Re: [IRCA] Cable connectors

[Russ Edmunds <wb2bjh@xxxxxxxxx>]

Vertical effect is simply the ability of the feedline to act like a vertical antenna and pick up signals itself - particularly a problem in a strong-signal environment. But that's all I can recall as to why this was done, and I'm not sure I understand "how" it was supposed to be more effective that way.


Russ Edmunds
Blue Bell, PA ( 360' ASL )
[15 mi NNW of Philadelphia]
40:08:45N; 75:16:04W, Grid FN20id
<wb2bjh@xxxxxxxxx>
FM: Yamaha T-80 & Onkyo T-450RDS w/ APS9B @15'
AM: Modified Sony ICF 2010 barefoot


--- On Mon, 9/6/10, Nick Hall-Patch <nhp@xxxxxxxx> wrote:

> From: Nick Hall-Patch <nhp@xxxxxxxx>
> Subject: Re: [IRCA] Cable connectors
> To: "Mailing list for the International Radio Club of America" <irca@xxxxxxxxxxxxxxxx>
> Date: Monday, September 6, 2010, 8:33 PM
> I believe that Gordon's low
> capacitance cable might also have been needed to reduce the
> capacitance seen at the output of his FET loop amplifier,
> otherwise it would be more prone to
> oscillate.   
> 
> My old NRC antenna reference manual, says that the feedline
> was used to eliminate "vertical effect".  I wonder if
> twinax or something like it would worked
> similarly?   The amplifier was meant to be
> attached to the balanced input of an R390A,  so it was
> important that one side of the balanced feedline didn't see
> more "vertical effect" than the other.   
> 
> Nick
> 
> 
> 
> 
> At 00:11 9/7/2010, you wrote:
> 
> >---- Russ Edmunds <wb2bjh@xxxxxxxxx>
> wrote: 
> >> I seem to recall that 'back in the day', Gordon
> Nelson was concerned about keeping the feedlines from his
> loops as short as practical for the application. Realizing
> that his recommended feedline was car radio cable with the
> original center conductor removed and replaced by insulated
> #22 or so ( with the braid soldered together on each line
> about every foot ) I wonder if it is in fact possible to get
> what you're aiming for. 
> >> 
> >> I don't recall the specific electrical and/or
> magnetic characteristics of that type of feedline vs. coax,
> but perhaps that too has some relevance here in that he
> eliminated using coax for a specific reason, which alas I
> also don't recall.
> >> 
> >> Russ Edmunds
> >
> >The only thing I can think of would be to lower the
> capacitance (per foot) of
> >the cable itself. This is the reason that type of cable
> was spec'ed for
> >car radios which had a compression trimmer that had to
> be peaked (at 1400 kc)
> >for the specific car whip being used. Now that I think
> about it, real commercial
> >grade coax contains spacers to keep the center
> conductor equidistant from
> >all parts of the shield. Running in your own #22 wire
> for the center conductor
> >after removing the original wire (I guess it was too
> flimsy) would lead to the
> >wire being adjacent to the shield almost everywhere.
> Not sure how important
> >that would be. I did that once, 40 years ago, but
> forget the details.
> >
> >- Bob
> >
> >
> >
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> *****************************
> Nick Hall-Patch
> Victoria, BC
> Canada 
> 
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