Hi guys,
I thought the whole point of crystal oscillators is they're pretty damn stable,
I mean doesn't every PLL receiver use a crystal oscillator to generate a
base frequency. My thought is these tunable RF modulators use a simple
LC oscillator, probably with a simple varicap to adjust their frequency
In Britain, I doubt anyone would be penalised for something like a 10mW
transmitter drifting off the VHF broadcast band, indeed, *anyone* with a
transmitter in the 76-108MHz range needs a license. One thing I would
say is if it drifts above 108MHz, please don't use it near airports. Please.
Funny thing is, it's legal to sell transmitters on say 105MHz here, legal to
buy them, legal to own them, but illegal to use them. What the f**k do these
people think you're gonna do with such a thing if you buy one? Then again
everyone in the UK with a CB radio should renew their CB Radio Licence
annually-- I bet less than 5% of CB users have a license, the post office
probably gets more requests for dog licences than CB radio ones :-)
Cheers,
PrinceGaz -- "if it harms none, do what you will"
Email: [EMAIL PROTECTED]
Website: http://website.lineone.net/~princegaz/
ICQ: 36892193
I wrote:
> >Hi guys,
> >What puzzles me about these VHF modulators is why they drift off frequency
> >so much. I mean any half decent crystal-controlled oscillator's drift will be
> >negligible. Why isn't a unit released where you can plug a crystal for say
> >"107.9 MHz" or "101.7 MHz" or whatever. The unit will then produce that
> >frequency from a harmonic of the crystal and it'll *STAY* that frequency, not
> >wander all over the 76-108MHz VHF FM band!
Someone replied:
> The trouble is that with the heat and resistance changes they tend to
> drift unless PLL (Phase Loop Locked). That is why all good modern radio
> TX (transmitters) use PLL, and why such a big thing is made of them in
> tuners and portables. It is not just the crystal it also effects the
> other parts of the circuit including the divider/multiplier.
> From a radio point of view, here in the UK, not only can we not afford
> to lose listeners due to drift, but could be penalised by the Radio
> Authority.
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