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

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.

Perhaps not necessarily so rare. We had a 63" Samsung plasma set that made a horrendous racket on many of the HF bands. Could not go on 160, 80, or 40 meters when it was turned on. That TV was moved to another room where it is seldom used. In it's same physical place we put a 65" Panasonic SmartViera plasma set. Almost RFI-free. I can hardly tell when someone has turned on that TV when I'm on the radio. I'm happy that this set is not a problem-causer, because before we bought it we tried a 65" Sharp Aquos LED. No RFI, but the picture totally sucked. Sad but true - a $2,600 TV with sports movement artifacts and a teensy viewing angle.

I feel for those folks plagued by plasma RFI, but if you are shopping for a quality picture, don't completely rule out plasma. Make sure whoever you buy it from gives you a written statement that if it screws up your radio - it goes back - no charge to your pocketbook. We did that with Best Buy and the Sharp TV. Although it didn't cause RFI, it wasn't a keeper - they came and hauled it away when they delivered the Panasonic. Didn't cost us a penny extra.

I have a Bencher YA-1 Low Pass Filter that I'm planning on listing for sale. Don't have the original box or manual. Looked all over the Internet but I'm unable to find anyplace where I can get hold of the instruction sheet / user manual / brochure. I would prefer to sell it with some sort of documentation, and not just a naked piece of gear.

Does anyone have a PDF or scan of their YA-1 manual they'd be willing to email me?

Thanks, Jim / W6JHB

But, as I posted, the reactance on that Inverted L is almost zero, so I don't understand why you feel that the reactance of the antenna counteracts the capacitance of the tank circuit. The amp IS followed by a tuner - the LDG AT-600ProII, which I figure would deal with any inductive or capacitive reactances as it finds a match. At any rate, the tuner has the ability to add C or L values to what it's computer came up with, so I can try simply adding some C to it after it goes through a tuning cycle and see if that makes the AL-811 happy. Will give that a try on Monday morning.

Frank - I have NOT tried the amp with a dummy load, as the only one I have at this point is a 300w air-cooled unit.

However I did some more testing this morning. Thought I'd explore as many avenues as possible before I either called Ameritron or heated up the soldering gun again. The testing I've been doing had been with my 80 meter Inverted L with a K2AV FoldedCounter Poise (FCP). I have an AIM-4170C analyzer and connected it to the Inverted L this morning, just to be sure I was not messing with a broken antenna! This antenna has a flat 1.4:1 or better SWR from just below 3.500 up to 3.600. The impedance showing on the '4170 graph runs from about 40 to 42 ohms from 3.500 to 3.600. Return loss runs from 19 dB to 24 dB in that same frequency range. Phase is around -6.4 in this range. All in all, it appears to me that this antenna should be liked by just about any tuner, exciter, or amp. In fact, the K3 and LDG AT-600ProII have no issue "tuning" it. I did the amplifier Loading / Tuning testing with this antenna going through the LDG tuner AND with it in bypass mode. No change in the readings - the Load control winds up down at zero when I'm on 3.510 and moves up into the 2-1/2+ range up at 3.570.

So, this morning I tried a different antenna with the amp. This is an 88-foot long doublet at 45 feet. It goes from the LDG tuner through six feet or so of RG-8X into a home brew 1KW 1:1 balun, 100 feet or so of 450 ohm ladder line, 15 feet or so of 600 ohm open line and then the antenna. With the amp in standby and the LDG tuner in bypass, I can turn on the K3's tuner and surprisingly it is able to get a match to the antenna. I turned off the K3's internal tuner, took the LDG out of bypass and told it to give it a try. It was also able to get a 1.5:1 or so match to this antenna. OK, now I put the AL-811 into Operate mode. Hmmmmm.... I was able to load it up without the Load control going to zero. When fully "tuned", the amp had it's Load control sitting at about 3. However, even with 90 watts of drive, I was unable to get more than 400 watts output. Interesting, but I don't want to use this antenna to operate - it's pretty much an NVIS antenna on 80.

So, now I'm confused. Why would the amp balk at operating properly with what is, in my view, at very well tuned antenna, but instead work fairly well with one that must be off the charts as far as resonance without the tuner in line? Arrrghhhhhh!!!!!

This morning I removed the 360 pf cap that was factory installed. Put it on my meter and it read 385 pf. The new one I got from Ameritron read exactly the same, so I did not bother inserting it in place of the factory installed cap. Instead, I went directly to plan "B", which was to put the second 500 pf cap in parallel with the original 500 pf cap. Put the cabinet back together and fired up the K3 and amp. It works better, but not perfect. On 3.560 mHz, with 70 watts of drive from the K3, I get 475 watts out, with Load at 1.5 and Tune at 3.0 - I'm sitting at 450 ma Ip and 100 ma Ig. Up ten more kHz (3.570) and the load sits at 2.5, Tune at 3, Ip at 475, Ig at 90 and about 475 watts out. However, moving to the bottom of the band, 3.510 - not so good. At that frequency, even with 80 watts drive, the Load goes to zero, with Tune at 2.75 - 525 ma Ip and 90 ma Ig. So, it looks to my untrained eyes that 1,000 pf is still not enough for the very bottom of 80 meters. I could care less about 75 SSB, so adding more to make the CW part of the band work "may" be the answer. I was tempted to slide that new 360 pf cap in parallel with the two 500's already there, but I'll wait to speak with Ameritron on Monday and see what they say. One poster replied that he had moved the tap on the tank coil a bit. I hope I don't have to do something that drastic!

