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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>>>>>
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