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
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>>
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