[Premium-Rx] The "Sound" Of Receiver IF Amplifiers

[Bob Milne]

Hi Richard,

I may be able to so some manual frequency response measurements if the
HP 651B I just bought arrives in good shape. Don't have a distortion
analyzer yet.

But in my opinion those kinds of measurements are of limited
usefulness. It's how the receiver (or its IF section) and the AGC
circuit responds to real-world dynamically changing signals, noise,
and transients that account for a lot of the differences--not to
mention the phase/delay characteristics of the IF filters. You can
take a lot of measurements on two different receivers, but they won't
necessarily tell you how they are going to "sound" to your ears. Kind
of like measuring the chemical composition up of two different wines
and trying to predict how they will "taste." Lotsa Luck!!!

I recently listened to one of my old, big Grundig radios on SW, and on
strong signals it's sound blew away any of my expensive receivers. The
other surprising thing was that the Grundig produced a lot less
distortion on signals with selective fading. That probably has
something to do with the broad IF filters with lousy shape factors and
a not-very-high-gain AGC circuit. Also it probably has an IF response
with a peak at the center frequency which gives it a degree of carrier
exaltation. Of course the Grundig's SW performance in every other
respect was (by our standards) lousy; drift, images, poor sensitivity,
etc. So there's always tradeoffs. But as far as producing pleasant,
listenable sound, it's awesome.

Regards....
....Bob

On Tue, 07 Oct 2003 10:16:18 +0000, you wrote:

>Hello Bob,
>
>Very interesting stuff. 
>
>Are you able to try audio sweeps (on an RF carrier) to do comparisons? 
>Would be interesting to see what the responses actually looked like,  how much
>distortion is being produced - and who are the worst culprits.
>
>Thanks....  Richard
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