ladder line construction methods?
Larry Gagnon
it with homebrew open ladder line. Would anyone care to reply as to how
to construct ladder line easily and effectively? How does one determine
spacing to get X ohms impedance line?
Also any ideas on how such line can easily be fed in through a window
with a wood frame would be greatly appreciated.
Larry Gagnon VE7EA
--
********************************
to reply via email remove "fake"
Cecil Moore
> Hello to all. I intend to erect an 80 meter full size dipole and feed
> it with homebrew open ladder line. Would anyone care to reply as to how
> to construct ladder line easily and effectively? How does one determine
> spacing to get X ohms impedance line?
Spacing is not critical. How about a 4" spacer made out of irrigation
plastic tubing?
--
73, Cecil, W5DXP
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'Doc
Boy, are you gonna have fun! As Cecil said, spacing isn't
all that critical. Use whatever you can find enough of, to make
the 'spreaders', as long as it's not conductive it should work.
The simplest way to feed ladder line through a window is to
make a 'spacer' board to fit in the window. Drill a couple of
holes in the board, the correct distance apart, feed the line
through the holes, 'hot glue' in place (or however you can get
it to stay put. Have to remove the screen...
'Doc
PS - The real 'trick' is to keep the line from 'swarming' on
you when you finish.
Tom Bruhns
logarithm, and D is the wire spacing, center to center, and d is the
wire diameter. Assumes round wires, and air dielectric. You can
rearrange that: if you want x ohms and have d diameter, D =
d*exp(x/120)/2, where exp(x/120) is "e to the x/120 power". If you
don't have a calculator that handles that sort of math, this table
will probably get you close enough:
D/d impedance, ohms
1.9 150
2.8 200
6.2 300
22 450
75 600
Construction depends a bit on how much you're making and what you have
available for materials and tools. People used to use wooden spacers,
boiled in parafin wax. Someone gave me a bunch of PETE
tensile-strength test strips that are a good size. You can make
spacers from PVC pipe. You can thread wires through holes (generally
not so efficient), or fit wires into notches and secure by with a
plastic or wire wrap, or by melting the wire into an undersized notch,
or with various glues. Undoubtedly lots of other ideas, both
tried-and-true and just waiting to be tried for the first time.
You can drill holes through the glass and install feedthroughs (but
probably not if it's double-pane!), or drill a couple over-size holes
through the wall or possibly through a wooden window frame member, or
install a wood or plastic piece in a partially-open window. You can
also possibly inductively or capacitively couple through the window.
If you decide to go through wood or wall materials, plan to make
oversized holes, lined with decent electrical/RF insulation. What
strikes your fancy?
Cheers,
Tom
Larry Gagnon <laga...@fakeuniserve.com> wrote in message news:<106jk0i...@corp.supernews.com>...
JGBOYLES
>to construct ladder line easily and effectively? How does one determine
>spacing to get X ohms impedance line?
One of many ways is to use plastic coathangers for spacers. These are
readily available, and have the added advantage that you can choose your color.
Just chop them up to whatever spacing you desire.
If you are planning on just a single band antenna, I would feed it with coax.
However, if you are going multi-band with a tuner, use the open wire line.
The Impedance is not critical. Use 2" to 6" spacing.
73 Gary N4AST
Bob Miller
<laga...@fakeuniserve.com> wrote:
>Hello to all. I intend to erect an 80 meter full size dipole and feed
>it with homebrew open ladder line. Would anyone care to reply as to how
>to construct ladder line easily and effectively? How does one determine
>spacing to get X ohms impedance line?
>
>Also any ideas on how such line can easily be fed in through a window
>with a wood frame would be greatly appreciated.
>
>Larry Gagnon VE7EA
As an alternative, you can try the website for w7fg. He makes and
sells open ladder line, as well as dipoles with the ladder line
attached.
bob
k5qwg
Lloyd Mitchell
sense. I can recommend his version highly.
Its easy to put up and you dont have to worry about the center connection
coming loose..*there is no center connection*
He uses one continuous wire from feeder to end of the dipole on each
side..smart...
Mitch KD4HTW
KA9CAR
consuming. I now buy it.
I purchased wire "staples" These are plastic bridges with holes for nails.
You pull out the nails and install your feed line.
