It is a WAY cheaper foreign tube. I asked about getting one tubed in EIMAC.
She said the difference was somewhere in the range of simply purchasing the
EIMAC tubes. On that amp, the screen voltage is held way back and the way
things are set up, I don't see how you would run into grid problems on
either tube under 3k out. One tube 4cx1000 or 1500 could handle the rated
capacity of the amp in full duty cycle. It could also do it with low drive.
I think they only run the screen voltage about 250v. If you upped that a
bit, you would have a 4k out amp. I don't know if the tank could take it but
it looks like the PS would for casual use. I really like this amp.
Everything seems to be conservatively built and I like the 4cx1000 platform
because of the number of tubes out there. On top of that, there are two of
them. I do worry about the proprietary items that inevitably accompany the
newer amps. What chips will no longer be made, or whatever. Seems that
lifecycles are shorter all the time. That is what I love about the big henry
amps. Excpepting the tank inductor. Most everthing else was off the shelf.
Sam N9FUT
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Damon Stewart
Sent: Monday, April 04, 2011 12:09 PM
To: amps@contesting.com
Subject: Re: [Amps] VTX-X118 Tetrode mytery tube?
On 4/4/2011 1:38 AM, KL7RA wrote:
> Originally the new AP8410 used the Eimac 4CX1000A tubes but they made a
> switch to the VTX-X118. Seem to be a mystery tube, can't find the spec
sheet
> and never heard of them.
>
> Anyone know anything about this tube? My guess is Alpha used the 4CX1000A
> but got them with a higher grid rating? It looks like this tube number is
an Alpha
> part number to me.
>
> 73 Rich KL7RA Alpha amp owner
>
> > From Alpha:
> The amplifier uses the Alpha Power brand VTX-X118 tubes, a ceramic,
external-anode,
> indirectly heated tetrode that, unlike the excellent Eimac 4CX1000A, is
qualified to handle
> the grid current that might be experienced in the AP8410.
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
For what its worth. The most grid current I have ever seen out of my
8410, even when testing its limits, has been less then 1mA. In the
serial data string the grid current is read in tenths of a mA. I
usually see somewhere in the 0.2mA to 0.5mA range with CW output well
over LL.
From many of the reports I have seen and my own testing, the VTX-X118
seems to be a slightly improved Chinese version of the Eimac 4cx1000a.
Damon Stewart, KJ7E
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