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

[Marcus D. Leech]

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
http://www.sbrac.org