John,
Sorry I didn't respond to your earlier request. The equivalent amp from
Alpha is the 87A. I have a 2000A and an 87A, using them for SO2R (single-op,
two radio) contesting. Here are some thoughts:
- They are both terrific amps -- well designed and very well built. I'm sure
you would like either one.
- The designs are similar, although the 87A uses the Eimac 3CX800 and the
2000A uses the Svetlana 4CX800. The latter is much less expensive, but may
have more reliability problems. I had a bad tube when my 2000A was new. The
replacement has been fine for a couple of years.
- The 87A uses pin diode T/R switching, which is ultra fast and silent. The
2000A uses a Jennings-style vacuum relay, which is slower and generates a
tiny bit of noise. H
- The 87A is programmed to trip on SWR greater than 2:1, while the 2000A is
more forgiving and easily handles SWR as high as 3:1. It's not clear why the
87A trip level is lower. I've heard that it's because the pin diodes can't
take the reflected power, but I've also heard it claimed that other parts of
the output network aren't beefy enough.
- The 87A blower is reasonably quiet - it sits on my desktop about two feet
away from my radio. But the 2000A blower is much quieter. It sits on the
floor about five feet from where I sit and I can't hear it at all.
- The 2000A has a remote control unit (RCU) that sits on the desk. It's
about the size of a paperback book. The interface is excellent, easy to use
and great diagnostic informative (messages on an LCD screen.) The 87A has
front-panel controls that are also easy to use, but the diagnostic display
is primitive.
- On the other hand, the 87A has a better computer interface. You can hook a
terminal or computer communication program to the RS232 interface and get
good diagnostic info. It's not quite as complete and informative as the
2000A RCU, but it's more than adequate.
- Alternatively, the 87A has Alpha Remote, which is a nice control and
diagnostic program for Windows. It takes that RS232 info and displays it on
the CRT. It's a nice, simple program to use, but not terribly robust. There
is a third-party control program for the 2000A. It's OK, but kinda clunky to
use. It has some interesting features, like the ability to automatically
retune the amp based on a frequency entered in a program. There's an
interface to the Writelog contest logging program for this. Writelog reads
the frequency from the rig and sends it to the 2000 for retuning. Although
both the 2000A and 87A have automatic retuning whenever you transmit, this
feature allows retuning when you change the frequency on receive. Nice for
retuning when you change bands on the search-and-pounce radio.
- In some sense, this somewhat obscure feature is important for contesting.
That's because there's a major difference in the way the 2000A and 87A do
their automatic retune. Both work such that if you send a dit or speak after
changing the rig's frequency, the amp will automatically retune. The 87A
will send the code element or speech at low power while retuning, but the
2000A shunts the input RF to a dummy load while switching. In other words,
it's lost. So, if you change bands and then try to send your call to another
station, there's a good chance with the 87A that the call will be heard at
the other end. With the 2000A, the first letter will be lost or clipped.
That's one reason why the control program has this elaborate interface.
- Speaking of tuning, the two amps are rather different in this regard. Both
were originally designed to store tuning parameters (band switch setting,
LOAD and TUNE cap positions) for small band segments (50KHz-100KHZ) in
memory. When setting up the amp, you select a desired antenna and tune it
for each segment on each band. When RF at a particular frequency is
detected, the amp selects the matching tuning parameters and uses stepper
motors to retune the amp. The first difference is in setup. On the 87A, you
do the tuning of each segment manually, using front panel TUNE and LOAD push
buttons. There's a nice TUNE mode and procedure that makes this relatively
quick and easy. When each segment is tuned, you push a couple of buttons to
store the parameters in memory. The 2000A offers a much more automatic way
to preset tuning for each segment. You set the desired frequency on the
rig, pick an antenna, select TUNE mode on the RCU and transmit about 20W of
RF. The 2000A automatically optimizes tuning for the selected antenna on the
selected frequency segment and stores the parameters in memory. Much faster
and easier than the 87A and quite accurate. There's even a DOS program that
will let you step through frequency bands quickly or initiate an automatic
sequence to tune the entire amateur HF spectrum.
- It might sound like the 2000A is the winner in this department, but Alpha
has something that may be even better -- dynamic tuning. Using a feature
called AlphaMax, the 87A can automatically optimize tuning on the amp while
you are transmitting. When you first setup the amp you go through the preset
storage procedure outlined above, but thereafter the amp will optimize each
segment dynamically. This is especially useful if you have more than one
antenna per band. When you switch antennas, any tuning differences are
automatically made by AlphaMax.
- The 2000A doesn't have dynamic tuning, but it does allow you to store
parameters for up to 10 antennas for each segment. So, if you have multiple
antennas on a band, you do the preset storage procedure for each antenna in
each segment (real fast and easy with the DOS program.) When changing
antennas while operating, you simply hit a couple of buttons on the RCU to
select the desired antenna parameters. Not quite as automatic as the 87A,
but adequate.
- As I mentioned, the build quality of both amps is superb. Service is
excellent from both companies. There was a time when it was a bit difficult
to get info from Alpha, but that has really changed. I've been able to make
repairs to my 87A several times with help from the factory (it's seven+
years old.) I found a firmware bug a number of years ago and the factory
helped me patch it (not sure if the 2000A has any patching capability.) I
fixed a bad op amp on the low power supply that was making an IP current LED
flicker annoyingly. I also diagnosed a bad replacement tube with the
factory's help (symptoms were obscure.) I'm pretty comfortable working
inside the 87A. As I mentioned, the 2000A had a bad tube when new. I ended
up taking this to the local repair depot (in MA, not that far from where I
live.) I think I could have done the troubleshooting and replacement myself,
but ACOM tends to want you to send the amp in. They are very fast on the
turnaround, though. Tube replacement is more complicated on the 2000A than
the 87A -- you have to set some bias pots. The factory has supplied me with
detailed instructions for doing so (not in the user manual.) In general,
when I've asked the ACOM factory for info, I've gotten incredibly detailed
e-mails back from the lead technician that describe the design,
construction, firmware algorithms, etc. Really first-rate response. I also
had a bad vacuum relay when the amp was new, part of a bad lot of Kilovacs
they got. I happened to have a compatible Jennings replacement and installed
it myself with a little guidance from the factory. They sent me a
Russian-made relay that I keep as a backup. No problems with the Jennings
relay, though.
- My feeling is that the 2000A has much better firmware and diagnostics than
the 87A. Not surprising, since it was designed at least 10 years later.
Hope this helps!
73, Dick WC1M
> -----Original Message-----
> From: amps-admin@contesting.com [mailto:amps-admin@contesting.com]On
> Behalf Of Cleeve
> Sent: Thursday, December 05, 2002 3:57 PM
> To: Amps@contesting.com
> Subject: [Amps] Acom 2000A + Alpha
>
>
> I would like to thank all those who gave me advice and comments on the
> Acom 2000A, from the response, the manufacturers should be very
> happy...I will continue drooling, and drop some very pointed hints
> towards Father Christmas, but he might need to reinforce his
> sledge......and me, my Christmas Stocking!!!
>
> Just one further question.....is there an equivalent Alpha amplifier,
> and how does it stack up against the Acom 2000A. sincerely, John. G3JVC.
>
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