[TenTec] Omni C on 17m

Tue Aug 19 16:37:53 EDT 2003

Sounds like the PA is unstable on this rig. Or there is one heck of an
amount of feedthrough from a mixer.  Stink-o!

73
Bob, K4TAX

----- Original Message -----
From: "Mike Hyder --N4NT--" <N4NT_Mike.Hyder at charter.net>
To: <tentec at contesting.com>
Sent: Tuesday, August 19, 2003 1:54 PM
Subject: Re: [TenTec] Omni C on 17m

> About the strength of the spurs: my Omni-C on 17 meters put out 100 watts
> key down and 2 or 3 with the key up.  Assume best case, the difference
> between 100 watts and 2 watts of spurs is 17 dB.  So the total spurious
> output would be 17 dB below the rated and actual output.  With key up, the
2
> watts are 100% of the output so are not attenuated at all.  Different
units
> varied in the spurious output but according to Garland they tried and
tried
> to get acceptable performance from the Omni-C on 17 meters and never could
> clean it up on most rigs, finally advising people like me to get a
different
> rig if I wanted to operate the 17 meter band.
>
> You guys are beating a dead horse.  The only suggestion I've seen with
merit
> was that by Jerry to change the mixing scheme and that may not be
feasible.
> In the Omni-C, two of the bands use one crystal -- I'm not sure which two
> but have the feeling one of them is 18 MHz.
>
> Good luck and 73, Mike N4NT
>
> ----- Original Message -----
> From: "Bill Fuqua" <wlfuqu00 at uky.edu>
> To: <tentec at contesting.com>
> Sent: Tuesday, August 19, 2003 1:16 PM
> Subject: Re: [TenTec] Omni C on 17m
>
>
> >        Interesting question. All radios put out spurs,harmonics,
splatter
> > etc. It is a matter of level. An example; years ago I heard a lower
> > sideband signal on the upper part of 10 meters and waited for an ID.  It
> > was a local ham. I did a comparison of his real signal (on 10 meters but
> in
> > the more used area) and the other one  I was receiving. The spur was
very
> > low in level compared to his real signal ( more than 60 db down).
> >        My next question was," is this signal an image or something from
my
> > receiver or was it his transmitter?"
> > I changed receivers, he was rag chewing for some time, ( a boatanchor
with
> > a completely different conversion scheme) and the signal was still
there.
> > Yes, it was a spur but it was not one beyond the specs for that
particular
> > transceiver (TS520).
> >        So the real question is what is the level of the spur in absolute
> > terms (dbm) and in relative terms when  compared to the real signal
> > (db).  This can only be done by measuring the signal levels at the
antenna
> > connector into the constant impedance of a dummy load.
> >      A calibrated coupler with lots of attenuation and a general
coverage
> > receiver would be a start. Just a simple capacitive coaxial coupler
> > calibrated at the various frequencies ( it would be frequency dependant)
> > would be a start. You don't have to have elaborate spectrum analyzers or
> > megabucks of test equipment to make fairly good measurements as long as
> you
> > have a calibrated signal generator such as an URM 25 or TS497 or HP606
or
> > anything similar that you can get at hamfest relatively cheap. Just
don't
> > blow out your test receiver.
> >
> > 73
> > Bill wa4lav
> >
> > At 11:36 AM 8/19/2003 -0500, you wrote:
> > >To further stir the pot about the Omni C on 17m, I have received
several
> > >emails from people using them on 17m saying that they were told that
they
> > >were putting out spurs.
> > >T Ts standing is that they are ok on 17m. Does that mean that they are
> clean
> > >or just that they will tx and rcv on 17m? BIG difference
> > >What my real question is, has anybody tried a spectrum analizer on one
> and
> > >found where the spurs are? I have had enough response to my original
> > >question about them on 17m that I have no doubt that they are putting
out
> > >spurs somewhere and because of the IF being what it is probably no
chance
> of
> > >cleaning it up.
> > >
> > >73 & Thanks Paul K9OT
>
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