There is a photo of a 1/2 inch section at this URL.
http://user.mc.net/~jdewey/Ham_radio/grounding_relay.jpg
I used larger staples for my main feed line.
http://user.mc.net/~jdewey/Ham_radio/doublet.jpg
John
KA9CAR
"Bob Miller" <bxmi...@texas.netNOSPAM> wrote in message
news:drdk60ptd7ulaumdt...@4ax.com...
Drbob92031
>make a 'spacer' board to fit in the >window. Drill a couple of
>holes in the board, the correct distance >apart, feed the line
>through the holes, 'hot glue' in place (or >however you can get
>it to stay put. Have to remove the >screen...
'Doc
on the incomming lines.
de wa2eaw...Bob
zeno
'Doc wrote:
PS - The real 'trick' is to keep the line from 'swarming' on
> you when you finish.
What does this mean? I am unfamiliar with the term.
Zeno
zeno
Zeno
zeno
time ceramic insulators with the hole down the middle, you know,
those 4 or 5" long while tubes that were used in the knob&tube era
of electrical wiring. Since I would be making my own feed line
here, I could rejoing the pair on the other side of the wall and
continue with my spacers until I reached the ceiling, and then to
the process again, eg. putting each wire thru its own tube and then
continuing with the spacers on the other side.
It is either this or using that idea of double coax feed with the
coax grounds connected to each other at one end and grounded to the
tuner (?), anyone have sucess with this method of coming into the
shack via balanced lines?
Zeno
zeno
so its impedance matches the characteristic impedance of the antenna
itself at its feed point?
The theoretical feed point impedance for a full wave loop antenna is
approximately 100 ohms, (but this does change, and is dependent upon
antenna height above ground, near-by structures, and ground conductivity.)
Should I try to make my ladder line to get as close as possible to this
100 ohm? In other words, does it make any difference reallly if my (12
guage insulated) ladder line uses 4" spacers (550 ohm) or 2" spacers (468
ohm) or 1" spacers (385 ohm) in the final analysis? Should I just go with
the 4" spacing because it looks cool?
Anyone think that maybe non-insulated would be a better way to go?
Zeno
Cecil Moore
> What is a good type of wire to use? Stranded ok? Insuluated ok? what is best?
I made mine cheap out of #16 stranded insulated house wire available at
Home Depot.
--
73, Cecil, http://www.qsl.net/w5dxp
Cecil Moore
> If one is constructing ladder line, is the point to design the ladder line
> so its impedance matches the characteristic impedance of the antenna
> itself at its feed point?
The point of using ladder-line is so the antenna impedance doesn't
matter (within reason). SWRs on the ladder-line range up to 30+:1
with small ill effects. A 30:1 SWR on ordinary coax is a signal
killer.
Consider that the feedpoint impedance of an all-HF-band antenna
might range from 60 ohms to 3000+/-j3000 to 6000 ohms. The SWR on
Z0=600 ohm line would be around 10:1. The SWR on Z0=50 ohms would
range up to 100+:1.
> The theoretical feed point impedance for a full wave loop antenna is
> approximately 100 ohms, (but this does change, and is dependent upon
> antenna height above ground, near-by structures, and ground conductivity.)
> Should I try to make my ladder line to get as close as possible to this
> 100 ohm?
Nope, go for simplicity. There's not much practical difference between
Z0=400 ohms and Z0=600 ohms. And you may be able to use the impedance
transforming properties (on a line with reflections) to your advantage.
> Anyone think that maybe non-insulated would be a better way to go?
Non-insulated wire allows one to hang parallel stubs up and down the
line, useful for matching purposes. It also allows one to measure
actual feedline voltages.
Richard Clark
>Should I just go with the 4" spacing because it looks cool?
Fer Sure, Dude!
The choice is simply one of maximizing copper to minimize loss. If
you expect a wide variation of Z through using the radiator across a
larger variation of frequency, it is hard to choose one single
determiner of line Z outside of this consideration. You could use the
same logic to select 50 Ohm line (there is absolutely nothing magical
about the value); however, cost becomes prohibitive due to a larger
conductor for the inside lead driving the size of everything else to
obtain the same loss figure as the cheaper, simple twin lead
construction.
So, there you have it, cool and cheap (true to only the frugal
Amateurs's perception of reality).
