On 7/10/2014 7:07 AM, Bob McGraw - K4TAX wrote:
I can hear a -121 dBm signal equally and quite well on each one.
Every radio I've used on 6M has needed a preamp in a quiet location,
with the exception of the new KX3. The K3 is pretty deaf until you add
an outboard preamp. I bought an ARR GasFET preamp when I still lived in
Chicago to use with an ICOM 746, and I'm now using it with my K3 at the
RX patch point. On a good day (little or no local noise in the direction
of my antenna), I can hear well below -121 dBm.
A good test to determine whether you need a preamp is to look at the RX
noise voltage with AGC off and no antenna connected, then add the
antenna. If the RX noise voltage does not increase by 10 dB, a preamp
will help you hear weaker signals. Obviously, that test takes your local
noise into account.
73, Jim K9YC
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