Manager


Manager - NA4M
Manager Notes

Reviews For: Ameritron AL-811H

Category: Amplifiers: RF Power - HF & HF+6M

eMail Subscription

Registered users are allowed to subscribe to specific review topics and receive eMail notifications when new reviews are posted.
Review Summary For : Ameritron AL-811H
Reviews: 187MSRP: 899
Description:
160-10 meter RF Amplifier. 4 811A tubes
Product is in production
More Info: http://www.ameritron.com/Product.php?productid=AL-811H
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
24.51874.5
VK2ANS Rating: 2013-06-29
Needs work! Time Owned: more than 12 months.
My AL-811H amplifier was quite susceptible to self-oscillation - especially up on 10m - even though this model has RF negative feedback fitted. After much experimentation, I found I had to unwind all four plate parasitic suppression coils by one turn each and insert a 100 ohm 3W non-inductive resistor inside each coil in order to stabilise this amplifier. I made sure each coil was air-wound (not close-wound) around each resistor. Next, I removed the 2 wire links from the 10m PA coil and the bandswitch, replacing them with a 10mm wide thin silver plated copper strap from the 10m coil tapping to the bandswitch. This resulted in about 50W more carrier output (50W drive) and smoother tuning. I then moved the 20m/30m tapping further down and onto the top of the PA coil, effectively adding 1/2 a turn. This improved 30m band output at no expense to 20m band output. The 80m tapping did not need altering. I then checked and retuned some of the input coils. My excellent Coaxial Dynamics 83000-A true peak reading RF wattmeter indicates around 1kW SSB output on most bands with 100W of drive. These amplifiers should never be continually driven that hard, of course. I find it's best to start tuning up this kind of "low plate dissipation" glass tube amplifier with only 5W of drive. The best drive level for testing and experimenting is 50W. My spectrum analyser shows its spectral purity is reasonable (at best), being around -20dB for the 2nd and 3rd harmonics - but it's a heck of a lot more stable now!! Ameritron really should upgrade these amplifiers by fitting a new bandswitch with individual WARC bands selection, better quality HT supply resistors and electrolytic capacitors. A bigger mains transformer would certainly help - especially with the AL-811HD 572B 4-tube version.
RA2FN Rating: 2013-03-27
This is a good device! Time Owned: more than 12 months.
This amplifier is already used 4y. For this time he much worked in field conditions. Has Proved;proven to be itself reliable device, nor reek did not conk. Not very heavy. It Is Intended and undemanding in usages. The Price wholly acceptable.
I am a dialect yes this amplifier!
WH7DX Rating: 2013-02-05
Happy User Time Owned: more than 12 months.
After a year of use, I'm still satisfied with the 811H. Pushing 75w from my Kenwood 570, into a hexbeam and dipoles, I'm getting 600-700w and solid signal reports and audio reports. I prefer to use about 75% output for a clearer signal it appears.

I give it a 4 versus a 5 because of the click on TX but that's not a big deal for me.

For about $900 it's certainly worth the price. I just can't see spending $1000-2000 more for a couple S units.. if that.

Like everyone else, post the best load and plate settings for band right on the amp and tuning isn't a big deal.. I kinda enjoy it.

73
WH7DX

N4WRE Rating: 2012-12-27
All you need Time Owned: more than 12 months.
I have had my 811H several years now, bought it used and have no complaints. It is really all the amp anyone should ever need. Cheap tubes, plugs in any 110 outlet, and just plays. On the air I bet you can't tell any difference between the 811 and my 1500 or 1200. I would like to have another one or two. Hard to beat for the money..

