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Author Topic: Ameritron AL-811HD  (Read 2684 times)
N3OQD
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Posts: 104




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« on: May 11, 2009, 09:52:35 PM »

Recently saw this newer HD series amp for sale.  I don't see any reviews nor a schematic for this one. MFJ states three things.  "Higher power tank circuit", "grid protection circuit", and 572B tubes instead of the regular 811's.  I am almost cirtian that all the rest of parts in the amp are the same as in the original design.  What I wonder is with the original power supply as the other two models, can the original  transformer keep up with the newer advertised duty cycle expectation (like running a good long AM ragchew)?  My purpose of this is to strike up a colourful conversation about this "new" model.
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WB2WIK
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« Reply #1 on: May 12, 2009, 08:19:22 AM »

Advertised duty cycle?   Where'd you see that?

The Ameritron website lists this model but tells nothing about it (that I could find, anyway)...

The AL-572 was already a product using four 572Bs and listed at 1300W PEP.  The AL-811HD is listed as four 572Bs and 800W PEP, so I'd assume its power supply is smaller and lighter than the AL-572s and it's bascially an AL-811H with 572Bs in it instead.
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KA5N
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Posts: 4380




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« Reply #2 on: May 12, 2009, 08:36:40 AM »

Since the Ameritron web site has "photo comming" and no manual listed it seems unlikely that you can have a "colorful conversation" until more information is avaiable and some of these amps have been shipped.
What little info is listed sounds like the AL-811H has been upgraded as has the price.
Allen
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KI4GOP
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Posts: 5




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« Reply #3 on: May 12, 2009, 08:50:48 AM »

Looks like I got my 811H, Just in the nick of time!
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N8FGB
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Posts: 12




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« Reply #4 on: May 12, 2009, 04:14:43 PM »

It is just an 811H with 572b's. Run an AL572 in the low voltage position, and you have the same thing. Then when you need more punch, flip the switch.
Rich
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VR2AX
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Posts: 963




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« Reply #5 on: May 13, 2009, 05:45:51 AM »

Check the yahoo Ameritron reflector, this question has come up there recently.

Same basic amp, apparently, but with the 572b in place of 811a. As the tubes share a common grid structure (max 50mA grid current/tube), the HD has a protection circuit to prevent overdriving the tubes.

The result seems to be you can't (or should not) drive the HD to higher power output, but if driven correctly the tubes should withstand a higher duty cycle. Presumably this shifts the weakest link to the transformer.
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KD8GEH
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Posts: 620




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« Reply #6 on: May 19, 2009, 12:54:58 PM »

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 (not higher power as noted hefore).

Hope this  helps.
73
Dave KD8GEH
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