2m/70cm Diplexer

2m/70cm Diplexer

In May 2018  Wijnand PD5WL came over for a weekend to get out, to enjoy the night life in Almelo (especialy Cafe de Stam) and to do some hamradio stuff. One thing he brought with him was a Arrow II 2m/70cm antenna clone (link) which needed some calibration and he would like to try out in the field (which we did see our Field report of 20 May 2018 ). One thing we where missing was a 2m/70cm diplexer so the 2 antennes could be used on a single handheld or portable station.

Some googling around for "2m 70cm diplexer" you find some big (which work perfect) and some small versions.

The last one was a nice small version which would perfect fit into the Arrow antenna. But we thought it over and decided that a SMA version would be better for future modifications and experiments. Some adition googling we found a a design from kolaCZek (link) and you can order the PCB on oshpark (link),

When the PCB's where orderd (which took a little longer then expected because of the holidays) the hunt for the components was on. And when I finaly got the  last parts in the mail for the SMD 2m 70cm diplexer I started to build 3 of them. One for myself, one for my friend Wijnand and one extra for stock and experiments.

Build and ready for testing. But when you don't have spectrum analyzer with a tracking generator, you have to be creative. So I just used my RigExpert AA600 for that by connecting it to the common connector and using a SMA dummy load for  the part under test (photo below showing the dummy load on the 70cm part).

Same setup but then with the dummy load on the 2m part.

Same setup with dummy load on 70cm part.

Again dummy load on 2m part (showing SWR graph)

Again dummy load on 70cm part (showing SWR graph)


A few weeks later I could use the Rigol Spectrum Analyzer of my hamradio group.

Note : TG signal level is -12dBm.