Dummy Load Guidelines for JUMA TC circular polarization
A very good benefit of the quadrature hybrid is that it provides SWR 1:1 for whole the band when running circular polarization. The reflected power is dumped to the dummy load. With max 200W the JUMA TC internal dummy load is sufficient up to SWR 3.0. But in case of QRO power an external dummy load is needed to operate in the band edges with worse SWR. Here are the guidelines for the dummy load requirements.
Reflected Power to Dummy Load versus SWR and Transmit Power.
SWR
 TX 100 W Reflected power
 TX 1000 W Reflected power
 TX 1500 W Reflected power
1.0
 0W
 0W
 0W
1.5
 4W
 40W
 60W
2.0
 10W
 100W
 150W
2.5
 18W
 180W
 265W
3.0
 25W
 250W
 375W
3.5
 30W
 300W
 450W


An example of an external dummy load for 250W. Note the thermal paste below the power resistor. A bigger heatsink is recommended for legal power.
Update 2021-08-29 OH7SV

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