As for another question about coming in through the wall. You idea
would work suitably. The only problem is in having it penetrate house
insulation that is foil-backed (without you being aware of that being
so). Some would offer the penetration presents no problem as it is
for a very small interval. In the large scheme of things, quite true;
and yet as a site dislocality (humorously called a bump in Z) this is
where additional SWR will be present with a corresponding
magnification of V and the possibility of breakdown. This is
unlikely, but this would be where it happens if "likely" occurs. As
things go, it is all a probabilistic issue - the insurers have tables
for this.
73's
Richard Clark, KB7QHC
Andy Cowley
> Larry Gagnon wrote:
>
>> Hello to all. I intend to erect an 80 meter full size dipole and feed
>> it with homebrew open ladder line. Would anyone care to reply as to how
>> to construct ladder line easily and effectively? How does one determine
>> spacing to get X ohms impedance line?
>
>
1/4" / 6 mm PTFE rod. From Radiospares in the U.K.
but there must be suppliers in the States. Cut into
suitable lengths with a hobby knife - I used 125 mm
but not critical. Drill holes 5 mm from each end,
making sure they are parallel. Holes should be about
1/2 mm smaller than the wire you are going to use. I
used 19/0.2 silver plated copper with a PTFE jacket.
PTFE is fairly soft and easy to work with hand tools.
The stuff available here is white and surprisingly
very unobtrusive visually, certainly a lot better
than black windowed 450 ohm twin.
Slit from the holes to the ends of the rod with a
hobby knife. Ease open with finger and push the wire
in. I used an aluminium ruler to push with. It will
'click' into place. You can adjust the spacer positions
easily but the grip is enough, even with PTFE, to keep
the spacers in place. Space the rods 12" to 18".
This will also work FB with bare copper conductors.
Apart from its excellent electrical characteristics
the PTFE is very good at shedding rainwater, which
can be a problem if you use other plastics, especially
tubes.
You now have some very posh mil-spec ladder line. I
can easily make 30' an hour with hand tools.
vy 73
Andy, M1EBV
zeno
likely use the uninsulated wire for the diy ladder line. Although I do
not quite understand the thing about stubs and am not sure how I would be
able to measure anything along the ladder line since it is actually high
up in the air for the most part (I might be able to measure something at
its ends tho....what exactly does one need to be measuring up there?).
Sorry to be so Elmer-needy....
I just happen to have a bunch of that black poly 1/2" irrigation tubing,
which cuts up easily, and is apparently a good choice for diy ladder line
because of its UV tolerance.
There is no foil-backed insulation to worry about coming into the house
peak or ceiling. I have a bucket of those old porcelin knob&tube feed
thru dealies out in the barn.
I am making some masts out of whatever I can recycle, mostly old metal tv
telescoping masts. I will have to guy them if I get them up as high as I
possibly can for the four corners of the loop. I was thinking of using
pulleys and dacron for the guys, pulleys so I can redo the guys after
years...and they look like they are about to fall apart etc. without
having to take down the poles.....or should I use wire for guys? The
masts are metal anyway, maybe wire guys are ok, what do you think?
-Zeno (although I probably will be "Bill" when I finally get on the air
again)
They just gave me KG6UHM, but I think I either want my old expired call
back or concoct something new....with good cw rhythm....and "phonetics"
which reads like a novel......
Richard Clark
>I just happen to have a bunch of that black poly 1/2" irrigation tubing,
>which cuts up easily, and is apparently a good choice for diy ladder line
>because of its UV tolerance.
Hi Bill,
Black is usually indicative of carbon content; but I wouldn't let that
stop me the first time around if it was handy (pop it into the
microwave and nuke it to see if it gets hot - this is not about
microwave frequencies, merely tendency to conduct and to dissipate).
>There is no foil-backed insulation to worry about coming into the house
>peak or ceiling. I have a bucket of those old porcelin knob&tube feed
>thru dealies out in the barn.
Sounds like a done deal.
>
>I am making some masts out of whatever I can recycle, mostly old metal tv
>telescoping masts. I will have to guy them if I get them up as high as I
>possibly can for the four corners of the loop. I was thinking of using
>pulleys and dacron for the guys, pulleys so I can redo the guys after
>years...and they look like they are about to fall apart etc. without
>having to take down the poles.....or should I use wire for guys? The
>masts are metal anyway, maybe wire guys are ok, what do you think?
Dacron, I think, is the more long-lived, goferit. Use wire, don't use
wire; it won't matter much.
