[John Byrns]

In article ,
flipper wrote:

On Sun, 28 Aug 2011 20:09:47 -0500, John Byrns
wrote:

In article ,
John Byrns wrote:


I will try to post a schematic of my proposed 12SN7 transmitter circuit
later
tomorrow.

It also occurs to me that the "plate" winding of the oscillator
transformer
can
probably be translated to the cathode circuit without changing the AC
equivalent
circuit. This would allow the use of a single winding coil with my
partial
"fix" idea. I will try to post a schematic of this too.

I have posted a schematic of my "Twin Triode" AM Transmitter proposal he

http://fmamradios.com/TTAMXmtr.gif

This version incorporates my "fix" for the grid bias modulation problem and
also
illustrates the use of a coil with a single tapped winding, the two winding
AES
(P-C70-OSC) coil is not required for this version.

Oh, ok. Well, that's what I called the typical AA5 'cathode-grid'
Hartley. Except, of course, there's not a modulator under it in the
AA5.

Well, we know circuitmaker isn't modeling the other one right so for
what it is or not worth circuitmaker says the AM envelope is not
symmetrical. The 'upper' envelope is a smaller amplitude than the
lower.

However, I think that's again due to the strange osc cathode voltage
it comes up with and, so, 'not right'.

That is a disappointing result, I wonder if the problem is somehow inherent in
the morphed circuit, or if I morphed it incorrectly as I didn't draw out the
steps as I had planned to and instead morphed it in my head, or is it a problem
with the simulator? Did you use the same component values & 12AU7 as in your
original "sim", to eliminate double diddling?

That circuit wasn't the one I originally planed on posting first, I had intended
on posting my preferred "two winding" design first, as it has fewer changes from
your circuit. It would be interesting to see what your simulator does with my
preferred proposal. There are two steps to my preferred circuit. The first
step is to move the lead of C2 that is connected to L1 pin 3 to L1 pin 4
instead, and then scale the inductance of L1, adjust the core in the physical
implementation, to maintain the same carrier frequency so that the reactance of
C2 at the carrier frequency will remain the unchanged, before running a "sim".
The second step, which yields my target design, is to split the tapped coil into
two separate windings by disconnecting the grid part of the coil from the center
tap at pin 4, along with the end of C2 that had been moved to pin 4 in the first
step, and then reconnecting them both to the oscillator cathode, yielding my
proposed two winding circuit.

--
Regards,

John Byrns

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