[TenTec] Omni C on 17m

[Mike Hyder --N4NT--]

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