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Newbie taking the plunge

PostPosted: Sun Dec 18, 2011 6:33 pm
by ND9B
I just ordered a board set from Steve. Can anyone recommend a heat sink for the PWM module? (Must be a bunch on eBay.)

BTW, is there any way of reducing the output of a Class E transmitter for setting the antenna tuner?

Bobby Dipole, ND9B

Re: Newbie taking the plunge

PostPosted: Sun Dec 18, 2011 7:39 pm
by kf1z
Welcome.... another one gets submerged.... :-)

First off.. what size transmitter?
I ASSUME the 400 watt rig on Steve's page?

For that one, you only need 2 mosfets and 2 diodes in the modulator...
So the heatsink can be very small, like around 4" x 4" with 1" fins is plenty. though if it was 5" tall, may offer
a little more leway for mounting..

It doesn't need much at all, basically whatever the mosfets, diodes need for space.

Again, if you are using the designa on Steve's page, look closely at the PWM power supply,
You'll notice an arrangement with relays to switch the center tap of the transformer.

This provides 1/2 voltage, which is 1/4 RF power output. Just for tuning up.
You don't have to follow that power supply exactly, but you definately should work in
a similar method for tuning.

If you need parts, let me know !