If you must use FT240-61, then in a single layer about 18 turns of RG58 would
fit,
which should give you ~600 Ohms on 1.8 MHz. That would be very good for a
dipole,
but for a Beverage a much higher impedance is needed. Try to fit as many turns
as possible, until there is no more room in the center of the core.
Alternatively, use RG174. In a single layer you should be able to put ~32 turns,
which will give you a respectable 2000 Ohms on 1.8 MHz. But in this case take
care
to make all coax joints (RG174 to RG58) completely shielded, eg. by using a
copper foil.
73,
Sinisa YT1NT, VE3EA
----- Originalna poruka -----
Pošiljalac: JC <n4is@comcast.net>
Datum: Ponedeljak, Oktobar 12, 2015 15:40
Tema: Re: Topband: Commond mode choke for Beverage
Primalac: 'Filipe Lopes' <ct1ilt@gmail.com>, 'topBand' <topband@contesting.com>
> 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] On Behalf
> Of Filipe
> Lopes
> Sent: Monday, October 12, 2015 8:46 AM
> To: topBand <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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