Having successfully bench & on-air tested a x2 harmonic amplifier method of driving my G0MRF Class D LF transmitter, I ran a beacon last night (Saturday 19th) on 137.500 kHz.

An extract from my previous e-mail description is shown at the end.

Using the equipment & method described below, the ERP from my 12 metre vertical antenna was around 150mW. The mode was ROS MF-1, 100 Hz bandwidth.

I received the following report from Michel, F5WK in JN18HP, a distance of 410 miles (661 kilometres) in daylight.

>> Not even a faint trace on a QRSS3 spectrum but:

>> RX1: 19:23 @ 5.9 Hz: 9 <STOP> -37 dB
>> RX1: 19:28 @ 5.4 Hz: O4WGT <STOP> -34 dB
>> RX1: 19:33 @ 5.4 Hz: G4WGT <STOP> -31 dB

The x2 harmonic low level amplifier is a simple way of driving a Class D type of transmitter which employs a divide by 2 drive chain. My limitation with multi tone drive is that my DDS VFO will only produce 2 frequencies ie. the main frequency & a CW/Rx offset which has previously limited me to 2 tones as with RTTY & DFCW modes.

Please bear in mind that it will not be suitable for modes like PSK were tones are transmitted simultaneously.

At the moment the 2 small PCB's are precariously lying on the desk, when I have cased them I will publish the circuit & pictures.

73

Gary - G4WGT.