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Hy-Gain AV640 (Patriot) problem, or Bugs in the Antenna
I put up a Hy-Gain AV640 a few years back for a backup and as the HF
antenna for my shop. The antenna was on top of a 32 foot aluminum tower at the West end of the shop. The match on all the bands was near perfect, or at least it was slightly better than I'd expected with 1.1:1 at resonance. Bandwidth on each band was more than adequate and much wider than any trap, multi band vertical id used in the he past. I had mainly been listening to W1AW code practice on 40 but did make a few contacts on 40 and 6-meters. I recently replaced the old Henry 2K4 with a Tokyo Hy-Power HL-1.5KFX solid state amp which happens to cover 6-meters as well. With the little Yaesu FT-897D it also gives auto band switching and will remember which of two antennas connected to the amp you were using for each band. At-any-rate a couple weeks back 6-meters opened up and a spent a few hours making contacts from the East, West, and Gulf coasts. (no DX sigh) When I went to operate on 40 the amp was kicking out due to high SWR and started doing the same on six. Both 40 and 15 were resonant about 1 MHz below the bottom end of the bands. Minimum SWR at resonance had gone from 1.1:1 to between 1.6 and 2:1. We (several other hams and myself) let the Tower/antenna down. It had one broken insulator which would not have caused the problem, but I built a new one out of Lexan which is a lot more sturdy than the old *stuff*. THEN I got to the matching network. That thing was packed solid with Wasp nests and crispy crittered Wasps along with a pile of dead Wasps and Wasp *goo* on the coax chassis connector in the bottom of the box. That goo made it through the chassis connector and badly corroded about 3' of 9913 which is being replaced with LMR-600. NOTE the original drain holes are just a tad too large and just right for Wasp entry for their new home. So if you use one of these antennas, plugging the drain holes and drilling a series of smaller ones might be in order. OTOH Hy-Gain does state you should take the antenna down and clean out the matching network every year or so. (Wasps can build a *big* nest in a few days) Apparently there is some truth to the RF exposure hazard, or there was for the wasps in close proximity to high power on 6-meters. None of them complained when I cleaned the nests out. BTW I had to completely remove the tuning unit from the box to be able to get the nests and *glue* they make off the torroids. Having the antenna down, I took the opportunity to give it an overhaul. I cleaned all the connections which looked pretty bad (lots of white powder), used a tiny bit of nolox (similar to Pentrox) on each coil and jumper connection after cleaning, which was then sealed with liquid electrical tape. The jumper from the tuning unit to the counterpoise had to be replaced. After 5 years the fiberglass is showing some deterioration due to UV exposure. Be careful about coating these coils while trying to protect the fiberglass. The coils are right under the top hats and clear Krylon or liquid electrical tape may add a bit of capacitance in parallel to the coils and with them being right under the capacitive hats a little capacity can go a long way resulting in the resonant frequency going down substantially for that specific band. I put the antenna back up on a 14foot pole anchored to the NW guy anchor for my big tower. On checking, the SWR for 40, 20, and 6-meters is just where it's supposed to be as is the resonant frequency and the SWR at resonance is showing 1.0:1. However two bands, 15 and 10 are showing 1.6:1 and 1.9:1 at resonance. (resonance is back where it belongs) All solder joints in the matching network have been resoldered and checked. Wires and cores were also checked for insulation and burn marks. Tech support told me not to worry about running 750 watts output PEP even though the ratings show 300 watts for 6-meters as long as there were no signs of overheating or arcing. The network should handle that with ease. So the problem, or question is, why the change in minimum SWR on 15 and 10 meters? What may I have missed? The analyzer is no help for this. I gotta get that antenna system on the big tower repaired and the rotator reinstalled for the DX season. Then maybe I can set up an interconnect so I can use those antennas from the shop as well while keeping the AV640 as a backup. I rebuilt the PST-61 (seals failed and water took out the main bearings) and it's ready to go back in. Unfortunately nature gave me a bit of a set back last April and I had to learn to walk again. However I'm about ready to tackle the tower work real soon. I've been working at 30 to 40 feet, but that doesn't take near the energy of climbing to 100', working for a couple hours, and still have the energy/strength to climb back down. BTW I had been working on top of the guy anchor post Thursday afternoon for about a half an hour when I noticed a couple of bees flying around. They weren't bothering me, but when I looked down into that 5" pipe I saw a very large Wasp nest with Wasps crawling all over it. At that point I hosed it down with Wasp and Hornet killer. I decided I had pushed my luck far enough. Roger (K8RI) |
