One of the first mods I made was to add a transmit detection relay, presented via a phono (RCA) socket. This is useful if you want to trigger an SDR RF switch or an amplifier. Using a relay for this allows for a modest amount of current to pass if required. Photos are a bit crap but you get the idea. Essentially it uses the 3V3 from the TX LED to drive a PN2222A transistor using an 800-2K6 Ohm resistor. This transistor is used to energise the relay. The gain of this transistor is β100. The relay should only require 100mA but I think mine is drawing a bit more, hence using a relatively low value resistor to ensure it engages. The emitter attaches to ground, the base to the LED (via your chosen resistor) and the collector goes to one side of the relay coil - the other side of the coil to 5V. The COM and NO are then attached to the phono port. Don't forget a flyback diode across the relay coil. The 5V source is TP1 and ground can come from anywhere suitable, such as one of the exposed GND pads. The generic blue 'Songle' branded 5V relays fit perfectly in the case if you mount it on its side. It is a affixed in the open space on the PCB with thin double sided sticky foam. Note: I highly reccomend hot gluing the wire coming from the LED as it's fragile. Also ensure it is not going to short against the back panel as it will be right at the edge of the PCB - a wee bit of tape should suffice just in case the paint scratches and conducts. Let me point out the obvious - you could do this without the relay. However, I wanted complete isolation and the ability to switch unknown voltages & currents so using a relay here gives peace of mind. Using just a transistor is fine when you know how the equipment connected to it is going to behave. You can of course get more fancy with optoisolators etc but this was intended to be a quick win. This might be an easy one for Harry to implement out-the-box (even without the relay), if enough people think it adds value and doesn't affect the BOM costs too much etc.