Does anyone have recent experience with the old HA-201 walkie talkie
amplifiers? They use electronic transmit/receive switching. They are
rated for 8 Watts out for 1 Watt in, and 10 Watts out for 1 1/2 Watts
in, using a 13.6 Volt power supply. Maximum drive is 3 Watts. The
amplifier uses a single 2N5590 transistor.

Back in the 70s, I built an HA-201 and worked on at least one other. I
can not remember much about them, except it was impossible to stabilize
them per Heath's instructions and technical notes. I found a "fix", but
don't recall from where.

At a recent Hamfest, I obtained a couple more of these amplifiers. They
both tuned up per instructions, but at a slightly low output power and
with the instability as noted on an AM radio. Adding the stability
"fix", the power output was still the same.

Since both units seem to perform the same, I wonder if the design is
just not able to put out rated power from rated input? I used a Kenwood
Handheld as a source with 20 feet of RG-58 to knock the power down to 3
Watts. For 3 Watts input, they both put out 11 Watts. Using a
different Handheld with 2 Watts output, they put out about 8 Watts.

If anyone is interested in the stability "fix", it involves using a
tantalum electrolytic capacitor (low ESR) in parallel with the 100 UF,
and a 330 Ohm 1 Watt resistor in parallel with the RF Choke.

Fred
K4DII