[Linrad] MAP65 for SDR-IQ

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

Hello Moonbouncers,

Many people have asked about a version of MAP65 that could 
be used with the SDR-IQ receiver.  I'm happy to report that 
an operational version of "MAP65-IQ" now exists.  It should 
be ready soon for testing by others.

You'll recall that MAP65 works together with Linrad in a 
dual polarization or "stereo receive" system.  It takes 
advantage of many of Linrad's excellent features -- the 
waterfall displays, noise blanker, dual-channel coherent 
processing, etc. -- as its receiving "front end".  Partially 
processed data are sent from Linrad to MAP65, which searches 
for all JT65B signals in a 90 kHz bandwidth, measures the 
polarization angle of each one, and decodes them all.  The 
Linrad sample rate must be set to 96000 Hz.

MAP65-IQ differs from the standard MAP65 in respects:

1. MAP65-IQ is intended for use with single-polarization 
systems.  (Thus, no polarization matching can be done.)

2. MAP65-IQ uses a slightly different sample rate, 95238.1 
Hz, in order to be compatible with the SDR-IQ hardware.

MAP65-IQ appears to work very well.  In one test using the 
H-polarization (horizontal) data from 11 minutes of the 2006 
ARRL EME Contest, MAP65-IQ decodes 82 messages from 24 
different stations spread over the range 144.100 - 144.160 
MHz.  For comparison, the standard MAP65 decodes 127 
messages from 36 stations in the same 11 minutes of data, 
using both H and V polarizations.  For a rough sensitivity 
calibration, I was using a pair of 2MXP20 yagis when these 
data were recorded.

These results are just what one would expect: the somewhat 
smaller number of messages decoded by MAP65-IQ is a result 
of its having no access to data in the "other" polarization.

In order to make tests of MAP65-IQ you'll need a receiving 
setup with Linrad and an SDR-IQ, and you must be familiar 
with the use of JT65 in WSJT.  If you meet these 
requirements and would like to participate in early tests of 
MAP65-IQ, please send me an email with some details.

	-- 73, Joe, K1JT

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