I’ve used three models of SS amps here.
The dirtiest of them all is the Tokyo HyPower 2.5. Next up is the SPE 1.3K,
which uses a single LDMOS. Cleanest is the Power Genius XL (2 LDMOS) which
is under beta test here.
I think the concern about SWR and ruggedness is based on outdated info. The
latest LDMOS devices by design can tolerate high SWR, up to 66:1. With
de-rating the devices can handle around 3:1 SWR continuous at reduced
power. The limitation is in the output filter which are limited by
saturation of toroidal inductors. The newest amps are also microprocessor
controlled and protected to the hilt. I am more concerned I will blow up a
tube amp than I will a modern solid state.
IMD is less of a concern with two devices as there is plenty of headroom
and again - microprocessor control of biasing and other parameters such as
is done with MEffA in the PGXL produces a very clean signal, even without
adaptive predistortion.
I do agree that in a K3LR type of environment there is little benefit to
change out all of those existing, working tube amps for SS ones. That is,
other than as a trial run, or experiment to see how well they can do.
However if designing from scratch or expanding, amps can be shared between
run and mult stations in M/S or M/2. Even in M/M it provides some
redundancy.
Ria
N2RJ
On Mon, Dec 25, 2017 at 9:07 PM Tom Georgens <tomgeorgens15@gmail.com>
wrote:
> I have been using home brew SS amps at my 8P5A station exclusively for the
> last two years. The flexibility and increased operator efficiency are a
> big advantage. As such, I am a true believer for this use case.
>
> However, I am not sure that they are a better solution than single band
> amps
> for the pure Multi Multi. With the operating efficiency of instant band
> change largely moot, there is less to offset the down sides. With
> potentially 6 full power signals at once, and in band receivers, signal
> cleanliness is a key factor. The LDMOS parts simply do not have the IMD
> specs of tubes. K3LR has supreme engineering skill and may be able to
> design around some of these limitations on a per band basis. Plus, the
> predistortion techniques are very exciting, but not limited to SS amps.
> Overall, if it can be done, K3LR will find a way, but I would not be sure
> that current off the shelf solutions would be the cleanest for M-M.
>
> Overall, I think creative engineering can help with IMD, but it is not
> standard today. Also, the parts have come a long way, but the LDMOS
> transistors are not as rugged as tubes in most fault situations. If kept
> cool, reliability will be fine with well matched antennas, but will not be
> as tolerant of antenna system faults. Without the need of the flexibility
> of instant band switching, I am not certain that SS amps are a better
> option than single band tube amps for the dedicated M-M station.
> Situations other than M-M can be good matches for SS Amps, but the need for
> a well controlled environment and well matched antennas is still there.
>
> Just to be clear, I am not claiming to have solved any of these problems,
> just that I feel the advantages outweigh the risks in my case. YMMV
>
>
> 73, Tom W2SC 8P5A
>
>
>
> -----Original Message-----
> From: CQ-Contest [mailto:cq-contest-bounces@contesting.com] On Behalf Of
> Jeffrey Maass
> Sent: Friday, December 22, 2017 10:13 AM
> To: cq-contest@contesting.com
> Subject: [CQ-Contest] Solid State Amps in Multi-Multi Stations?
>
> Is anyone using solid-state amps at a competitive multi-multi station?
>
>
>
> Which? Any problems?
>
>
>
> 73, Jeff K8ND
>
>
>
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