[TowerTalk] TH7-DX 15M problem

Radio K0HB kzerohb at gmail.com
Thu Aug 27 09:57:21 EDT 2015


Don't have a second amp, but the amp plays just fine on a different antenna.









__73, de Hans, K0HB

"Just a Boy and His Radio"™

On Thu, Aug 27, 2015 at 8:51 AM, john at kk9a.com <john at kk9a.com> wrote:

> Trying a different amp could rule it out.
> John KK9A
> To:	"'Ham - Tower Talk'" <towertalk at contesting.com>
> Subject:	Re: [TowerTalk] TH7-DX 15M problem
> From:	"David Robbins" <k1ttt at arrl.net>
> Date:	Thu, 27 Aug 2015 11:19:54 +0000
> No, running the amp into a dummy load won't rule out the amp.  A high swr
> like
> that caused by the amp is because the amp starts detuning and generates
> harmonics, it’s the harmonics that would be reflected causing the high
> reverse
> power.  Running into a dummy load would likely not show that unless there
> were
> a good lowpass filter in between to reject them.
> David Robbins K1TTT
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Robert
> Harmon
> Sent: Wednesday, August 26, 2015 21:32
> To: Ham - Tower Talk
> Subject: Re: [TowerTalk] TH7-DX 15M problem
> Hans,
> I would have suspected the 15 meter traps too.
> I would start doing the process of elimination to narrow down the culprit.
> Disconnect the coax feeding the TH7 in the shack and put a coax jumper to a
> dummy load and run the amp full bore on 15 and see if the SWR stays ok.
> I know you think the amp is OK, but this will rule it out.
> Then reconnect the TH7 coax and go up to the TH7 and disconnect the coax from
> the TH7 connection terminals.  Connect the coax to the dummy load again.
> Back to the shack, load it up on 15 again and see what happens.  If you still
> have the swr anomoly, then you have ruled out the amp and the feedline.
> It is in the antenna.
> I had a similar problem with a KLM KT34XA one time and went thru this,  then
> lowered the antenna down to sawhorses in the back yard and cleaned, and
> reconnected every element connection point and found a connection to one
> of the
> linear loading tubes that was squirrely.  Put the antenna back up and all was
> good.
> Bob
> K6UJ
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