[Amps] wires through center of coax

Fuqua, Bill L wlfuqu00 at uky.edu
Mon Dec 20 13:53:55 PST 2010


Under the right conditions it can be done. 
________________________________________
From: amps-bounces at contesting.com [amps-bounces at contesting.com] On Behalf Of Jim Thomson [jim.thom at telus.net]
Sent: Monday, December 20, 2010 11:04 AM
To: amps at contesting.com
Subject: [Amps] wires through center of coax

Date: Mon, 20 Dec 2010 00:12:23 -0700
From: John Lyles <jtml at losalamos.com>
Subject: [Amps] wires through center of coax

Bill - WA4LAV
I hope that running wires through coax center conductor like this won't
cause problems because I am doing it with the 9 3/16 inch diameter
output feeder of a new amplifier I have been working on. I have a
mechanical linkage going through the middler of the center conductor to
the tuning paddle in the cavity amplifier. Also, have a RTD applied to
the back of the paddle (inside) to measure temperature when it is
running. The linkage and wires run through a 1/4 wave stub into the 3
megawatt PA.

73
John
K5PRO

###  Running compressed, dry air, < 5% RH  [ typ 2-3 psi]   up through the  center conductor has been done for a long time..and ditto  with the cavity between the outer and inner conductor's.  U have to..or u will get condensation inside em...
esp  when used outdoors.. for broadcast use  up tall tower's.     Running wires inside the center conductor should not be a problem... Until   the wire exits out either end... or through the sides  via a special fitting.

Jim  VE7RF



>      I give up. I think most everyone else gets it. It is like a conversation I had with some old hams, not much older than I am aboiut some large coax.
> They were convinced that since the center conductor was hollow you could run wires up thru it to carry current to lights and rotators without affecting the
> impedance of the coax. Their argument was that current only  flows on the outside of the conductors. But that is not always true.
> Current flows on the surfaces and in the case of a hollow conductor it is true it will flow on the outside as long there is nothing to electric
> create fields on the inside. There are electric/magnetic fields between the outside of the inner conductor and the inside of the outer conductor. But once you put a conductor on the inside of the hollow inner conductor you have created a new bit of transmission line, there are fields now between the new conductors and the inside on the inner conductor. That changes everything.
>
> 73
> Bill wa4lav
>



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