Marty N4WRE
K1EHZ Rating: 2012-09-29
Excellent Value Time Owned: 3 to 6 months.
This is my first power amplifier after several years of 100watt transceiver operations and some QRP. My operating position is compact so among the considerations for getting an amplifier was power requirement, size, and placement. I decided to re-configure some shelves and squeeze the amp onto the table next to the ICOM-736 that drives it. I bought the 811H used, in fine shape and wired for 120v. After reading the helpful articles by W8JI, I also bought a matched set of un-installed Taylor 572B tubes from another ham. After trying out the amp to be sure it survived shipping, I performed the grid grounding mod recommended by W8JI and added the gas clamp tubes, now available from Ameritron, on each side of the filament circuit. I re-assembled the amp and installed the 572Bs. The amp has worked very well. The ICOM 736 and the 8llH are doing fine on a single 15amp circuit along with a few small accessories. The 811H is forgiving when I forget to change the band switch or inflict some other insult on it. Power out is normal across all bands, though on 10m I need to increase the drive. I usually drive with 65 to 70 watts and get 700 to 800 watts out. 10m needs a little more drive so I may tweak the adjustable coil for that band. I receive good audio reports and the additional power is very helpful in DX pile ups. Anyone contemplating an 811 series amplifier should review the pertinent material on the W8JI web site (he designed them) at http://www.w8ji.com/Amplifiers.htm. I should mention that I upgraded all of my coax jumpers and runs to the antennas to RG-8U type, although some say short runs of lighter coax should work. The 811H is a great value and I am very pleased with the results.
K5BJM Rating: 2012-06-02
Good Amp Time Owned: 6 to 12 months.
I bought mine used with new china 811 tubes in it. It worked fine but I know that the 572b tubes are much tuffer so I went ahead and bought 4 matched RF Parts Taylor tubes and installed them with no problems. The amp is easy to tune, gives me 800 to 900 watts out with 70 watts in on all bands. With these tubes I think this Amp is one of the best values for the money of ANY AMP made today. I recomend the amp even if you dont replace the 811A tubes with 572B tubes. The 811A tubes will work fine with same output.
K4BN Rating: 2012-05-14
Nice Little Amp Time Owned: more than 12 months.
I drive it with 65 watts out of a TS-590 with no problems. I've had a couple of questions and Ameritron's tech support (so far) has been excellent. I think it's the best amp for the money right now.
W1LC Rating: 2012-05-03
Nice Amp for the money! Time Owned: more than 12 months.
I thought I had already posted a review on this great little MF/HF AL-811H Amplifier, but apparently it was just a contribution to a forum on circuit/cooling improvements for this model. Well, I bought mine new from KJI Electronics (NJ-based ham dealer) for $760 at the ARRL Convention/Flea Market in Boxboro, Massachusetts in August 2006 (Serial No. 21219). It came with the usual four 811A Glass Tubes, and other than some minor "clean up" I did of the internal wiring harness (I found a portion of same lying in close proximity to the Plate or Loading Capacitor, which I just thought to be very poor practice/bad QC and a problem waiting to happen), it performed reasonably well on all Bands from 160-10m with peak outputs of between 650-820 Watts. I did tweak some of the tuned input slug adjustments to obtain either a better match in the band of interest, or to better balance the match on Bandswitch positions where Two (2) separate ham bands are covered (i.e., 20/30 and 15/17). In the former position, I simply set it to favor 20 Meters as I don't operate 30 at all. Being a frequent AMer, I noticed the 811A tubes were clearly breaking a sweat and burning off their nomenclature printed on the glass envelope with keydown AM at even just a 175-200 Watt carrier output level. So it wasn't long before I splurged on a matched-quad set of Svetlana 572B tubes from RF Parts. At the time, they cost almost $250, including freight to my qth. Two of the four tubes exhibited some "new tube" instability, arcing over inside and blowing the hell out of their associated grid resistors (47 or 51 Ohms from memory). It sounds like a gun going off when they "pop". It took two of those tubes a few more pops to stabilize and they would usually blow the OEM grid resistors. One tube was especially stubborn and took a few weeks to FINALLY calm down, and I got tired of taking the amp apart and replacing the grid resistor, so I sized-up to a Mouser MOF axial resistor rated for maybe 2 watts which took the temporary, occasional arcing pulse inside the tube without needlessly blowing a cheap carbon grid-bias resistor. It has been very stable now for over five (5) years, and the Svetlana 572B tubes have served me well on both AM and SSB. [Please note that when an 811A or 572B arcs internally and causes a grid resistor to blow, the tube will be "cut off" and this changes input impedance causing a change in SWR, i.e. Higher SWR!] The Svetlanas loaf in this Amp anyway with the lower plate voltage. They are rated at up to 2,750 Volts on the plate. I also rewired the power transformer for 240 Vac and that improved line regulation a little. For cooling, replacing that el cheapo low-flow Mishina fan with an EBM-Pabst 8500DP from Mouser (for under $40) was another easy improvement, to improve pressurized cooling within. I love this amp, no cross needles, just two easy-to-read illuminated meters and plenty of RF Output power in a light-weight, but well-made package. I do slow-start it with a variac, but ramp it right up. Probably overkill, the variac! ;-) This is a reasonably well-designed, and well-made MF/HF Amplifier, considering what I paid for it new. Very happy!!
K4HPP Rating: 2011-12-20
Very Good Amp Time Owned: 6 to 12 months.
I bought my AL811H earlier this year. I was skeptical at first, due to the many comments about MFJ quality from many users. I have experienced some quality issues with MFJ products over the past few years, but decided to give this amplifier a chance. Nobody else offers an amp that matches the power output and that uses inexpensive tubes for this price. I was not disappointed! The quality of construction is better than anticipated and after getting the bubble wrap off the tubes; I had the amp up and running in 30 minutes including doing the 10/12 meter “mod”. The tuned inputs did not have to be touched and provide less than 1.5:1 input SWR on all bands (except – of course on 30 meters). With less than 50 watts of drive from my IC7600, I get over 650 watts output on 80, 40, 20, and 15 and over 600 watts output on 17, 12, and 10 meters. I’m running it on a dedicated 120 volt, 20 amp connection. At full output, the HV is greater than 1500 VDC (as advertised). After a few weeks, I picked up four 572B tubes from RF Parts and did the swap with no problems and no retuning required. I’ve put the 811s away for “emergency” backup spares.

To fund this purchase, I sold a very clean Collins 30L1 that had new tubes and the power supply modifications. I was never able to get more than 550 watts out of this amp. The tuned inputs were so far out (I was never able to get them tuned in) that I had to use the 7600’s tuner just to get it to put out enough power to drive the thing. It took over 75 watts of drive just to get to the 550 watts – and on 10 meters, I only achieved 400 watts! It ran so hot with the little “phonograph” fan motor that you couldn’t keep your hand on the case. I guess the 30L1 was good for the sixties, but this AL811H is a better amplifier – maybe not as gutsy – but you can still buy parts and keep it running!

This amp is a 5 and I’d buy another one.
WW1I Rating: 2011-11-19
Simple and works.... Time Owned: 6 to 12 months.
This is a simple amp. that works just fine. I can tune it up in a matter of seconds and be back on the air. If you need to bump your signal out of the noise but don't want to spend a fortune, this is a great amp. With 45 watts of drive, I get 600 watts PEP and not even close to the maximum limits.

There are much better amps out there, but not a better value.