Do you detect obvious output power change with changes in PA temperature?
I see about a 10% reduction with the 1K, approaching 15% when the PA deck
starts getting really heat stressed. While operating in CW mode at 1500W,
does the amp ever kick to the MID power setting?
----- Original Message -----
From: "Joe Giacobello, K2XX" <email@example.com>
To: "Paul Christensen" <firstname.lastname@example.org>
Sent: Wednesday, April 25, 2012 12:04 PM
Subject: Re: [Amps] Expert Amps 2K-FA: Any Opinions ?
> I've owned the 2K-FA since about the first week of 2012. So far, I'm
> quite happy with it. It replaced a TenTec Titan 425 and a Command
> VHF-1200. I was getting ready to contribute a write-up on it for the
> Contesting.com site, but I wanted to evaluate it for a few more weeks
> before doing so. Here are some initial assessments.
> It easily puts out 1500W on all bands from 6-160M with about 30W
> drive. I have seen the output power go as high as 2,200W out on
> some bands when running it in MAX power mode and allowing the ALC to
> limit the drive. With 1500W out, you're limited to about 15 seconds
> or so key down and then it automatically switches to MID power
> mode. (Power was measured with a fairly recently calibrated LP-100A.)
> Utilizing the ALC and maximum exciter drive (200W), as recommended
> by the manufacturer, in MID power mode, it puts out about 1,100W. The
> ALC action throttles the drive to about 40W. Presumably, the
> key down time under these conditions is quite long, since MID power
> is recommended for RTTY by the manufacturer.
> The amp is set up for connections to two different exciters and band
> switching can be accomplished automatically through parallel
> connections to the exciters' serial ports or via the amps internal
> frequency counter. The manufacturer recommends using serial port
> switching rather than relying on the frequency counter. Having all
> switching done internally in the amp has really simplified and
> reduced the number of coax links and external manual switches in the
> shack. I think the exciters will also switch automatically with
> applied RF, but I've never tried it.
> The amp has a port for connection to a Steppir control box for
> automatic band selection on their antennas. I haven't hooked this
> up yet.
> I have run 200W through the amp in standby mode without any
> problems. However, because of the internal switching, the exciters
> are not connected to an antenna unless the amp is turned on.
> In contrast to its predecessor, the 1K-FA, fan noise is barely
> The internal tuner seems to work as advertised, but I never use it
> since I have all resonant antennas or an external Matchbox.
> The only serious problem I've had is that one of the six antenna
> ports doesn't work at all. The domestic distributor (Expert Amps
> USA) offered to fix it on the spot if I brought it with me to the
> Orlando Hamcation. But since I could live without one of the ports,
> I decided not to bother. In talking there with the owner and
> designer, Gianfranco I0JY, he thought it might be a relay. (It also
> might be a cable problem, but I haven't gotten in there to check.)
> I don't operate RTTY or contests (seriously), so I've never seen the
> internal temperature exceed 50C. I believe that the amp shuts down
> if the temperature gets to 76C.
> One problem that I have is that there is no service manual. Apparently,
> the manufacturer is concerned about protecting his
> design. (OTOH, it seems to me that it could be easily reverse
> engineered.) Nevertheless, the service guru is a W5 who shows up on
> the reflector to answers questions, etc.
> I'm not sure that I understand Joe's (W4TV) comments regarding the antenna
> issues when operating SO2R, but that's probably because I don't work
> The bottom line is that with the exception of the antenna port problem,
> the unit has worked flawlessly so far.
> 73, Joe
> On 4/25/2012 9:57 AM, Paul Christensen wrote:
>>> I would also be concerned about cooling (and noise) with that much
>> dissipation in such a small box.
>> I have the 1K version of the SPE amp. Nice, compact and reliable design.
>> If the League's QST product review is to believed, IMD performance is
>> excellent for a solid-state design.
>> No contesting here but when using CW in say....a 2-3 minute exchange, the
>> deck becomes quite hot and the fans are running "full tilt," resulting in
>> what sounds like a jet engine. That, together with output power that
>> changes with PA deck temperature seems to be problematic with most
>> commercial solid-state amps. SPE does use a very well designed
>> system. In effect, a high-speed bus is created to kill bias to the PA
>> transistors when one of about a half-dozen faults occur.
>> I like the amp for its instant-on, compact design, but I would never use
>> as a replacement for a good VT amp. I saw the 2K amp recently at the
>> Orlando hamfest and for folks wanting a solid-state amp, I think it's
>> considering. But if noise in the shack is bothersome issue, ask other
>> owners about noise level with varying duty-cycle at full output power.
>> I believe the 2K version has a vacuum relay option that adds several
>> dollars to the purchase price. In my 1K, its T/R frame relays were way
>> loud. I ended up modifying the amp's logic for use with an Ameritron
>> The interface between the two units is optically isolated and a schematic
>> shown on my QRZ.com page. Much happier with this arrangement as it's
>> silent, and no truncation of keyed elements.
>> Paul, W9AC
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