Keying a radio through DTR

I’m very happy with my v1.9 digirig interface. Great little product. I’m using it with several radios (FT817, FT857, Xiegu G106). What I’m missing is the possibility to use DTR to key the radio through my application for CW operation. Maybe in a future revision will be added the possibility (optional, through PCB jumpers) to use current 3V3 pin from the CAT jack for DTR output using the same circuit as for RTS. For the moment I’ve build a small PCB with the two transistors and 3 resistors for this purpose. Is mounted on top of the digirig PCB using double sided tape. 73 Dan YO3GGX

This was the option in Digirig 1.5, but wasn’t a popular feature. I still have a unit around if you want it. With the latest revision you can do CW by RTS and configure break-in in the transceiver (PTT by CW).

digirig-mobile-1_5-schematic.pdf (91.0 KB)

I already modified my digirig 1.9 and added an extra circuit for DTR (using the 3V3 pin that I don’t need). The problem is that some radios require separate lines for PTT and Keyng. You cannot use only RTS for both without an extra manual switching. From what I see in the v1.5 schematic, DTR and RTS share the same lines with RxD and TxD, so this is not an option for me, as I need CAT at the same time.
73 Dan YO3GGX

This will need two more transistors and some resistors. I’m pretty much out of room in the enclosure unless I use the second rail. So far the small size is more popular feature than dual switching lines, but I’ll keep my ear to the ground for more requests like this. Maybe implement it in a different variant of the interface.

Yes, I just replicated the circuit used in your design for RTS (using 1206 resistors, as this is what I have). I’ve seen that there is no more space available on the PCB, maybe to be built as a piggyback board, just to provide the 4 pads to connect to (DTRin/DTRout/GND/Vcc). Is not so easy to solder a thin wire directly on the CP2102 DTR pin. There is plenty of space in the metallic case for such an approach. Some LEDs for power, RTS and DTR may be useful too (eventually mounted on the back of the PCB (close to the case bottom wall), with some holes in the case covered with transparent plastic. .

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By the way, on my Xiegu G106, I have to use 100Kohm resistors in series for both Audio In and Audio Out. As I want to keep digirig unmodified, I added the two resistors in the cable, but it may be sometime required to have an attenuator for Audio In too (as it is now for Audio Out).

There is a wide range of audio adjustments for the direction from Digirig to transceiver. Did you have all the software options exhausted? (e.g. playback level at 1 in Control Panel, input sensitivity in transceiver at minimum, level set in software at minimum etc) .

I am aware about that, but using just software controls the sound is still distorted, even I can reduce the volume (input circuits are overloaded before the volume control in CM108). From radio side, There is no way to lower the volume of Audio Out in the radio. With the 100Kohm in series with radio Audio Out, the level and sound quality are both perfect. I can keep the software controls around half.

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