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

[Lamar Owen]

[forgot to reply-all. Argh]
On Monday 06 June 2005 14:14, Marcus Leech wrote:
> What's the bandwidth of the 10.7Mhz output of the R8500?

It's designed for video capability;  our technical director, Charles Osborne 
(K4CSO, President of the Society of Amateur Radio Astronomers (SARA)) tells 
me it's not real flat, but is probably about 3-4 MHz wide.

> Was this a drift-scan, or were you tracking?

Drift, for testing.  The 26m's are outfitted with a DFM Engineering variable 
frequency AC motor drive, and will track at sidereal rates.  But rather than 
power up the two 15 horsepower motors, I just left it at zenith.

> Fellow radio astronomers want to know :-)

Understood.

> I have an USRP on the way from Matt along, with a pre-release DBSRX.  It
> will be interesting
>   to compare my spectral observations with yours, in the fullness of time.

I have a TVRX (and a basic RX/TX pair) on my personal unit; the PARI unit is 
outfitted with two basic RX and two basic TX.  The TVRX can do 70MHz direct; 
I might try that at some point.  There's a significant electrical storm here 
now, so I have everything disconnected.... :-)

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