[TenTec] Paragon 585 question

Dr. Gerald N. Johnson geraldj at storm.weather.net
Thu Apr 20 10:05:13 EDT 2006


On Thu, 2006-04-20 at 08:26 -0400, Paul Sojka wrote:
> I like to occasionally do a little AM band DX. The manual for the 585 states, "Connector 16 (on the RX high pass filter board) supplies 0.1-1.6 MHz band information to the 1st mixer board to disable the RF amplifier on that band." It does cause about a 2 S-unit increase, on the broadcast band,  when disconnected. My question is, will it affect any other bands? It doesn't seem to, and will it cause any long-term damage?
> Thanks,
> Paul
> KS2S
> 
My Corsair II disconnects the RF stage for its input attenuator effect.
It certainly helps the high end dynamic range taking out the limitations
of the RF stage and reducing the maximum signal seen at the mixer input
but at the same time it increases the noise figure of the receiver and
the minimum detectable signal. In the AM BC band its unlikely to improve
anything more than the s-meter reading, not to actually let you copy a
weaker signal unless you have a really poor antenna, because atmospheric
noise should still be significantly greater than the internal receiver
noise. If you are using a Beverage or small loop for BC receiving,
having more front end gain may be of benefit. And other than intermod on
a good antenna, the RF stage won't hurt being enabled on the BC band.
Lots of manufactures cut the gain for the BC band because local signals
tend to be so large they can't get around intermod problems otherwise.

If you copy weaker signals with the preamp on, its a benefit, but you
may find them obscured by intermod products from strong local stations.
You can only tell by making the preamp on/off selection accessible while
using the radio and trying it both ways.

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer



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