Re: [Discuss-gnuradio] PNG's of a neutral hydrogen observation at PARI with a USRP.

[Lamar Owen]

On Monday 06 June 2005 15:28, Matt Ettus wrote:
> Actually, you can do 70 MHz directly into the BasicRX.  Just set
> everything like you are using a 6 MHz IF (70-64=6).  No need to use the
> ICOM R8500 at all.

Hmm, not sure what the passband of the 70MHz filters is.  Shouldn't be too 
much aliasing; I'll give it a whirl.

> > As to the DBSRX, I mentioned to Charles Matt's statement of the 'less
> > than 8dB noise figure' and Charles wasn't real impressed;  need pretty
> > good amplification ahead of it to get a useful noise temp.  We have a few
> > front ends with less than 3 dB NF here, and we will soon have better.  No
> > cryo here, yet.

> The DBSRX is not intended to be used for RA applications without an LNA
> in front of it.  Besides, even if it had a 0 dB NF, you would still have
> to run the coax from your feed all the way to it, which could be 10+ dB
> of loss.

Well, in our case we were thinking of the USRP potentially in a cabinet with 
an embedded PC in each feedbox (they're about 4 feet cubed).  Either that or 
a frontend with a fiber transmitter in the feed and fiber receivers in the 
control room; we have 12 strand singlemode fiber run to the feeds.

You need to come visit after SARA at Greenbank. :-)

> The DBSRX is even has a connector for providing LNA bias over the coax.

This is nice.
-- 
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772
(828)862-5554
www.pari.edu