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Author Topic: DOA Hy-Gain av-640  (Read 2149 times)
KQ6I
Member

Posts: 5




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« on: July 16, 2009, 07:04:18 AM »

I took delivery of a new av-640 a few days before Field Day this year. Meticulously assembling the vertical, being careful with the manual dimensions. The first raising suggested DOA with experiences of high SWR displayed on my ZM-30 (greater than 10) on every band. Fresh coax stranded 400 and mounted about 20’. I suspected the matching unit and after two attempts to bravely remove the board – success. Scrutinizing the solder joints, I soldered two suspect previously soldered spots. Reassembled and still high SWR remained. A couple of times of removing and reinspecting the matching unit grew old fast. My next thought was not high enough, and the vertical found its way to the roof apex. But alas, still high SWR, a second matching unit from Hy-Gain results in no better (same).

And now the kicker; It was during one of my many sojourns up the ladder, removing the matching unit, shaking the antenna mast, and ritualistically sacrifing a small rodent in hopes of appeasing any Gods that would listen. It was late evening, sun barely down, temperature decreased to around 70f and lo and behold. Heart attack, the SWR had dropped reasonably lower (would require a bit of tweaking). I do not know what happened or what I may have did or if I even contributed, but I will take it. The next morning proved to be a fluke. My short-lived euphoria dissipated and was rewarded with high SWR once again. Few ideas, the next couple of days and evenings, I monitored the SWR. To my amazement during the day hours, the SWR exceeded 10, but like clockwork, evening and sunset with temperature 70 brought reduced SWR. We are talking going from >10 to 1.4-1.9 depending on the band. 2 bands require serious tweaking to adjust the SWR, but first I need to fix the main SWR troubles. Please, can someone offer up some ideas? Contact directly please.


rgrds
Craig
kq6i at ARRL dot net
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K3WACKY
Member

Posts: 59




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« Reply #1 on: July 16, 2009, 11:03:57 AM »

Hello OM,

Looks like a possible mechanical connection, or still a soldered connection problem.

Some things to try.

See if you can localize the problem to a section of the antenna.

Can you get the freeze spray (component cooler spray) and spray parts of the antenna to see if the swr changes when you spray a particular section or part? It would be best to monitor the swr with an antenna analyzer connected if you have one or can borrow one.

For the 100th time, make sure that all metal parts are touching as they should, and the ones that shouldn't be touching aren't. Make sure no paint, insulated parts impede electrical conductivity, and that no metal burrs, wire, or screws are touching where they shouldn't.

For parts that should conduct over a mechanical joint, use an ohm meter to confirm a good connection.

Use the hammer method - use the handle of a screw driver and tap (not too hard to cause damage) on various sections of the antenna and see if tapping on a particular part or section improves the swr

Hopefully someone with the same antenna can chime in and maybe give you this antenna model specific things to check

Good luck!
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KB1GMX
Member

Posts: 1485




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« Reply #2 on: July 16, 2009, 07:33:41 PM »

You have a local broadcast station driving the meter nuts.

My Par EF40, Par EF40/20/10 and the Butternut HF2v (80/40m) all have this problem during the day when a daytime only BC station is active. The MFJ259 without
the highpass filer option cannot measure the SWR of those. Using the TX and Bird 43 at 10W I can get an accurate SWR during the day.

Allison
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KH6AQ
Member

Posts: 7718




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« Reply #3 on: July 16, 2009, 07:45:09 PM »

Your Palstar ZM30 is being overloaded by KBLY radio located 2.5 miles from your QTH. It runs 5 kW by day and 64 W night.

Although it is more difficult to tune with, a good old SWR meter will do the job.
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