Topband: Share of a common mode current experience

[Jim Sullivan]

I am gathering info on a common mode 'turns through the toroid stack' choke.
After reading this thread of EMAIL and reading K9YC great article
"A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing",
I am  ready to gather the toroids and give it a try.
 
I checked on the cost of the toroids and the 2.4" #31 units seem to be >
$15.00 each.
As a result I have 4 questions.
 
1) Increasing the turns reduces the number of toroids required for the
target 5K ohms
   What is the down side of using fewer toroids?  (dissipation?)
 
2) Can I use teflon coax like RG142B/U (.195" diameter) to allow ~15 turns
with
    fewer toroids to achieve the same 5K ohms?
 
3) Does the diameter of the turns passing thru the Toroid stack effect the
predicted Rs.
 
4 Does anyone know which of the fair-rite distributors gives the best prices
for 
    quantity 10-15


I am new to the reflector, and I hope these questions do not waste bandwidth
 
Jim W7EJ CN2R



>Several problems. You cannot get more than 7 turns of RG8
>through a FT240 core, and about 12 turns of RG8X or RG6. AND,
>that larger cable will have more stray capacitance. This means
>that the turns MUST be widely spaced. It also means that the
>stray capacitance, even with wide spacing, will move the
>resonant frequency lower with fewer turns. Bottom line -- 7 or
>8 turns through 7 #31 cores is a pretty good choke for 160-15M,
>but you'll need nearly twice as many #43 cores. And with twice
>as many cores, the resonant frequency will be lower, so the
>choke will probably only be good 160M-30M.