[R-390] New R-390A owner

[Thomas W Leiper]

> --- Ronald Davis <RDavis24@carolina.rr.com> wrote:
> [can I] run a QRP transmitter [with] R-390A as a receiver?
> I have two different antennas but they are close in one point
> [would] 5 watts ...harm the front end of the R-390A?
> Also is there a way I can mute the receiver

The most important thing is to keep the AGC from having to
fluctuate wildly, escpecially when operating CW where often
the slow AGC mode is the best to use for reception. I think the
best solution for your setup is to use a TR relay in reverse in
front of the receiver. The relay switches your receiver input
between the receiving antenna and either a dummy load or
short piece of wire or rubber duckie antenna. The idea is to
be able to use the R-390 as a sidetone receiver, as well as
to help tune and net your transmitter, so you antenuate the
transmitter signal to the "average" signal level you would be
getting while receiving normally off the antenna. You would
be switching between a "receiving" receiving antenna (the
normal one) and a "transmitting" receiving antenna (the dummy
load, short piece of wire, etc.)

Although I do not transmit, I have the same setup on my
receiving antenna here to mute (and protect all my gear from)
nearby lightning crashes. I made a BC band RF detector and
DC amplifier that switches the relay (and receivers) over to a
UHF rubber duckie (junk box item) with a off-delay of about
a half second. You could just connect a diode and 10K resistor
to your receiving antenna and amplify and filter the signal to
drive the relay directly. Whatever, you get the idea.

Tom