[TenTec] Orion II AT tuner question

[Duane A Calvin]

Gerald - isn't that the purpose of attenuators?  I'm not sure what
benefit is to be gained by mismatching RX antenna impedance, although I
agree it's not highly critical they be exactly matched.

I was thinking Merle might have a point - I'm trying to set up the
conditions where I saw the attenuation on a different band when
accidentally working cross-band, but I'm not able to replicate that
result at the moment.  However, on 30m, where my G5RV Jr is definitely
non-resonant, 4.5 - 5:1 SWR, as a result of using the tuner, band noise
goes from S 3.5 to S5 (relative S-meter reading.)  If the tuner is not in
the RX antenna path, how would this be explained (single VFO, simplex
operation)?  Selecting a different band on the TX VFO causes the tuner to
turn off, but the S-meter still reads S 3.5. I'm on an original Orion
with 2.56 level firmware in case anyone else is also trying this.  If I
had an RF signal generator, I could do better measurements, but I'll have
to live with noise level at the moment.

73,  Duane


On Fri, 31 Mar 2006 21:55:10 -0600 "Dr. Gerald N. Johnson"
<geraldj at storm.weather.net> writes:
> On Fri, 2006-03-31 at 22:35 -0500, Carl Moreschi wrote:
> > Of course what you said is true, but it is still better to have a 
> matched
> > antenna on receive.   There is always the possibility of very low 
> atmospheric
> > noise on a given night and the extra signal just might make the 
> difference,
> > especially on 10 meters.  Why do people insist on using a 9 to 1 
> balun on
> > receive only beverage antennas?
> > 
> > Carl Moreschi N4PY
> > 121 Little Bell Drive
> > Bell Mountain
> > Hays, NC 28635
> 
> There are cases where a matched antenna is a benefit, where the 
> receiver
> noise isn't so good. Most users of 10m antennas already build them
> pretty well matched, because matching at the transmitter end of the
> feedline makes the transmitter happy but doesn't guarantee the 
> largest
> radiated signal, mostly because of the added losses of the 
> transmission
> line with significant VSWR.
> 
> And then there are situations were maximum signal to the receiver is 
> the
> worst of conditions. Because it allows the local signals to 
> overdrive
> the receiver obscuring the desired weak signal by clipping or by
> reciprocal mixing due to phase noise. Or there's a thunderstorm in 
> the
> state or closer doing both of those. Something the NR and NB won't
> handle and the ringing Collins filters can't hack. Then its handy 
> to
> reduce the power from the unwanted signals sacrificing the desired
> signal, hoping to remove the bad effects of the unwanted signals 
> before
> loosing that weak desired signal.
> 
> -- 
> 73, Jerry, K0CQ,
> All content copyright Dr. Gerald N. Johnson, electrical engineer
> 
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--------------------------------------
Duane Calvin, AC5AA
Austin, Texas

http://home.austin.rr.com/ac5aa