As for measuring stubs. Not sure how that appeared as a concern, but
as to measuring in general, attach a known mismatch at the far end and
measure the SWR across frequency. If the readings look better than
you would have reckoned, then you have something wrong along the way
(loss tends to sweeten the appearance of problems). The known
mismatch could be as simple as a direct short at even multiple of
quarterwaves away (or open on odds - whichever). Make sure to account
for velocity factor, or simply compare the physical length to the
measured electrical length of the short/open. This, too, will give
you an indication of line health. You can go farther and calculate
the actual line Z, but who cares? Only guys like me (and that hardly
counts for much).
'Doc
Zeno,
"Swarming" means that because of the 'memory' of the wire
used to make the 'twin lead', when it's turned loose from
whatever you fixed it to to build it, it tries to assume it's
former shape. Usually results in a 'rat's nest' of wire in
a not so compact ball, LOL! Not really something to waste a
lot of worry on, just be aware that it can happen.
'Doc
'Doc
No reason why it wouldn't work, just use the normal care
in selecting a 'spot' in the wall that doesn't hold any
other wiring, etc. Using feed-throughs like that is sort of
'permanent', can't remove it without repairing the holes.
The board in the window thingy isn't 'permanent', just take
it out of the window and replace the screen (if any). The
choice is your's and your 'significant other's (probably more
her's, than your's, right?)...
'Doc
Cecil Moore
Tying the ladder-line to the trailer hitch of my GMC pickup and
stretching it a bit solved all those problems.
--
73, Cecil http://www.qsl.net/w5dxp
Irv Finkleman
Perhaps the term 'Sproinging' might be better. You take it out in a
neat roll, let go, it goes 'Sproing!' and you have a rats nest. When
you get ready to put it up, call a couple of chums over for an
antenna raising party and let them loose the coil -- then let them clean
up the ball of wire! :-)
Irv VE6BP
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/
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--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada
zeno
Sometimes that phenomenon is real comedy material. I can just
see Laurel and Hardy putting up a short wave antenna......
"swarming" hmmmmm, like you disturbed a hornets nest eh?
Now that I think of it, the actual physics behind "swarming"
would be pretty darn sophisticated stuff.....
Bill (aka Zeno, aka, etc...)
zeno
Either that or they should sell wire in straight lengths.....
One of my favorite (and boring) routines at the Home Depot, while awkwardly tooling
around with 20 Foot pipes in the shopping cart nearly causing bodily harm when
negotiating a turn down an isle, is to ask one of the managers, "where do you keep
the 1000 footers?"
Getting home with a 500 foot straight length of wire would require a few red flags
in back.....
-Zeno
zeno
Would this be a good reason to use solid core copper wire?
After tying one end of my ladder line to a short (PVC) pole at
the house roof peak (this is to keep it high and away from some
other lines), I need to carefully arch (arc) it around and into
the side of the house (or into a modified "window" that
ventillates the attic space up there. I might use a "stick" or
something to make sure the ladder line stays where I want it
here. The ladder line at this point has to go through a space
between a cable tv and a telephone line. If the ladder line is
kept in place, it will be 2-3 feet away from the other lines
which are perpendicular (and thus only in proximity at a one
point).
It is because of these other lines that I perhaps might have to
consider other alternatives, but I thought I would first try the
idea of running the ladder line all the way into the station in
the house. If there is a problem with interference, then I might
have to consider the system, I have seen mentioned, where you
run double coax lines into the house for the last section with
the shields tied together (anyone actually tried that, does that
work well, any problems, etc.?)
My point being that solid core wire is easier to "mold" into
shape. My only concern is that sometimes solid core could break
if there is a repetitive friction type bending stress along the
way (wind, or who knows).
Zeno
zeno
Richard Clark wrote:
>
> Black is usually indicative of carbon content; but I wouldn't let that
> stop me the first time around if it was handy (pop it into the
> microwave and nuke it to see if it gets hot - this is not about
> microwave frequencies, merely tendency to conduct and to dissipate).
Wouldn't sticking my multi/ohmeter into the material at a couple of points
tell me if it dielectric or not? I did that and it would seem that this black
poly pipe is totally non-conductive. If it contained carbon it would be like
a composition resistor and register something (no?).
