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Old June 12th 09, 04:15 AM posted to rec.radio.amateur.antenna
[email protected] nm5k@wt.net is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 757
Default Coax + Ladder Line

On Jun 11, 11:17*am, "Kash J. Rangan" wrote:
Thanks for all your responses and ideas.

Yes, I do have an antenna tuner. The maximum length of the antenna I can
hope for can only be about 65ft because of the placement of trees in my back
yard and access to my shack. At this time I will be happy if I can tune to
some bands up to 40M. I did not want to drill any additional holes for
outside access if I can help it amd make use of the existing one. I also
wanted the option of total disconnect from the outside. My equipment has
been fried by lightning in my previous QTH.

I figure it would be about a 60 ft run to the feed point. I am aware that
certain feed line lengths are to be avoided to minimize transmission line
radiation and tuning problems. In addition to low loss I thought ladder line
would be much lighter than coax. I don't have any way to support my antenna
at the center so I am trying to keep it as light as possible. *Not sure of
the wind loads though but I will have a modest workable antenna up soon.

You all have been very helpful in sharing your thoughts.

73

AG4EL, Kash


If it were me and I were using a tuner, I'd just run ladder
line the whole way. I've noticed that even if you pass
the line across a metal window frame, there is usually
no noticeable change to speak of. If you have to do that,
it's best to keep the line at right angles to the frame to
keep it as balanced as possible.
You could easily chunk the line outside during storms,
or you could rig up a way to disconnect by using
banana plugs, etc.. That way you can disconnect but
not have to fiddle with unplugging from the rig.
I would prefer to have those outside, so when
disconnected the line is totally out of the house.
It's probably quite well known on this group that
I don't like mixing feed line types in a case like this. :/

Running ladder line the whole way is the least lossy
vs mixing ladder line with coax, choke, etc..
Using G5RV type feeding schemes will work, but they
can take a decent hunk of your RF and turn it to heat
in many cases.
Even with a 80/1 mismatch, ladder line has low loss.
If the length of coax is short, the loss will be fairly low.
But.. many add a choke, etc, and I think the choke
is where a good portion of the loss is on these type
of feed systems. Some of these might use fairly long
coax lines, and the loss could add up vs ladder line.
BTW... Tune the tuner using the least inductance
needed to get a usable match whichever way you go.