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Author Topic: Ameritron 811H tuning, again, (Sorry)  (Read 2092 times)
W9KDX
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Posts: 770




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« on: March 02, 2013, 04:43:13 PM »

Hopefully a quick question, at least I am learning as I get older.

When looking at Tom's 811 tuning supplement there are two things in the difference between pulsar and CW key tuning I question.

The Pulsar method says set the transceiver for 80 watts.  The CW method says 60 watts.

Both methods say "In operation or tuning, never exceed or go above the following chart currents:

For the 811H it is 750mA and 200mA.

I use a pulse tuner and when I get to 65 watts, I am at the 750mA setting, which I obviously cannot see with the pulsar.  I do a quick key down reading to see where I am.  I know a lot of people tune at higher than 65 watts and many just go right to 100 watts.  I prefer not to peg the meters, especially since Tom says not to, so here is my question.

Is there any downside to tuning with a pulsar at 65 watts and then reducing to the input I want?  I would guess not as I am close to the power input for the CW method and we are both shooting for the same settings.  I have also read that the input network of the AL-811H has a tunable coil (with no instructions) so it would not be surprising if different users find different drive level are needed so 65 watts might be right for my amp.

Thanks
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Sam
W9KDX
N3QE
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Posts: 2159




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« Reply #1 on: March 02, 2013, 08:23:03 PM »

I too am a little confused at W8JI's recommendation to start tuning at 80W.

I do both CW and RTTY with my amp. Maybe there's something magical about "80W" with SSB users, after all they care about "PEP" ratings, and me being a CW and RTTY guy, I am looking at rated key-down output.

If I'm tuning without a good starting point I always start low (like 20W exciter output) and then after I get a decent match there, I go up to final exciter power (most often 40 to 50W ballpark) and I do some final tweaking.

There's very very little different knob settings between the peak I got at low power and the peak I got at 50W exciter output.

I can't think of ever running my exciter at 80W with this amp, that seems like too much drive. Confused why anyone would ever run 100W to this amp. I don't think the 811A's are as fragile as say the 8877's in terms of immediately dying upon getting too much drive, but it still can't be good to put 100W into an 811A type amp.
« Last Edit: March 02, 2013, 08:52:34 PM by N3QE » Logged
K4RVN
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Posts: 761




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« Reply #2 on: March 02, 2013, 08:47:51 PM »

Sam,
I subscribe to the method used by N3QE. I tune using the presets on my AL 811 three tube and AL 80A with about 20 watts and then run the drive
up to around 65 watts depending on the band. Some take more drive than others. I have 6 bands to use with a 5 band hex and a 40 meter antenna.
I use the watt meter to load not worrying about the meters on the amp unless they pin indicating something is wrong. I am very quick on tuning.
You are right about the tuned inputs on your amp. I have tweaked mine to favor 17 over 15, and 12 over 10 meters. Adjusted  for lowest swr on other bands with max output using very low drive. 55 to 80 watts is my normal final drive power to these amps and well within the manual instructions. I also use the CW position only to tune, then operate SSB only so keep that in mind before considering my comments. I do check the meters after final tune and on SSB they are way below the max milli amps usually less than half of tune up.

Frank
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W8JX
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Posts: 5657




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« Reply #3 on: March 02, 2013, 08:55:11 PM »

I too do not buy into this max drive on initial tune up. Never saw value of a pulse tuner either. If you need on it is because you are exceeding tubes ratings (which is easy to do on a AL811 amp trying to make rated output) A properly rated amp does not need pulser to survive tune up.  Also the max ICAS rating for 4ea 811's is 700ma not 750.
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W1QJ
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Posts: 1444




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« Reply #4 on: March 03, 2013, 04:54:56 AM »

I too do not buy into this max drive on initial tune up. Never saw value of a pulse tuner either. If you need on it is because you are exceeding tubes ratings (which is easy to do on a AL811 amp trying to make rated output) A properly rated amp does not need pulser to survive tune up.  Also the max ICAS rating for 4ea 811's is 700ma not 750.

One must remember  that tube ratings are for 24/7 key down service (CCS).  Ameritron bumps the rating because of the ICAS service.  It is not unusal to see this providing the cooling needed is available.  The AL-80B stretches the plate current about 100ma.  It handles it in SSB operation.
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W9KDX
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Posts: 770




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« Reply #5 on: March 03, 2013, 06:53:31 AM »

I too do not buy into this max drive on initial tune up. Never saw value of a pulse tuner either. If you need on it is because you are exceeding tubes ratings (which is easy to do on a AL811 amp trying to make rated output) A properly rated amp does not need pulsar to survive tune up.  Also the max ICAS rating for 4ea 811's is 700ma not 750.

I don't use the pulsar because I exceed the tube ratings at tune up.  I use it because it is less stressful on the tubes than a flat out key down and because I can tune now in less than 5 seconds.

At least I am not the only one who wonders about this question.

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Sam
W9KDX
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