Has Hy Gain ever built a good balun or matching network? I fried a BN-80
(I think that was the #) on a TH6 around 1966 with just a NCL-2000. I
replaced it with a coil of coax as Mosley used. The antenna never did
stack up against monobanders and that was my last multiband antenna.
Over the years Ive heard of many balun and performance problems.
Carl
KM1H
----- Original Message -----
From: "Roger" <sub1@rogerhalstead.com>
Cc: <amps@contesting.com>
Sent: Saturday, April 25, 2009 2:26 PM
Subject: [Amps] The AV640 saga continues with a new? Problem.
> Hi SWR would be appropriate for the subject title, but I figured no
> one
> would read it. :-D
>
> I finally was able (got around to it) to lower the 40' tower with the
> AV640. The new arrangement makes this an easy task and with the
> sawhorses placed properly it makes the antenna easy to work on.
>
> The matching network consists of a 9 turn current choke/balun at the
> input, followed by a 4:1 balun (bout 11 turns) to match the impedance.
> Both consist of two fairly large cores. There is a coupling cap to
> the
> radiator, a tap to the counterpoise, and a choke from the radiator to
> ground for protection. My guess as to the reason it's derated on
> 6-meters is due to core heating.
>
> "This time" I found the choke across the output of the matching
> network
> fried. (I say fried, but there were no visible marks). I clipped it
> out
> at Hy-gain's suggestion. Removing it brought resonance for all of the
> bands back to the proper location and the SWR was near perfect.
> Soooo... I raised the tower back up to do a test starting with 40
> meters. It was working great at 100 watts so I kicked the amp on and
> started bringing up the power. Each key down was just long enough to
> get
> a steady reading or about one second each. At around 500 watts out,
> the
> power and SWR started jumping around which appeared to be an
> arc...which
> is where I called it quits for the night. Sad too as that evening I
> was
> hearing a lot of European stations quite strong. One Italian station
> was
> between 10 and 20 over 9. The next day (Yesterday) the antenna
> analyzer
> showed a high SWR, but the resonant frequencies were OK and no jumping
> around for output power or SWR. I think that's a pretty good
> indication
> of the coupling cap to the active element being shot although it looks
> OK on a ohm meter.
>
> Yes, I checked everything between the rig and antenna by substituting
> with a single run of coax from the antenna to the rig. I have blown
> out
> N connectors before, or at least nature has.
>
> No work on antennas today with high winds and severe thunderstorms. I
> can see a big batch of them headed this way at 50 - 60 MPH. A small
> batch went through early this morning at roughly 100 MPH and a bunch
> of
> hail.
>
> So, other than waiting for a new cap, does any one know what value
> they
> might use. I'm guessing it's probably just a standard 0.01 that could
> stand to have higher current and voltage ratings.
>
>
> 73
>
> Roger (K8RI)
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