Ameritron AL-80BQ (with QSK-5PC installed)
Figure 1. Front panel of the Ameritron AL-80B, tuned up and ready on 80 meters.
Full Break-In CW at High Power
Over the last 40 years, I have owned a couple of linear amplifiers for my ham radio use. The first was a Henry Radio 1KD-5 that I bought in about 1980. It was a beauty, very well built, and a pleasure to use. It had a single 3-500Z triode, and put out about 800 watts, never seeming to work very hard to do so. I sold it only because we lived in an apartment, and running that power level living in that close proximity to that much consumer electronics was not a great way to ease neighbor relations. In about 1987 I bought a Heathkit SB-200 from K0OV, and used it for several years. It was seriously cute, and packed quite a lot into a small space. It had a pair of 572B triodes, and put out about 600 watts. I sold it because we were financially strapped, and it was the easiest thing to do without.
This year I have been looking for a new linear amplifier, and thinking about what it is that I want from such a thing. I do not need to run the full legal power limit, but I would like on occasion to have more available than the 100 watts that the Yaesu FT-1000 Mark-V Field produces. I want to use a real transmitting tube, and one which is not marginal for the task. Some amplifiers seem to be pushing their components well-beyond their inherent capabilities, and this does not appeal to me. I also wanted to be able to use full-break-in (QSK) on CW, and to have the ability to run most any digital mode (with the tight turn-around time requirements). This last requirement severely limited me as to what was available to do the job.
The simplest solution for me would be to buy a Yaesu Quadra system. My friend Barry Johnson (W4WB) has one and it is a beauty. It is fully solid state, and has its own internal antenna tuner built in. It will run full-break-in very nicely, and will completely slave to the FT-1000MP Mark-V Field radio. Unfortunately, it costs in the neighborhood of US$4500, and that is way out of my price range. I need the power, but at a quarter of that price. So in the end I settled upon a less expensive solution.
Ameritron makes quite a number of amplifiers, ranging from marginal ones using three or four antique 811 triodes in parallel, right on up to high-dollar units using the Eimac 8877 and 3CX1200 triodes. I looked for something in the 1KW category, and settled on the AL-80B, which is based on a single 3-500Z triode. I was pleased with the last 3-500Z amplifier I owned, and it always seemed that the 3-500Z was a well-designed tube for this power level. I downloaded the manual and took a good look, and it looked like a quite competent design. But the thing which cinched it was that it is available from the factory with their QSK-5PC full-break-in kit installed. I expected to have to special order it, but it turned out that R&L Electronics had one in stock. Now the QSK-5 is a PIN diode based T/R switch system which allows the amplifier to work with my Yaesu FT-1000MP Mark-V Field transparently in full break-in mode, with totally silent high-speed T/R switching. There are no clacking relays to have to endure. This was exactly what I was looking for.
Figure 2. Rear panel of Ameritron AL80B.
There are several things about the Ameritron AL-80B which have been especially interesting to me:
The first interesting thing is the silence. Unless I turn off everything else in the room, I cannot rell that the amplifier is on. The cooling fan moves a lot of air, but is a slow-turning, quiet model, and well-placed to conceal what noise it does make. Furthermore, with the QSK-5PC PIN diode T/R switching kit installed, there are no relays which activite when the amp goes from transmit to receive or back. Operation is nearly totally silent. This is impressive.
The second interesting thing is how cool it runs. Ameritron has a bias switching arrangment which biases the 3-500ZG to cutoff whenever there is no signal to amplify, even when it is in the transmit mode. Once a signal is present on the input, the tube is biased for normal AB2 operation, with an idling current of about 75 milliamps, at a plate potential of about 2950 volts. That is approximately 220 watts not dissipated unless it is necessary.
The third interesting thing is how very well the QSK-5PC PIN diode T/R switching kit works with the Yaesu FT-1000MP Mark V Field transceiver. That radio also used electronic switching, and has no relays in its T/R switching. For the radio and amplifier combination, then, there is no noise to indicate that the system has gone from receive to transmit and back. Using CW, I can literally hear between my dits, and can work just fine without my headphones if I choose to do so. This is very impressive.
