[CQ-Contest] New Amps: Elecraft KPA1500 & FlexRadio/4O3A PGXL

[Ria Jairam]

We live in very exciting times and I predict that for serious stations,
tube amps will soon be a thing of the past.

IMD of the Elecraft amp should be very good. It uses two devices instead of
one. With adaptive predistortion it will be even better.

Separate power supply may be advantageous in some situations such as easy
field replacement or even powering from battery power in a pinch
(DXpedition/mobile). I don't like the idea that it is 240v only because
sometimes for portable operation you only have 120v available. PGXL and SPE
expert both can run at 120v, at reduced power.

No SO2R is puzzling. It is so easy to do, and is going to be the standard,
I think and is one of the advantages of a solid state amp.

An ATU is nice to have. It is also going to be limited because beyond 3:1
SWR at legal limit you're going to run into the limitations of toroidal
coils and relays. Roller inductors would be the only way, but see the Alpha
4040 which is a complicated piece of machinery. I wouldn't put too much
stock in the lack of a tuner in any amp, but it's a nice to have for sure,
and to me is more of an equalizer with tube amps that can tolerate a high
SWR by tuning the tank circuit to compensate. But nice to have. I should
point out that PGXL while it doesn't have a tuner can work up to 2:1 SWR
without issue, it just derates. The LDMOS devices can handle up to 66:1
SWR, it's just that the filters and other components cannot. SPE Expert
amps can handle up to 3:1 with automatic tuning but you can tune it higher
manually, just be careful with the power level you use.

The ethernet port is very interesting. I am hoping they can eventually use
it with Flex and Anan transceivers, or maybe natively remote. Even the Icom
7610 apparently has an ethernet port now.

I am hoping that this would push the FCC to consider Bob Hardie's petition
to finally get rid of the outdated 15dB rule. This way a K3/10 can easily
drive an amplifier to full legal limit. As it is a 100 watt PA is a waste
in any station that uses an LDMOS amplifier. You can get full legal limit
with only 1-2 watts drive without the pad attenuator designed to satisfy
FCC regulations. My SPE 1.3K-FA is an import (personally imported) so it
doesn't have such a restriction and it is really nice to drive to 1kw and
beyond with just 5-8 watts.

73
Ria, N2RJ

On Fri, Apr 21, 2017 at 8:11 AM, David Siddall <hhamwv at gmail.com> wrote:

> Interesting, both of the above-referenced amplifiers are due out this
> summer.  Both are solid-state from first class manufacturers and therefore
> we can expect very reliable units.  Both designed to work with most current
> radios on the market.  Both aimed at contester and DXer markets.
>
> No IMD and other actual test details yet, but both promise signal sample
> outputs that can be used for adaptive pre-distortion.
>
> The main differences that I discern from an operational (not technical)
> standpoint:
>
> KPA1500 includes antenna tuner; PGXL does not (separate unit planned).
>
> PGXL is S02R capable (minimum 70 dB isolation within amp); KPA1500 is not.
> (Interestingly, this capability was touted years ago when prior Elecraft
> 1500W amplifier was pre-announced, as has been noted in earlier postings on
> PVRC reflector.)
>
> KPA1500 with separate p.s. totals 37.2 lbs.;  PGXL with internal p.s. but
> no antenna tuner weighs 33.0 lbs.
>
> KPA1500 RF deck is 4.5 X 13.5 X 11.5 & p.s. is another cabinet of identical
> size; PGXL is 5 X 13 X17, incl. p.s. in same cabinet.
>
> Links to specs and other details:
> http://www.flexradio.com/amateur-products/powergenius-xl/
>
> http://www.elecraft.com/KPA1500/KPA1500%20FAQ%20rev%20A1b.pdf
>
> Undoubtedly both will be highlighted at Dayton next month, after having
> been previewed at Visalia this weekend (where KPA1500 was announced).
>
> 73, Dave K3ZJ
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