[linrad] MAP65 Experiment

["Joe Barger" <aero.org; barger@xxxxxxxxxxxxxxxx>]

I'm thinking about how to easily adapt my EME station to take advantage of 
MAP65, initially receive only.

The receive side my station consists of two phased yagis, preamp, Elecraft 
144 transverter, and SDR-1000.  I'm considering removing the power splitter, 
rotating one of the yagis 90 degrees and duplicating the receive components 
to have duplicate H and V RX paths.

My main questions involve how closely the two RX paths must match in 
amplitude, phase and frequency.  Amplitude I can probably adjust reasonably 
well in the SDR-1000, and I can probably adjust the RX frequency in both 
SDR-1000s to initially be pretty close, but the SDR-1000s are not locked to 
the same LO so they will drift apart after some period of time.  In 
addition, the relative phasing will be unknown and probably also change over 
time.  Hopefully amplitude will remain fairly stable.

I think Dphi will compensate for initial phase errors between the channels, 
but how sensitive is the system to drift between the two SDR-1000 LOs (and 
corresponding phase and frequency errors)?  I think the SDR-1000s (and 
transverters) will stay within a couple hundred hertz of each other for a 
reasonable period of time, but if the relative frequency and phase in the 
two channels must stay locked to within a few hertz/degrees then I think 
there is no hope with this approach.  I'll probably just have to wait for a 
couple of the HPSDR Mercury boards ... or buy another SDR-IQ (if the LOs can 
be locked ... I don't remember if they can).

If this hardware approach works, the next issue will be how to get two 
instances of PowerSDR, one linrad and one MAP65 all working happily on the 
computer resources I have ...

Thanks

joe n6kk






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