Sunday, 24 July 2011

Doubling digimode output power with a fan

In CW and SSB transmitting a typical 100W transmitter deals easily with the power set to full, because there are always the pauses between the peaks in those transmitting modes. In contrary, most digimodes send for long times without pausing; full duty. The transmitters aren't built for handling full power for longer times: the heating becomes the big problem. The commonly used way to deal with it is to half the transmitter power to 30-50W. That is OK for normal e.g. PSK QSOs. In some big RTTY pileups I started to long for the full 100W, so I took a 12V computer fan, and installed it like this:
The fan is blowing towards the hot part of the transciever.
The 12V power is easily got from the transceiver DX source.
I tried this installation in a few long digimode sessions, using the full power. The transmitter remained cool, so this seems to work. I gained 3dB, a half S unit. Sometimes it may make a difference! Can you get a 3dB gain cheaper than this?

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