[RFI] Fair-Rite Common Mode Chokes

[Joe]

Thanks Frank,
Now 1/4 or 3/4 I'm assuming free space not figureing in velocity factor?

I am old school when I came to dipoles been a ham since 1975 and field 
day since 76. and most dipoles have been the simple split the coax and 
solder. bo baluns no chokes etc.

This year we actually did some antenna placement thought to lessen multi 
station interference, and we had a 3 foot vertical and then placed a 
regular dipole so the vertical was off the ends of the dipole, and we 
were actually amazed a FT-8 station and CW station had no real issues 
being on like 20 meters at the same time.

So thinking if we are gonna re do the dipoles to light weight ones. mat 
as well do it right and help minimize interference as much as possible. 
and hence the thought of the balun to choke off the coax, so I am to 
assume the 1/4 tor 3/4 is acting like what to keep rf off the braid?

Joe WB9SBD
Sig
The Original Rolling Ball Clock
Idle Tyme
Idle-Tyme.com
http://www.idle-tyme.com
On 7/18/2019 9:04 AM, donovanf at starpower.net wrote:
> Joe,
>
>
> We use a fifty foot length of RG-8X on each of the nine dipoles used at
> the W3AO mega-Field Days. We then transition to hundreds of feet of
> RG-213 to reach the centrally located tent on our 1000 foot x 200 foot
> Field Day site. We use lightweight Budwig insulators and lightweight
> dacron rope.
>
>
> A choke is unnecessary on a monoband dipole, simply grounding the
> coax shield approximately 1/4 or 3/4 wavelengths from the feedpoint
> is completely adequate. Only a short ground is needed.
>
>
> 73
> Frank
> W3LPL
>
>
> ----- Original Message -----
>
> From: "Joe" <nss at mwt.net>
> To: "Roger (K8RI)" <k8ri at rogerhalstead.com>, rfi at contesting.com
> Sent: Thursday, July 18, 2019 1:15:25 PM
> Subject: Re: [RFI] Fair-Rite Common Mode Chokes
>
> To change the subject some here,
>
> After a slight mishap at field day, a Dipole fell down in a storm, and a
> ceramic insulator hit a cars window and broke it.
>
> So the plan is to make an ultra light set of dipoles. Plastic
> insulators, coax fed with 58 size coax. etc.
>
> Now what cores, how many, etc. should I use instead of a heavy balun to
> make the choke? Low barefoot rigs 100 watts. so trying to keep things as
> light as possible.
>
> Joe WB9SBD
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 7/18/2019 12:22 AM, Roger (K8RI) wrote:
>> I (so far) use ferrite cores only for common mode chokes and I've made
>> and used many particularly for 160. 75, and 40 center fed slopimg
>> dipoles and half slopers.
>>
>> 73, Roger (K8RI)
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