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

[Leif Åsbrink <leif.asbrink@xxxxxxxxxxxxxxxxxxxx]

Hi Roger,

> What is the practical effect of feeding in 2 receivers with no 
> common oscillators
> which have a gradual frequency drift with respect to each other.
> 
> I understand that the phase of the signals will not be locked, 
> and that the phase
> will rotate at the frqeuency difference between the 2 receivers.  
> But with what I am
> doing just feeding in 2 receivers and lining up the frequencies 
> using the high
> resolution display, things 'seem' to work OK.  Are they really?  
> I don't seem to get
> any nulling of the signal, for example, due to out of phase interference.
If you set amplitudes equal and select fixed polarisation
you should get nulls.
 
> I have a few other questions.
> 
> > Yes, The little box immediately to the right of the angle 
> > value in the polarisation graph.
> 
> Do you mean the little green bar with the white [or yellow] line 
> that I can move to the left or the right?
Yes (there are two of them, one for phase and one for the time constant.
Use the F1 key;) 

> > > 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.
> 
> Well, if I put it on 'fixed' polarity and turn on 'X + Y' and 
> disconnect one input I
> get almost no signal in either ear if I have pol on 90 degrees 
> and good signal in
> both ears if I have it on 0 degrees.  Things appear as expected 
> on the baseband
> display.
Something is wrong. Seems one channel is routed to both outputs.
Maybe there are switches to set in the soundcard.
This implicates that none of the other stereo modes works either.

Try to save a wav file to verify that the channel data is correct.

> If I don't have X+Y turned on, then as expected I get 
> NO signal at all if I
> have one input disconnected and if I have the pol set to that 
> vaule (0 or 90
> degrees).  Thus what turning on "X+Y" does, is the equivalent of 
> reducing the
> 'channel separation' to use a stereo hi fidelity term.
I do not quite understand what you observe.
You say "almost no signal" above (????)

Does the soundcard work in stereo when you run other applications?

> > > Has anyone else tried this?
> > http://antennspecialisten.se/~sm5bsz/linuxdsp/demo/demhf2.htm
> 
> THIS IS VERY INTERESTING!  What were the 2 antennas or receive systems?
Two wires of about 15 meter length separated by about 50 meters.

73

Leif  /  SM5BSZ



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