Hello! The Brittish Short Wave magazine had a long series of articles on a
very advanced power supply for the K2RIWs and a lot of valuable info on
screen grid tubes. Also in an old issue of the Radcom there was an article
how to feed your screens with tube type regulators. If I only can find those
articles in my file, I will send you info about it.The only advantage I can
see in the K2RIWs is that new 4CX250Bs are becoming very cheap now a days,
at least in Sweden. There has also been an article in QST about using 8874s
and 8930s (?= SVETLANA 4CX400 ). 8874 is out as it is very expensive. Try
one of those Russian inexpensive instead and start from scratch.
HJej daa de Hans SM5KI
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>Från: "G0MJW" <mike@g0mjw.freeserve.co.uk>
>Till: "Joseph Rodgers" <jarodger@airmail.net>, <amps@contesting.com>
>Ämne: Re: [AMPS] K2RIW 432 Mhz Stripline Amplifier (Dec 72 QST)
>Datum: mån 1 nov 1999 09.52
>
>
>The PSU is 2000-2500V at 500mA to 1A for the anode. The screen grid requires
>a stiff supply at 350V that can source and sink 20mA per valve. Grids
>are -55ish volts for a standing current of 100mA per valve. Several designs
>fo supply boards exist, Downeast Microwave Tetrode boards (AKA G3SEK) will
>do what you need.
>
>I had a K2RIW chassis that I could never get to work - so beware. It was a
>pretty accurate copy of the ARCOS design. K2RIWs can be/are difficult. If
>yours has never worked, it may be better to forget it and go for a different
>design using a triode, especially when you consider the PSU complexity. You
>can buy an AM-8155 for less than it will cost you for the K2RIW PSU that
>reportadly gives 400W on 432 MHz.
>
>My chassis is now a 70MHz amplifier where it can rather easily produce the
>160W required. It is easy to modify the chassis for bands from 50MHz through
>144 MHz.
>
>Mike
>
>
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