‰  NOW 40 WPM  ‰  
BUT VARIES WITH FREQUENCY AND POWER LEVEL.  TO COMPENSATE FOR THESE
COMBINED EFFECTS, SELECT A CAPACITOR VALUE CX THAT RELIABLY TRIGGERS THE RF
SWITCHING CIRCUIT.  THE RF SENSING LEVEL IS SET BY CONNECTING A SUITABLE
CAPACITOR AT THE SENSE SCREW TERMINAL CONNECTOR.  FOR LOW RF POWER, 47 OR
100 PF IS NEEDED, BUT 10 PF WILL SUFFICE WITH HIGHER POWER LEVELS.
TEMPORARILY INSTALL THE SMALLEST VALUE CAPACITOR AT THE SCREW TERMINAL
LOCATION PROVIDED AND VERIFY THAT CORREC

A VERSATILE T/R SWITCH FOR SDRS AND VINTAGE RADIOS THIS RF ACTUATED SWITCH
CAN BE USED WITH ANY TRANSMITTER AND RECEIVER COMBINATION, BUT IT IS
ESPECIALLY WELL SUITED FOR SOFTWARE DEFINED RADIOS.  ROBERT NICKELS, W9RAN
IN MY JANUARY 2013 QST ARTICLE, CHEAP AND EASY SDR, I INTRODUCED MANY HAMS
TO THE WORLD OF SOFTWARE DEFINED RADIO SDR THROUGH INEXPENSIVE DVB T RTL
SDR DONGLES AND OTHER SDR RECEIVERS LIKE AIRSPY, SPY VERTER, HF, SDRPLAY
RSPS, HACKRF ONE, AND MORE THAT HAVE SINCE BECOME PART OF MANY HAM SHACKS.
ADDING AN UPCONVERTER LIKE MY RANVERTER AVAILABLE AT WWW. HAYSEEDHAMFEST.
COM TURNS INEXPENSIVE DONGLES INTENDED FOR DIGITAL TV RECEPTION INTO USABLE
HF RECEIVERS WHEN OPERATED WITH PC BASED SOFTWARE SUCH AS SDR.  BUT AFTER
SOME INITIAL FUN, MANY SDR RECEIVERS END UP IN A DRAWER, BECAUSE THEY LACK
SEVERAL KEY COMMUNICATIONS RECEIVER FEATURES NEEDED FOR USE ON THE AIR.  I
DESIGNED MY VERSATILE T/R SWITCH WITH THESE NEEDED FEATURES A PROVISION FOR
MUTING THE SPEAKERS WHEN TRANSMITTING SIDETONE TO MONITOR CW KEYING A
CONVENIENT MEANS OF SWITCHING THE ANTENNA BETWEEN THE TRANSMITTER AND THE
SDR RECEIVER PROTECTION FOR THE RECEIVER INPUT DURING TRANSMIT A WAY TO
OVERCOME DIGITAL SIGNAL PROCESSING LATENCY, WHICH MAKES IT IMPOSSIBLE TO
MONITOR ONES OWN SIGNAL, AS CAN BE DONE WITH A CONVENTIONAL RECEIVER.  WITH
THESE FEATURES, ANY SDR RECEIVER CAN BE CONVENIENTLY USED AS PART OF A HAM

STATION, EITHER AS A PRIMARY RECEIVER OR S A PANADAPTER OR DSP SECOND
RECEIVER CONNECTED TO THE IF OF AN EXISTING RECEIVER.  EVEN AN INEXPENSIVE
RTL SDR CAN BECOME A VERY USABLE RECEIVER WHEN THE NEEDED FUNCTIONS ARE
PROPERLY INTEGRATED.  VERSA TR PUTS EVERYTHING ONTO A COMPACT PC BOARD SEE
THE LEAD PHOTO USING ALL THROUGH HOLE CONSTRUCTION.  THE VERSA TR ALSO
WORKS WITH CONVENTIONAL ANALOG TRANSMITTERS AND RECEIVERS OR TRANSCEIVERS.
SOME POSSIBLE STATION CONFIGURATIONS INCLUDE A CONVENTIONAL TRANSMITTER
WITH AN SDR RECEIVER, A CONVENTIONAL TRANSMITTER AND RECEIVER, A
CONVENTIONAL TRANSCEIVER WITH AN SDR PANADAPTER OR SECOND RECEIVER, AND A
CONVENTIONAL TRANSMITTER WITH MULTIPLE RECEIVERS.  THE VERSA TR
INCORPORATES A VERSATILE RF SENSING RELAY THAT CAN ALSO BE USED FOR KEYING
A LINEAR AMPLIFIER OR LIGHTING AN ON AIR SIGN.  CIRCUIT DESCRIPTION THE
VERSA TR SCHEMATIC DIAGRAM IS SHOWN IN FIGURE 1.  IT INCLUDES FOUR MAJOR
CIRCUIT FUNCTIONS AN RF ACTUATED SWITCH, ANTENNA RELAY, MUTING RELAY, AND
SIDETONE OSCILLATOR.  A VERSA TR HOOKUP IS ILLUSTRATED IN FIGURE 2.  THE
BOARD REQUIRES 5 V AT 200 MA, PROVIDED BY THE 5 V USB POWER SUPPLY VIA A
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