[linrad] RE: Using Linrad as a Diversity Receiver?

[Leif Åsbrink <leif.asbrink@xxxxxxxxxxxxxxxx>]

Hello, All!
 
> A thread on another reflector prompted me to consider using 
> Linrad as a diversity
> receiver (after all, the Dual Polarity receive is just a special 
> case of diversity
> receiving) , by feeding one receiver into one input channel and 
> the other receiver
> into the other input channel, just as one would do with H and V 
> elements for 144 MHz
> EME, for example.
Yes, this is one of the intended usages:)

> I first tried this with 2 receivers with two different 432 MHZ 
> antennas [one a
> circular satellite antenna, the other a vertical stack of 4 Hpol 
> yagis] listening to
> a 432 MHZ CW beacon about 45 miles away.  Using Linrad for 
> diversity reception in
> this fashion seems to work pretty well, but I wonder if the time 
> constant of the best
> linear combination machine [that is likely a misnomer given my 
> math and recall
> abilities] is a bit too slow for non-polarity-related diversity 
> reception.  Is there
> a way to change this time constant?
Yes, The little box immediately to the right of the angle 
value in the polarisation graph.

> How does it relate to the  setting of the 'usual'
> parameters?
I do not remember off hand, but I think it is related to the
baseband bandwidth you have selected.

> I also noted that hitting "X+Y" in the baseband window with 
> polarity fixed and at
> zero does not send one input channel to one ear and the other 
> input channel to the other ear as I expected it to.
????
You get the green spectrum of the baseband graph into one ear and the
magenta curve into the other.

Then there is the pol default settings. For an X type cross yagi
you set channel 1 at 45 degrees and for a + type yagi you
set it at 0 degrees.

Do you get the baseband spectra right, but not the sound?
 
> I plan to put up another HF antenna to try diversity reception 
> with 2 HF receivers and 2 antennas and Linrad.
With common local oscillators;)
The phase would rotate at the difference frequency so the
frequency error should be below 0.05 Hz if the receivers are
not locked;)
 
> Has anyone else tried this?
http://antennspecialisten.se/~sm5bsz/linuxdsp/demo/demhf2.htm

73

Leif / SM5BSZ


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