KC8AON's QRP PROJECTS
A SIMPLE QRP POWER OUT INDICATOR

A FRONT PANEL POWER OUT INDICATOR FOR YOUR QRP RIG


SW-30+ CW Transceiver
 
GIVES YOU AN INDICATION THAT YOU DO OR DO NOT HAVE POWER OUT OF YOUR TRANSMITTER AT A GLANCE
 
Ever call CQ over and over while in the field without being answered and wonder if you are putting out any power ? With this little device, you can tell at a glance if your transmitter is or is not putting RF into the antenna by just watching a front panel mounted LED when you key the transmitter. If the LED illuminates, you do have power out, and if it does not, well then something is wrong. What it does not do is tell you how much power you have going out, it's just an indicator telling you if you do or don't. It looks really neat flashing along with your keying, and if someone is observing you operate, they could possibly copy what you are sending just by watching the LED ! Caution ! Cover it up when in presence of enemies ! LOL
 


Its a very simple circuit to produce. It consists of an FT37-43 toroid with 7 to 8 turns of #22 or #24 magnet wire to form an RF sampling sensor that connects through a 5K ohm mini pot and then terminates to an LED that is mounted on the front panel of your QRP tranceiver. Mount the sensor near the antenna jack with insulated wires routed to the front panel mounted LED. The antenna lead from the transmitter to the antenna jack passes through the center of the sensor to supply RF to the circuit. Use the 5K pot to adjust the brightness of the LED. I have installed this circuit in each of my 3 SW rigs from Small Wonder Labs, and they all do 2 watts or less and I did not need the 5K pot. The LED's brightness was just right without it. But with a transmitter that does more than 2 watts, I would say use it to prevent blowing the LED out. Keep the antenna lead as short as possible. If you must lengthen it to use this circuit, then use some RG174 coax for the antenna lead. I use the RG174 on all my QRP rigs, but I just mount the sensor on the center conductor at the antenna jack, then secure it with a dab of hot glue.

 

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