Creeping senility is such an ugly thing ....
While working outside on a project I realized I had referred to K9YC as
Gary, when everyone (including me) knows his name is Jim. My sincere
apologies ...
73,
Dave AB7E
On 8/23/2010 1:12 PM, David Gilbert wrote:
>
> 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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