On Sep 25, 3:20*pm, "Mike Kaliski" wrote:
Hi Owen,

Point taken. The standard Marconi ship station fed the receive antenna
through the back contacts of the key, so the receiver was always
disconnected whenever the transmitter was operating. I remember having to
pay about £15 extra for my CMOS TTL electronic keyer to be fitted with a
changeover relay rather than direct keying so I could use it with the
standard Marconi ship installation. Still working fine today after 34 years
of use!

I don't recall ever operating close enough to any other stations for the
diodes to cause me a problem, although I did once upset a Russian warship
when operating from Angola. My signals were apparently overloading their
equipment...

Regards

Mike G0ULI

"Owen Duffy" wrote in message

...

"Mike Kaliski" wrote in
:

...
Any protection is better than nothing,

... unless it lulls you into a false sense of security ...

a spark gap (old automobile
spark plug) or small neon tube, a couple of back to back diodes and a
5 megohm or higher resistor across the diodes to provide a static
discharge path will do the job for pennies.

as most of these may.

I do recall taking an early (probably the first) Collins digitally tuned
receiver to a coast radio station for evaluation. It had inverse parallel
diodes across the RF amp input for protection of the FETs and was totally
unusable as when the on-site 500kHz transmitter was keyed up, it wiped
out all of the receivers (not just this one) with broadband noise. It
took a few minutes to realise what was causing ALL of the ROs to hear the
station callsign, not as a beat note, but as noise as if it was near to
where they were listening and just needed to be tuned in. Whilst the
Collins was connected to an antenna, it caused havoc, even if powered
off!

Beware of the effects of inverse parallel diodes across the antenna.

Owen

I found that all very interesting. Mike stick around