[TenTec] On Noisy Transmitters

[Peter Bertini]

Synthesizer phase noise wasn't always the cause for transmitter broadband
noise issues.

Back in the 1960s I used a Heathkit Hx-10 Marauder transmitter with a
transverter to
operate on six meter SSB. I also used a homebrew 4CX250B to generate around
250
watts into a modest beam.

Several locals noted that I had broadband noise on either side of my
signal, extending
for a few hundred kHz, whenever the TX was keyed.

Subsequent mail correspondence with a engineer at Heath revealed that they
were
aware of the problem:  the IF crystal filter was placed before the IF
amplifiers and the
design required a second filter after the IF gain stages.

The issue was broadband noise generated in the IF stages. On my end, the
system
worked flawlessly.  But, for other operators within a 30 mile radius the
shortcomings of
the transmitter design were painfully obvious.

Today, I could easily remedy the problem, but back then, as a newbie teen,
the problem
was overwhelming, and I replace the rig with one that was more friendly to
my six meter
neighbors.

Pete K1ZJH