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Ameritron 811h

552fl

Active Member
Mar 29, 2018
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One of my neighbors purchase a ameritron 811h three or four months ago from DX engineering.. has become very ill and needs to sell it as not used to it no more than 10 hours he says.. says he paid 1100 for it .. said he would sell it to me for $700 does that sound like a fair price?like I really need another amplifier since I've got the black cat jb150 fixed and mako 75 pumpkin face Fixed and the thunderbolt 305 wolf has refurbished all of them for me and they work excellent.. but I am a amplifier hoarder slash collector I guess..
 

The current price from DXE is $1199.95.
$1149.95 from Gigga parts
..... both plus taxes


$700 is a "fair" price, considering the low hours.
You can find them for about $50 less on most forums, but, you KNOW ther seller and the amp history

does it have the 811a or the 572b tubes?

I would expect to see 811a's in it. that's the ones MFJ puts in them.

No need to ask about the green wire, it's a simple snip
He should also have some sort of cable to key the amp, it is not RF keyed like most CB sweep tube amps are.

What are you intending to use for a driver?
 
The green wire has already been snipped.. I am using a Galaxy DX 2517 with a Texas Star modulator v plus with variable guess I will have to use a foot pedal until I can get it to Wolf for him to install a relay to key it up.. like he installed into my sb-220... I thought that was a pretty fair price it does have the 811 tubes in it though
 
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...edit... until I can get it to Wolf for him to install a relay to key it up.. like he installed into my sb-220..

The SB 220 has "about" 235 VDC on the keying circuit.
He must have put in a transformer somewhere, to get it lower to where your radio wouldn't let the magic smoke out. and then a relay to ground it for keying the amp.


the AL811H already has 12 VDC relay installed.
 
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He did not tell me what he installed but he's been doing it for a long long time check out his or website when he was down in fort Lauderdale wolf radio.com I'm glad he moved up here 30 minutes from me in the middle of the state. He installed a standby switch to in it for me.. so what would I need to key up the Galaxy 2517?
 
Maybe some numbers on the dial of the Tune and load that's close to 11 to get me started to if anyone knows
 
The SB 220 has "about" 235 VDC on the keying circuit.
He must have put in a transformer somewhere, to get it lower to where your radio wouldn't let the magic smoke out. and then a relay to ground it for keying the amp.


the AL811H already has 12 VDC relay installed.

The SB-220 has an antenna keying voltage of about 120 vdc give or take a few volts, but it is nowhere near 235v. The best "interface" to use to lower that keying voltage is a solid state circuit using a MOSFET to key the high voltage and the keying voltage then becomes just that required by a small 2N222 transistor, which any radio can handle. Not many HAM amps perform very well on 10/11 meters to begin with and if you are a CBer only, the way to go is to have a vintage type amp like an SB-220,SB-200, Clipperton L, AL-811H or any amp you could afford and have it modified for "CB ONLY". When that is done it will just about 50-100% better than it did as a multi-band amp.
 
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235 vdc, 120vdc,..... really isn't the point.

It was clear to me that the OP didn't understand the amp keying circuit and what is required to key the amp using a CB radio.

in fact, in post #5 he still has it (kinda) backwards " so what would I need to key up the Galaxy 2517?"

I just didn't want him to wire it incorrectly and to realize that this is not a 12 vdc CB amp and that there are lethal voltages in the 811H.

When he said " I will have to use a foot pedal until I can get it to Wolf for him to install a relay to key it up." , the bells and alarms went off.
 
I don't know why more people don't take that approach and put a relay in their radio. I offered to do this for a guy that was complaining about his ssb delay and had issues with amp relays failing. He wasn't interested.

The export manufacturers should incorporate this feature into their radios. Every other "ham radio" has one.

Some mics have unused contacts on the ptt switch. They could be put to good use and trigger a relay that can key the amp.
 
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The current price from DXE is $1199.95.
$1149.95 from Gigga parts
..... both plus taxes


$700 is a "fair" price, considering the low hours.
You can find them for about $50 less on most forums, but, you KNOW ther seller and the amp history

does it have the 811a or the 572b tubes?

I would expect to see 811a's in it. that's the ones MFJ puts in them.

No need to ask about the green wire, it's a simple snip
He should also have some sort of cable to key the amp, it is not RF keyed like most CB sweep tube amps are.

What are you intending to use for a driver?

I wasted my money on a set of 572B tubes for my 811H several years ago & was very disappointed in the time that they lasted which was about half the time of a set of New 811A's.The only thing I noticed when using the 572B tubes was that the amp seemed to run cooler with them in.Output no different but the 572B tubes cost me as much as two sets of 811A's.Live & learn & I know others who made the same error but like me went back to the 811A tubes when the 572B's went flat.

SIX-SHOOTER
 
I wasted my money on a set of 572B tubes for my 811H several years ago & was very disappointed in the time that they lasted which was about half the time of a set of New 811A's.The only thing I noticed when using the 572B tubes was that the amp seemed to run cooler with them in.Output no different but the 572B tubes cost me as much as two sets of 811A's.Live & learn & I know others who made the same error but like me went back to the 811A tubes when the 572B's went flat.

SIX-SHOOTER
How did you flatten out 572b tubes in an 811h? Something wrong there.
 
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How did you flatten out 572b tubes in an 811h? Something wrong there.

Powering it from a 120-Volt outlet with excessive voltage sag under load.

So long as your 120-Volt outlet is no more than 8 or 10 feet from the breaker box, wired with number 12 wire you're probably okay. Any farther than that, or if the outlet is fed with #14 wire and you'll get voltage sag under load. The biggest wire it's legal to use for a 120-Volt outlet is number 12.

This reduces the temperature of the filament wires. Unless the temperature is maintained properly, the chemistry on the surface of the tungsten cathode wires is disrupted, and the emission will suffer. The tube just gets "weak".

Most famous example of this was the old Black Cat JB2000. Too many folks would run it from 120 Volts, because it was all they had available. In six months or less the RF power would fall to about half what it was to start. The cathodes in the 3-500Z tube are made from the same thoriated-tungsten alloy as the 811A and 572B. Same hazard from running them with low filament voltage.

Simple way to check for this hazard is to peer inside so you can see the yellow-white light from the filaments. The color of a piece of hot metal tells you its temperature.

If you see the color of that filament light change when you transmit at full power, that's a bad sign. Tells you the temperature of the filaments is falling because of power-line voltage drop. How soon that temperature drop under load will weaken the tubes' emission is hard to predict, but seeing that temperature drop is a bad sign no matter what.

Using a 240-Volt source improves the picture two ways. The current draw is half what it was on 120. This reduces the voltage drop in half, even if the wires in the wall are the same size and length as the 120-Volt outlet used.

The second advantage has to do with the filament transformer's step-down ratio. The filament voltage will fall only half as much per Volt of power-line sag, since it's being stepped down by a factor twice what it was at 120 Volts.

I call this one-two punch the "double whammy". All other things being equal, the filament voltage will sag by four times as much running from 120 Volts as it would running from 240 Volts.

But that's my educated guess.

73
 

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