[R-390] IF sweep alignment

[Curt Nixon]

Yes..that is absolutely correct.

One can identify the frequency peaks via Spectran, but they are at the 
frequency of the audio input.

It would require an additional step with a signal gen to get the whole 
response at a particular frequency.

For those of us without a lot of test equipment, it is definitely worth 
looking at I think, but as I indicated, I haven't actually performed a 
real alignment this way..just looked at the end to end response 
including the audio response.  Picking off the audio at the detector 
output helps eliminate the audio response issue.

It sure was nice when I could just go to the demo room and check out 
what I needed ;)

Thanks for your input.

Curt


2002tii wrote:
> Curt wrote:
>
>   
>> Use a noise generator..lots of info around..basically a conducting diode
>> junction.  Feed into the rig.  THis produces a broadband"flat" input.
>> Now, look at the output of the rig in the frequency domain using one of
>> the free PC software tools like Spectran.
>>
>> What you see is a perfect, textbook display of the response of the DUT.
>>     
>
> If by "output" you mean the audio output, one potential problem with 
> this method is that you see the response of the IF convoluted with 
> the response of the audio section.  Since many radios have tailored 
> (or just funky) audio response, this can cause you to misalign the 
> IFs.  What you really want to do is use the IF output.  If you have a 
> spectrum analyzer that covers the IF frequency with sufficient 
> resolution, you can use it directly.  If not (for example, if you are 
> using PC soundcard tools), you would need to build a flat detector.
>
> Another potential problem, if you are aligning a stagger-tuned IF, is 
> that you can't easily find the exact frequencies of the peaks and 
> dips as you adjust each section -- it's only really useful for peaked IFs.
>
> Best regards,
>
> Don
>
>
> Copyright (c) 2011.  Not for redistribution
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