[Elecraft] Strange SWR change on 20 at

[Ron D'Eau Claire]

Hi Dave: I thought you said it happened after you sent CQ+Call a few times.
When a core heats to its Curie temp, the inductance change happens
"instantly". You are right - if it happens instantly when you hit the key it
is not heating. Something is breaking down. 

73, Ron AC7AC

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Dave
Cole
Sent: Saturday, May 13, 2017 10:39 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Strange SWR change on 20 at

I added the SWR meter...  My actual SWR jumps instantly up about1 SWR
unit...  I believe it is a bad connection on the Challenger where the main
antenna connects to the 20 meter tuning stub...

Just sort of surprised me to see a second person with the exact same issue
is all...  SWR change is instant, so it is not heating...  Happens at 30
watts, or 1 KW...  Time for a rebuild.

73s and thanks,
Dave
NK7Z
http://www.nk7z.net

On 05/13/2017 10:07 AM, Dave Cole wrote:
> Hmmm...  I am having the exact same issue...  My SWR changes after a 
> few transmissions, then returns...  Up until now, I have been 
> suspecting my antenna...  Time to add an external SWR bridge between 
> the tuner and antenna as a permanent thing...
>
> 73s and thanks,
> Dave
> NK7Z
> http://www.nk7z.net
>
> On 05/13/2017 09:07 AM, Terry Brown wrote:
>> I recently started using my horizontal loop that is about a full 
>> wavelength on 80, for 20 meters.  I took down my yagi as we are 
>> moving; drat!  My Horizontal Loop is at 40 ft.  height and fed with 
>> 450 window line into a 4:1 voltage balun with about 15 ft. of coax to 
>> rig.
>>
>>
>>
>> I am running 100 watts through my KXPA100.  I tune a frequency in the 
>> CW portion of 20 to about 1.2 :1 and start sending CQ.  After about 3 
>> to
>> 4  3x3
>> CQ's,, the SWR goes off the charts and power drops to zero.   I can
>> retune
>> the antenna and the process repeats itself.  20 meters is the only 
>> band affected.
>>
>>
>>
>> I am wondering if I am having RF problems in that part of the 20 
>> meter bands This only occurs on 20 meters.  The Amp is grounded, but 
>> the KX3 is not bonded to the Amp.
>>
>>
>>
>> I would appreciate any advice.
>>
>>
>>
>> Thanks and 73's,
>>
>>
>>
>> Terry de N7TB
>>
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