[Amps] 'good engineering'

[Alex Eban]

So very right!
Years ago we used to say of an enclosure :" if it doesn't hold water, it
won't keep RF in".
This one reason why the military tend to use die cast plenums for the power
stages of high power amplifiers: to keep seams to a minimum. Not very
accessible for us, but if you ever get a chance to make an enclosure with
welded seams, you'll se the difference!
Sometimes, even the direction feedthroughs are installed can be decisive as
to stability.
Seriously, guys, any amplifier is basically, potentially and usually an
oscillator with too little positive feedback. Just give RF a chance and it's
going to do its tricks. 
Alex		4Z5KS

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Gary Schafer
Sent: Sunday, March 28, 2010 4:35 AM
To: 'Jim Thomson'
Cc: amps at contesting.com
Subject: Re: [Amps] 'good engineering'

Jim,
I think that Bill needs to do a lot of reading. Orr's book is an excellent
start.

In his chapter on amplifiers he specifically spells out what happens to the
cathode current of a GG amp when no tuned input circuit is employed. He
describes how the cathode current follows the coax cable out to the exciter
and back. If Orr is not believable have a look at some of the Collins
material.

As to RF passing thru the chassis, again turning to Orr will explain it in
detail of how RF does not pass thru the chassis metal but thru holes in the
chassis. He specifically states how current on top of the chassis reaches
the bottom side of the chassis.
 For anyone that would like to read this it is in chapter 17-4 of the 17th
edition of his handbook. That is page 364. 
With a different version of his book the chapter will probably be different,
but it is under "transmitter design, grounds".

As to Orr stating that "a GG amplifier doesn't need to be neutralized" that
is not true. What he does say is "it makes neutralization unnecessary in
many cases". Then he goes on to describe various neutralization methods in
the next few pages and tells you why some tubes may need it.
And I think that Orr knew what the phase relationship between plate and
cathode were.

Sometimes a little reading is better than inventing explanations. All of
this stuff has been done before.

73
Gary  K4FMX


> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]
> On Behalf Of Jim Thomson
> Sent: Saturday, March 27, 2010 11:27 AM
> To: dezrat1242 at yahoo.com
> Cc: amps at contesting.com
> Subject: Re: [Amps] 'good engineering'
> 
> 
> 
> --------------------------------------------------
> From: "Bill, W6WRT" <dezrat1242 at yahoo.com>
> Sent: Saturday, March 27, 2010 6:20 AM
> To: "Jim Thomson" <Jim.thom at telus.net>
> Cc: <amps at contesting.com>
> Subject: Re: [Amps] 'good engineering'
> 
> >>## Remember that argument
> >>about how a simple tuned input works, and how, without one,  the
> return
> >>current is via the coax shield going back to the xcvr, then up 
> >>through
> the
> >>load cap of xcvr.. and back down center conductor, back to cathode.
> You
> >>still  don't believe it, even after  Tony King posted the Orr 
> >>classic diagram on the other reflector.  I bet you $1000.00  CASH, 
> >>that's  how it works.IOW, put up or shut up.
> >
> > The Orr Classic diagram proved nothing because the supposed "return 
> > path" you were so hot about actually ended in mid-air and wasn't 
> > connected to anything. Remember? Where's my money?
> 
> &&  say what?    It ends up back at the cathode, completing the loop,
> Fig 22
> in any orr book.  'Untuned cathode circuit grnd return'.   Cold ends of
> tune
> + load
> caps... along the chassis, down the braid of coax to exciter... up 
> through load cap of xcvr... down the hot side of the coax..... back to 
> coupling cap...
> which
> bonds to
> cathode, completing the loop.    We  are talking about the 210 deg
> pulses
> from the
> anode... which are aprx 3 x the dc plate current.  [ IF a PI  tuned 
> input is used, the C2 cap of the tuned input, has to handle these 
> pulses.. PLUS normal current from the xcvr. ]
> 
> &&  Bill, it appears you have missed the basic concept of how a GG amp 
> works.
> Perhaps a review of Ch 15 is in order.   RF  just doesn't.. ..'end up in
> mid
> air'
> >

> >>Now ur spewing BS, about how RF  bores right through solid 1/8" AL.
> >
> > Proven by two independent experiments with copper sheet, not 
> > aluminum and it never was about anything 1/8" thick. Pay attention.
> 
> &&  depth of penetration is  .05mm  on 160m... and .01mm on 10m.  Sez 
> so, in Bings RF software package.
> There are a LOT of holes  surrounding the tube /socket.  Has to be... 
> to get the pressurized air  from below chassis.. to above chassis.
> 


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