Linrad + SDR-IQ. Please help

["Gabriel - EA6VQ" <vhfdx.net; ea6vq.1@xxxxxxxxxxxxxxxx>]

Yesterday I made the first test with Linrad and the SDR-IQ, trying to
receive JT65B EME signals on 144 MHZ, using an SSB-Electronics 144 MHz
downconverter.  My intention was to compare the performance of this setup
with my usual receiver (TS-790), so I was receiving in parallel with both
rigs and using two separate computers.  The computer running Linrad 2.35 has
a 2x2.4 GHz processor and 2 GB of memory, and it's running Windows XP.

The results with Linrad and the SDR-IQ were absolutely disappointing, but
I'm sure that it must be because I have wrongly configured something, so I
will appreciate your help.

I have noticed three major problems:

 1.- The signal repeatedly seems to drop for some seconds and then return to
the normal level. I looks like if someone was switching on and off the
preamplifier all the time.  This does not happen with SpectraVue or WinRad,
so I don't think it's a problem of the SDR-IQ. You can see a screenshot of
this effect at http://www.vhfdx.net/temp/lines_linrad.jpg

 2.- Signals are drifting up. In the baseband waterfall I can see how all
signals I receive are always drifting up. The same signals received with the
TS-790 were absolutely stable.

 3.- Signals in the middle of the receiver bandwidth are noticeably stronger
that near the edges. You can also see this effect in the screenshot at
http://www.vhfdx.net/temp/lines_linrad.jpg

I used M_CIC2 [16], M_CIC5 [13], M_RCF [2], OL_RCF [7].  You have the Linrad
configuration files I used at http://www.vhfdx.net/temp/linrad_parms.zip

Many thanks & 73. Gabriel - EA6VQ
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