The AM Forum

As part of my downsizing program, I have a 40 watt (at carrier) class E transmitter (class H audio) that is surplus to my needs.

This is a quick and easy way to get on the air with a high quality AM signal. This low power class E / class H transmitter is easy to use and very forgiving (because the r.f. input to output current gain is relatively low compared to high power class E transmitters).

I built this after I built my 200 watt (at carrier) class E (class H audio) transmitter... just to see how compact it would be. At this point, I do not need both transmitters.

Specifications:

Size: approximately 12 inches wide, 9 inches deep (including the heat sink on the back), and 8 inches high (not including two meters mouinted on top of the heat sink... that add another 3 inches to the height).

Design: Single FET class E (40 watts at carrier) r.f. output stage, 2-FET class H modulator (WA1QIX  design)

Includes (above or below the 8 x 12 chassis):

a) Toroidal transformer-based bridge rectifier power supply.

b) RF driver that presents a 50 ohm input impedance (carbon swamping/termination resistor), and requires only a few tens of milliwatts of RF input as a VFO. I was running it with my Flex SDR-1000 providing 100 mW of unmodulated carrier input.

c) Built in DPDT antenna relay

d) Built in PTT circuit (apply 12VDC across the RCA PTT connector to activate the relay)

e) High quality audio with line level input (unbalanced RCA audio input jack)

f) Over-current protection circuit

g) Output coils for 80m and for 160m (input is 50 ohms)

h) voltmeter and ammeter

This transmitter produces superb AM audio quality (as per feedback received from  contacts I have made). I have used it both: "barefoot" at 40 watts (carrier level), and with a linear amplifier.

Parts cost was around $500.00 (toroidal transformer, chassis and heat sink,  tuning capacitor, loading capacitor, 12.6V transformers for the class H modulator low-level circuit baord, relays, WA1QIX class H modulator circuit board, etc)

Sale price: $200.00 (pickup preferred) + shipping

Contact: sdp2@verizon.net (please do not use this board to reply)

Stu
AB2EZ