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!!

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.
--

"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.

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/

In article ,
Ian Jackson wrote:

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.

Some of the early BBC FM transmitters did exactly that, FM a crystal
oscillator.


Regards,

John Byrns

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

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

Not really. It's done all the time in temperature-compensated oscillators,
simply by varying the series or load capacitance.

In message , William
Sommerwerck writes
You would find it rather difficult to FM a crystal oscillator.
Possible, but difficult.

Not really. It's done all the time in temperature-compensated oscillators,
simply by varying the series or load capacitance.


OK then - 'Possible, but much more difficult than with a free-running
L-C circuit'.

When an oscillator is crystal controlled, to get a lot of FM, it usually
takes a bit more than 'slipping a variap' into the circuit. You usually
have to use some form of VXO circuit. Even then, the amount of FM you
get can depend a lot on the characteristics of the crystal. And it may
not be very linear. But it all depends on what you need.

Some early crystal-controlled FM equipment avoids the problems of FMing
the crystal itself. Instead, in a later stage they phase-modulate the
signal (producing a predictable amount of PM) and, of course, multiply
up to the final frequency.

Ian.
--