[TowerTalk] Solenoid or Binocular configuration?

[K8RI]

On 10/22/2012 9:16 AM, Mike wrote:
> 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?

Pretty much... On the beams they really serve as a stable mount for the 
chokes and on 160 are part of the feed connection.

On all the other antennas they just hang out in the elements.
http://www.rogerhalstead.com/ham_files/AntennaFeed1.htm
( 80 M fan dipole )Haven't had any problems with center conductor 
migration ... yet.

73

Roger (K8RI)


>
> 73, Mike NF4L
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