Homebrew 2m/70cm duplexer for 23 and 13cm SOTA activations. Why buy one when you can make your own?
All components are mounted on a single sided copper clad board.
I will use my FT-817 at 1 watt to drive the 23 and 13cm transverters via the duplexer. The duplexer will permit instant band chages. SG-Lab transverter IF input frequencies are:
- 23cm (1296.150 MHz): IF = 144.150 MHz
- 13cm (2.403150 GHz): IF = 435.150 MHz
Test instruments used; NanoVNA, RigExpert AA600 antenna analyser, Diamond SX40C VSWR meter and a wideband IC-R20 receiver. You will require two 50 ohm dummy loads.
The NanoVNA is a handy RF signal injection source which was injected in to the duplexer output and input ports and non-scientifically measured using the IC-R20 S-meter. The IC-R20 antenna socket is connect to the corresponding duplexer BNC socket via a short length of 50 ohm coax. With caution in mind, I reduced the IC-R20 RF antenna gain to ‘minimum’ and activated the RF attenuation option. Good news, this experimental non-scientific option worked and the IC-R20 isn’t damaged 🙂
I adjusted each of the four variable capacitors, one at a time, while monitoring the IC-R20 S-meter. With the capacitors adjusted for maximum and null signal strengths, I checked the VSWR on each band using the RigExpert AA600.
Satisfied with the results I conducted an on air test while monitoring the duplexer input VSWR using a Diamond SX40C meter, perfect!
When I’m not using the duplexer to drive transverters, it will be handy for SOTA activations on 2m 144.2 MHz SSB and 70cm 432.2 MHz SSB.