[Milsurplus] Re: [Boatanchors] Speech Amp Again

[Revcom]

Re: [Boatanchors] Speech Amp AgainGene,

Regarding the use of shielding on twisted pairs, I will refer you to an engineering article on same.  To ground one end or the other
is often a "trial and error" to avoid ground loops/hum/RF pickup.  By grounding at termination end involving RF you minimize the
effect the shield has as an antenna to radiate down the line.  Assuming you have a good earth and chassis ground at the transmitter.

If both components are equally bonded -chassis to chassis- and share a common earth ground, any effect is greatly reduced.

Refere to www.rane.com/note151.html for twisted pair applications and you can make your own evaluation on this.  

Rod
K0EQH

  ----- Original Message ----- 
  From: eugene at hertzmail.com 
  To: Revcom 
  Sent: Wednesday, November 19, 2008 4:18 PM
  Subject: RE: [Boatanchors] Speech Amp Again


  Hi Rod, question for you. why does the shielding occur at the far end, not the source? What is the rationale for that? I  am very interested in learning about that.
  thanks



------------------------------------------------------------------------------
  From: boatanchors-bounces at mailman.qth.net on behalf of Revcom
  Sent: Wed 11/19/2008 4:40 PM
  To: Barrie Smith; rbethman; boatanchors at mailman.qth.net
  Subject: Re: [Boatanchors] Speech Amp Again


  Twisted pair works well, if you have shielded cable, just ground the shield
  at one end, the
  driven end, not the source.

  Using 600/500 ohm audio on bcst stations, twisted pair works well in the
  10KW AM transmitter
  building OK.

  Rod

  ----- Original Message -----
  From: "Barrie Smith" <barrie at centric.net>
  To: "rbethman" <rbethman at comcast.net>; <boatanchors at mailman.qth.net>
  Sent: Wednesday, November 19, 2008 12:59 PM
  Subject: Re: [Boatanchors] Speech Amp Again


  > Good Day:
  >
  > Should the leads from the speech amplifier, or the matching transformer,
  > to the input of the HT-4B be shielded?
  >
  > 73, Barrie, W7ALW
  > _______________________________________________

  _______________________________________________

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