Anyway I am working on another source of rigid 3/8" dia. UV/PVC which might
work out better.
bill
Richard Clark
Hi Bill,
Being conductive and being lossy are not the same thing. You may have
both situations, or one, or the other; however "not being conductive"
does not necessarily mean "not lossy." The microwave test is hardly
conclusive unless you notice it heat up. Other testing is more
sophisticated.
zeno
>
> Being conductive and being lossy are not the same thing. You may have
> both situations, or one, or the other; however "not being conductive"
> does not necessarily mean "not lossy." The microwave test is hardly
> conclusive unless you notice it heat up. Other testing is more
> sophisticated.
>
> 73's
> Richard Clark, KB7QHC
Ohhhhh! I get it now. Its like why some kitchenware is ok for the microwave and
some not. The RF might be heating my spacers and if the spacers are the wrong
stuff, we have a melt down! Darn....why did all those neat industries making cool
things out of glass and ceramic dry up and disappear.....
with the collectible price of simple glass antenna strain insulators you would
think some industry would fire it up again, and while they are at it they could
make some of them out of purple glass and the collectors would go nuts unleashing
all kinds of cash on them. How hard is it to make things out of glass?
ps. has anyone actually heard of a diy ladder line having a spacer melt down
while running power? no reason why it couldn't happen....
Now that I understand, I will at least put my prospective spacers through the
microwave test....
-bill
Richard Clark
>ps. has anyone actually heard of a diy ladder line having a spacer melt down
>while running power? no reason why it couldn't happen....
Hi Bill,
This has never been reported here. Instead, it is noted by the
characteristic Z of the line being lower than computed. Such
measurements (of the characteristic Z) can be performed through a few
simple but still time consuming tests.
zeno
spacers?
-bill
Richard Clark
>Anyone tested that gray UV resitant PVC pipe? What about that for ladder line
>spacers?
Hi Bill,
Each formulation seems to be distinct, but offhand I don't recall
which is which. To broaden your experience with this forum, visit:
http://groups.google.com/groups?oi=djq&as_ugroup=rec.radio.amateur.antenna
and checkout their advanced search page. Use "PVC" and "Loss" as
keywords in the search. The topic is not so novel as to be sparsely
represented in the archive.
Ralph Mowery
"zeno" <ze...@sonic.net> wrote in message news:4081E9B9...@sonic.net...
> Anyone tested that gray UV resitant PVC pipe? What about that for ladder
line
> spacers?
>
>
I can't say that I tested it but I have an 8 element 220 mhz beam on a 10
foot piece of the grey electrical conduit that has been up over 15 years. I
think it is about 1 1/2 inches in diameter.
zeno
Thanks for the link to the archives, I will check it out.
I imagine there a few hams who want to make their own ladder line these days. Other than finding some vintage ceramic spacers (rare) what are they using?
Apparently paraffin soaked dowels are not without some shortcomings. I think there is at least one ham who has a cottage industry selling his homemade version ladder-line which, from what I can gather, utilizes the black poly piping that I mentioned earlier.
I think I came across at least one ham who has used the grey UV/PVC pipe which he slices (saws) lengthwise and then drills holes and/or notches etc. This seems a bit labor intensive if one wants to make any quantity, but maybe not as much as I think.
If the UV/PVC pipe is a good solution, I might be able to track down a source of 3/8" UV/PVC pipe which I would not slice up, but just cut into 6" lengths and then devise a fastening system on either end for the wire.
Bill
Richard Clark
>If the UV/PVC pipe is a good solution, I might be able to track down a source of
>3/8" UV/PVC pipe which I would not slice up, but just cut into 6" lengths and
>then devise a fastening system on either end for the wire.
Hi Bill,
The sellers and methods are as diverse as the stars. It is really
very simple with few gotchas. It really is more a matter of build
and test - the only real validation you can trust.
JGBOYLES
>Other than finding some vintage ceramic spacers (rare) what are they using?
Hi Zeno, Read back thru this thread, there have been all sorts of suggestions.
You can use cut up plastic coathangers, plexiglass, PVC, cut-up vinyl chopping
boards ect., for spacers. The spacing can be 1"-6". The wire can be #14
insulated-#20 insulated or uninsulated. Saw a number of suggestions to get it
in the house.
