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Author Topic: AL-811(not an h) a good amp?  (Read 7494 times)
KA0NEB
Member

Posts: 1




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« on: August 29, 2015, 01:12:51 PM »

Hi Guys,

A local operator has an Ameritron AL-811, 600 watt three tube amp for sale.  It's two years old and am told the tubes are good, but I would need to see it run before buying.

Doing some research I see a lot of mentions of this amp, but it seems the discussion always turns into a discussion of the AL-811h and why it's different...I get it, it has four tubes, a neutralization circuit, etc. and if I were buying new I would opt for the h model.

I'm not buying new though, and the three tube model is what's available to me locally (so I can see it run and don't have any expensive shipping costs), so my question is - is this amp worth considering, or should I look for an h model?

My station is a Kenwood TS-590SG, an MFJ-993b autotuner, but I understand it won't handle the 811 - I also have a Dentron Super Tuner manual tuner, and it's tied to a ladder line fed 80 meter skywire horizontal loop antanna.

Any thoughts, comments, hints, tips, etc. would be much appreciated!

73s,

Steve, KA0NEB
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WB2EOD
Member

Posts: 264




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« Reply #1 on: August 29, 2015, 06:12:14 PM »

In terms of cost per watt, the 811 based amplifiers are probably the best bang for the buck in ham radio.  I own the 4 tube version.  I strongly suggest that you buy the 4 tube version.  That way you can get the same 600 watts without taxing anything to heavily.  My late father-in-law would advise me to buy the next model up from what you want.  If you buy cheap, you may regret it later.  If you buy better, you will never regret it.  If you can resist the temptation and you have a few extra dollars pass it up and look for the 4 tube 811H

73
WB2EOD
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K0ZN
Member

Posts: 1862




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« Reply #2 on: August 29, 2015, 07:02:16 PM »

I own an AL-811 (3 tube) which I bought as kind of a back up to my main legal limit amp. (I didn't want to fire up and put filament time on a pair of expensive 4CX800A7's to chat with someone 500 miles away.) The amp has some strong good and bad points. MAKE the time and effort to read the Product Reviews here on eHam about this amp. I have posted my experiences in detail; first after initially purchasing it and later on as a follow up.  Very short version: I had several component failures, mostly tubes, up front, but once sorted out, it has been quite reliable....but I make a strong effort to treat the tubes "kindly".

You need to understand what you are buying!  Contrary to what the MFJ ads say, the 811A tube is not "tough"... it is actually a pretty fragile tube that absolutely will not withstand abuse and particularly MIS-TUNING. The grid wires in that tube are tiny and fragile; excess grid current can kill the tube(s) quickly. Further, current production Chinese tubes are not as heavy duty as the old American tubes back in the day. You need to know the how and why of tuning up that amp or you will go through tubes in short order....and maybe some other components too. Operated properly and kept within the specifications for the 811A tube, the 811 series amps are decent. As far as watts for the dollar, it is hard to beat. (An RF watt is an RF watt, regardless of the price of the amplifier generating it!!) 811A tubes are cheap, fortunately, and it is an easy amp to work on if you are technically inclined. It is primarily intended for SSB use (e.g. low duty cycle). If you plan to operate CW or RTTY or other "continuous" modes, you must derate it significantly to keep the tubes inside their specs. Understand, particularly the 3 tube version was designed to be as inexpensive as possible to hit a price point....you are not buying heavy duty or "do everything"! That said, they can be quite reliable, especially in SSB service. MOST of 811A amps that fail are killed by operators!....usually during tune up. The good side is you can easily get them serviced by MFJ or other facilities.

Bottomline:  I am "happy" (while accepting its limitations and short comings) with my AL-811. Since the initial bugs have been sorted out, it has been reliable. Would I buy another one?...  NO.   (I would go to the AL-80 series amps). That said, the jump from 100 watts to about the 500 watt area seems to give improved results out of proportion to what you would expect. I find I can work 90% of the DX I hear (on CW) with the 400 watts from the AL-811 vs. the big amp. The bang for the buck jump from 100 to 500 is significant.

