Re: 5W Power Amp and the U3S; Options for a few watts

Vernon Matheson

I have been using the 5 watt PA for a couple of years. Have built 3 and blew up one :-)

I have never wanted to mount the amp inside the case for the simple fact that because the amp is not broad-banded I am constantly adjusting the bias on either the amp or the U3S.

If you try to max out a bit of wattage on say 10 thru 30 meters by adjusting the bias on the U3S and the amp and then switch to say 80m you will get a lot more than 5 watts going into a dummy load. Both my working amps with the bias counter clockwise will give you 4-5 watts on 80m.

I played with the setup a few days ago and found a happy medium for the bias on the that stays constant. However to play with all the bands I have to adjust the bias on the amp up and down so that I am not over or under powered.

Now maybe I have done something wrong but U3S can be in the case with the amp mounted on top leaving the amp open for adjustment and also in the open air for cooling or simply aiming a small muffin fan at it.



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