Topband: Signal source RF amplifier

[Roger Kennedy]

Steve, back in the 1970s, when I was too young to drive, I made a 160m
handheld transmitter!

I built it into an AM Transistor Radio (modified to receive Top Band), and
used the Audio amp in it to modulate the PA (just a little 1:1 transformer
in series with the Collector).  With just a 4ft whip, I regularly worked
stations 10 miles away on AM, just walking along.

It consisted of a BFY51 Crystal Osc (on 1880 kHz), feeding a BFY51 Class C
PA (with an RF Choke to ground from the base).  The output coil in the
collector consisted of 2 turns on a small ferrite core, with a secondary
winding of about 30 turns (thin wire). The capacitance of the 4ft whip
almost resonated the output coil, I just had a 50pF trimmer across it just
to peak it on resonance. (using my receiver)

Powered by the radio's 9V battery, it was running about 1 watt input.  I
don't think you could get anything simpler - it was built on a piece of
stripboard about 1 inch by 2 inches.

73 Roger G3YRO