#2
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Hy-Gain AV640 (Patriot) problem, or Bugs in the Antenna
On Thursday, September 6, 2007 at 3:46:50 AM UTC-4, Roger (K8RI) wrote:
I put up a Hy-Gain AV640 a few years back for a backup and as the HF antenna for my shop. The antenna was on top of a 32 foot aluminum tower at the West end of the shop. The match on all the bands was near perfect, or at least it was slightly better than I'd expected with 1.1:1 at resonance. Bandwidth on each band was more than adequate and much wider than any trap, multi band vertical id used in the he past. I had mainly been listening to W1AW code practice on 40 but did make a few contacts on 40 and 6-meters. I recently replaced the old Henry 2K4 with a Tokyo Hy-Power HL-1.5KFX solid state amp which happens to cover 6-meters as well. With the little Yaesu FT-897D it also gives auto band switching and will remember which of two antennas connected to the amp you were using for each band. At-any-rate a couple weeks back 6-meters opened up and a spent a few hours making contacts from the East, West, and Gulf coasts. (no DX sigh) When I went to operate on 40 the amp was kicking out due to high SWR and started doing the same on six. Both 40 and 15 were resonant about 1 MHz below the bottom end of the bands. Minimum SWR at resonance had gone from 1.1:1 to between 1.6 and 2:1. We (several other hams and myself) let the Tower/antenna down. It had one broken insulator which would not have caused the problem, but I built a new one out of Lexan which is a lot more sturdy than the old *stuff*. THEN I got to the matching network. That thing was packed solid with Wasp nests and crispy crittered Wasps along with a pile of dead Wasps and Wasp *goo* on the coax chassis connector in the bottom of the box. That goo made it through the chassis connector and badly corroded about 3' of 9913 which is being replaced with LMR-600. NOTE the original drain holes are just a tad too large and just right for Wasp entry for their new home. So if you use one of these antennas, plugging the drain holes and drilling a series of smaller ones might be in order. OTOH Hy-Gain does state you should take the antenna down and clean out the matching network every year or so. (Wasps can build a *big* nest in a few days) Apparently there is some truth to the RF exposure hazard, or there was for the wasps in close proximity to high power on 6-meters. None of them complained when I cleaned the nests out. BTW I had to completely remove the tuning unit from the box to be able to get the nests and *glue* they make off the torroids. Having the antenna down, I took the opportunity to give it an overhaul. I cleaned all the connections which looked pretty bad (lots of white powder), used a tiny bit of nolox (similar to Pentrox) on each coil and jumper connection after cleaning, which was then sealed with liquid electrical tape. The jumper from the tuning unit to the counterpoise had to be replaced. After 5 years the fiberglass is showing some deterioration due to UV exposure. Be careful about coating these coils while trying to protect the fiberglass. The coils are right under the top hats and clear Krylon or liquid electrical tape may add a bit of capacitance in parallel to the coils and with them being right under the capacitive hats a little capacity can go a long way resulting in the resonant frequency going down substantially for that specific band. I put the antenna back up on a 14foot pole anchored to the NW guy anchor for my big tower. On checking, the SWR for 40, 20, and 6-meters is just where it's supposed to be as is the resonant frequency and the SWR at resonance is showing 1.0:1. However two bands, 15 and 10 are showing 1.6:1 and 1.9:1 at resonance. (resonance is back where it belongs) All solder joints in the matching network have been resoldered and checked. Wires and cores were also checked for insulation and burn marks. Tech support told me not