along. To be fair, I haven't proven that this is happening, but I'm fairly certain it could easily be tested. The grease wasn't conductive, and would harden into an insulating layer of varnish. That forced the downlead to carry the discharge current. |
#32
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Antennae Booster
terrell. Nic
At the university where I worked, they had a ground potential across about 200' in their computing center built duting the big mainframe ERA. A motor-generator fed the building. During a storm, there was a potential that developed across the ground between one side and the other side of the building. They had to replace those lines with fiber. The rotor is an Eagle Aspen ROTR-100 which is pretty cool, but going to be repairable if it fails. min uses a coax for power/positioning. You can, but I didn't use it for the antenna feed too. You can even use it to power a pre-amp. it send DISEQ/C signals on the coax for positioning. One bad thing is that the readout is not real-time when the antenna is moving. The readout "pretends" to know where the antenna is. I did use a thrust bearing which isn't available anymore and I did replace the studs with stainless studs. 318 SS and anti-sieze if possible. All hardware went that route. The antenna mount is an eve mount made with Unistrut and I guy every 120 degrees using a non-conductive guy wire called Phillystran. I never got a chance to replace the aluminum mast wth fiberglass, When we had the tree trimmed, I offered to help take down the antenna. To do that, I install a 2 piece shaft collar under the antenna and loosen the antenna and remove the connections. The tree guy in the bucket truck just plucked the antenna off the mast. He did his thing and plopped it back on the mast and I could finish it after the install. I had to do some more important antenna stuff and I was unable to change the mast to fiberglass. I changed all of the U-bolts to stainless too. I didn't powdercoat the rotor brackets although I had plenty of time if i had planned it during the original install. |
#33
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Antennae Booster
On 9/23/2020 3:06 AM, Pimpom wrote:
On 9/23/2020 1:02 PM, Pimpom wrote: On 9/23/2020 3:26 AM, Dave Platt wrote: Stu jaxonÂ* wrote: Hi Group, can someone help please, I have an antenna booster that requires a power supply of 6v 100ma, can i use a variable power supply 6v 300ma??? Assuming that they're both DC supplies, and assuming that you get the polarity correct (positive-supply to positive-load, negative-supply to negative-load), and assuming that you're careful to not turn the variable power supply up to higher than 6 volts... yes, it should work.Â* The 300 mA capacity of the variable supply is greater than the 100 mA which the booster will draw, and that's OK.Â* However, turning up the supply to above 6 volts may damage the booster.Â* I'd recommend checking the supply voltage with a voltmeter before you connect it to the booster. Do be aware that "antenna booster" amplifiers can cause more problems than they solve.Â* In most cases you'll get better results by improving your antenna setup. Agreed on all points except that, in certain situations, using an antenna booster is the only way to get an acceptable reception. TV came to this remote corner of India in 1980 when some army people discovered that it was possible to receive stations in neighbouring Bangladesh. Due to the very hilly terrain, reception varied from fair to unusable within tens of meters, all with outdoor yagi antennas. Antenna boosters were a must. The boosters were all alike, made up of 4 or 5 bjt amplifier stages. Power was fed to the booster via twin 300-ohm cable from an indoor 12V AC supply and gain was adjusted by means of a series potentiometer. I was the local "expert" and I experimented with different antenna types, including yagi arrays and helical antennas with a 6-foot plane reflector. Some people claimed that reception was noticeably improved by hanging aluminium pans on their yagis. Once I even rigged up a passive re-radiator with a back-to-back pair of yagis on a hilltop for a client who had no reception at all in his house which was located on the blind side of the hill. It worked somewhat but was not really satisfactory. What I couldn't really explain was that reception slowly but steadily degraded in the decade from 1980 to 1990 (when cable TV arrived). In 1980, I could often get excellent reception in my house with literally an aluminium coat hanger plugged into the antenna socket. By contrast, I could watch the 1990 FIFA World Cup only with an array of four yagis *and* an antenna booster. Is it possible there was construction going on somewhere between the source antenna and your work? |
