RadioBanter - B&W Model 80 T-R switch

Jay, AA4FL wrote:
On Mar 5, 6:10 pm, "Jay, AA4FL" wrote:
Is anyone familiar with this TR switch? I was given one and it is
designed with only two SO-239, one marked for receiver, and one for
antenna. Can anyone explain this to me or supply a manual/schematic,

Hi, Jay

I have a B&W 380B electronic TR switch which looks as you describe.
You use a series UHF coax T-Connector mounted on the "Antenna" terminal
of the TR switch. One end of the T goes to the Transmitter,
the other end to the antenna. The "Receiver" terminal
gets a coax line right to the receiver.

It's also possible to use the TR switch between a separate
receiver antenna and the receiver.

I have no paperwork. B&W advertised it as good for a KW A.M.
on the HF bands.

The 380B uses a single tube, type 6AH6 pentode.
Mine required replacement of the two electrolytic
capacitors in the power supply, and the 1K resistor
from the power supply B+ to the tube.
The Selenium rectifier was OK.
There's a large bifilar choke under the chassis for the 6AH6
heater line, and a smaller ferrite rf transformer above
the chassis feeding the receiver. The 6AH6 rf amplifier
circuit is untuned. The 1.2 Meg grid resistor
furnished cutoff bias when the transmitter is on.

Don't forget to use a low pass TVI filter between the TR switch
and antenna.

The coax length between the TR switch and the transmitter should be
as short as possible, to minimize "suck out" effects -
possibly desensitizing the receiver at certain settings
of the final pi network.

Also, the transmitter and/or amplifier should be biased
to cutoff during receive, to minimize noise.

I added a fuse in the power cord -
the unit was originally unfused.

73,
Ed Knobloch