[TowerTalk] [RFI] Fair-Rite Common Mode Chokes

[Grant Saviers]

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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