#34
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Antennae Booster
On Wed, 23 Sep 2020 15:36:58 +0530, Pimpom wrote:
Once I even rigged up a passive re-radiator with a back-to-back pair of yagis on a hilltop for a client who had no reception at all in his house which was located on the blind side of the hill. It worked somewhat but was not really satisfactory. Passive repeaters like that don't work. For example, let's take an over simplified situation. This is for a direct path (no repeater) between the TV station and the receiving antenna. UHF 14 channel at 500 MHz. 10 mile path. 12 dBi antenna gain on the receiver end. https://www.proxim.com/en/products/knowledge-center/calculations/calculations-free-space-loss The 10 mile path produces a 110.6 dB path loss at 500 MHz. Add the 12 dBi antenna gain and the station to receiver path loss is: 110.6 - 12 = 98.6 dB loss Next is with a passive repeater installed at 9 miles from the TV station and 1 mile to the receive antenna. At the 9 mile point, there are two back to back 12dBi UHF antennas. This splits the calculation into two parts (9 miles and 1 mile). Note that there are three 12dBi antennas involved: The 9 mile path has a loss of 109.7 dB. The first 12dBi antenna reduces the 9 mile loss to: 109.7 - 12 = 97.7 dB loss The 1 mile path has a loss of 90.6 dB. The 2nd and 3rd 12dBi antennas reduce the 1 mile loss to: 90.6 - 12 -12 = 66.6 dB loss The total end to end loss (including the three 12dBi antennas) is: 97.7dB + 66.6dB = 164.3 dB path loss 164dB is a *MUCH* larger path loss than the original direct path of 98.6dB even though it includes the gain from 3 antennas (+36dB). Specifically, the direct path signal through such a passive repeater arrangement would be: 164.3 - 98.6 = 65.7dB or about 4 million times stronger (in terms of power gain) than the passive repeater derangement. This is why you don't see many passive repeaters, passive cell phone boosters, or flat panel reflectors, in service. What I couldn't really explain was that reception slowly but steadily degraded in the decade from 1980 to 1990 (when cable TV arrived). In 1980, I could often get excellent reception in my house with literally an aluminium coat hanger plugged into the antenna socket. By contrast, I could watch the 1990 FIFA World Cup only with an array of four yagis *and* an antenna booster. 1990 was before repacking and DTV (about 2009), so that wouldn't explain the signal loss. What seems odd is your "slowly but steadily degraded". That seems like some kind of TV receiver problem, mechanical problem (squirrel chewing coax, water in the coax, antenna rot), that gets worse over time, rather than a sudden change. Were the neighbors experiencing the same problem with the same station? Are you on a shared community or building distribution system? Were you listening directly to the unspecified TV transmitter, or were you listening to a station owned UHF repeater? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#35
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Antennae Booster
On Friday, September 25, 2020 at 4:15:06 AM UTC-4, Chris K-Man wrote:
On Tuesday, September 22, 2020 at 4:54:39 PM UTC-4, Stu jaxon wrote: Hi Group, can someone help please, I have an antenna booster that requires a power supply of 6v 100ma, can i use a variable power supply 6v 300ma??? Thanks, ____________ My idea of a "booster" or "signal amp" is a bigger/higher gain antenna. As far as language differences are concerned, England and India are forever bound by their use of English. Compared to them, what is spoken in the States is called AMERICAN: a rebellious corruption and *******isation of what is spoken/written in the two aforementioned nations. The UK spoke like Americans and Canadians until some time prior to the 1900s. Where else would they get the accent from? Pluto? Where else do you hear "nucular" routinely substitute for nuclear? Or plural's of item's succeeded with an apostrphe s? LOL! Canada and Mexico. This is North America we're talking. Forget? |
#36
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Antennae Booster
With the understanding that the proper job of the Village Idiot is to make the rest of the villagers look good by contrast, I ask all of you to join me in recognizing the masterful performance of our new incumbent!
Peter Wieck Melrose Park, PA |
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