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Ameritron AL811

Discussion in 'Amplifiers' started by okie, Nov 3, 2019.

  1. okie

    okie Member

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    I just bought a Ameritron AL811 on eBay. I realize this will not work 11 meters but wanted one of these as I plan on taking my Ham test at some time in the future.

    What dk and swing is needed to drive this? My base is a rci2995dxcf.

    Is the conversion as simple as snipping the green wire?



    And lastly, what am I going to need to key this with my rci?

    Thanks
     

  2. Dmans

    Dmans Sr. Member

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    Okie,
    See the .pdf attachment below.

    There are plenty of YouTube videos on this conversion. There is a green wire grounding the 10 meter coil. Removing this green wire either by "snipping" or de-soldering it will make the amplifier 10 meter capable. As for 11 meters-some tuning may be required. Your mileage may vary.

    Try one of these. You may have to change the plug on the end to match the amplifier?

    https://www.mfjenterprises.com/Product.php?productid=MFJ-1709

    73
    David
     

    Attached Files:

    okie likes this.
  3. 543_Dallas

    543_Dallas Sr. Member

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    The guy that designed some of the ameritron amps recommends no more than 15 watts carrier and 60 pep output per tube for AM service. For a 3 tube 811 that's 45 watts deadkey out of the amp and 180 pep out. Use your watt meter to figure out how much drive it needs to make this power. These amps are better suited for ssb. You can drive it as hard as you like and get a lot more power. If you do I recommend buying plenty of extra tubes.

    https://www.w8ji.com/am_linear_amplifiers.htm

    All you need to do to use it on 11m is remove the green wire hanging off of the band switch. Also know that the efficiency of most ameritrons is lower on 10 thru 12 meters. Don't try to beat the rated output out of it on 11m.

    To key it you need an rca cable to plug into the relay connector on the back. when the two conductors of the rca cable are shorted together the amp keys. you can do this with a foot switch or any other switch. You can also install a relay on your radio that will engage when you key the mic and use that to key the amp.
     
  4. okie

    okie Member

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    Received the amp today. Nothing seems broken but the tubes were unplugged. I plugged them back into what seems the obvious spot.

    Just wanting to make sure everything looks right to more educated eyes before I power it up.

    I snipped the green wire that is accessed through the panel on the back.
     

    Attached Files:

    357magnum likes this.
  5. 2NC995

    2NC995 WDX995 / DAN

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    Those numbers are not terribly exciting.
     
  6. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Perhaps no but 811A's going supernova is.
     
  7. 2NC995

    2NC995 WDX995 / DAN

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    Shouldn't be hard to see with a radio that does as much as the amp.
     
  8. 543_Dallas

    543_Dallas Sr. Member

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    No, the truth is disappointing. It takes a lot of plate dissipation and a hefty plate transformer to make a good, reliable linear amp for AM use.
     
    357magnum and AudioShockwav like this.
  9. AudioShockwav

    AudioShockwav Extraterrestrial Admin
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    AM is brutal on 811A tubes.
    Most of these amps were built with SSB in mind.
    And the 811 is a entry level amp.
    AND
    The output is even lower on 10 meters.
    Better look for a steel tube if you want a maul.
    73
    Jeff
     
    357magnum likes this.
  10. Ranch55

    Ranch55 Well-Known Member

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    Get the operating manual.
    You can download from the Ameritron website.
     
  11. blasphemy000

    blasphemy000 Active Member

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    I could be wrong here, but it appears that the safety switch that prevents operation with the lid removed is disconnected.
     
  12. Shockwave

    Shockwave Sr. Member

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    AM reliability improves with the use of 572B tubes.
     
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  13. 543_Dallas

    543_Dallas Sr. Member

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    I'd sell the thing to a ssb guy. A 3-500z is the smallest tube I would run on am. Let someone else waste money on replacement tubes.

    If you upgrade to the 572b (they don't suck as bad) you need to understand that the amp will not produce much more power. The 811s run at lower plate voltage and you will not get full power from the 572's. At the end of the day you could have gotten the same AM performance from a Texas Star 500.
     
  14. kopcicle

    kopcicle Sr. Member

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    Really? Do tell...
     
  15. 543_Dallas

    543_Dallas Sr. Member

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    I don't think I'll be able to help you understand but will try. The 4 2878s will have a higher duty cycle than the 3 811s. The 2879s are more reliable even if you abuse them.

    Why spend the money on an al811then buy some 572b's to have a 200 to 300 pep on AM? If the 2879s are ran at 60 pep for low imd (see spec sheet) you have 60 watts carrier and 240 pep.

    Filtering you say? Those are available at reasonable prices.
     
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