FM modulator

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

Pthoppay

Reply to
thoppay
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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.

Reply to
Rudolf Drabek

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

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Reply to
Frank Raffaeli

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

Reply to
Frank Raffaeli

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:

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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

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Reply to
Frank Raffaeli

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

John

Reply to
John Larkin

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

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

John

Reply to
John Larkin

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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

Reply to
RST Engineering (jw)

Right, that's one.

Anybody want to contribute others?

John

Reply to
John Larkin

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

Reply to
Phil Hobbs

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

Reply to
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

Reply to
Phil Hobbs

troll .

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

diodes

generator.

f****it and

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. ;-)

Reply to
Anthony Fremont

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......

Reply to
Anthony Fremont

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

Cheers! Rich

Reply to
Rich Grise

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

--
Siol
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Reply to
SioL
** 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 f****it and not a troll.

......... Phil

Reply to
Phil Allison

deviation?

When a newbie asks about a FM modulator it usually implies some kind of a FM radio band thingie and that implies fairly wide band modulation.

9 was just a first big practical number that popped into my head, but it'd probably have to be quite a bit more than 9 to get 75KHz with phase mod. I remember a ham 2m tx with a 8MHz crystal, phase modulator and a long series of multipliers to get it to 144MHz. And that was narrow band fm.

-- Siol

------------------------------------------------ Rather than a heartless beep Or a rude error message, See these simple words: "File not found."

Reply to
SioL

"Frank Raffaeli"<

** I see you like to beg the question.

** Your secret is safe with me.

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

Reply to
Phil Allison

"Anthony Fremont"

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

.......... Phil

Reply to
Phil Allison

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