[R-390] IF sweep alignment

[2002tii]

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


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