[CQ-Contest] What RF voltage OK at Rx in SO2R?

[Dave Lawley]

Here's an RX protector circuit I made up a couple of years
ago, following a posting here on the reflector by Tom N4KG.
Brought it with me to WRTC2000 and we used it on the second
rig, though the voltage levels didn't really warrant it.

Here at home I managed to squeeze a 260ft beverage 
diagonally across my garden, but it was only about six feet from
my 40m 4-square at the nearest point. The bulb lights brightly 
when I'm transmitting on 40m but the front-end of the FT1000MP
has held out fine.

Here's the circuit. The bulb is a 60mA grain of wheat type and
the whole thing is mounted in a metal box with a small hole so I
can see the bulb when it lights.

Dave G4BUO


  antenna --- bulb --- 0.1uF --- 33ohm 2W ------------- rx
                                            !     !
                                            !     !
                                            !     !  back-to-back 
                                            !     !  1N914 diodes, 
                                            !     !  4 in each string
                                            !     ! 
   ground --------------------------------------------- gnd


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