STRONG recommendation:  if you are not technically familiar with tube type amplifiers, regardless of what amp you get:  Take the time to go to W8JI.com and read EVERYTHING about tube amps and particularly about tune up procedures. The time and effort you spend to learn about tubes and tube amps on Tom's website will likely save you a lot of grief and probably money. Tube amps are not difficult, but they also are not plug and play consumer electronics. HEED the warnings in the Owner's Manual about keeping tune up key down time SHORT and grid currents within limits.

73,  K0ZN
« Last Edit: August 29, 2015, 07:09:16 PM by K0ZN » Logged
K4JK
Member

Posts: 456




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« Reply #3 on: August 30, 2015, 07:23:56 AM »

I also have a 3 bottle 811. I use it when chasing DX on 40 and 80 CW mostly. If you can get a good deal on a well-taken-care-of one locally, then by all means go for it.

It's a fine amp for what it is... "bang for the buck" at a certain price point. Like ZN said READ the tune-up procedure and always adhere to it.

Keep a copy of this near the amp: http://www.w8ji.com/al811h_and_811_tuning_supplement.htm  (use these instructions to tune the amp)

I taped a small piece of paper on the front of the amp with the max grid and plate currents, just to make it harder to forget them.

Most 811 failures are due to lack of heat dissipation on the anode... Usually caused by poor tune-up procedure or overdriving the amp.

Remember the 5 second key/15 second cool down procedure when tuning and the tubes should last if they are good tubes to begin with.



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ex W4HFK
K4RVN
Member

Posts: 261




Ignore
« Reply #4 on: September 02, 2015, 08:14:13 PM »

I agree with the previous post after owning one for three years no problems. I knew how to tune it after owning several tube amps. I used a watt meter to tune it and the presets in the manual as a starting point. It is a great little amp for the buck and I preferred it over the H model with 4 tubes. I did not use the exact tuning method in the manual and the grid and plate currents were always well below max. Start with about 20 watts drive and the presets for plate and load tune for max power out using watt meter. the turn drive up to about 50 watts and retune for max out. Don't run over  450 watts or even less until you can quickly tune the amp. I now have the AL 80 B and AL 80A amps for more power. Since W8JI designed the AL811 and others I would endorse the suggestion to read and follow his instructions over any ones including mine, mine works for me and that's how I have always tuned my amps. If you use modes other than SSB, You need to take extra care not to over drive the amp.
« Last Edit: September 02, 2015, 08:16:33 PM by K4RVN » Logged
AD5ZC
Member

Posts: 78




Ignore
« Reply #5 on: September 03, 2015, 02:54:55 PM »

I own an AL-811 (3 tube) which I bought as kind of a back up to my main legal limit amp. (I didn't want to fire up and put filament time on a pair of expensive 4CX800A7's to chat with someone 500 miles away.) The amp has some strong good and bad points. MAKE the time and effort to read the Product Reviews here on eHam about this amp. I have posted my experiences in detail; first after initially purchasing it and later on as a follow up.  Very short version: I had several component failures, mostly tubes, up front, but once sorted out, it has been quite reliable....but I make a strong effort to treat the tubes "kindly".

You need to understand what you are buying!  Contrary to what the MFJ ads say, the 811A tube is not "tough"... it is actually a pretty fragile tube that absolutely will not withstand abuse and particularly MIS-TUNING. The grid wires in that tube are tiny and fragile; excess grid current can kill the tube(s) quickly. Further, current production Chinese tubes are not as heavy duty as the old American tubes back in the day. You need to know the how and why of tuning up that amp or you will go through tubes in short order....and maybe some other components too. Operated properly and kept within the specifications for the 811A tube, the 811 series amps are decent. As far as watts for the dollar, it is hard to beat. (An RF watt is an RF watt, regardless of the price of the amplifier generating it!!) 811A tubes are cheap, fortunately, and it is an easy amp to work on if you are technically inclined. It is primarily intended for SSB use (e.g. low duty cycle). If you plan to operate CW or RTTY or other "continuous" modes, you must derate it significantly to keep the tubes inside their specs. Understand, particularly the 3 tube version was designed to be as inexpensive as possible to hit a price point....you are not buying heavy duty or "do everything"! That said, they can be quite reliable, especially in SSB service. MOST of 811A amps that fail are killed by operators!....usually during tune up. The good side is you can easily get them serviced by MFJ or other facilities.

