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[Discuss-gnuradio] Re: USRP at Ham Field Day
From: |
John Ackermann N8UR |
Subject: |
[Discuss-gnuradio] Re: USRP at Ham Field Day |
Date: |
Sun, 26 Jun 2005 21:29:43 -0400 |
User-agent: |
Debian Thunderbird 1.0.2 (X11/20050602) |
John Ackermann N8UR wrote:
> Good job on the hfexplorer software, Chuck! Just a couple of
> suggestions: (a) trying to tune in broadcast stations on AM resulted in
> horrible distortion -- sounds like extreme overload and clipping;
I just tried putting an AM signal into the USRP + BasicRX +
hf_explorer_9a and found a problem with the AM demod.
Putting in a signal with 30% modulation @ 1kHz at a signal strength of
up to about -55dBm (which shows about +15dB on the FFT) sounds just
fine, though there's a bit of hiss. But when you increase the signal
strength to ~-53dBm (501uV), it's as though an oscillation breaks out --
you hear another somewhat distorted tone along with the received signal,
and the level of that tone increases rapidly until at about -48dBm
(890uV) it maxes out, with quite a bit of distortion. The increase
between those two levels is almost a step function, it's that rapid.
John