In article ,
"Brenda Ann" wrote:

"Ian Jackson" wrote in message
...
In message , Dave M
writes
On Thu, 05 Jul 2007 19:00:17 GMT, "Johnny Byrns"

wrote:

TerryJ wrote:

Capable of 100% modulation and has fairly good fidelity.

How do I tell if it uses AM or FM transmission signals? The diagram
shows nothing in reference to a FM or AM transmission bands.


For one thing, the audio input is fed directly to a transformer in the
plate
circuit of the oscillator tube. Classic AM.
Next, the oscillator is fixed at 1 MHz by the crystal. No audio gets into
the
oscillator grid or cathode to FM it.

==============

Dave M

Never take a laxative and a sleeping pill at the same time!!

You would find it rather difficult to FM a crystal oscillator. Possible,
but difficult.
Ian.
--


Many early FM transmitters directly modulated the crystal. This gave only
very limited frequency excursion. Full deviation was acheived by frequency
multiplication. Long since, simpler methods have been used such as
heterodyning of a second, AFC controlled oscillator and of course the
currently common PLL systems.

Most early FM transmitters used frequency multiplication irrespective of
how they were modulated. In the US prior to the introduction of stereo
phase modulation was the predominant method of doing FM and required a
very high amount of frequency multiplication to achieve 100% FM
modulation at low audio frequencies. Even PLL type modulators like the
RCA system ran the modulated VCO at somewhere around 5 MHz and used
frequency multiplication to get up into the FM band.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/