My suggestion is to pick out a method and materials that you like, and try it
out. You will probably be pleased with the results. I like all my ladder
(open wire) line
73 Gary N4AST
zeno
wire, it was pulled out of my well (submersible 240V pump) a few years
ago. Any reason, aside from weight, not to use this #10 wire for
constructing diy ladder-line? I understand the bigger the wire the less
the loss (what little there is with ladder-line), also I understand that
solid core copper will stay straighter and maintain the spacing better
than braided. The insulation is kind of thick and rubbery (it went down to
the well submersible), would it be better to cut off the insulation or
just leave it? If cut off do I need to clean it up further or just leave
the residue on the wire? Since this is three wires braded together I would
have to do some major straigtening first. Maybe this is just a bit too
heavy, now that I think of it, there is alot of copper there. Any
motivating advantages???
Bill
Larry Gagnon wrote:
> Hello to all. I intend to erect an 80 meter full size dipole and feed
> it with homebrew open ladder line. Would anyone care to reply as to how
> to construct ladder line easily and effectively? How does one determine
> spacing to get X ohms impedance line?
>
Cecil Moore
> I just found several hundered feet of used #10 solid copper, insulated
> wire, it was pulled out of my well (submersible 240V pump) a few years
> ago. Any reason, aside from weight, not to use this #10 wire for
> constructing diy ladder-line?
Maybe you should patent the idea of a self-supporting transmission line?
zeno
tiny spacer every 5 feet or so. Was that you or someone else who made the
ladder line out of tubing shaped like a sine wave.... hi hi
seriously, though, if one needed a section of ladder line to really stay
put (say a section which gets nervously close to other naughty metal things
or wire, why couldn't you fabricate just that section out of copper tubing
and then go the rest of the way with wire? Are there impedance issues when
changing the wire thickness along the way?
73
Bill
Cecil Moore
> seriously, though, if one needed a section of ladder line to really stay
> put (say a section which gets nervously close to other naughty metal things
> or wire, why couldn't you fabricate just that section out of copper tubing
> and then go the rest of the way with wire? Are there impedance issues when
> changing the wire thickness along the way?
I have used solid copper wire sliding inside copper tubing to achieve
an adjustable length transmission line for matching purposes.
zeno
Cecil Moore wrote:
That's interesting, so you find wire whose OD is just right for the ID of the
tubing and that makes a good enough connection and is adjustable. How much
adjustment were you after, inches or feet?
-Bill
Cecil Moore
> Cecil Moore wrote:
>>I have used solid copper wire sliding inside copper tubing to achieve
>>an adjustable length transmission line for matching purposes.
> That's interesting, so you find wire whose OD is just right for the ID of the
> tubing and that makes a good enough connection and is adjustable. How much
> adjustment were you after, inches or feet?
I just relied on skin effect to effect the proper conductive function. RF
won't flow into the inside of the tubing if it has any other "choice". :-)
The thing was adjustable from 20 feet to 35 feet in order to make a G5RV
truly a fully functional all-HF-band antenna. It really did work nearly
perfectly and could be automated using something like a screwdriver motor.
Bob Miller
>Anyone just use lengths of copper pipe or tubing? You might only need a
>tiny spacer every 5 feet or so. Was that you or someone else who made the
>ladder line out of tubing shaped like a sine wave.... hi hi
>
>seriously, though, if one needed a section of ladder line to really stay
>put (say a section which gets nervously close to other naughty metal things
>or wire, why couldn't you fabricate just that section out of copper tubing
>and then go the rest of the way with wire? Are there impedance issues when
>changing the wire thickness along the way?
>
>73
>
>Bill
>
>Cecil Moore wrote:
>
>> zeno wrote:
>> > I just found several hundered feet of used #10 solid copper, insulated
>> > wire, it was pulled out of my well (submersible 240V pump) a few years
>> > ago. Any reason, aside from weight, not to use this #10 wire for
>> > constructing diy ladder-line?
Zeno, all of your suggestions would increase the weight of the
feedline, and possibly stretch the antenna. FYI, a 500-ft. spool of
#14 or #12 insulated, stranded copper wire from Lowe's Home
Improvement (or Home Depot) runs about $15.00
Bob
k5qwg
zeno
Bob Miller wrote:
>
> Zeno, all of your suggestions would increase the weight of the
> feedline, and possibly stretch the antenna. FYI, a 500-ft. spool of
> #14 or #12 insulated, stranded copper wire from Lowe's Home
> Improvement (or Home Depot) runs about $15.00
>
> Bob
> k5qwg
Hi Bob,
I did pick up a 500' roll of #12 insulated from the Home Depot here (current
price here is about $32), but it seems like this braided copper will require
too many spacers to keep it straight. I am thinking about returning it for some
solid copper #12. I think the solid will hold shape better as a ladder-line
with a minimum of spacers. Also I see no reason not to go with bare wire
instead of insulated.
