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[Linrad] Re: Linrad and MAP65-IQ

Hello Moonbouncers,

Back home again and with some free time on Sunday evening, I 
  fired up the EME station at K1JT and made some 
side-by-side tests of MAP65 and MAP65-IQ on 2 meters.  This 
note is a brief summary of the results.

My antenna on 2m is a 4x14 xpol array with separate 
tower-mounted preamps for each polarization and separate Rx 
feedlines.  In the shack the two signals go to a 
WSE-converter chain and then to a Delta44 sound card on 
"Computer A", running xlinrad under Linux.  MAP65 runs under 
Windows XP on Computer B, and the two computers share an 
ethernet connection.

For these tests I tapped off the V-pol signal at 10.7 MHz 
from the WSE-converter chain and used this as input to the 
SDR-IQ.  Computer B ran Linrad (version 3.02) and MAP65-IQ 
(r1089) as well as MAP65.  (Computer B is a 2.8 GHz 
dual-core machine with 2 GB memory, and it had no difficulty 
running Linrad, Map65, and MAP65-IQ simultaneously.)  Linrad 
was set to "Above Normal" priority.  The Windows Task 
Manager showed CPU usage <10% except near the end of each Rx 
minute, when usage rose for a few seconds to 100% as the two 
MAP65 programs did their decoding.  Linrad continued running 
smoothly during these times, with no glitches or 

As others have noted, this early version of MAP65-IQ has 
some rough edges.  Setting it up requires extra effort to 
get the frequencies right; and even when you have done this 
correctly, the displayed frequency and time information has 
some errors.  I assure you that these problems are trivial 
and temporary; they are a result of my wish to get this very 
first alpha release of MAP65-IQ quickly into the hands of 
some knowledgeable users, to gain some understanding of how 
it would play in other stations than my own.

All in all, I found MAP65-IQ to perform very well.  I made 5 
or 6 EME QSOs in a couple of hours, but mostly I just 
monitored the band and watched for differences between what 
was being decoded by the MAP65 and by its 
polarization-challenged little brother, MAP65-IQ.

You can get a fairly good impression of what I observed from 
snapshots of the "Band Map" and "Messages" windows of the 
two programs posted at the following links:


In these pictures the MAP65-IQ window is on the left, MAP65 
on the right.  (Please ignore the 600 kHz frequency offset 
and 4 hour time offset in the MAP65-IQ displays.  These 
errors will be fixed soon.)

If you need some help interpreting the pictures and haven't 
used MAP65, you may want to read the following two documents:

The side-by-side comparisons show just about what one would 
expect for single-polarization and dual-polarization 
systems.  The MAP65-IQ Band Map shows that 16 different 
stations were decoded over the past few minutes when the 
snapshot was made, while MAP65 decoded 25.

In the right-hand "Messages" window you can see exactly why 
several of the stations were not decoded by MAP65-IQ: for 
example, at 144.144 EB3DYS was received by MAP65 at 
polarization angle 45 deg and SNR=-24 dB.  With a V-only (90 
deg) polarization capability, MAP65-IQ would then see about 
SNR=-27 dB, normally too weak for decoding in a single 
transmission.  Similar conditions exist for K0AWU (pol=131 
deg, SNR=-25 dB) and K8TL (pol=161 deg, SNR=-24 dB), and 
several other stations that you would need to scroll back 
the messages window to see:  RZ4HF (pol=177 deg, SNR=-17 
dB), YU1IO (pol=23 deg, SNR=-20 dB).

Careful examination of the two Messages windows shows that 
MAP65-IQ and MAP65 usually report the same SNR for all 
signals with polarization angles within +/-20 deg of 90 deg. 
   (Note that MAP65-IQ always reports pol=0 deg; however, in 
this test it was connected to my V-pol antenna.)  Signals 
more than 20 deg away from vertical are weaker in the 
MAP65-IQ output by the expected amounts: about 1 dB down at 
+/-30 deg, 3 dB at +/- 45 deg, etc.

If you're confused by the multiple appearances of WA2FGK and 
K1OR in the pictures for the same decoding minute: Herb and 
John are within tropo range, so I often see their direct and 
aircraft-reflected signals as well as their EME signal.  The 
tropo signals are mostly horizontally polarized, so the 
V-pol MAP65-IQ system usually does not see them.

I had some fun when the callsign AA7A popped up on my 
MAP65-IQ screen.  I knew that Ned was testing MAP65-IQ at 
his station ... so when he finished a QSO, I called him on 
an arbitrary frequency some 30 kHz down the band.  Sure 
enough, he came right back on my frequency -- and we had a 
nice QSO, ending with Ned saying "I CANT HIDE".

I'm traveling for QRL again near the end of this week, but 
after that I hope to find time to put together another 
MAP65-IQ release with known bugs corrected.  I imagine that 
most potential users will opt to run both Linrad and 
MAP65-IQ on the same computer, under Windows, so I may try 
including the latest linrad.exe in the package, along with a 
full set of Linrad parameter files set up in a reasonable 
way for the SDR-IQ/Linrad/MAP65-IQ combination.  This could 
make it much easier for first-time users to get this 
somewhat complex system of hardware and software working.  A 
wideband, panoramic receiver that decodes every JT65 signal 
it finds is well worth the effort!

As always, your feedback on Moon-Net or the Linrad reflector 
will be appreciated.

	-- 73, Joe, K1JT

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