[Skimmertalk] The Red Pitaya 122.8-16 -- an important lesson learned.

[N4ZR]

I've been spending an absurd amount of time working with the new Red 
Pitaya 16 bit receiver on various projects, but in the process I've 
picked up someinfo others may find useful.

The Red Pitaya technical staff has explained to me that this unit has no 
filters at all between the antenna terminal and the DDC, not even a 
Nyquist anti-alias filter.  They explain that whatever we hams are using 
it for, the RP-16 is designed to be a multi-purpose instrumentation 
platform, and for that reason no filters are included in the input, 
because they might constrain uses other than as an SDR.

When I first got my RP-16, I had serious intermod on 21 and 24-MHz.  I 
wasn't sure what the source was, but suspected FM broadcast.  
RTL-SDR.com makes a very inexpensive FM band-stop filter that is 
available from Amazon, as is a similar filter for AM broadcast.  I 
placed the two filters in series between my RP-16 and my preamp, and the 
IMD totally disappeared.  It's not as elegant as having the filters 
inside the RP-16, but it remedies the one issue I've had with the 
receiver so far.

-- 

73, Pete N4ZR
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