model/dipole help
 

Hi
'
Ihave sgc 237 going into about 5ft of ladder line (mounted at base of
mast) to a horiz ctr feed dipole
'
it measures about 20ft 7" rf 'hot' side and 33' 7" rf gnd side


I am only haveing a mac, and never used any modeling software, can
someone help me out, and given the above data what are the

assumptions or pro's /cons' that would be expected at these dimensions?
(aside from the obv being it's kinda short)

The tuner will tune it all bands 6m to 160m my max swr is 1.5 and
usually is 1.2

my goal is to learn all about where i am /or not resonant , giving
harmonice or volt/vs currents etc (or perhaps that dosn't apply w/a
antenna mounted tuner)


Seems i also give a bit of tvi on 20m broadcast and a bit on 80m to the
direct tv


might just be rf overload however i'd like in general to learn about
my antenna and what the numbers mean



any help is greatly appreciated, perhaps i can use that info if my
antenna is at a really odd/bad length i could tweek it to make it better

thou i don't have much space left


thanks

ml wrote:
Ihave sgc 237 going into about 5ft of ladder line (mounted at base of
mast) to a horiz ctr feed dipole
'
it measures about 20ft 7" rf 'hot' side and 33' 7" rf gnd side

You have reasonable feedpoint impedances for 30m-10m
that the tuner should be able to match. Below 8.6 MHz,
the mismatch starts to climb. It's not bad on 40m but
very bad on 80m. So you have a reasonable setup for
40m-10m, pretty poor for 80m.
--
73, Cecil http://www.qsl.net/w5dxp

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In article ,
Cecil Moore wrote:

ml wrote:
Ihave sgc 237 going into about 5ft of ladder line (mounted at base of
mast) to a horiz ctr feed dipole
'
it measures about 20ft 7" rf 'hot' side and 33' 7" rf gnd side

You have reasonable feedpoint impedances for 30m-10m
that the tuner should be able to match. Below 8.6 MHz,
the mismatch starts to climb. It's not bad on 40m but
very bad on 80m. So you have a reasonable setup for
40m-10m, pretty poor for 80m.

thank you very much Cecil. I guess thats all do to the small size
(antenna :) ))

i really need to add some length to improve 80m and 160 i can do it
but not in a straight line,

at the end i'd hve to make a turn and go down the other side of roof
guess i'td end up sorta looking like a big fat square U shape thingy


greatful for the help

QUESTION:

if i swapped the hot w/the rf gnd effectively making
33.7hot 20f.7 gnd would that be better??

i make the gnd longer as it said to in the sgc manual


thanks again


m

On Sat, 11 Jun 2005 19:07:12 GMT, ml wrote:

if i swapped the hot w/the rf gnd effectively making
33.7hot 20f.7 gnd would that be better??

Hi Myles,

No such thing as hot/gnd as you use it. This is not household power
wiring. You can swap the connections, but this will accomplish
little. That is, unless you have failed to choke SGC wiring; then
although everything will be repeatable (even with new symptoms), why
it gives odd operation will be a mystery. (The solution to the
mystery will be choke all SGC wiring.)

73's
Richard Clark, KB7QHC

In article ,
Richard Clark wrote:

On Sat, 11 Jun 2005 19:07:12 GMT, ml wrote:

if i swapped the hot w/the rf gnd effectively making
33.7hot 20f.7 gnd would that be better??

Hi Myles,

No such thing as hot/gnd as you use it. This is not household power
wiring. You can swap the connections, but this will accomplish
little. That is, unless you have failed to choke SGC wiring; then
although everything will be repeatable (even with new symptoms), why
it gives odd operation will be a mystery. (The solution to the
mystery will be choke all SGC wiring.)

73's
Richard Clark, KB7QHC

thanks rich, for the reply, rest assured of one thing you taught me

i have chokes all over!!! :)

On Sat, 11 Jun 2005 11:13:57 +0000, ml wrote:


I am only haveing a mac, and never used any modeling software, can
someone help me out, and given the above data what are the

You should be able to run NEC on a Mac.

http://www.si-list.org/swindex2.html

This page has a guite to compiling NEC-2 and
Xnecview on a modern OS-X/Darwin Mac.

73, Ed. EI9GQ.


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On Sat, 23 Jul 2005 14:06:05 +0000, Eamon Skelton wrote:

This page has a guite to compiling NEC-2 and
Xnecview on a modern OS-X/Darwin Mac.

Doh! I forgot to include the URL.
http://www.scispot.org/archives/lab_..._mac_os_x.html


73, Ed. EI9GQ.

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