to worry about running 750 watts output PEP even though the ratings show 300 watts for 6-meters as long as there were no signs of overheating or arcing. The network should handle that with ease. So the problem, or question is, why the change in minimum SWR on 15 and 10 meters? What may I have missed? The analyzer is no help for this. I gotta get that antenna system on the big tower repaired and the rotator reinstalled for the DX season. Then maybe I can set up an interconnect so I can use those antennas from the shop as well while keeping the AV640 as a backup. I rebuilt the PST-61 (seals failed and water took out the main bearings) and it's ready to go back in. Unfortunately nature gave me a bit of a set back last April and I had to learn to walk again. However I'm about ready to tackle the tower work real soon. I've been working at 30 to 40 feet, but that doesn't take near the energy of climbing to 100', working for a couple hours, and still have the energy/strength to climb back down. BTW I had been working on top of the guy anchor post Thursday afternoon for about a half an hour when I noticed a couple of bees flying around. They weren't bothering me, but when I looked down into that 5" pipe I saw a very large Wasp nest with Wasps crawling all over it. At that point I hosed it down with Wasp and Hornet killer. I decided I had pushed my luck far enough. Roger (K8RI) Hi Roger, I just started having very high swr on my av-640 it was jumping around in high winds. So down comes the antenna when the winds stop. Go figure, I just received my flex radio... To your answer about 10m and 15m the 5ft sections of rod in my antenna are joined together by 4 inch sections of threaded rod when screwed together there was a gap of 1 to 2 inches between the sections. I seems either the threaded holes inside the ends of the 5ft sections were too short or the 4 inch threaded rods were too long. Either way, this made the overall length too long. Which changed the swr sweet spot which for me is the center of the voice band. So none of the av-640 settings worked for me without an antenna tuner. I have a table I created to measure the dimensions of each so I could compare to the stock dimensions. What was your dimensional measurement for the top part of the antenna to get swr lowest at 7.250 (40m). I had a real hard time to tune this as when you crank down the antenna parallel with the ground you can't get it right regardless of what you do. I do have an MFJ259-C antenna analyzer. I will probably have to take apart the black box and go thru it...... Art |
#3
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Hy-Gain AV640 (Patriot) problem, or Bugs in the Antenna
On Sunday, January 5, 2020 at 5:28:53 PM UTC-5, wrote:
On Thursday, September 6, 2007 at 3:46:50 AM UTC-4, Roger (K8RI) wrote: I put up a Hy-Gain AV640 a few years back for a backup and as the HF antenna for my shop. The antenna was on top of a 32 foot aluminum tower at the West end of the shop. The match on all the bands was near perfect, or at least it was slightly better than I'd expected with 1.1:1 at resonance. Bandwidth on each band was more than adequate and much wider than any trap, multi band vertical id used in the he past. I had mainly been listening to W1AW code practice on 40 but did make a few contacts on 40 and 6-meters. I recently replaced the old Henry 2K4 with a Tokyo Hy-Power HL-1.5KFX solid state amp which happens to cover 6-meters as well. With the little Yaesu FT-897D it also gives auto band switching and will remember which of two antennas connected to the amp you were using for each band. At-any-rate a couple weeks back 6-meters opened up and a spent a few hours making contacts from the East, West, and Gulf coasts. (no DX sigh) When I went to operate on 40 the amp was kicking out due to high SWR and started doing the same on six. Both 40 and 15 were resonant about 1 MHz below the bottom end of the bands. Minimum SWR at resonance had gone from 1.1:1 to between 1.6 and 2:1. We (several other hams and myself) let the Tower/antenna down. It had one broken insulator which would not have caused the problem, but I built a new one out of Lexan which is a lot more sturdy than the old *stuff*. THEN I got to the matching network. That thing was packed solid with Wasp nests and crispy crittered Wasps along with a pile of dead Wasps and Wasp *goo* on the coax chassis connector in the bottom of the box. That goo made it through the chassis connector and badly corroded about 3' of 9913 which is being replaced with LMR-600. NOTE the original drain holes are just a tad too large and just right