Message	Date	From	Subject
216	2006-11-26 18:35:20	Mike Czuhajewski	Microphonic mixer chips?
> Mixer is a MC1496 which in my opinion has less microphonics than some NE602 > and SA612 mixers. Fascinating. I had never heard that one before. Is there any data to back that up? I would expect microphonics to be generated by something other than ICs, although I suppose anything is possible. Perhaps other things in the circuits were causing the microphonics? Was the exact same test bed used to make a comparison? (Not just an identical circuit built from the same schematic, but a single collection of components with one mixer substituted for the other and results compared. That would eliminate all possible variables.)
217	2006-11-26 19:25:55	Loren Moline WA7S...	Re: Microphonic mixer chips?
Mike, I believe the microphonics or sound in receiver when it is moved is caused by some feedback within the mixer circuit. Sometimes there is more of the local oscillator component in the output of the mixer than others maybe attributed to the balance of the mixer and rejection of the oscillator. I believe even though the output is audio and filterted that some of the oscillator signal is not fully rejected which can cause problems in the following audio stage. I have built a direct conversion receiver from Ramsey and it does not perform as well as mine. And it does use the more modern NE602 mixer. Loren ----Original Message Follows----

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216

2006-11-26 18:35:20

Mike Czuhajewski

Microphonic mixer chips?

> Mixer is a MC1496 which in my opinion has less microphonics than

some NE602

> and SA612 mixers.

Fascinating. I had never heard that one before. Is there any data to
back that up? I would expect microphonics to be generated by something
other than ICs, although I suppose anything is possible. Perhaps other
things in the circuits were causing the microphonics? Was the exact
same test bed used to make a comparison? (Not just an identical
circuit built from the same schematic, but a single collection of
components with one mixer substituted for the other and results
compared. That would eliminate all possible variables.)

217

2006-11-26 19:25:55

Loren Moline WA7S...

Re: Microphonic mixer chips?

Mike,

I believe the microphonics or sound in receiver when it is moved is caused
by some feedback within the mixer circuit. Sometimes there is more of the
local oscillator component in the output of the mixer than others maybe
attributed to the balance of the mixer and rejection of the oscillator.

I believe even though the output is audio and filterted that some of the
oscillator signal is not fully rejected which can cause problems in the
following audio stage.

I have built a direct conversion receiver from Ramsey and it does not
perform as well as mine. And it does use the more modern NE602 mixer.

Loren

----Original Message Follows----