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Re: [Discuss-gnuradio] Power,Bandwidth and sp ectrum switch problems

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] Power,Bandwidth and sp ectrum switch problems
Date: Wed, 30 Jun 2010 20:41:00 -0400
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On 06/30/2010 08:05 PM, Eric Blossom wrote:
> On Tue, Jun 29, 2010 at 11:23:36PM -0700, Johnson_lu wrote:
>> Hi guys,
>> Could anybody can help me for these problems?
>> 1、I varied Tx_amplitude from 0.1 to 1 and measured the output with a
>> spectrum analyzer. But the changes are very little. The output is almost the
>> same when Tx_amplitude is 0.1 and 1.  How can I reduce the transmit power to
>> a very little value?
All else being equal that should produce a 10dB change in signal power,
unless *something* in the
  chain is already at saturation due to other factors in the Tx chain. 
Keep in mind that a 10dB change
  on a logarithmic scale isn't very much.

>> 2、How do I know bandwidth of transmission and reception channels in
>> tunnel.py? 
There seem to be *two* versions of tunnel.py in the examples--which one
are you talking about?
  Have you put the output of the transmit side on a spectrum analyser? 
That would tell you
  unambiguously what the bandwidth is, but also careful and
knowledgeable inspection of the
  code will tell you what the theoretical bandwidth is.

Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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