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Re: [Discuss-gnuradio] Problem using the dbs card

From: Marcus Leech
Subject: Re: [Discuss-gnuradio] Problem using the dbs card
Date: Wed, 12 Oct 2005 12:43:24 -0400
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030624 Netscape/7.1

When I first got my DBS_RX card, I plugged it into a low-noise amplifier, and tuned it to the
  GPS L1 frequency, with a circular waveguide feedhorn on the front of the LNA.  As expected
  the GPS L1 carrier appeared in the fft display.  Placing a sheet of metal in front of the feedhorn
  caused the L1 blip to go away.

Around this time (I got an early DBS_RX card), there was some concern about some resistor values in
  the amplifiers used between the MAX2118 and the A/D.  Some values caused "deafness".  Matt had
  published instructions on how to fix the problem yourself--assuming a steady hand, and excellent
  eyesight.  I think I've seen rotoviruses that were larger than some of the components on modern
  hardware :-) :-)

But I never saw the "deafness" problem, so I never bothered to implement the "fix".

EVENNOU Frederic RD-TECH-GRE wrote:
Problem using the dbs card

Hi everybody,

I started using the gnuradio platform some few weeks ago, and I've been trying to use the dbs_rx card. I made some few tests to practice myself on the way to use this card, but unfortunately I didn't have any successful result.

I've been using a python program named dbs_fft.py to have a look at the spectrum in a range of frequencies that I specify. I made some few tests by emitting a sine wave at 1GHz (and then around this frequency), but I've never been able to get it with the dbs card, whereas I can see it very clearly on a spectrum analyzer (level == address@hidden). At emission, and reception, I have some antennas working in that band and antennas are separated by 50cm. On my display screen I just receive some noise so I must receive some samples from the dbs_rx card.

I made the same test at lower frequencies and using the TVRx card to receive the signal, and it works pretty well.
Did someone have the same problem with this card, and is there anything special that can be done to check if my dbs_rx card works properly ?

Thanks for your help

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Marcus Leech                            Mail:   Dept 1A12, M/S: 04352P16
Security Standards Advisor        Phone: (ESN) 393-9145  +1 613 763 9145
Strategic Standards
Nortel Networks                          address@hidden

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