Why not use Old Bill's Approach in a Class E transmitter to double the frequency

[AB2EZ]

Looking at Old Bill's schematic of a 2 meter plate modulated transmitter... it occurred to me that the approach used in that transmitter might be a good one for doubling the frequency of a Class E transmitter. I.e. to use 40 meter technology to build a 20 meter transmitter.

The concept is to drive two parallel rf modules 180 degrees out of phase (as most of us do today)... but to combine them in phase.

The above approach would be almost trivial for converting a 40 meter transmitter to 20 meter operation (for example)... with only the output tuned circuit to be modified by using a smaller inductor.

The above approach would require an appropriately high Q output tuned circuit to suppress the 2nd harmonic of the 20 meter signal (in this example)... but that is not a big deal.

Actually, I am aware of folks who have built Class E transmitters with push-pull output modules... and where they accidentally combined the outputs of the modules in phase. They were wondering why the output of the transmitter was at twice the desired frequency. It didn't occur to me, up to now, that this "mistake" could be used to extend the frequency range of Class E transmitters whose switching devices are already at their limits.

Comments?

Stu

[WBear2GCR]

If there is a problem with the idea it may be in two areas:

- the need for high Q to get rid of harmonics, somewhere in there
- the loss of automatic supression of even order harmonics via the p-p scheme - which is why it is being used.

                    _-_-bear

[DMOD]

There is a way to operate at higher frequencies with ClassE and that is called the "BiHarmonic" circuit, but as usual, it is a more complicated circuit.

Phil - AC0OB

[WA1GFZ]

Push - Push doubler?

[WA1QHQ]

I wonder about what kind of impedance will be reflected back to the amps at the fundamental drive frequency.

Mark WA1QHQ

[WA1GFZ]

Mark,
Remember the Receiver I had on the table so Mrs. Shore the crazy lady could monitor WWV from outside. Well that had a push- push to make the second LO. Tuning and loading were very critical to get a clean output. Drive level was also critical to keep the conduction angle small enough. AM Modulating it may be an issue.
My name is Mrs. Shore and I'm snooping at your door...drove through the old hood last summer