I will also put in a plug for the PGXL.
I used a PGXL for the first time while guest operating in CQWW CW. This was
probably the most demanding application possible. I had never operated at the
station before. The station host was 7000 miles away. I used SO2R and 2BSIQ,
with 200 msec switching times for band changes. The duty cycle was very high.
The antenna SWR was highly variable, depending on band and antenna
configuration. 4200 QSO's. Absolutely no amplifier issues.
73,
Steve, N2IC
On 03/10/2020 04:29 PM, rjairam@gmail.com wrote:
LDMOS itself does not require perfect SWR. The older MOSFETS did. LDMOS do
not. They can be operated at 66:1 SWR. This is a dead short at full output.
There are videos of them arcing with them and welding. Probably not for
extended duty cycle, but guess what- neither can your ceramic tube amp with
tubes made of unobtainium.
The fragile parts in a solid state amp that are affected by high SWR are
the filter network, the capacitors and inductors.
The software in modern amplifiers, if properly implemented will absolutely
protect your amplifier and antenna system. If you throw high SWR it will
shut down or fold back (de-rate).
The KPA1500 has an internal antenna tuner that can handle up to 6:1 SWR.
Other amplifiers such as the PGXL (which I have) can operate at high SWR
with no tuner. I can run mine at 2.5:1 with software derating. I get about
1.3kw out of it at that high SWR. With about 3:1 SWR I can do about 500w
depending on the band. Beyond that I get a fault. With 2:1 SWR I can do
1.5kW. There is a tuner being developed for that one as well. I don’t abuse
it and I try to run my antennas resonant. I’ve had this amp since it was
being alpha tested and run it through a variety of antennas and duty cycle.
I also ran an Alpha 91B so I have an idea of what a tube amp can do. The
solid state amps work well and in terms of SWR tolerance are pretty good.
Elecraft and SPE did a very good thing by including built in antenna
tuners. The SPE implementation is excellent as it follows CAT. From my
limited use of the KPA1500 it seems To do the same thing.
This is based on my actual experience and not assumptions.
73
Ria, N2RJ
On Tue, Mar 10, 2020 at 6:11 PM <john@kk9a.com> wrote:
Those are two completely different animals, one is lightweight and has
LDMOS finals that need an antenna tuner or a perfect antena and the
other uses a ceramic tetrode that can tolerate 3:1 SWR. A tetrode
tunes differently than a triode but perhaps the auto tune takes care
of this. I am not sure if there is an OM power list but there is an
Elecraft list where you can follow any issues or complaints that
people may have. Is quietness a concern? Is quickly setting it up
without a lot of adjustments a concern?
FWIW, I have used an Acom 2000A several times and basically I just
plugged it in and it worked plus it's super quiet. The only issue I
have saw with this amp is that it is sensitive to arcs in the antenna
system.
John KK9A
K4XS wrote:
Looking for a backup amp for the new station. Probably going to run
SO2R so auto-tune is important. I'm running a K3S and the second
radio will also be a K3S. I really don't care if the amp "matches"
the K3S in looks. Like most of you guys I'm concerned about
performance. Both rigs are equal in price.
Here's the question: If you were buying a new amp and were buying it
to satisfy the above criteria, which would you choose and why?
K4XS
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