[RFI] Common mode choke on 4 Square feedlines without skewing phasing?

[Andy KU7T]

Thanks for everyone’s input. I did some measurements.



I can do about 4 turns of 5” diameter of the coax and still reach the phasing box, bury the cable in a few spots where it goes over a walkway in conduit. In a few spots I have to run slightly elevated and also run up to the vertical feed points in 45 degree angles. Its not a big deal as this is in the woods and I do not care about esthetics.  My elements are not exactly on the same elevation, that’s why I am loosing a foot or two in length in a few of those coax. If it was all flat, I think I could do 6 turns or so…



So, I am contemplating putting up 4 turns x 7 #31 2.4 “ cores = 4000 Ohm at 4 Mhz. Maybe I can squeeze 10 cores on there, then I would be above 5000 Ohm.



Thanks again for the inputs.



73

Andy

KU7T





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________________________________
From: RFI <rfi-bounces at contesting.com> on behalf of Jeff Blaine <KeepWalking188 at ac0c.com>
Sent: Wednesday, January 23, 2019 12:44:51 PM
To: rfi at contesting.com
Subject: Re: [RFI] Common mode choke on 4 Square feedlines without skewing phasing?

I've had a number of different elevated radial configurations with a 40m
4SQ and from my personal experience the addition of ferrites to the
individual feeds did improve the directional characteristic
significantly.  The data is not clear because this is a subjective
observation, and in each case the elevated radial configuration was
improved as well.

When I put the 4sq down to ground level, with on-ground radial fields, I
did not use ferrites on the feedlines - the feedline was buried about 1
inch below ground level.  The directional characteristic in this
configuration is excellent as well.

In both configurations there has been a serious coax choke at the hybrid
on the main feedline from the shack.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com<http://www.ac0c.com>

On 23-Jan-19 2:06 PM, Don Moman VE6JY wrote:
> On all the 4 squares here (2 on 80 and 1 on 160m) I have both buried and
> put ferrites (lots) on all the lines to the individual vertical elements.
> With the phasing lines I used there wasn't much excess length after burying
> so the ferrite beads were always the plan.  The 4 sq's tuned up and
> performed as expected and whether the ferrites are enough or not, they
> don't have any negative impact.  I routinely use them as my primary rx
> antenna on both those bands.
>
> 73 Don
> VE6JY
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