On 6/30/2020 6:27 PM, Mail 10 wrote:
I read somewhere that one test for a receiving antenna is to compare the
received noise floor against no antenna, during the day with little
atmospheric noise. There should be a *slight* lift in the noise when the
receive antenna is connected. This is as little as 2-3 dB at my QTH, a
rural area.
Not quite right. A good number to remember is that in order to hear the
weakest signals, noise picked up on the antenna should be at least 10 dB
stronger than circuit noise by the time it reaches the first gain stage,
whether that first gain stage is an outboard preamp or the receiver’s
input stage. At this level, signal to noise ratio will be degraded by
only 0.4 dB. Increasing the ratio to 13 dB makes it 0.2 dB.
73, Jim K9YC
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