[TowerTalk] Solenoid or Binocular configuration?

[Mike]

On 10/21/12 10:51 PM, K8RI wrote:
> On 10/21/2012 6:09 PM, Jim Brown wrote:
>> On 10/20/2012 7:23 PM, K8RI wrote:
>>> My question is about the difference between the 6 cores stacked or two
>>> stacks side by side.
>>
>> For a ferrite choke with close-spaced turns, it does not matter if he
>> cores are together or separated. What matters is the number of turns and
>> the number of cores.  The inductance increases with the square of the
>> number of turns, and in proportion to the number of cores. The
>> capacitance increases with the number of turns and with close spacing.
>> What you want is the lowest practical resonant frequency, and you can
>> use the measured data in my RFI tutorial as a guide.  So for the lowest
>> possible resonant frequency you want more turns and more cores, tightly
>> spaced.
>
> Thanks Jim,
>
> It's pretty much what I figured. I actually super glue the cores into 
> a stack. Just 4 tiny dots of glue and then pressure for about a minute.
> From the tutorial I figured 6 cores in a stack with about 9 or 10 
> turns of RG-400 although I can close space it all the way around the 
> inside, tack each turn in place with a dab of epoxy and let the 
> outside take care of itself.  That results in a coil about 3 to 4 
> inches longer than the stack but with the RG-400 flush against the 
> core on the inside and close to that on the outside. Stacks this long 
> start making 7 turns of the larger cable a lot of work.
>
> If find a need to use the larger cable (run out of RG-400) I'd go to 
> the binocular format as I can wind a coil with 7, or possibly 8 turns 
> in a single plane that takes up less than half the volume of one wound 
> on a solenoid stack. It also makes for a nice, tight, and neat close 
> wound coil that will fit in a 6 X 6 X 4" or 8 X 8 X 4" PVC box under 
> the boom.  I think I'll have enough RG-400 to build these though.
>
> I'd have to go back and look at the tutorial again, but IIRC 4 or 5 
> cores will be enough for the tri-bander and much more effective than 
> the original "cores over the coax" used.
>
> 73
>
> Roger (K8RI)
>
Roger,

What purpose does the box serve? Protecting the connectors?

73, Mike NF4L