[Boatanchors] 8122 Suitability/Selection

[Carl]

Attack mode shut off Glen unless needed later (-: and unless you keep 
mentioning the M word in every post.

I dont know the development history of the 8072 but it was used in a wide 
range of equipment.

For amateur use it was Signal One.

It has also been use in HV regulated lab supplies by HP and others using a 
BeO block to a finned heatsink with 4 used per PS.

It was also rebranded as an 8122 by Penta USA with the addition of a pretty 
gold anodized aluminum anode cooler. I have a pair of NOS ones here I like 
to show off to visitors.

I have used as 8122 replacements by sweating off 4X150A anode coolers, 
adding copper pipe centers and sweating on the anode. With a clean and lubed 
NCL-2000 blower they have run in my 6M NCL for a few years with no apparent 
discoloring at 1200W of CW and SSB. The chimneys are identical between the 2 
tubes as are the clamp diameters. IMO a 400W rating by RCA for the 8122 was 
a real stretch. The Svetlana 4CX400A has the cooler diameter of an 8930 
which is more believable.

For grins and giggles I also busted a bad 3-500Z, removed the anode and 
clamped to a 8072. I bet it would handle some decent power but havent built 
anything yet.

As far as running them at 900MHz that is a real stretch, do you have details 
on this?

Carl
KM1H


----- Original Message ----- 
From: "Glen Zook" <gzook at yahoo.com>
To: <james.liles at comcast.net>; <boatanchors at mailman.qth.net>; "D C *Mac* 
Macdonald" <k2gkk at hotmail.com>
Sent: Wednesday, July 06, 2011 2:20 PM
Subject: Re: [Boatanchors] 8122 Suitability/Selection (was: 6146 
discussionon )


> Hoping not to be attacked!  The 8072 is basically the same tube as the 
> 8122 EXCEPT that the 8072 was designed to be used in cavity type 450 MHz 
> amplifier designs.  As such, there is no heat sink on the tube.  It is 
> possible to fabricate a suitable heat sink which allows air cooling of the 
> tube so that I can be used in place of the 8122.  Also, in some cases, a 
> heat sink from a defunct 8122 can be used.
>
> Whereas the 8122 tubes are both expensive and hard to find, the 8072 tubes 
> are plentiful and relatively inexpensive.  This is because Motorola, as 
> well as other commercial two-way manufacturers, extensively used the 8072 
> in their 450 MHz base station units and in a relatively few mobile units.
>
> Although I do not have any equipment that uses either the 8122 or the 
> 8072, I do have a number of the 8072 (mostly brand new, a few used) that I 
> acquired the tube stock from a large, self maintained (over 300 base 
> stations and 3000 mobile units), that went to an 896 MHz trunked system a 
> number of years back.  Most of the tubes were made by RCA.
>
> If someone wants to adapt the 8072 tubes I can probably be traded out of 
> some of the 8072 tubes.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Wed, 7/6/11, D C *Mac* Macdonald <k2gkk at hotmail.com> wrote:
>
> Might I ask how Burle 8122s can be correctly chosen for use in the 
> National NCL-2000 amp?
>
> I have previously been advised that original NOS RCAs are no longer 
> available at decent cost.
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