[Elecraft] OT; Feedline question

[Matt Zilmer]

Very true!

Got back in front of my desktop 'puter and made an Excel worksheet to 
calculate the characteristic impedance at various spacings and wire 
sizes.  The real variable is the ratio of spacing divided by wire 
diameter (only the ratio matters). Everything else in the formula is a 
constant for our purposes.

16 AWG, 1 inchspacing:  Zc = 436 ohms

16 AWG, 2 inchspacing: Zc= 519 ohms

16 AWG, 3 inch spacing: Zc= 567 ohms

18 AWG, 1 inch sp:  Zc = 464 ohms

18 AWG, 2 inch sp:  Zc = 547 ohms

18 AWG, 3 inch sp:  Zc = 595 ohms

Or for you QRO ops: 3/0 AWG, 9 inch spacing: Zc = 450 ohms.  3/0 
(three-aught) is quite hefty, being 0.4" in diameter. Probably overkill 
for the average Joe Ham.

The commercial ladder line I use is 18 AWG with about 0.9" spacing (hard 
to measure), giving 451 ohms. I think there is a lot of this type in use.

Anyway, for the wire sizes and spacings we would normally use, the Zc is 
nearly the same value, which is all I was saying before.

The formulas for all this are pretty well documented at 
http://hamwaves.com/zc.circular/en/index.html.

73,

matt W6NIA


On 4/15/2017 10:52 AM, Lynn W. Taylor, WB6UUT wrote:
> Off-list one person learns.  On-list we all learn.
>
> On 4/15/2017 10:16 AM, Matt Zilmer wrote:
>> This is an amateur topic, so there's no reason to take it offline, imho.
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-- 
"A delay is better than a disaster."
-- unknonwn

Matt Zilmer, W6NIA
[Shiraz]