[Elecraft] Question for Wayne about your OCF Dipole

[Buck]

Wouldn't two 50 ohm cables in parallel result in 25 ohm impedance?


k4ia, Buck
K3# 101
Honor Roll  8B DXCC
EasyWayHamBooks.com

On 9/18/2017 10:06 PM, Wayne Burdick wrote:
> 
>> On Sep 18, 2017, at 5:31 PM, Don Wilhelm <donwilh at embarqmail.com> wrote:
>>
>> Wayne,
>>
>> Actually, parallel coax runs make a good choice for shielded parallel feedline.  The paralleled LMR-400 lines should produce a feedline characteristic impedance of 100 ohms.  It is normal to connect the shields together at both ends.  At the antenna, the connected shields are left floating, but at the rig end, are connected to chassis common (your BL2 ground lug) - perhaps "floating" is what you meant by "unterminated".  Are the shields connected at the antenna end?
> 
> Yes.
> 
> 
>>
>> As I recall, the matched impedance loss would be twice the loss of a single run of the coax, but at reasonable distances and the low loss of LMR-400, it should not be a problem at HF.
> 
> Agreed.
> 
> 
>>
>> The advantages of using parallel coax for a balanced feedline is the same as using coax over open-wire or ladderline.  It can be run on or in the ground, run next to or thorough conducting metallic surfaces, or coiled up with no ill effects.
> 
> That’s what I was dealing with. The house was built in 1929, so in the crawl space there’s legacy plumbing, knob-and-tube wiring, heating ducts, and spider webs that at least look conductive.
> 
> Wayne
> N6KR
> 
> 
> 
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