As a side note, I took another look at the 160 tuning data. No problem. On 1.810 kHz, with 50 watts drive, the Load sits at 5, Tune at .5 and I've got 375 ma Ip, 90 ma Ig, 450 watts out. And yes, the antennas for 80 and 160 ARE different. Both are Inverted L's and both are resonant at the bottom of the band.

Dang 80 meters - the ONE band I really need some oomph in my signal!! Well, I'm not done yet, so once again - stay tuned.

No problem! Got the intercom fixed - put ferrite beads on every wire entering the control box, in addition to the wires going to each remote unit. No more RFI hitting the intercom!! Now I can concentrate on that 80 meter loading issue on the amp. Stay tuned (literally!).

Jim / W6JHB

Have no fear - I will update this thread when I've gotten back into the amp. I had spoken with Rick at Ameritron day before yesterday and the engineer he spoke with (back room guy) said that "maybe" my 360 pf cap was bad. In any case, they mailed me a replacement 360 pf and a 500 pf cap. I got them in this afternoon's mail. THAT was fast shipping!! I hope to pop the cover tomorrow (Saturday) and see what I can do. Rick said to first try replacing the 360 with the new one they shipped. If that didn't fix it, to pull the new 360 and put that second 500 in it's place, giving me a total of 1,000 pf padding. I'll post back what the results are.

In the mean time I've been tearing up our home intercom system, adding ferrite beads on every lead I can. What's been happening is that the speakers on each intercom unit (there are five of them) thump when I operate 40 meter CW at 450 watts out. Doesn't happen with I run the K3 barefoot at 100 watts - only at high power. As I type this note, the intercom system is in total dis-assembly state as I put on the ferrites. Of course, when they built the house in 1990, they didn't leave a lot of slack cable, so on quite a few leads I've had to solder in four or five inches of extension so that I can wind the cable through the bead several times. If all this doesn't resolve the issue, I may have to get out the .357 magnum and put the darn thing out of my misery! 

Just got off the phone with Rick at Ameritron. They are sending me a 360 and a 500 pf replacement padding cap. The engineer he spoke with said that perhaps the 360 in the amp is defective. I'm supposed to replace the 360 first and see if that resolves the issue. If not, pull the new 360 and put the new 500 in it's place, giving me two 500 pf caps in the unit. It looks like it'll only be a medium P.I.T.A. to get at those two caps. 

Interestingly, I've got no problem on 160 - only 80 meters.

Is that "tuning pulser" worth the $65 - anyone using it here?

So far it seems that 80 meters is the only problem with this unit. I pulled the cabinet off again and checked - it does have all THREE padding caps on the bandswitch. Rick from Ameritron asked me to call him back if I get the same result of Loading at zero when I drive the amp with 100 watts on 80. With 90 or 100 watts drive I can get 500+ watts of output, but the loading still goes to zero. I tried the amp on 160 and there is no "Load" issue there - only on 80 meters. On 160 I have to run the Tune control nearly to the full clockwise position for 450 watts out, but that's not a problem. Time to call Ameritron back.....

Thanks for the links to W8JI's tuning info and the padding cap thread. I'll play around with the amp a little more on Wed morning. My operating is about 90% CW. Since it is a new amp, I "assume" it has the additional cap, but I'll pull the cover and take a look anyway. As to pushing it to max (550-600 watts) - I really don't need to do that - 500 watts out would suite me just fine. The additional couple watts aren't going to make much difference on the other end anyway.

I find it interesting that their manual indicates removing 12 screws to take off the cover. There are 16 - only removing 12 would NOT make one a happy camper!

Forgot to mention in the original post that I had called Ameritron support this afternoon. Before we got disconnected, the tech told me that all AL-811's after a certain serial number (including mine) has some new bias circuitry in it that allows more than 50-60 watts drive. He said that if need be, I could run up to 100 watts of drive w/o hurting the amp.

Just unboxed and hooked up a band new AL-811. Driving it is an Elecraft K3/100. Behind it is an LDG AT-600ProII tuner (with M-600 meter), and the antenna is a 45-foot high 88-foot long doublet, fed with a 1:1 KW balun and 100+- feet of 450 ohm ladder line. I've come across two "issues".

I have three pieces of documentation on this amp. One was a manual downloaded from the Internet (this site, perhaps), one is the manual that came in the amp's box, and the third is a separate piece of paper that came with the amp. They have differing numbers when it comes to max plate current. The manual I downloaded from the web sez never exceed 700mA of plate current during tune-up. The manual in the box sez 600 mA, and the single sheet of paper in the box also sez 600 mA. However, the two manuals say to never have a plate current more than 450 mA. What's going on here? What is a safe number for these 811A tubes? If I try to keep the plate current at 450 mA, there is no way to get much more than 400 watts out. I CAN get close to 500 by running the Ip up to about 475-500 mA. Is this going to severely shorten the lives of those three tubes?

On 40-10 meters, it seems to load up pretty well and I can get close to 500 watts out (with the high plate current). However, 80 meters is a different story. I use an Inverted L on that band, and it has a 1:1 SWR. The problem here is that I have to turn the Load control all the way to zero to get a lot of output. The manual sez that's not good to do. If that's true, any idea why this only manifests itself on 80 meters?

  Yep, that's probably a good idea, since it's not a huge manual anyway. Thanks for the suggestion!