[TenTec] open wire feed line

[NJ0IP]

YES.  600 OHM

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of Denton
Sent: Friday, September 30, 2005 9:02 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] open wire feed line

Does this mean that one should homebrew or purchase true ladderline. If this

is the case, would 450 ohm or 600 ohm ladderline be more  appropriate for 
multiband doublets?
----- Original Message ----- 
From: "Sinisa Hristov" <shristov at ptt.yu>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Friday, September 30, 2005 2:50 PM
Subject: Re: [TenTec] open wire feed line


> NJ0IP wrote:
>
>> Paul, just a word of caution when sourcing the stuff.
>
>
> One more word of caution:  most plastic ladder lines
> use copper clad steel conductors. Such lines are only
> suitable for low SWR applications, and in this respect
> they behave more like RG8 coax than like true open wire lines.
>
> Copper clad lines will introduce several dB's of loss
> in a typical "multi band doublet" applications.
> Depending on circumstances, this may or may not be acceptable.
> To me, it was acceptable until few weeks ago, but not anymore :-)
>
> Also, "multi band doublet" applications need significantly
> higher characteristic impedance than found in plastic lines.
>
> Here is some measured data on "450 ohm ladder line,
> #14 gauge, stranded wire" bought at Radioworld,
> Toronto, ON, http://www.radioworld.ca :
>
> k = 0.91
>
> Characteristic impedance  Zo = 335 Ohms
> (considering wire gauge and distance,
> Zo cannot be over 360 Ohms even without plastics,
> i.e, the distance is too small)
>
> DC resistance = 91 mOhm/m  (7.5 times that of copper!)
>
> matched loss at 14 MHz:  0.71 dB/100 ft
>
> this translates to 2.65 dB/100 ft with SWR = 10,
> and to 4.25 dB/100 ft with SWR = 20;
> SWR = 20 is easily achieved with multi band doublets
> because the Zo is too low
>
> matched loss at 42 MHz:  2.12 dB/100 ft
>
>
> 73,
>
> Sinisa  YT1NT, VE3EA
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>
> 


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