[ARC5] Spotting

[David Stinson]

I have SCR-274N, ATA/ARA and AN/ARC-5 sets in original- 
design operating configuration, save what I'm about to detail.

Here's the 2x3 274N in HF configuration from an special 
event station some years ago (that's a B-17 in the background):
http://home.netcom.com/~arc5/SCR-274Na.jpg

Here is the 1x1 AN/ARC-5 station (scare MF configuration)
when it was about 95% completed:
http://files.qrz.com/s/ab5s/160ARC5.JPG

In the original design, each receiver audio output is routed through
a "muting" relay in the receiver rack which disconnects the receiver
outputs during transmit.   These relays are connected to
pins 5 and 6 on the 6-pin sockets at the side of the receiver racks.
Pin 6 supplies A+ to the relays from the modulator 
and Pin 5 is the keying buss, grounded at the modulator end on "transmit."

In my sets, I use a small SPST switch that opens the Pin-5 lead,
leaving the receiver audio outputs active during transmit.
This allows me, through the BFO, to "net" the receivers 
and transmitters.  Works very well for me and will not harm
the receivers.

73 OM DE Dave AB5S

p.s. I also parallel an external relay across Pins 5-6
and use it to key an external amplifier.