[Elecraft] RF feedback? only when using KXPA100

[Bob McGraw K4TAX]

Just as a comment.   PL-259 connectors are all created equal. Some are 
great looking connectors and are just pure crap!   The plating makes for 
good looks but poor performance.

To that end, I always and every time snug my PL-259 connectors with a 
pair of 4" Channel Lock pliers.   Finger tight is never good enough!    
You'd be surprised at the number of RFI issues I've corrected  with this 
approach.

73

Bob, K4TAX


On 8/7/2017 4:59 PM, David Bunte wrote:
> Jim -
>
> I recently sent my K3 to the 'Mother Ship' for some upgrades while my wife
> and I took a 3 week road trip. I hooked up the returned rig over the
> weekend. Much to my chagrin, I was extremely high SWR. I verified that I
> had the RF path correct from the K3 through assorted other devices and to
> the antenna. While doing so I noticed one coax connector that was about 1/4
> to 1/2 turn loose. I tightened it, and all was fine... for about 30
> seconds.
>
> Remembering what a wise man once said I suspected a bad piece of coax. I
> checked the same connection again... it was loose... as I tightened it, all
> of a sudden it became loose again. This was a 1 foot jumper, from a company
> that advertises heavily. I had been using it for several years from the
> output of my KPA500 to the sensor for my LP-100A. The threads did not
> appear to be stripped, although it felt like it. I looked like the threads
> were cur very shallow. I replaced it with a jumper I made many years ago,
> using
> Amphenol connectors, and all is now working as it should.
>
> Well... not quite all... I have made some nice CW QSOs, but decided to
> check SSB operation. It is not working on that mode (which I almost never
> use), but I will tackle it to see what is not set correctly.
>
> Dave - K9FN
>
> On Mon, Aug 7, 2017 at 5:28 PM, Jim Brown <jim at audiosystemsgroup.com> wrote:
>
>> On 8/6/2017 5:25 PM, David F. Reed wrote:
>>
>>> It was a connection to my coax switch; take it out of line, it goes away.
>>> re-connected, it comes back.  Cleaned the connections and reconnected, it
>>> is gone.
>>>
>> Many years ago, a very smart guy said something it the effect that with
>> any problems with TX or RX, ALWAYS check for bad coax FIRST. From lots of
>> experience, I've learned the value of that. First things to check are the
>> SHIELD connections, any junk connectors and adapters (if it doesn't say
>> Amphenol, it's probably junk).
>>
>> If you "cleaned the connections" and fixed it, there's a good chance that
>> the problem is still there, lurking as an intermittent shield connection
>> that will return. Or maybe the switch is poor.
>>
>> 73, Jim K9YC
>>
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