Re: What your mother didn't tell you about transmission lines

Posted by Jack Smith-6 on Sep 11, 2011; 1:01pm
URL: http://elecraft.85.s1.nabble.com/What-your-mother-didn-t-tell-you-about-transmission-lines-tp6780383p6780755.html

A few years ago, I measured a length of plastic (some form of vinyl, I
believe) insulated zip cord with the loss results below.

Impedance over the range 300 KHz - 30 MHz varied from 118 ohms to 124 ohms.

Jack K8ZOA


Frequency MHz Loss (dB)/100 ft
5 2.3
10 3.5
15 4.6
20 5.5
25 6.9
30 8.1
35 8.7
40 9.2
45 10.4
50 11.6



On 9/11/2011 8:20 AM, Bill W4ZV wrote:

> Fred Townsend wrote:
>> Rubber (parallel) lamp cord can be used as transmission line and it is
>> cheap. Z0 runs 95 to 120 Ohms depending on insulation thickness.
>>
> True, but it has very high loss (especially at higher frequencies) and
> should only be considered as a last resort.  About 10 years ago ET3PMW was
> attempting to get on the low bands and only had zip cord available for
> transmission line.  I thought it should work fine for 80 and 160.  However,
> on 80m running 100 watts he was barely detectible here using a 1200'
> Beverage for receive.  Once Paul got some good ladder line, his signal was
> typically S8 on 80m and S6 on Topband, where he made several hundred QSOs
> with North America even in summer QRN (June/July).
>
> There is a loss graph on page 2 below but I believe ET3PMW's losses were
> much higher.  Of course this could have been due to poor quality wire
> available in Ethiopia.
>
> http://www.we0h.us/Amateur_Radio_stuff/Antenna/ZIP-Cord-Antenna/Zipcord-Antenna-7903031.pdf
>
> 73,  Bill
>
>
> --
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