[Boatanchors] SWEEP TUBES AND FPM 300S

[Jim Liles]

Take a look at the link.  It is not finished --- only has narration for the 
6146.

Note the control and screen wires.  I pulled a few of the screen wires aside 
on the 6KD6 but it is still clearly visible how the beam tetrode is built 
and how difficult it is the perfectly align those wires to prevent the 
cathode from seeing the screen and the control grid from seeing the the 
plate.  If they are perfectly aligned the bias will be as low as it gets and 
the dynamic plate to control grid capacity also will be at the minimum.

Each pair of those wires along with the adjacent pair form a channel/beam 
between them.  Reduces screen current, inter-electrode capacity, and 
eliminates the need for a suppressor grid.

http://k9axn.com/_mgxroot/page_10886.html

If you should decide to dissect a tube with an oxide coated cathode be 
careful.  The Barium and Strontium oxides form a powder or kind of dust when 
removed from the cathode.  The Strontium is not a problem but the Barium 
oxide is Caustic like powdered drain cleaner.  If you shake that oxide 
around and it gets in the air you will immediately sense irritation. 
Neither is radio active.

Use protective gloves and rinse the whole tube once open --- removes the 
oxide.

Have a super day kindest regards Jim K9AXN



-----Original Message----- 
From: Bry Carling
Sent: Tuesday, January 12, 2016 7:34 AM
To: Rob Atkinson ; Boat Anchors List
Subject: Re: [Boatanchors] SWEEP TUBES AND FPM 300S

So Rob, you obviously feel quite strongly about this.

Are you saying that all those 1960s amateur SSB transceivers with 500 watts 
p.e.p. promised by the
manufacturers, and requiring AC line power of 120 Volts 60Hz at only 3 amps 
couldn't really produce 800 watts? Why that would be just downright 
dishonest of them - grin!

> Date: Mon, 11 Jan 2016 12:04:59 -0600
> From: ranchorobbo at gmail.com
> To: boatanchors at mailman.qth.net
> Subject: Re: [Boatanchors] SWEEP TUBES AND FPM 300S
>
> On Mon, Jan 11, 2016 at 2:23 AM, Dennis DuVall <duvallddennis at gmail.com> 
> wrote:
> > Overall, I would say sweep tubes were a great gift to the Ham community.
> >
>
> they were employed in cheap poorly constructed lightweight table top
> SSB transceivers with crappy audio and drifting VFOs so hams who had
> been brainwashed into hating AM could get on "phone" inexpensively.
> If you like "vintage SSB" have at it, but these days I see no reason
> why anyone would want to run such rigs even now, when there is the
> KWS1 and 75A-4 or the CE phasing rigs available.
> The sales job, or snow job, involved exaggerated power claims
> specified in p.e.p. watts input.
>
> This was no gift, or rather, if you think this was a gift, I'd hate to
> see what you think of as being a consolation prize.
>
> 73
> Rob
> K5UJ
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