FM modulator

Hi,
Could anyone help me in designing a FM modulator with varactor diodes
and a signal generator.

Pthoppay

 

If you have an old trans. radio with AFC you simply cut the AFC circuit
anf instad of the control voltage you can put in Audio signals.

A sine osc. I assume is available.

 

** NOTICE :

We have another " gmail" & GG poster with a funny name.

As such, he is to be automatically treated as a hostile invader / troll .

** You cannot externally alter the output frequency of a signal generator.

Now come back and post a reply that demonstrates you are not a fuckwit and
not a troll.





.......... Phil

 

I thought this group was unmoderated? If the OP has a "design" question
and it's not homework, I would be happy to help.

BTW, I like GG.

Frank Raffaeli
http://www.aomwireless.com/

 

"Frank Raffaeli"<

** I see you like to beg the question.

** Your secret is safe with me.



............. Phil

 

troll .

If you say it's so Phil, it really must be true. yaaawwwwnnnnnn

That's funny because the el-cheapo POS that I have has a sweep input. I
didn't get it from DSE, so maybe that's why it's so fancy. ;-)

 

"Anthony Fremont"


** Wot - to cold for you to troll the public conveniences today ?





........... Phil

 

Amazing what your selective trimming can do for the meaning of my post
.... ;-)

What's your gripe with the gmail folks with a funny name? I assume you
believe they're all after high-tech secrets, etc.

Your presumptions may outweigh you.

Frank Raffaeli

 

"Frank Raffaeli"

** Yours are like a mill stone necklace right now.



......... Phil

 

Where is my post Phil? As usual you have snipped away the context. If
you'd like to debate with me, I'd appreciate it if you'd keep to the
subject at hand even when you know that you're wrong. What about the
sweep input Phil, couldn't the OP use that to FM the output signal?
Waiting with bells on......

 

My apologies to the OP, for the diversion. If you need a VCO circuit,
you need to specify the constraints. As for the FM modulation part -
same story. Here is one that will do -120 dBc from 55MHz to 110 MHz:

http://www.aomwireless.com/resources/circuits/vco_110a/vco_110a.gif

There are a couple layout quirks, so write me before impementing it.

To the wordsmith troll and self-appointed moderator: should you have a
genuine contribution to this thread regarding VCO's, now would be the
opportune time to produce it.

Frank Raffaeli
http://www.aomwireless.com/

 

Actually, you can. It's called the "phasing method" of generating FM.

John

 

Audience note:
A nice piece of artistic indirection--Phil is trying to get us to believe
that the *other* guy is the troll. Note however that he always makes his
entrance from under the stone bridge in the left background of the scene.

We now return you to our normal programming.

Cheers,

Phil Hobbs

 

Indeed, but not in a wideband manner, which is probably what he wants.
Not without multiplying it 9 or more times at least afterwards.

 

The (vanished?) OP didn't specify. But with enough phase-shift
stages...

And there are other ways to FM a fixed-frequency input.

John

 

">>
Where did the magic number 9 come from, especially without specifying the
deviation?

Say, for example, a phase locked loop with the filter time constant chosen
so as to not pass audio signals.

Jim

 

Right, that's one.

Anybody want to contribute others?

John

 

A motorized trombone line;

A cascade of varactor-tuned 0/pi phase shifters (the ones with the +-1
gain amplifier and the RC lowpass on the + input, or the ones with a
quadrature hybrid);

SSB mix with a high frequency tunable oscillator, run the results
through a fixed delay, and mix back down again;

running it through a CCD delay line with a variable clock frequency;

Or even recording on reel-to-reel tape it and slowing the takeup reel
with your thumb.


Cheers,

Phil Hobbs

 

Uurgh, haven't had my coffee this morning. Should have read, "Or even
recording it on reel-to-reel tape and slowing the takeup reel with your
thumb."

Cheers,

Phil Hobbs

 

6V lantern battery, a 555, and a carbon mic. ;-)

Cheers!
Rich