Bottomline:  I am "happy" (while accepting its limitations and short comings) with my AL-811. Since the initial bugs have been sorted out, it has been reliable. Would I buy another one?...  NO.   (I would go to the AL-80 series amps). That said, the jump from 100 watts to about the 500 watt area seems to give improved results out of proportion to what you would expect. I find I can work 90% of the DX I hear (on CW) with the 400 watts from the AL-811 vs. the big amp. The bang for the buck jump from 100 to 500 is significant.

STRONG recommendation:  if you are not technically familiar with tube type amplifiers, regardless of what amp you get:  Take the time to go to W8JI.com and read EVERYTHING about tube amps and particularly about tune up procedures. The time and effort you spend to learn about tubes and tube amps on Tom's website will likely save you a lot of grief and probably money. Tube amps are not difficult, but they also are not plug and play consumer electronics. HEED the warnings in the Owner's Manual about keeping tune up key down time SHORT and grid currents within limits.

73,  K0ZN
You can close the thread now
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ZL3NB
Member

Posts: 7




Ignore
« Reply #6 on: September 07, 2015, 01:45:08 AM »

Been using a AL811 (brought new) since December 2004. Apart from issues with 811A Tubes the amp has performed well. Being a CW op and the fact its 100 percent duty cycle on that mode the 811A's never held up well but since replacing them with the more heavy duty 572B' back in 2008 the amp is very reliable running 500 watts (CW) and 650W (SSB) with ease. Can push it up to over 700 watts but what's the point.
You need to be able to tune the amp properly. Yes they are somewhat forgiving at times but one needs a RF Watt Meter to assist in properly tuning it as stated in the manual and do not just rely on the manual settings like some I know have....Your asking for trouble.  Wink
Have thought about upgrading to something newer but when one takes into account the cost of a fancy amp at many thousands of dollars and  their actual operating requirements  this Amp is the best bang for buck around. (my opinion of course).  Smiley
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KB6HRT
Member

Posts: 327




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« Reply #7 on: September 16, 2015, 05:59:17 PM »

Went back and read my review wrote in 2002 of the  AL-811 I used, rated it a 5 never had a problem with the amplifier, I don't know why but it alway putout 800-900 watts, It was not the only 811 doing that well.  I used the AL 811 only for 75m on 3942.5 everyday till Feb 2007,  traded it for a PW1 with a lot of cash! did have to replace the tubes once, after replacing the tubes has the same power output, when I brought the AL811 it always put out 800+ watts for 75m lots less for  40-10m, I tuned the amp only twice for 75m,  tuned 40-10m once for checkout then back to 75m for the rest of its life on 75m If the newer tubes hold up like the one's used then. Would say its a very good amplifier, mine was!.........73s........kb6hrt
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W8JX
Member

Posts: 13268




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« Reply #8 on: September 17, 2015, 05:04:16 AM »

when I brought the AL811 it always put out 800+ watts for 75m

I suspect your watt meter. Whenever you exceed about 600 watts on a AL811H you exceed tube ratings. Real amps and tubes have continuous plate dissipation ratings equal to at least 1/2 of rated output or more. This amp only has 180 watts of continuous safe dissipation.  Simple math. This is why there are tmps with 3-500z's, 8877's 3cx800's and even 572's because they can handle higher dissipation without playing Russian Roulette with tubes. 
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--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..
WB2WIK
Member

Posts: 21837




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« Reply #9 on: September 17, 2015, 10:38:12 AM »

when I brought the AL811 it always put out 800+ watts for 75m

Wattmeter error, possibly due to elevated SWR.

Remember nearly all wattmeters only indicate forward power accurately when SWR = 1.0:1.  When reflected power increases, so does the forward power indication, so the P(ref) must be subtracted from P(fwd) readings to arrive at a more accurate and meaningful reading of forward power.
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N9AOP
Member

Posts: 1173




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« Reply #10 on: September 17, 2015, 01:00:07 PM »

I had an 811H for 10 years as a second amp before I sold it.  I never had any trouble with it and used it on SSB every day but never pushed it over 500 or 600.  The ratings that MFJ gives on some of their amps is pedal-to-the-metal.  If you can buy the 3 tube amp for a good price and operate it conservatively, it should be problem free.  If I were doing it over buying a starter amp,  I would look for an 80B.
Art
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