Tuna RF MonitorPrice: $30.00
The Tuna RF Monitor is a variation on the Tuna Helper kit. The purpose of the kit is to provide a novel display to monitor the output of your QRP transmitter. The Tuna Helper board has a lot of 'Limerick' pads on the underside of the pcb to enable custom modifications. This is MY idea of a cool use for the pads....
The RF sensing circuit on the Tuna Helper kit is used to automatically switch the antenna between the Receiver and Transmitter. The antenna is NORMALLY connected to the Receiver but when the sensing circuit detects RF coming out of the Transmitter, it switches the antenna to the Transmitter jack automatically. When the RF signal ceases, the Helper returns the antenna back to the Receiver.
For the Tuna RF Monitor modification, I eliminated the antenna switching relay and action by hard wiring the Antenna jack to the Transmitter jack. The relay control circuit is then used to turn on a batch or SUPER bright LED in sync with the detected RF. Another ORANGE LED is powered on all the time to simulate a hot cathode. Both the LEDs are on the bottom side of the pcb pointing up through a hole in the board. Other holes are then drilled in the pcb to mount a vacuum tube so that it is centered over the LEDs. The overall effect is that the RF monitor looks like vacuum tube glowbug kit where the tube light brilliantly in sync with the transmitter output.
Documentation is coming...
A YouTube video of the evolution of the RF Monitor kit can be found below.