Passive RX input Filter for VR-500

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Posted by:  Sam AE4GX

Posted On:  03/23/01

Subject:  Passive RX input Filter for VR-500

Message Posted:

The little circuit in an Altoids box ( as big as the RX HeeHee) as saved the
day for my VR-500. I almost returned it to the store after getting it home
and realized that it was trying to hear everything simultaneously. This
simple circuit makes the RX very useable for QRP Rxing on the road. Without it the VR-500 is severely limited for ham band use.

The tuning range is up to you. I wanted something that basically covered the
ham bands particularily 40/20. So it works for me as is but you can easily
change to specific ranges.

Tuning through the proper freq. for the area you're monitoring is dramatic.
The signals of interest just pop up out of the crud.

It could be made into a 1 X 1 X 1 enclouser but I just haven't had the time
to take it further.


What about the 1K POT?

It serves as an RF gain control and plays a very important role in
overload protection. Even if the LC circuit is tuned correctly adjacent
signals can overload the RX so the passive gain control is used to
reduce the singal levels to something the RX can handle. the RX does
have a fixed ATTN pad that can be turned on but the variable RX POT
gives a much better degree of control.

Sam Billingsley AE4GX Atlanta, GA




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