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

To: Richard Solomon <dickw1ksz@gmail.com>
Subject: Re: [Amps] Expert Amps 2K-FA: Any Opinions ?
From: "Joe Giacobello, K2XX" <k2xx@swva.net>
Reply-to: k2xx@swva.net
Date: Fri, 27 Apr 2012 11:55:30 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
I've not seen it switch to MID for no reason.  However, the key down 
time at 1500W output can be quite short before it switches to MID.

I was checking the power drift issue last night on 80M with a dummy 
load.  My comments regarding the power drop-off at 1500W in the MAX mode 
were based on casual observation of the power output as shown on the 
amp's power meter readout.  Using the LP-100A on the dummy load, I 
observed little, if any, drop-off while sending a series of V's.

I'll try to check more thoroughly on all bands today.

73, Joe

On 4/26/2012 6:24 PM, Richard Solomon wrote:
> That seems like a lot of thermal drift (~ 13%).  Has anyone
> experienced it switching
> to MID for no reason ? (OK, there must be a reason, but I haven't heard one).
>
> 73, Dick, W1KSZ
>
> On Thu, Apr 26, 2012 at 10:05 AM, Joe Giacobello, K2XX<k2xx@swva.net>  wrote:
>> Paul, yes, I have noticed a drop-off in output power with keying when
>> operating at 1500W out in MAX mode.  The output drops by as much as 200W
>> before leveling off.  Presumably, it is a temperature effect.  I'll
>> monitor it more carefully in the future so I can provide a better
>> description.
>>
>> When operating in MID power mode with ALC control and about 1100W out,
>> the output is quite steady.
>>
>> I forgot to mention in yesterday's post that I have detected some RX
>> "hash" when switching from STANDBY to OPERATE.  However, it's been
>> inconsistent.  So I want to check it more thoroughly across all bands to
>> make sure that it's not something else in the shack misbehaving.
>>
>> 73, Joe
>> K2XX
>>
>> On 4/25/2012 12:13 PM, Paul Christensen wrote:
>>> Joe,
>>>
>>> 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?
>>>
>>> Paul, W9AC
>>>
>>> ----- Original Message -----
>>> From: "Joe Giacobello, K2XX"<k2xx@swva.net>
>>> To: "Paul Christensen"<w9ac@arrl.net>
>>> Cc:<amps@contesting.com>
>>> 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.
>>>>
>>>> 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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