[Amps] Expert Amps 2K-FA: Any Opinions ?

[Joe Giacobello, K2XX]

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.

 1.

    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.)

 2.

    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.

 3.

    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.

 4.

    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.

 5.

    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.

 6.

    In contrast to its predecessor, the 1K-FA, fan noise is barely
    noticeable.

 7.

    The internal tuner seems to work as advertised, but I never use it
    since I have all resonant antennas or an external Matchbox.

 8.

    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.)

 9.

    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.

10.

    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 contests.

The bottom line is that with the exception of the antenna port problem, 
the unit has worked flawlessly so far.

73, Joe
K2XX


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 PA
> 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 protection
> 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 it
> 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 worth
> 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 hundred
> dollars to the purchase price.  In my 1K, its T/R frame relays were way too
> loud.  I ended up modifying the amp's logic for use with an Ameritron QSK-5.
> The interface between the two units is optically isolated and a schematic is
> shown on my QRZ.com page.  Much happier with this arrangement as it's fast,
> silent, and no truncation of keyed elements.
>
> Paul, W9AC
>
>
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