[linrad] Re: linrad as sun noise measurement tool

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hello Christophe,
 
> I am using more and more sun noise as a tool
> to optimize the frontends on 6, 3 and 1.2cm. What is the "best" way to do
> this with linrad. For now, I just read the main dB scale visually, which is
> quite easy to do up to say 0.1 dB. But maybe more intelligent things can
> be done with other windows, averaging or numerical display of values?

The S-meter window is actually a very good way of getting averaged RMS
readings in Linrad. Make sure you have an "M" in the upper right corner
to average RMS power. ("P" = peak power in a long time gives a far less
stable reading)

The bandwidth is of course important. Make sure your system is calibrated
so you have a flat passband, then select a high output speed.

On my system (WSE units) the standard is 96kHz for input and 48kHz maximum
for output. By selecting 48 kHz for the output I can get a bandwidth of
35 kHz and then the S-meter graph gives data points that are to 90%
within 0.03 dB when the graph speed is 1 point per second.
By pressing F2 one can get an average over as long time as desired, 
but I think it is better to use the S-meter graph because system
stability is likely to be more important than the statistical
uncertainty.

73

Leif  /  SM5BSZ



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