technical question: PLL synthesized freq.
 

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Hello everybody,

I have a technical question about old analog receivers.

How difficult would be to replace/modify the local oscillator(s) of an
analog receiver in order to make it PLL? Is it actually feasible?

Thanks a lot,

Nic. Santean
http://www.csd.uwo.ca/~nic




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"Nicolae Santean" ) writes:
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Hello everybody,

I have a technical question about old analog receivers.

How difficult would be to replace/modify the local oscillator(s) of an
analog receiver in order to make it PLL? Is it actually feasible?

Thanks a lot,

Nic. Santean
http://www.csd.uwo.ca/~nic

YOu disable the existing local oscillator, and feed in an external oscillator
at that point. Really quite simple, as long as you have the external
oscillator.

But, it gets trickier depending on the receiver. The old single conversion
types with a low IF would have the front end tuning ganged with the oscillator
tuning. If you add an external oscillator, you now have two knobs to turn as
you tune. More important, if the IF is a small percentage of the signal
frequency, this lack of tracking will probably mean you'll be tuning the
image frequency one moment, and the desired frequency the next.

Michael

"Nicolae Santean" wrote in message
...
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Hello everybody,

I have a technical question about old analog receivers.

How difficult would be to replace/modify the local oscillator(s) of an
analog receiver in order to make it PLL? Is it actually feasible?

Thanks a lot,

Nic. Santean
http://www.csd.uwo.ca/~nic



Are you looking for anything in particular such as a digital frequency
display? Those can be added externally:

http://aade.com/#dfd

Are you looking for improved frequency stability? There's alot of claims
made for the Huff 'n' Puff oscillator stabilizer circuit.

Frank Dresser

Nicolae Santean wrote:

Hello everybody,

I have a technical question about old analog receivers.

How difficult would be to replace/modify the local oscillator(s) of an
analog receiver in order to make it PLL? Is it actually feasible?

Thanks a lot,

Nic. Santean

It's feasible but not practical, unless you want to do it as a learning
experience. You would have to build an outboard (external) VCO which is
controlled by a PLL system. The output of this VCO would be injected
into the receiver's mixer stage like the original oscillator, which
would have to be disabled and disconnected from the mixer. I suppose it
might be worth the effort for a really good analog receiver, like some
of the old vacuum tube models (boatanchors) but otherwise I wouldn't
bother with it.

I'm assuming you're not confusing a PLL design with a digital frequency
display. You can add a display to most any analog receiver but it will
still have analog tuning.


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I'm assuming you're not confusing a PLL design with a digital frequency
display. You can add a display to most any analog receiver but it will still
have analog tuning.

Certainly. The analog I have in mind is a RF2600 - with digital display. I
was just thinking to make it more stable. However, I give up if there is no
simple solution, since my RF2600 works exceptionally good and I don't want
to mess it up.

Nic.
http://www.csd.uwo.ca/~nic







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Are you looking for improved frequency stability? There's alot of claims
made for the Huff 'n' Puff oscillator stabilizer circuit.

Yes, that's what I have been thinking of. Where can I find a simple solution
for that (I have a RF2600)? Now, I wouldn't experiment on my receiver, since
it works well enough to not take any risks. However, I would go for some
improvements which are easy to make and proven to work.

Nic.
http://www.csd.uwo.ca/~nic






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"Nicolae Santean" wrote in message
...
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Are you looking for improved frequency stability? There's alot of
claims
made for the Huff 'n' Puff oscillator stabilizer circuit.

Yes, that's what I have been thinking of. Where can I find a simple
solution
for that (I have a RF2600)? Now, I wouldn't experiment on my receiver,
since
it works well enough to not take any risks. However, I would go for some
improvements which are easy to make and proven to work.

Nic.
http://www.csd.uwo.ca/~nic



I don't know anything about the RF2600, and I've never built a huff and puff
oscillator stabilizer, so I don't know if it's suited to what you want. But
here's a place to start:

http://www.hanssummers.com/radio/huffpuff/contents.htm

Frank Dresser

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I don't know anything about the RF2600, and I've never built a huff and
puff
oscillator stabilizer, so I don't know if it's suited to what you want.
But
here's a place to start:

http://www.hanssummers.com/radio/huffpuff/contents.htm


Thanks a lot for the link. I will be looking into it.

Cordially,

Nic. Santean
http://www.csd.uwo.ca/~nic





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