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"Ralph Mowery" wrote in
m: .... That is what I am using on a home built version. Using a 4:1 voltage balun at the feedpoint and the ferrite bead type about 20 feet down from the feedpoint. The ferrite choke is doing something as it gets warm while running around about 1 KW to the antenna. Doesn't heat up when going into a dummy load. I am not surprised at your results with a dummy load. If it is a well screened unbalanced dummy load, you should expect zero dissipation in the balun cores. The fact the balun cores are heating in the antenna scenario indicates there is some common mode current. You probably have no idea of the current. Something to keep in mind is that the average power of uncomressed voice SSB is about 3% of PEP, so if your 1kW was uncompressed voice SSB, the average transmitter power might be more like 30W, or half that in a 50:50 over scenario over the long term. Another thing is the ferrite toroids heat and cool very slowly, so the operating temperature might still be rising half an hour after the transmitter is applied (so long as you haven't exceeded their Curie temperature). It would not surprise me if the common mode choke consumes a significant portion of transmitter power on some bands, the portion will depend a lot on your own scenario. Owen |
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