At 04:04 PM 27/09/2010, DAVE WHITE wrote:
>The GU81Ms do indeed have a good reputation here in Europe as being
>a tube that can withstand fearful abuse. They keep on working long
>after they should have melted. I bought a load of these things for
>about 10 Deutchmarks each 10-12 years ago and never did anything
>with them (I got some 3CX3000A7s instead), so sold them on to a
>Tesla Coil builder not too far from here. I hear the same takes of
>indestructability and barn door engineering from him too.
>
>I understand that the GU81Ms are good up to about 21MHz but are less
>efficient above that.. I'd intended to use four of them in a
>topband amp, so high freqency efficiency wasn't really a design
>criterion for me.
>
>I hope to hear VK6APK as an S9+ signal on a frequent basis :-)
>
>BTW Alek, what are your thoughts on the upcoming Ashes series - will
>you be following it? Apparently England are rated 11/8 to retain
>the urn - though I think that's a bit optimistic from our side!
>
>cheers
>
>Dave G0OIL
G'day Dave,
Yes, I would envisage a low frequency, monoband amp with the GU81M's.
Dunno about 4 of them. I'm sure 2 will do.
I've always fancied the idea of having a microwave oven door glass
and screen on a large glass tube amplifier. I reckon these babies
would look spectacular in full colour on a cold winter's morning.
The Ashes is the be all and end all of cricket. Eveything else is
just practice. Australia versus England is the only game that matters.
It really will be a good series and I would of course like to think
we can snatch it back but I think it will be a daunting task, even on
home soil.
Best of luck,
Alek. VK6APK
>--- On Mon, 27/9/10, Alek Petkovic <vk6apk@bigpond.com> wrote:
>
>From: Alek Petkovic <vk6apk@bigpond.com>
>Subject: Re: [Amps] Why are 833s so Expensive
>To: "Roger" <roger@rogerhalstead.com>, amps@contesting.com
>Date: Monday, 27 September, 2010, 4:13
>
>Yeah, I've just bought 4 GU81M's and Dr Alex is posting me a pair of
>sockets as I write.
>
>Should be an interesting project. . . . if I can ever find the time.
>
>73, Alek
>VK6APK
>
>
>
>At 08:28 AM 27/09/2010, Roger wrote:
> >Subject pretty much says it all. 833s are running over $125 ($258 for a
> >pair) each although they vary from $100 to $200 each on e-bay. I don't
> >know if they are selling any, but the price has been that way since last
> >spring.
> >
> >OTOH the RUSSIAN GU-81s (similar to, but not quite as strange looking as
> >the 833) are running from $22 to over $100 (typical $35 to $45 USD) plus
> >shipping which is roughly $20. Now there is a monster that will help
> >heat the shack with it's warm glow. <:-)) A pair is good for close to
> >the legal limit out without forced air. OTOH they are definitely not
> >the first choice for VHF.<:-)) Still, a pair would look great running
> >in a glass enclosure.
> >
> >73
> >
> >Roger (K8RI)
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