My new to me Ameritron 811h

[Sonwatcher]

I just got this. It is very little used. I used it on 10m and got some very clean audio reports. I have to wait until I get a tuner to use it elsewhere on HF.

 

[Moleculo]

Nice! What rig did you hook that up to?

 

[Sonwatcher]

My Yaesu 757gx. The amp has 4-572b tubes and factory upgraded power supply. I was nervous to attempt to tune it. I have never had a tube amp. I read and reread the tuning procedure and called Roger- (Airplane1) to ask for any pointers to help get my nerve up. I wanted to make sure I did everything correctly .Once I finally went to it it wasn't as bad I was anticipating . I'm not planning on running it high. I had it running about 400 PEP .

 

[Quiksilver]

That's a very nice amp. I wish I could run tubes...........

 

[Captain Kilowatt]

That's a very nice amp. I wish I could run tubes...........

Why can't you? Tubes are easier to run then solidstate stuff when high power is involved.

 

[Captain Kilowatt]

I just got this. It is very little used. I used it on 10m and got some very clean audio reports. I have to wait until I get a tuner to use it elsewhere on HF.

Why wait? The Pi output section of a tube amp IS a tuner. It tunes the plate impedance of the amp to the impedance of the antenna,whatever that happens to be. Fire it up and keep an eye on grid and plate current and be happy. I rarely use a tuner with my TS-820S with tube finals except for the odd occasion when I am loading into a really weird (low) impedance and you KNOW I do not want to harm that baby. It still has the original factory Japanese S2001A tubes in the finals and they are pushing 30 years old.

 

[bamacj]

My 811h has been a great little amp, I usually cruse at 5-600 watts. Congrats.

 

[pro151]

What we want to know is how it "gets out" on 19. :laugh:

 

[hookedon6]

... The amp has 4-572b tubes and factory upgraded power supply..

i wasn't aware that there was a "factory' (ameritron?) power supply upgrade. do you have any specs on the new ps?

also, when this amp is using 572b's, you (as odd as this may sound) only need to use three tubes, leave the hole next to the fan empty op:

 

[HiDef]

Why wait? The Pi output section of a tube amp IS a tuner. It tunes the plate impedance of the amp to the impedance of the antenna,whatever that happens to be. Fire it up and keep an eye on grid and plate current and be happy. I rarely use a tuner with my TS-820S with tube finals except for the odd occasion when I am loading into a really weird (low) impedance and you KNOW I do not want to harm that baby. It still has the original factory Japanese S2001A tubes in the finals and they are pushing 30 years old.

That's true but there are limitations. Old rigs like the Johnson Ranger will tune into just about anything but you can actually load up on the second harmonic if you aren't careful.

Modern linears are usually not designed to work into a VSWR over 2:1.

Solution?

No bux?

Build a tuner from junk parts. They are a great project.

 

[26AC148]

Does the Ameritron 811h work okay on the 11 m band ?

 

[n8fgb]

Ameritron offers a HD version. It comes with the 572b's already installed. They beef up the pwr sply. The amp runs better with 572b's than 811's, because it runs cooler.Everybody I have talked to runs 4 of them, not 3.
Rich

 

[airplane1]

Very good Ron. You will love it the more you use it. That amp will last forever running it with low out put. Tune for max then lower driver power for desired amp output.

I am getting 572B tubes for mine and want to upgrade the transformer too.

Hope to hear you on 10 soon.

AP

 

[hookedon6]

Ameritron offers a HD version. It comes with the 572b's already installed. They beef up the pwr sply. The amp runs better with 572b's than 811's, because it runs cooler.Everybody I have talked to runs 4 of them, not 3.
Rich

perhaps they do in the "hd" version, most don't in the "standard" 811h.

i know they offered the amp with the 572's, but didn't know about the ps upgrade too. guess they had do more than just the tube change for the $300 difference

i won't post the link, but there is an article on e-ham (do a search there) with the title: AMERITRON AL811H TUNING written by N6MW on 12 jan 2008. in the article, Tom Ranch (w8ji) makes some comments, IMO no one knows more about an 811/811h than him.

its a long read, but it is worthwhile. i won't paste the entire thing here i'll just paste some of tom's comments here: (bold emphasis is mine)



"Let me weigh in on this since I understand the history of tube failures quite well.

The single dominant failure in the 811 tube is excessive dissipation as a function of time and dissipated power. It is NOT drive, it is virtually never a grid (I've never seen a bad grid in dozens and dozens of bad tubes I've looked at).

The typical failure by far is the anode get heated so hot it actually starts to melt a hole in the anode. At that point materials are liberated from the anode and the tube is poisoned.

Anode damage is always a function of time and anode power dissipation level. Dissipation is somewhat less than Pin/Pout, since not all of the wasted energy is in the anode. That's close enough however.

It's ALWAYS a fuction of time vs heating energy when dissipation is the failure mode. Something has to get hot enough to reach a critical temperature. It isn't drive power, it isn't output power. It's time vs heat.

Long actual transmitting times (when RF is coming out) at high dissipation kills the tubes. It's always time and heating power.

The reasons the manual advises extra heavy loading are linearity and voltage on tank components. Linearity is a non-issue on RTTY and the ALC, after an initial overshoot, has time to catch up. On CW or SSB the ALC can overshoot hundreds of times in a single QSO, and it can cause bandwidth issues as well as stress on tank components if the loading is too light for the overshoot power.

Rigs like the IC706 and FT100 have horrible overshoot. The IC775DSP is another terrible rig, as are some Kenwoods. On the other hand the FT1000D has virtually no overshoot and can be run down to a few watts with no overshoot. An IC775DSP I owned was well over 200W on peaks when I had it set at 50-60 watts carrier. I looked at a rig for Varian that was eating 3CX800A7's up (Ten Tec amp) and found the 3CX800's were being hit with 250 watts at the leading edge of every envelope rise from zero.

This is why the exciter should roughly be sized to match the amplifier, and why lowering drive power often doesn't make things cleaner. It is actually better to run nearly at full output on the radio and use an attenuator pad to reduce drive power in the PA.

Metal oxide cathode tubes are an entirely different animal. The dominant problem in them is grid dissipation and peak cathode emission.

Tube dissipation is always the biggest field problem.

If you remove the four 811's and replace then with three 572B's, there will be virtually no change in SWR or neutralization.

The available dissipation will be more than 2-1/2 times higher, and the thermal lag of a 572B is significantly longer. This results in a significant life increase if you are a bit slow on tuning or run high duty cycle modes at high power.

if you have life problems with tubes that you can't cure with a change in operating methods then the simple solution is to use 3 572's to replace the four 811's, leaving the socket nearest the fan (right rear socket) empty and removing that plate cap.

73 Tom

 

[Sonwatcher]

From Eham-

AL-811HD is listed as four 572Bs

Talked to Mike from Ameritron on this very subject at the Dayton Hamvention Saturday. He said this was the 572 version with a beefed up power supply more for the higher duty cycle users

This is from MFJ site-