[OKDXA] Antenna issue really puzzling me

Sat Apr 20 22:06:46 EDT 2013

I have had similar issues.
And from my experience the answer is probably-yes.
Doesn't make sense to me, but probably-yes ???
Bob's explanation an comments reflect mine.
Just an additional comment----- use it more an the problem may go 
away...  Hi HI
K9KK Rick

On 4/20/2013 8:52 PM, John G. wrote:
> Hi Bob,
>
> I have thougt of that and do plan on cleaning and redoing all of the 
> connections, and replace the balun and feedline.  Would the oxidation 
> make it affect some bands but not others?
>
> 73 John AF5CC
>
> ----- Original Message ----- From: "Robert Redmon" <k5sm.bob at gmail.com>
> To: "Oklahoma - DX news and information" <okdxa at mailman.qth.net>
> Sent: Sunday, April 21, 2013 12:27 AM
> Subject: Re: [OKDXA] Antenna issue really puzzling me
>
>
>> John,
>>
>> You have oxidation on some contact or connector between your rig and 
>> the antenna. My remote antenna switch uses relays to switch between 
>> antennas, and from time to time I have the same symptoms as 
>> you....and the same temporary fix...just hit a dit or click the mic 
>> switch. That tiny amount of rf is enough to blow through the 
>> microscopic layer of oxidation and all will then be well until you 
>> let it set for a while....and the oxidation returns. I clean the 
>> contacts in the switch using brown paper as a mild abrasive, pulling 
>> it between the contacts. This fix lasts for a few weeks (or months), 
>> but the problem always seems to eventually return.
>>
>> Bob
>> On 4/20/2013 6:24 PM, John wrote:
>>> This is DX related in that it involves my antenna, which allows me 
>>> to work
>>> DX,
>>> and you can reply to me off the list if you like also to keep the 
>>> reflector
>>> from
>>> getting too far off topic. I am hoping I can rely on the collective 
>>> wisdom
>>> of
>>> list members who know far more than I do about antennas and 
>>> electronics.
>>>
>>> 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. I then use a MFJ949D manual antenna tuner.
>>>
>>> About a year ago I noticed the receive level in my Icom 706 was 
>>> starting to
>>> dropping down, first on 12m, and later on on some other bands, and 
>>> coming
>>> back
>>> after you click the mic or key putting the rig into transmit. That 
>>> first
>>> suggested to me that it might be a relay problem, specifically on 
>>> the low
>>> pass
>>> filter board since it wasn't happening on all bands. I did go 
>>> through and
>>> try
>>> to test things in the antenna system after a friend say he had had a 
>>> similar
>>> problem once with a connector going bad in the feedline. I tested 
>>> the coax
>>> jumpers, low pass filter, tuner, and they all looked ok.
>>>
>>> One test I also made 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. 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!
>>>
>>> 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. 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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>>
>> -- 
>> Robert Redmon K5SM
>> AMA 58073
>>
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>
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