Hi Felipe
It works like a voltage divider where the impedance to ground should be lower
as possible to give you more attenuation like 1k/500ohms versus 1K/5 ohms
divider. You should use the choke near a good ground before entering the
station. If you switch box have a good ground it’s a good place to install it.
More turns better, but it is limited by the diameter of the coaxial cable, like
RG58/RG142 allows 12 to14 turns. RG213 only 8 turns.
Jim K9YC and a fantastic documentation about chokes. Please read this document
http://audiosystemsgroup.com/RFI-Ham.pdf
You will be a specialist after reading this guide.
Regards
JC
N4IS
From: Filipe Lopes [mailto:ct1ilt@gmail.com]
Sent: Monday, October 12, 2015 9:52 AM
To: JC <n4is@comcast.net>
Cc: topBand <topband@contesting.com>
Subject: Re: Topband: Commond mode choke for Beverage
Hello JC,
Thanks for your answer.
I just ordered a few 2631803802 and 5943003801 from mouser.
With these ferrites I ask the same question, should I put the choke close to
the 9:1 Balun or near the switching box and how many turns? some bevs have the
feed point at +- 60m away from the switching box.
73's Filipe Lopes
CT1ILT - CR6K
F4VPX - TM3M
2015-10-12 15:40 GMT+02:00 JC <n4is@comcast.net <mailto:n4is@comcast.net> >:
Hi Filipe
Zero , you should use material #31 or #77 , The core you have is not good
for low bands.
JC
N4IS
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com
<mailto:topband-bounces@contesting.com> ] On Behalf Of Filipe
Lopes
Sent: Monday, October 12, 2015 8:46 AM
To: topBand <topband@contesting.com <mailto:topband@contesting.com> >
Subject: Topband: Commond mode choke for Beverage
Hi guys,
I am about to add a common mode choke to isolate the antenna from its
feedline to each of my beverages and I only have FT240-61 ferrites. My
question is how many turns should I do on the ferrite using RG58 (all my
bevs are fed with RG58). Also should I put the choke near the 9:1 balun or
near my bev switching box?
Thanks in advance.
73's Filipe Lopes
CT1ILT - CR6K
F4VPX - TM3M
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