Re: [Amps] Switch-mode HV power supply

["Ian White, G3SEK" <G3SEK@ifwtech.co.uk>]

> Does anyone recall the URL for the switch-mode HV power supply that was 
> featured in QST New Product some months ago?
>
> Has anyone tried it?
Thanks to everyone who replied: it's http://wattsunlimited.com

The reason for this inquiry is that I'm preparing a talk on power amps 
for the GM DX Convention. They have asked me to include some comments 
about "tubes v transistors" with a focus on DXing, contesting and 
DXpeditions. Comparing cost, size, weight and reliability for the two 
different technologies, an interesting question pops up: are our 
existing tube amps as small and lightweight as they could be?

The answer seems to be "no, not yet". We really haven't explored the 
possibilities of SMPS instead of heavy iron... and we haven't even fully 
explored the potential of compact, lightweight mains transformers.

G3WOS's website has a very interesting project description of an 8877 
DXpedition amp for 6m, that fits into an airline pilot's flight case and 
weighs in at just 40 lb - for the complete amp and power supply! 
(Compare this with 70 lb for an Acom 1000, which most people would 
regard as a reasonable size and weight for a 1kW desktop amp.)

http://www.gare.co.uk/amplifier/dxpedition_amplifier_overview.htm

G3WOS uses a custom transformer with a strip-wound core, from Heritage 
Magnetics in the USA - plus a *lot* of detailed attention to making all 
the parts fit into the box without wasted space. Admittedly this is a 
monoband amplifier, and the output circuits for an all-band HF amp would 
need more space... but it does show there is more that could yet be done 
with the "old technology".


--
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
                           Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek
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