Jim and Tom, many thanks for your replies. Let me tell you what I'm up to.
I would like to put up an 80M EDZ between two towers. However, my
towers are only 300' apart and I need about 340'. I have considered
drooping the ends vertically, but I thought either a folded dipole or
linear loading a few feet on the ends with ladderline would allow me to
fit it inside the 300' span. I use EZNEC 4+ for modeling.
I wonder if minimal lengths of ladderline for linear loading on each end
would provide the shortening while making the high resistance losses
arising from lower Q negligible? I haven't tried modeling it yet. I
thought I'd first see if anyone had successfully modeled ladderline as
an antenna element.
73, Joe
P.S. Tom, I wanted to comment on your replies regarding tuners with
balun inputs. I will do so in a separate post later.
Jim Lux wrote:
>At 02:32 PM 10/23/2005, Joe Giacobello wrote:
>
>
>>I am thinking about using ladderline for a folded dipole or for linear
>>loading a wire antenna. I wonder if anyone has successfully modeled
>>ladderline and, if so, what parameters they used for the insulation. I
>>assume that the insulation is PVC, but what is the thickness and how are
>>the alternating windows accounted for?
>>
>>I'd appreciate any information that members of the reflector can provide
>>on this subject.
>>
>>73, Joe
>>K2XX
>>
>>
>
>what program are you using to model it?
>If NEC, insulation models assume uniform thickness around the conductor,
>which is not representative of ladder line, so the "fine scale" details of
>the field in proximity to the ladder line will not be correct.
>
>
>Since the windows are very much less than a wavelength long, you can
>probably model it as a suitably insulated pair of wires with insulation
>properties chosen to match the actual properties of the wire.
>
>Even better, you could probably represent the ladder line as a suitably
>built NT card for the transmission line properties, and a single insulated
>wire to represent the "common mode" properties.
>
>If you're hoping to model the effects of things within, say, 5 times the
>cross sectional size of the ladder line, NEC is probably not a good tool.
>You need something like HFSS or one of the other programs that models
>dielectrics. Method of Moments (MoM) just isn't all that great at handling
>dielectrics.
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>
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>
>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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