Featured: Ameritron AL-811H amplifiers and parts on eBay.
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The Ameritron AL-811H is a well-known tube amplifier for HF. DX Engineering currently lists it as Not Available new, so eBay is where many operators now look for used units, manuals and parts. Searches turn up instruction manuals, replacement 811A tubes and repair and upgrade kits, along with the occasional complete amplifier.
What the AL-811H is
DX Engineering's listing describes the AL-811H as an amplifier with four 811A tubes and 800 W output PEP, covering 160-15 meters, running on 120 Vac with a 10 A maximum and a 5-15P plug. The listing gives output power as 800 watts PEP and 600 watts CW, with 400 plus watts on demanding continuous modes like RTTY, SSTV, FM and AM.
Ameritron's manual says the AL-811H uses four 811A tubes in a class AB2 grounded grid circuit. It lists typical drive for rated output as 65 watts and maximum drive power permissible as 85 watts, with a no load voltage of 1700V and a full load voltage of 1500V. The listing also points out that Ameritron mounts the 811A tubes vertically, not horizontally, to prevent hot tube elements from sagging and shorting out.
Buying a used one
- Get the manual. If a used amplifier doesn't come with one, a manual is worth buying before you power anything up.
- Ask about the tubes. Find out whether the 811A tubes are original or replacements, and how the amplifier has been used.
- Ask about the power supply. Aging filter capacitors are a common restoration item in any older tube amplifier, and power supply rebuild kits for this model have been listed on eBay.
- Plan for shipping risk. Tube amplifiers are heavy and fragile in transit, so check how the seller will pack it and what happens if it arrives damaged.
Drive level
Drive matters with this amplifier. Many transceivers can put out 100 watts, and Ameritron's manual says that under most conditions destructive levels of drive power are those above 100 watts, with 85 watts as the maximum permissible. Turn the exciter down and set drive carefully rather than running the radio flat out.
High voltage
Ameritron's manual warns: never remove the cover of this amplifier with the unit plugged into the power line. Power supply filter capacitors can hold a lethal charge, so unplug the amplifier and confirm the capacitors are discharged before working inside it. If you are not experienced with high-voltage equipment, have a qualified person do the work.
The manual lists the RF output as SO-239, 50 ohms, with full power into any SWR below 3:1. Even so, tune into a good dummy load first and keep the antenna match reasonable.
And the usual reminder: external linear amplifiers are not legal for use on CB radio. The AL-811H covers the amateur bands and belongs in a licensed amateur station.
Where to get it
Browse current listings: Ameritron AL-811H amplifiers and parts on eBay.
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