AL-811 Newbie Questions

[W6JHB]

Adding / Subtracting values of L and/or C via the LDG tuner pretty much had no effect on how the AL-811 worked on the bottom of 80 meters.

The amp came with three padding caps installed: two 360 and one 500 pf units. I'd replaced the 360 with a 500 last week - it helped, but I still found the variable capacitor plates fully meshed and the Load control at zero when trying to run the amp on 3.510 mHz. At 3.570 it worked fine. So, I added a fourth padding cap: another 360 pf. I now have two 360's and two 500's. The amp loads very nicely now at 3.510 and continues to work quite well up at 3.570. I'm getting out about 450 watts, with around 110 ma grid current and 475 ma plate current. I have no doubt that if (1) I had an antenna for the top of the band (75 meters), or (2) had a desire to operate up there - it most likely would not work. Just a WAG. But that's fine with me as I don't ever venture up there - I'm CW only on 80 meters. Just for the heck of it, I tried 160 again this evening. The amp also loads up well on 160 without having either the Load or Tune control going to max, so the change of those padding caps didn't mess up 160. This is down at 1.850.

So, bottom line for me is that I'm now happy with the operation of the amp on the lower bands. 

Thanks to those who offered ideas on how to figure out the problem.

[K4RVN]

Glad you can use the 811 amp Jim, and thanks for posting the solution.

Frank

[K7MH]

So did you end up with both 360pF caps together and the 2 500pF caps together or one of each together?

[W6JHB]

So did you end up with both 360pF caps together and the 2 500pF caps together or one of each together?

Mike - sorry for the delayed reply - been in football mode all day and just this evening got the time to unscrew those damn 16 screws holding the cabinet on to take another look! Here's the status on my AL-811:

It came with a 360 pf cap that appears to be switched in when the band switch is on 40, 80, and 160 meters. I did not mess with that one. There were two others installed at the factory - a 360 pf and a 500 pf, both of which get switched in for 80 and 160 meter operation. Ameritron mailed me a new 360 pf and a new 500 pf. I clipped out the 360 that the factory had installed for 80/160 and replaced it with the new 500 they sent, giving me two 500's in parallel. That helped but I still wasn't satisfied. I then soldered in the new 360 that they sent me, giving me two 500's and a 360 in parallel.

So......, what I've got now is the original 360 when the band switch hits 40 meters, and when it gets to 80 and 160 meters, there are 1,360 pf additional being switched into the circuit.

Like I mentioned in my last post, it works OK for my 80 and 160 meter CW operation. More than likely far too much capacitance for the higher end of those two bands. But I have no way of trying it. YMMV 

Hope that helps.

Jim, W6JHB