[Linrad] MAP65 and the SDR-IQ

[Joe Taylor <Princeton.EDU; joe@xxxxxxxxxxxxxxxx>]

Hi Dom and all,

You are 100% correct that a big part of the value of MAP65 
is its polarization-matching capability, separately matched 
to the exact polarization angle of every received JT65 
signal.  As has been discussed on this list in the past, in 
some detail, a single channel receiver like the SDR-IQ 
cannot provide such capability.  [Of course, two SDR-IQs 
would also not work, because they could not be properly 
synchronized.]

Nevertheless, there is great interest in having a 
single-channel version of MAP65 that is capable of working 
with the SDR-IQ.  There are several good reasons for this:

1. At 1296 MHz and above, nearly everyone uses circular and 
therefore polarization diversity is not required on receive.

2. On 144 MHz many people have single-polarization antennas 
and nevertheless want to have wideband panoramic reception 
of JT65 signals, even if it does not have the 
polarization-matching capability.

3. The SDR-IQ is well engineered, highly capable, and 
relatively inexpensive.

These are the principal motivations that have encouraged me 
to make a "MAP65-lite", which I have called MAP65-IQ.  The 
program is now happily running in my lab, receiving very 
weak JT65B signals from a QRPP transmitter about a mile 
away, on the dead 10-meter band. A few more details to be 
improved..., but it works very well!  :-)

The MAP65-IQ screen display looks almost exactly like those 
of MAP65:

http://physics.princeton.edu/pulsar/K1JT/MAP65.pdf
http://physics.princeton.edu/pulsar/K1JT/EME_Florence_2008.pdf

... except that the "measured" polarization angles are 
always zero.

	-- 73, Joe, K1JT

f6dro wrote:
> Hello Joe,
> 
> in my idea , the greatest interest to use MAP-65 , is when a dual polarity 
> system is  the antenna is use , then , a dual RX system is necessary. I dont 
> think it is possible to use 2 SDR-IQS for dual polarity. If I recall rigth , 
> even using  commons LO on the V/UHF converters and SDRIQs  , is not enougth 
> , am I rigth? I recall I've asked abt this in a mail a long time ago , and 
> have been replied " common LO's not enougth3 , there are some issues in 
> SDR-IQ ( software , DIGITAL CONVERTERS or what?)
> 
> 73
> DOM 
> 
> 
> 
> > 

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