[Drake] Re: R4C Low sensitivity

[Jim Roik]

When checking the apparent low sensitivity of the R4C using the S meter, be
open to many possibilities for why it might appear to be low.

 

I have an R4C that seemed to be dead as far as the S meter responded.
However, when I connected a signal generator to the antenna and input a
signal I found that I was able to receive wuite weak signals. They just did
not cause the S meter to respond as one would have thought.

 

In my case the problem was the overall gain of the receiver. One of the
filters had been replaced with a GUF and it was the cause of the low overall
gain. I put the stock filter back into the set and the S meter began to
respond the way I expected it should.

 

I don't have any way to sweep the filter I took out so don't know if the
overall gain of the filter is low or if the centre frequency has shifted
placing the signal on the edge of the filters passband.

 

The moral of this story is that if using the calibrator and s meter to
indicate receiver performance, it is possible that alignment may not be the
problem. Using a calibrated signal generator will tell you how sensitive the
receiver is and give you some good clues. If you can hear a weak signal but
the S meter doesn't respond, keep in mind the overall gain path of the
receiver.

 

Good luck.

 

Jim  VA7JR