[TowerTalk] Antenna issue still puzzling me

[n8de at thepoint.net]

My guess is that the balun has a cold-solder joint in it.

73
Don
N8DE

Quoting Jim W7RY <w7ry at centurytel.net>:

> Check all of your antenna's connections. Anyplace there is a nut and
> stud, can cause corrosion and poor connections. Or anyplace something
> relies on a bolt or screw.
>
> I have had this problem before on a 40 meter beam as well as a TH6.
> Traps are a good place for this to show up as well as the studs on the
> balun etc...
>
> 73
> Jim W7RY
>
>
>
> -----Original Message----- From: John
> Sent: Saturday, April 20, 2013 4:22 PM
> To: towertalk at contesting.com
> Subject: [TowerTalk] Antenna issue still puzzling me
>
> A couple of weeks ago I posted an email about the receive in my Icom 706
> occasionally dropping down on some bands, and coming back after you click
> the mic or key putting the rig into transmit. After some testing of things
> in the antenna system-coax jumpers, low pass filter, tuner, I concluded
> (with help from the list) that it must be in the rig. I sold the rig as a
> fixer upper and got a good deal on a replacement. Well it has the same
> problem! Same symptoms, same bands (different brand and model of rig)
> everything! Talk about frustrating!
>
> One test I made in the past was to switch over to the 6m yagi and see
> keying the rig would bring the receive back, since it is on a different
> feedline from the dipole I am running. It did, which is one reason I
> concluded it must be a rig problem. I now see that there probably was a
> little energy making it to the dipoles feedline anyways, since both
> antennas were on an antenna switch in the tuner, and I know that isolation
> isn't perfect. Tried hooking the 6m antenna straight up to the rig and
> didn't witness the receive level dropping at all. That tells me it must be
> something in the antenna system.
>
> Here is my antenna system-105 feet or so of copper wire, attached to Radio
> Shack 300 ohm twinlead, about 20 feet or so of that. The twinlead runs to a
> 4:1 voltage balun, which transitions to RG-11 75ohm coax, which then runs
> to the shack. Given this system, where is the problem likely to be-and more
> importantly, why would it occur on some bands and not others. It happened
> mainly on 12m and 15m, and was starting to happen more on 17m and 30m. I
> never saw it occur on 10m or 20m, and only very rarely on 40m.
>
> Anyone have an idea as to what might be going on?
>
> 73 John AF5CC
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