[Amps] Expert Amps 2K-FA: Any Opinions ?
Richard Solomon
dickw1ksz at gmail.com
Thu Apr 26 15:24:21 PDT 2012
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 at 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 at swva.net>
>> To: "Paul Christensen"<w9ac at arrl.net>
>> Cc:<amps at 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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>>>>
>>>>
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