Re: [Discuss-gnuradio] RA Receiver front end

[Marcus Leech]

If you're going down the USRP path, you can indeed "chuck the back end".

The whole point of GnuRadio/USRP/whatever is to do as much of the
 processing in software as possible, at as high a rate a possible.
 Several Mhz of both spectral and continuum bandwidth are
 possible using USRP and a suitable daughtercard.

The nice thing about doing things in software is that they don't
 drift at all.  That's when you discover that you still need to
 pay attention to analog drift in other components in the chain
 leading up to the computer....:-) :-) :-)

For example, in software, detection is simply a matter of
 squaring every sample.  Integration is the same as a low-pass
 filter, etc.

With some exceptions, the "big boys" of radio astronomy have been doing
 those functions in software/digital-hardware for quite some time.
 There are some exceptions.  For example, Ken Tapping at DRAO
 has been doing 2.8Ghz solar observing using nothing more than
 a tuned amplifier chain, and a zero-bias schottky-diode detector.
 The detector is thermally bonded to a *massive* heat sink that
 keeps the drift very, very, low.  This then goes to a standard
 amplifier chain, etc, etc.

Frank Rawlins wrote:

> Thank you Marcus & Jeff - gives me something to think about.
>
> I do have a USRP with one basic receive board.  Unfortunately my 
> back ground is hardware (technician level) and I am finding 
> building the software very difficult.
>
> I have built the receiver back-end ( from site of Uni of Indianapolis): double detector (drift free, hopefully) - DC amp/integrator - 
> A/D converter -   to skypipe (all this works fine).  I really do not 
> know which way to jump with the front end unless I concentrate on 
> the USRP and chuck the back end that I have built.
>
> My back yard is only 54 feet x 26 feet and have a 8.5 feet dish (I 
> could enlarge it to 12 feet) so I am very limited.
>
> Many thanks,
>
> Frank G0OFX  (missed G0OFY by one place!)
>
>
>  

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