The fourth interesting thing is how well the Ameritron AL-80B is built, considering who makes it. Ameritron/MFJ/Hygain/Mirage have a reputation for being cost effective, not necessarily for making the nicest of equipment. The Ameritron AL-80B is an interesting exception because it looks good, works well, and is very well made. The high quality of the parts used in the power supply and RF deck, and the clean assembly are indicative of a high-quality product, one better than what I expected.
The fifth interesting thing is how easily it meets its power output specifications. If I simply tune for maximum power, it will easily put out a 1000 watt carrier, which is significantly more than the 800 watt specification. When set for the specified 800 watt CW output, the Ameritron AL-80B is obviously well within its ratings. I have a best-case scenario as far as input line voltage and current are concerned (250+ volts to the primary winding set with the 250 volt taps) which helps make this possible. Nevertheless, I am very pleased with the Ameritron AL-80B as it can obviously put out 25% more than its advertised power output.
Good Signal Reports – I do not, nor do I intend to push this amplifier to its limit. I want to have a nice clean signal that can be considerably louder when it is necessary. As compared to the exciter alone, the AL-80BQ gives me another 8-10dB of signal, and gets excellent signal reports.
Nicely Built – Ameritron products are not known for being cosmetically as fine as some of the competition, but internally they are well-made. The component quality is better than I would have expected. The design takes a lot into consideration. For instance, I particularly like the way the multi-tap power transformer is implemented. There are primary windings which allow the amplifier to not only be run on either 120 or 240 nominal volts, but also a two-tap boost/buck winding which allows the voltage to be set to match local line voltage conditions. For instance, our local line voltage is quite high, and there is a 250 volt setting which gets within 1% of our typical line conditions. This allows the user to operate the 3-500Z very close to its specified filament voltage, and with a plate voltage very near to what the designer intended.
Well-Metered – The two dual-movement meters allow all of the critical currents and voltages to be monitored, in an intelligent way. The left meter reads out plate and grid current simultaneously, and the right meter reads forward power continuously, and allows measuring several other parameters as required. This is an elegant way to allow the user to get all of the required operating information with just two meter cases.
Easy to Tune – It does help to read the manual, and understand that maximum loading is a very good thing for this type of amplifier. Once that is understood, the tuning is simple and predictable. The vernier drives on the tuning and loading capacitors provide a good feel, and the pointers show where the user is at any time. I typically make paper pointers for my common operating frequencies, and it is simple to return to a formerly used setting.
Excellent Full-Break-In Operation – The QSK (full break-in) operation is totally silent. It goes from transmit to receive and back without making a sound, beyond the normal hum of the transformer and the whir of the fan. The feel is that of finesse rather than brute force. I like that.
WARC Bands – Due to the limited number of positions on the band switch, certain bands are combined. So for instance, 15 and 17 meters share a switch position. The difficulty is that the SWR presented to the transceiver cannot be flat on both simultaneously. Using the AL-80BQ with the Yaesu FT-1000MP Mark-V Field I can overcome this easily, by using the internal antenna tuner on the Yaesu when operating on 17 meters. It can match the impedance of the AL-80BQ quite well, and so there is no problem for me. Without the tuner, it might well be necessary to readjust the input tuning network on the amplifier when changing to certain WARC bands.
Good Value – As far as value received for the dollar paid, the Ameritron AL-80BQ is a winner. It works just as advertised, and produces the power I need in a seemingly effortless fashion. I am confident that, given the opportunity, I would buy this amplifier again.
An Inside Look:
Figure 3. Here is the AL80B shown from the RF deck side.
Figure 4. Here is the AL80B shown from the power supply side.
Figure 5. This is the QSK-5PC board, mounted on top of the power supply board.
Figure 6. This shows the parasitic suppressor, which is one quarter of the one from the AL-572.
Figure 7. This shows the "Taylor Tubes" 3-500ZG, and the RF components. Taylor Tubes is a registered trademark of RF Parts Co., and the tube is apparently made in China, as evidenced by the "PRC" markings.
Figure 8. This shows the input circuits. To enable the amp on 12 and 10 meters, cut the green wire.
The Verdict – I like this thing!