Gysel couplers

The Gysel coupler (under construction)


There are many ways in combining amplifiers. Wilkinson dividers, hybrid couplers or rat-race couplers are the best known couplers in amateur radio. I came across another type of coupler: the Gysel coupler named after Ulrich Gysel. This coupler can be made with ready available pieces of coax cable, 75 Ohm and 50 Ohm peces of cable all being a quarter wave long. Isolation is very good and even up to 1296 MHz couplers can be constructed and an isolation of 18dB or so can be archieved. An advantage of this coupler is that there is no phase difference between the inputs (or outputs if you wish). The phase is equal. Another advantage is that even 3 ports or 6 ports maybe constructed.


The 2 port Gysel coupler




The 3 port Gysel coupler

I never build this one. The problem here is the 45 Ohm piece of coax. Old computer cable might do the job. Or a quarter wave transformer build out of brass tubing.


The 4 port Gysel coupler






Below is a picture of a low power version to split some mW into 4 equal signals. Upper right and below right you can see the 4 dummy loads, consisting of 4 2W SMD resistors.



This is the higher power version. It has been used up to 200W on 432. Dummy loads are mounted on a small heat sink.



Measurements to follow.