[hpsdr] High S meter reading on noise floor.

[Helmut Oeller]

Ari,

 

terminate your radio  with a 50 Ohms load, select SigAvg at the meter and
select bandwidth e.g. 2700 Hz.

Read the meter value in dBm. 

Now select bandwidth 500 Hz and you will observe that the meter reading
drops down by 7.3 dB, which is equal 10 log (2700/500).

 

If the radio is well calibrated - usually ex factory-  you can even
determine the noise figure of your radio without external instrumentation
using the well known equation:

 

Noise figure  NF = MDS + 174 dBm - 10 log Bandwidth

 

MDS means 'minimum discernible signal' measured in dBm.

Same procedure works with the noise floor shown in the Panadapter, where Bin
width has to used for the correction term.

 

73, Helmut, DC6NY

 

 

 

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