[Boatanchors] SWEEP TUBES AND FPM 300S

[Bry Carling]

Thank you. We are talking about sweep tubes. 

Say what? That was a pretty deep answer to my question and not very conclusive. It seems almost unrelated.

> From: hallicrafterssr2000 at k9axn.com
> To: af4k at hotmail.com; ranchorobbo at gmail.com; boatanchors at mailman.qth.net
> Subject: Re: [Boatanchors] SWEEP TUBES AND FPM 300S
> Date: Tue, 12 Jan 2016 10:32:39 -0600
> 
> 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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