On 12/8/2012 7:57 PM, Ron D'Eau Claire wrote:
Well, putting the KAT3 in operation will "correct' whatever is causing the
high VSWR in the KPA500 by providing a conjugate match, but when the KPA500
is in Standby it passes the K3 output through to the KAT500. Now the input
to the KAT500 is no longer the same value it was with the KAT3 bypassed so
it needs to retune too.
Too many K's, P's, T's and A's. :-) Let's start over.
1. Original config on *all* bands was: KAT3=BYPASS, KPA500=OPER,
KAT500=tuned [all segments, all bands, all applicable antennae for each
band].
2. In original config, SWR seen by K3=1.1:1 max, often 1:1. SWR seen
by KPA500=whatever the KAT500 could produce, always below 1.5:1. All
this is as expected.
3. Still in original config, I started ARRL 10 CW and after awhile
noticed K3 SWR=1.5:1 and wondered if something had gone south in the
KPA500 input circuit. Note: KAT3 is still in bypass, SWR seen by
KPA500 is still 1.1:1 where it was when I started on 10M.
4. Posted a question to the list, Gary offered: "Put KAT3 in AUTO, do
ATU TUNE on the K3, put KAT3 back in BYPASS. When I did this, three
things happened:
a) I heard the KAT3 tune, and I heard a quick relay noise from the
KAT500 [not the amp], as if it *too* was adjusting.
b) The SWR seen by the K3 went to 1:1
c) The SWR seen by the KPA500 was now off scale, and it faulted.
5. I then did a TUNE cycle on the KAT500, and SWR seen by KPA500 went
back to 1.1:1 where it had been. SWR seen by the K3 [i.e. looking into
the KPA500] remained 1:1.
<digression>When I did all of the above, I was somewhere between 28000
and 28050. It was late afternoon Sat, contest activity was waning, and
I ended the day without going above 28050. This AM, there was contest
activity up to about 28075 or so. The first time I tried transmitting
in that segment, I had to do a TUNE cycle on the KAT500, which is even
more puzzling since I had already done it in that segment and the KAT500
had memorized it.</digression>
I understand your reply, that's not what puzzles me:
-- With KAT3 in BYPASS, is the K3 not looking directly into the input
impedance of the KPA500? SWR seen by K3 should be 1:1 [or very close].
It wasn't, that's what started this puzzle in the first place.
-- Obviously, I can use the KAT3 to minimize the SWR seen by the K3 ...
shouldn't have to but I can. And yes, that has side effects should I go
to low power with KPA500 in STBY. Remember though, after doing the ATU
TUNE on the K3, *the KAT3 went back to BYPASS*.
-- If "BYPASS" on the KAT3 really means what it says, the sequence:
"KAT3 AUTO, ATU TUNE [on K3], KAT3 BYPASS" should do nothing to the
original issue ... 1.5:1 seen by the K3 ... but it did, just like Gary
said it would.
-- Regardless however, messing with the load seen by the K3 should not
affect the load provided to the KPA500 by the KAT500, but it seems it did.
-- Why would doing ATU TUNE [on K3 feeding the amp] cause the KAT500 to
do anything?
I've checked all the K's, P's, T's, and A's in the above and I'm
convinced I got them all right. You have to read carefully. :-))
I haven't figured out how to repeat the issue since I don't know how to
get the KAT3 back to whatever it was doing in BYPASS when this all started.
73,
Fred K6DGW
- Northern California Contest Club
- CU in the 2013 Cal QSO Party 5-6 Oct 2013
- www.cqp.org
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
