[600MRG] Rx noise 630m

[Roger Graves]

FWIW, a few years ago I did a test on 630m.

A friend about 60 miles away ran WSPR during stable daytime groundwave. Decoding was 100%.
I then lowered the input signal with a 1 dB step 50 Ohm attenuator until the signal dropped slightly below 100% decoding.
The noise with antenna at the point where the decoding began to drop was 18dB above the noise with 50 Ohm dummy load.
For this much I am pretty confident of my recollection. For how the noise level was measured, I think it was what was shown on the PowerSDR dBm readout.

Note that WSJTx tells you to set the signal level at 30 dB on that little bar graph, presumably with it on zero with no antenna, which would be another potential way to set the input level. (I am not certain whether this depends on the receive bandwidth.)

73,
Roger 


> On Mar 18, 2023, at 12:11 PM, Dave Riley via 600MRG <600mrg at mailman.qth.net> wrote:
> 
> Saying good bye to seasonal DX..
> 
> Think the bulk of QRN has been nulled out here but still, the difference between antenna and a short is about 13db
> 
> Not much difference in noise level with loop spun around either..
> 
> Maybe there is 8 db ambient noise average, some say that is low..
> 
> What you say??
> 
> TNX Dave @ W1FRV
> 
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