[AMPS] TS-940S/AT Spurs?

Gary McAdams g.m.mcadams@worldnet.att.net
Tue, 12 Sep 2000 06:37:55 -0700

 Hi all,

 I've got a question for the equipment guru's out there. This was
originally posted to the rec.radio.amateur.equipment news group,
but no replies were forthcoming. I know that this is not amp related.
I just thought that since there in an abundance of extermely smart
fellows on this reflector, possibly I could learn a little about the
exciter, since I learning so much about the TL-922...

 I have a TS-940S/AT that appears to have some spurs when used on the ten
meter band. At least that is the tentative conclusion that I have reached.
someone else may have a better explanation.

 A little background...

 For some time, I have been using a converted 11 meter antenna on ten. SWR
was ok, about  1.5:1 or so. I've used that antenna for years, with no
So this antenna becomes the "known good" quantity.

 I've been interested in installing other antennas here for some time, and
that end I purchased a used Nye-Viking MB-V-A. A nice tuner for 10
through 160 meters. Just for the heck of it, I used the tuner to flatten
out the SWR on the vertical antenna. So far, so good. The SWR was
flattened and all was FB.

 I then constructed and installed an eighty meter doublet antenna, fed with
ladder line and a  4:1 balun. The tuner handled the matching duties on
all bands, but there were interesting things happening on ten meters.

 The tuner would match the antenna with no problems when a steady carrier
mode was used, be it AM, FM or CW.  Standing wave  1:1, no problem.
Then when I went to SSB the SWR would vary, running at times all the
way to 2:1. This only occurred when on the doublet antenna, not
on the vertical, even if both were being fed through the tuner.

 At first I thought that there was a problem with either the tuner or the
doublet antenna. After a bit of thought, I connected a different radio,
a TS-120S, to the tuner. Now the antenna/tuner combination works
as expected. There is no variation in SWR in any mode
after initial tune-up.

 I have also noticed that, when using the 940, if I used the internal tuner
in conjunction with the external everything would be OK, just as it was
with the 120. That kind of leaves me with the impression
that some kind of spur is being generated internally in the 940, and only
on ten. I'm thinking that the internal tuner usage suppresses the spur
and all is OK at the tuner. All reports on ten are that the rig sounds fine,
and no complaints so far about out-of-band signals.

 Short of putting the rig on a spectrum analyzer, how can I verify this


 Gary, WG7X

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