Monday, December 16, 2019

Ameritron AL-80B AM Operation

Since I get into a bit of AM on 75 m, I had wondered about using my AL-80B for some extra Amplitude Modulation power :-)

While chatting on 75 m AM today I raised the question about using an AL-80B on AM. A couple of the ops in the round table we had going said they work great, in-fact one who later joined-in was using an AL-80B!

Setting up an AL-80B for AM use is pretty simple, the goal is 100W unmodulated carrier power on AM from the amp.
  • With the Icom IC-7300 set to 30% / 30W on RTTY mode, tuned the amp, this delivered about 400W output.
  • Switching to AM I reduced the drive power (to 20% in my case) to where I got 100W unmodulated carrier power from the amp, modulated voice peaks are around 300W PEP.

With this configuration I found that anode would start to show a dull cherry red color after a few minutes of transmitting which is perfect for the 3-500Z tube.

Signal reports from the group indicated going to 100W carrier power made a worth while improvement over the 25W carrier / 100W PEP from the IC-7300 on AM.

The AM operators in the Pacific North West are a friendly bunch, if you enjoy informal round table QSOs that can last a while, then this is the place (3.870, 3.877 and 3.885 MHz).