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Re: [RFI] Fair-Rite Common Mode Chokes

To: Joe <nss@mwt.net>, RFI@contesting.com
Subject: Re: [RFI] Fair-Rite Common Mode Chokes
From: Grant Saviers <grants2@pacbell.net>
Date: Thu, 18 Jul 2019 10:06:03 -0700
List-post: <mailto:rfi@contesting.com>

The smaller #31 cores (1-1/8L x 1-1/8" dia Fair-Rite 2631101902) and 1/8" RG316 TFE coax can make a choke, but not the R of a 240 size. About 4k ohms 160, 6.5k 80m, 4k 40m with 10 turns (max that fits). I 3d printed an ABS fluted internal mandrel for disciplining the coax so windings never overlap per K9YC's work. RG316 coax is good enough for 500w to 100MHz. QRO on 80m.

On 80m 316 has 1.5db loss/100' so not great but about as small & light as practical. Transition to lower loss coax to keep the vertical 316 short.

Here is a loss calc with RG316 and SWR losses estimated
 https://owenduffy.net/calc/tl/tllc.php

The Times calc shows the power capacity of 316
https://www.timesmicrowave.com/calculator/

I use the Budwig Hye-Q insulators for DXpeditions, small light and pretty tough although it is easy to break off segments of the disks, a bit brittle. The rope holes are too small for para-cord so I drill them larger.


Grant KZ1W

On 7/18/2019 6:15 AM, Joe wrote:
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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