ng of a Johnson Ranger, Drake 2B, and
Hallicrafters TO keyer. One last item I needed was a T/R relay. Dow Key relays are
getting hard to find and the cost can be high, so I looked into making my own T/R switch.

Lead lengths and their associated inductances are very forgiving in the HF range. The
important thing is the relay contact current rating and the relay coil voltage. My Johnson
Ranger has a 117VAC relay driver output voltage. A good relay is the All Electronics
(
www.allelectronics.com
) RLY-2120 DPDT w/10 amp contact ratings ($2.75 each).

Below is the schematic for the T/R switch. I used SO-239 connectors for the RF
interfaces, and an RCA phono jack for the mute interface. For a box, you might
consider the All Electronics FNS-2 A/B Phone Switch ($4), though any metal box that
fits everything is fine. To mount the relay, I hot-glued it to the bottom of the aluminum
box. The photos show my final creation.

Notice that the DPDT relay does several things:
1)

It switches the antenna between receiver and transmitter.
2)

It provides the necessary mute control to the receiver (ground for receive,
open for mute).
3)

It grounds the receiver antenna input when transmitting.

I use the mute function when operating phone with my Ranger. I leave the receiver un-
muted for CW, since I want to monitor my signal directly. The combination of fast AGC
and a shorted receive antenna input during transmit works very well.

Phil AD5X

Antenna
SO-239
Receiver
SO-239
Rcvr Mute
Phono Jack
Transmitter
SO-239
DPDT 117VAC Relay
(All Electronics RLY-
2120 or equivalent).
Ranger/Drake 2B T/R Switch
117VAC input
pendant cable with
whatever connector
is needed

TR Switch Inside Wiring

TR Switch Connector Interface