Can anyone run down the pros and cons of bare vs. insulated for ladder-line. I
understand there is ever so slightly less loss with bare wire.
Bill
zeno
spacers and a variety of wire: stranded #12, and solid #12, and
then solid #14 (all insulated).
I think I am going to pass on this process. The only way I can see
this homebrew ladder line holding its shape (spacing configuration)
is to keep it under quite a bit of tension, a situation which may
not actually be appropriate to my specific installation parameters
here.
I am now thinking: how bad could those commercially manufactured
window lines be?
Any recommendations on a specific type of commercially made window
(ladder) line? I see that it comes in a variety of configurations
and slight differences in Z.
This feed line will be for a full wave 160m loop.
I am not all that convinced that the effects of weather on this
commercially available balanced line would be that much more
negative than what it would be with any homebrew line I could
construct.
I am under the impression that homebrewed ladder line should strive
to have as few spacers as possible, eg. 3' for straight runs, 1-2'
for curves. Using these guidelines it seems like what I would come
up with would not maintain a precise spacing and the temptation
would be to use a spacer at every foot. Wouldn't it be undesireable
to use so many spacers?
Somebody out there must like commercial window ladder line?
Bill
'Doc wrote:
> Larry,
> Boy, are you gonna have fun! As Cecil said, spacing isn't
> all that critical. Use whatever you can find enough of, to make
> the 'spreaders', as long as it's not conductive it should work.
> The simplest way to feed ladder line through a window is to
> make a 'spacer' board to fit in the window. Drill a couple of
> holes in the board, the correct distance apart, feed the line
> through the holes, 'hot glue' in place (or however you can get
> it to stay put. Have to remove the screen...
> 'Doc
>
> PS - The real 'trick' is to keep the line from 'swarming' on
> you when you finish.
zeno
How close do these spacers appear to be.
Bill
Richard Clark
>Any recommendations on a specific type of commercially made window
>(ladder) line? I see that it comes in a variety of configurations
>and slight differences in Z.
>
>This feed line will be for a full wave 160m loop.
Hi Bill,
You repeatedly characterize this as 160M and given the size and height
- Why do you think you need ladder line when it will in all
probability fit quite nicely into a coax?
In free space, it may show as much as 140 Ohms R; however, within the
cold embrace of earth only 50 feet away, you will barely muster 35
Ohms at resonance.
Cecil Moore
> Any recommendations on a specific type of commercially made window
> (ladder) line? I see that it comes in a variety of configurations
> and slight differences in Z.
I use Wireman #554, #14, stranded, copper-clad steel. It's
virtually indestructible. http://www.thewireman.com
Cecil Moore
Using a tape measure, they appear to be 21 inches apart.
Irv Finkleman
>
> I tried practicing making some diy ladder line...
> I am now thinking: how bad could those commercially manufactured
> window lines be?
>
> Any recommendations on a specific type of commercially made window
> (ladder) line?
I used 300 ohm TV twin lead for years. Why the concern about 600 ohms? It
really doesn't matter unless you have a 600 Ohm feedpoint. The losses are
still very low regardless of conditions, and as for dirty or rain, I had
some up from 1983 to 1996 -- and never noticed any changes. When I took
the antenna down the twinlead was as good as new and I used it for other
things.
Irv VE6BP
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/
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Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/
Irv Finkleman
>
I should have added that the Twin Lead was the cheapest stuff available as
I just tried it for an experiment! It was a 60 foot run as well!
Irv
Cecil Moore
> I used 300 ohm TV twin lead for years. Why the concern about 600 ohms? It
> really doesn't matter unless you have a 600 Ohm feedpoint. The losses are
> still very low regardless of conditions, and as for dirty or rain, I had
> some up from 1983 to 1996 -- and never noticed any changes. When I took
> the antenna down the twinlead was as good as new and I used it for other
> things.
