The future is all for semiconductors although tubes are more friendly
and convenient for home brewing and for an elite of individuals (RF
technicians) that's anyway disappearing from the world.
Several reasons will turn to produce only solid state RF amplifiers in
a short term, at least up to medium power AMPs (30KW) and up to VHF.
One practical reason is the cheaper way to produce semiconductors
(although relatively high priced), another are the new products that
comes out (i.e. big MOSFET) almost continuously, another is the
commercial "power" gained by semiconductors manufacurers Vs that of
tube manufacturers, another reason is the event that an old tube
becames no more available in a close future.
An objective reason in favour of semiconductors is also the neeed of
modular products (i.e. for DAM or PDM) or using combiners, or cheap
amplifiers that doesn't involve precision parts (mechanical) and
dangerous high voltages, or are relatively lightweight, etc.
Probably, one of the most important commercial feature for an amplifier
(I'm in the Broadcast but it sounds good also for amateur market) is to
be easy to be used, even by the most idiot (un)qualified "technician".
Inherently, a solid state amplifier MUST be fully protected and by
design has to fit the above requirements.
Inherently the protections have to be very fast (less than 10 mS) to be
really effective or semiconductor like Mosfets will die anyway.
Inherently a switching supply without an isolation transformer won't
protect semiconductors from lightening spikes on the mains.
The overall efficiency of a solid state amplifier is finally not so
better than a vacuum tube amplifier like it's often claimed.
By personal experience I can say that, all considered it's not easy to
produce a solid state amplifier having all the requested features.
On the other hand, also a full protected self tuned (matched) tube
amplifier won't be cheap or easy to design, and manufacturers will
never invest in a new product that's fundamentally old.
More or less this is the story and a well designed solid state PA is an
excellent unit without gaps, generally such units are not cheap at all.
73,
Mauri I4JMY
>
> I am old fashioned, and have been working in the semiconductor
industry too
> long. As a result, I prefer tube amplifiers. One advantage of the
Acom is that
> it meets the new ITU Radio Regulations on harmonics - I'm not sure if
the ICOM
> does (-50dB for powers over 5 watts)
>
> Has anyone on the reflector any experience with solid state amps and
lightning
> induced EMP damage?
>
> Another possible problem if you are to operate a multi tx contest is
cross or
> intermodulation in the solid state PA which can be far worse than
tube PAs -
> partially because of the SWR protection circuitry operating from pick
up. Having
> said that, it appears that 9M0C and D68C haven't had any problems in
that
> respect, but I don't know how much spacing they have between antennas.
>
> 73
>
> Peter G3RZP
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