G0CWT Power Tower

The Power Tower

 I had a large junk box with all the bits for a Linier Amplifier using PL509s, and the winter was about to descend on us so I decided it was time to do what I had been putting off for many years and build a Linear Amplifier.

There are numerous circuits available and I chose to follow them for the main part but I did use ferrite tubes for the input choke and the grounding choke at the antenna output.

At one point, I also used a ferrite tube for the anode choke but decided after a time to go back to the tried and tested method of winding a choke onto a tuffnal former.

This was because the environment next to the valves was much to hot for the ferrite core causing it to saturate after long over.

My choice of case was because I did not want to take up to much room on the bench and after looking through my stock (in the attic, where else) I found a case that was 19 by 9 by 7.5 inches.

It had a lid and louvered vents on all sides on the ends where handles.

I removed the lid and one handle and stood it on end then set about making an amplifier to fit.

The transformer is a 450 by 450 volt that came out of an early TV camera control unit and I bolted it to what is now the bottom along with the electrolytic capacitors etc.

It gives a good weight and the case now stood on end is very stable and would be difficult to knock over.

The height of the power supply is 5,inches which leaves me with 14 inches to contain the valve amp chassis and above that the pi tank circuit.

I have used a small computer fan, which is not required all the time. due to the vents in the side of the case. 

I made sliding supports for the valve amplifier chassis and above that the pi tank cct.

I have placed pictures below.

The finished amplifier easily gives the legal limit on all bands from 160 through 80, 40, 20, and 17, it then falls off to about 250 watts on 10 meters.

Not bad for a footprint on my bench of only 7 inches by 9 inches.