Thanks for the feedback, Rick ... good comments. I wasn't really trying
to simulate what happens in a receiver, though, because there is no way
I can account for all the various receiver characteristics of AGC
threshold and non-linearity. I own an Elecraft K3 that has a very wide
range of possible settings, and I know from personal experience that it
is possible to make multiple weak signals virtually unintelligible if I
try hard enough.
Based upon your comments and those from Gary, K9YC, though, I think I
will go back to the original .wav files and remix them, then feed them
into my backup rig (756Pro) with it transmitting into a dummy load. I
can then record the result as received by my Elecraft K3 to see if the
results are significantly different than what I already have. I'll
give it a try with and without mixed background noise and see how it works.
Thanks es 73,
Dave AB7E
On 8/23/2010 11:43 AM, Rick Karlquist wrote:
> The intent of these tests is good. It is always good
> to get confirmation that a 2 dB difference in S/N
> is significant. That's why I run 150W in low power
> contests instead of 100W, if the rules permit.
>
> There is some question as to the validity of your
> experiments. It sounds like you added perfect audio
> tones to receiver background noise. This isn't
> necessarily equivalent to actually receiving signals
> through the receiver. The receiver could have some
> nonlinearity and the receive filter could have some
> ringing.
>
> Rick N6RK
>
>
> David Gilbert wrote:
>> I've added a page to my web site covering some investigations into how
>> much difference in signal strength might be noticeable in weak signal
>> and/or contest conditions, with several audio files included as
>> illustration. Please don't consider any of it to be authoritative since
>> I am not an audio professional, but maybe some of it will be useful to
>> someone. If anyone has suggestions for different comparisons, please
>> let me know.
>>
>> http://www.ab7e.com/weak_signal/mdd.html
>>
>> 73,
>> Dave AB7E
>>
>>
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