TenTec
[Top] [All Lists]

Re: [TenTec] [Fwd: Line Isolator Balun (sorta) question.]

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] [Fwd: Line Isolator Balun (sorta) question.]
From: Richards <jruing@ameritech.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 08 Aug 2010 15:19:19 -0400
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Hi Jim.... I am working my way through your piece, and getting the
drift that  clamp-on ferrite beads do not typically hurt me, but unless 
I have A LOT of them, they won't help much (if at all).

I did like this quote (taken slightly out of context, of course...) :

        Receiving Antennas benefit significantly from the addition
        of a common mode choke to isolate the antenna from its
        feed line. Both ends of the RG6 feed line to each of my
        Beverages takes 8 turns through one of the Big Clamp-Ons.

And yet, if I read your Figure 35  on page 26 correctly  (unlikely, but 
I will try, anyway...)  it seems to say one needs A LOT of ferrite beads 
to make a substantial difference - on, say 40-10 meters, even more on 
lower bands - but the chart indicates numbers tested were like 20 and 40 
beads... and if those are the typical 1/2 inch long beads (or the .19" 
beads mentioned int he text),  then it seems one needs just 20-25 inches 
of beads to have some meaningful
impact / effect.   THAT seems tolerable if one was going to use clamp-on 
beads - as did W0IYH using a string of clamp-on beads on his 10M 
antennas - with good effect  (acknowledging he preferred them over other 
types for convenience and specific reasons associated to a phased 
cabling already in place...)

So, they seem to have some positive effect -  BUT AM I CORRECT THAT THEY 
HAVE NO SIGNIFICANT DELETERIOUS OR HARMFUL EFFECTS if placed on the coax 
near the feed point?

I am especially interested in whether or not they might have more or 
better impact on a receiving antenna than on one I transmit with.   I 
use several receive only antennas, and anything to lower noise thereon 
is a bonus.   I would anticipate they would be more benign in a receive 
only setting than on a transmit -  receive setting.

Any traction?   Or just wasting my time.

=============================  JHR  =============================




On 8/8/2010 1:05 PM, Jim Brown K9YC wrote:

> benefit from reading my tutorial on coaxial chokes. Dissipation can be
> made quite small if you make R large enough, and, as it turns out, it's
> easy (and inexpensive) to do that if you understand the materials.
>
> http://audiosystemsgroup.com/RFI-Ham.pdf
>
>  =================================================================
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec

<Prev in Thread] Current Thread [Next in Thread>