IC8POF's Fan Noise Reducer for any RF amplifier.
but not only .


Idea&Construction: many years ago \ writting ott'06, gen'07.
This project works with fans running on 220vac,

Almost all RF Amplifiers have fans, few are quite, some are noisy , some other are VERY noisy .
Specially when doing lot of swl.ing with the PA in standby.
The solution is very simple : to add a VAC dimmer and a little timer.
The only requirement is that the dimmer must have an external insulated potentiometer.

fan-reducer schema The PTT input is High in RX and Low in TX.

and can be mounted on a little perf-board .

With the dimmer's potis we choose what the minimum speed will have the fan during RX time and the timer will be set to a delay
of +-1 minute during which tha fan runs at maximum speed and then returns to low speed during RX mode.

The minimum speed is to be monitorized with a digital thermometer to be sure that the temperature stays on low values
even at low fan speeds.

Using a double pole relay, one switch will short the potentiometer contacts for the maximum speed and the second part
of the relay will switch on an indicating led. That is all.
I have tried various dimmer and ended the search with a german model sold by www.conrad.de, its catalog nr. is 130004

here are some pics showing how i did mount the dimmer into the Commander chassis.


discover the fan wires and insert the dimmer on one of them and the game is ready.

v1.0 - mar2007, dic2011