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KG6BAJ > NWSGRP 25.09.09 03:46l 39 Lines 1381 Bytes #999 (0) @ WW
BID : 11927_N1OES
Read: GUEST
Subj: Re: HELP WITH LADDER LINE CALCULATIONS.
Path: DB0FHN<DB0FOR<DB0SIF<HB9EAS<DB0ZAV<CX2SA<N6RME<KG6BAJ<KG6BAJ
Sent: 090924/1600Z @:KG6BAJ.#NCA.CA.USA.NOAM #:11927 [Grass Valley] InterGate $
** NEWSGROUP: rec.radio.amateur.antenna
** FROM : Owen Duffy <none@no.where>
steveeh131047 <google@karinya.net> wrote in news:11c60904-d961-4e70-9b60-
51e8a463fb89@o13g2000vbl.googlegroups.com:
...
> For example in this month's QST magazine there's an article on using a
> 40m full-wave loop on 80m. The designer uses a series quarter-wave
> section of 450 ohm ladderline to make the impedance "more manageable".
> He quotes 300+j8000 at the antenna end of the ladderline. Now plug
> those values into Owen's calculator, using something like Wireman 551
> for the line, and you'll get 7dB of feedline loss.
Steve,
It may even be worse than that as TLLC models skin effect in a
homogenouse conductor, and some ladder lines use copper clad steel that
will have higher loss at the low end of HF where the coating thickness is
less than several skin depths. This is especially true of the more
expensive stranded CCS types.
But, yes... QST runs stories from time to time that reinforce the myth
that ladder line is so good that you *never* need to consider its loss.
Here is are reviews of a couple of older articles discussing the relative
merits of ladder line and coax:
http://vk1od.net/blog/?p=316
http://vk1od.net/transmissionline/LOLL/
Owen
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