for Wasp entry for their new home. So if you use one of these antennas, plugging the drain holes and drilling a series of smaller ones might be in order. OTOH Hy-Gain does state you should take the antenna down and clean out the matching network every year or so. (Wasps can build a *big* nest in a few days) Apparently there is some truth to the RF exposure hazard, or there was for the wasps in close proximity to high power on 6-meters. None of them complained when I cleaned the nests out. BTW I had to completely remove the tuning unit from the box to be able to get the nests and *glue* they make off the torroids. Having the antenna down, I took the opportunity to give it an overhaul. I cleaned all the connections which looked pretty bad (lots of white powder), used a tiny bit of nolox (similar to Pentrox) on each coil and jumper connection after cleaning, which was then sealed with liquid electrical tape. The jumper from the tuning unit to the counterpoise had to be replaced. After 5 years the fiberglass is showing some deterioration due to UV exposure. Be careful about coating these coils while trying to protect the fiberglass. The coils are right under the top hats and clear Krylon or liquid electrical tape may add a bit of capacitance in parallel to the coils and with them being right under the capacitive hats a little capacity can go a long way resulting in the resonant frequency going down substantially for that specific band. I put the antenna back up on a 14foot pole anchored to the NW guy anchor for my big tower. On checking, the SWR for 40, 20, and 6-meters is just where it's supposed to be as is the resonant frequency and the SWR at resonance is showing 1.0:1. However two bands, 15 and 10 are showing 1.6:1 and 1.9:1 at resonance. (resonance is back where it belongs) All solder joints in the matching network have been resoldered and checked. Wires and cores were also checked for insulation and burn marks. Tech support told me not to worry about running 750 watts output PEP even though the ratings show 300 watts for 6-meters as long as there were no signs of overheating or arcing. The network should handle that with ease. So the problem, or question is, why the change in minimum SWR on 15 and 10 meters? What may I have missed? The analyzer is no help for this. I gotta get that antenna system on the big tower repaired and the rotator reinstalled for the DX season. Then maybe I can set up an interconnect so I can use those antennas from the shop as well while keeping the AV640 as a backup. I rebuilt the PST-61 (seals failed and water took out the main bearings) and it's ready to go back in. Unfortunately nature gave me a bit of a set back last April and I had to learn to walk again. However I'm about ready to tackle the tower work real soon. I've been working at 30 to 40 feet, but that doesn't take near the energy of climbing to 100', working for a couple hours, and still have the energy/strength to climb back down. BTW I had been working on top of the guy anchor post Thursday afternoon for about a half an hour when I noticed a couple of bees flying around. They weren't bothering me, but when I looked down into that 5" pipe I saw a very large Wasp nest with Wasps crawling all over it. At that point I hosed it down with Wasp and Hornet killer. I decided I had pushed my luck far enough. Roger (K8RI) Hi Roger, I just started having very high swr on my av-640 it was jumping around in high winds. So down comes the antenna when the winds stop. Go figure, I just received my flex radio... To your answer about 10m and 15m the 5ft sections of rod in my antenna are joined together by 4 inch sections of threaded rod when screwed together there was a gap of 1 to 2 inches between the sections. I seems either the threaded holes inside the ends of the 5ft sections were too short or the 4 inch threaded rods were too long. Either way, this made the overall length too long. Which changed the swr sweet spot which for me is the center of the voice band. So none of the av-640 settings worked for me without an antenna tuner. I have a table I created to measure the dimensions of each so I could compare to the stock dimensions. What was your dimensional measurement for the top part of the antenna to get swr lowest at 7.250 (40m). I had a real hard time to tune this as when you crank down the antenna parallel with the ground you can't get it right regardless of what you do. I do have an MFJ259-C antenna analyzer. I will probably have to take apart the black box and go thru it...... Art KB1YAP Cape Cod |
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