Here's the 600 ohm concern. A dipole's feedpoint is likely to vary from
about 60 ohms min to about 6000 ohms max. With 300 ohm line, the SWR varies
from 5:1 to 20:1. With 600 ohm line, the SWR is relatively constant
at 10:1, i.e. 600 ohm line gives more consistent SWRs over the entire
HF range than does 300 ohm line - just my two cents.
zeno
My beginner's understanding is that I would have a better multi-band
antenna utilizing a balanced feedline than with coax. I had seen a couple
of recommendations by doing internet searches. Several operators spoke
highly of the ~540' loop with balanced feed. I have a nice old 250W
Johnson matchbox on hand. Again, my beginner's understanding, the more
wire=the better, so I figured this long loop would be a good antenna for
"all" bands.
I am just now setting up a station for the first time. I need to think I
know what I am doing long enough to simply put something into action for
fear I will spend forever in a complex endless decision making matrix. I
enjoy trips to the hardware store and the junkyard, I haven't even been
on the air yet......(or at least since 1953....).
I figure antenna concerns are first, a good ground, then I need to think
about some serious equipment. This can be a bit overwhelming. Ihis next
Sat. I will be going to a local hamfest (my first one), hopefully to meet
some locals and make friends (mentor's, Elmers, etc.), also to track down
the guy with the bow and arrow who can get a line up my Eucalyptus tree
(165'+) for another possible antenna in an alternate shack on the
property......
actually, now that I think of it, my whole involvement in ham radio at
this moment (besides the fun of studying for the exams last month) is
dreaming of antenna farm.
just the other night while listening to some local maniacs on 3840, now I
realize I need to get my Extra if I want to be able to chime in at that
frequency.....those guys last night almost shattered my naive expectation
that hams are always gentlmen, a pursuit of integrity I personaly fully
intend to promote in my own operating demeanor. Apparently there is some
"famous" AM talk show host involved with that little late night net.....
shame on them....
Great, now I have a shopping mission.....go out and buy the Extra exam
book.....I do actually enjoy studying and learning.....
Now....a trip to the junk yard to find an old fashion DPDT Knife switch
I can mount on the wall so I can switch my incoming balanced line from
the Johnson to the Kenwood tuner....
help!.....
73
Bill (KG6UHM)
zeno
I will check that out.
While playing around with wire last night, seriously, the diy that
looked like it would work best was the sample I put together with some
#10 bare copper!
I have been known to end up doing things the hard way, and overdoing
things....
so why not this #10 bare copper ladder line?
73,
Bill
zeno
The 300 ohm TV line I am sure works, but it does not appeal to my tendency to
want to make everything "industrial strength" as if we were all going to live
for ever. I am finding it difficult at the moment to resist the idea of
making my ladder line out of #10 bare copper, thus insuring I will have a
*&^%$#@!!!!! time up on top of a ladder yelling and screaming things like
("why do I always make things so difficult) hi hi. Actually I think that the
#10 bare copper ladder line with my secret hardware store insight spacers
will look impressive.... (who am I trying to impress is the question) I need
to get my butt on the air otherwise I be only a "theoretical" ham.....
Secret hardware store spacer insight: the 4" uv/pvc ferrules that come with
the gutter spikes!....no I didn't say gutter snipes.....hi
73
everyone was working this guy in Lithuania on 20m this morning....can't wait
to get in there...... fun.....
Bill
Irv Finkleman
Understood, Cecil, but when the SWR losses are of so little concern
then the SWR consistency becomes likewise, at least IMHO.
Irv
JGBOYLES
>then the SWR consistency becomes likewise, at least IMHO
Hi Irv, Excellent point! Although I am sure Cecil put it in there as
Point/Counterpoint.
73 Gary N4AST
Cecil Moore
> so why not this #10 bare copper ladder line?
For one thing, it is overkill. And if it is solid,
it is subject to failure from fatigue. Many, many
hams have had trouble with breakage of solid wire
ladder-line.
Cecil Moore
If the SWR on 300 ohm twinlead is 5:1, the impedance at the current
maximum point is 60 ohms. If the SWR on 300 ohm line is 20:1, the
impedance at the current maximum point is 150 ohms (3:1 SWR).
If the SWR on 600 ohm line is 10:1, the impedance at the current
maximum point is 60 ohms NO MATTER WHAT THE ANTENNA IMPEDANCE.
The impedance at the current maximum point for a 6000 ohm antenna
fed with 600 ohm line is the same as the impedance at the current
maximum point for a 60 ohm antenna fed with 600 ohm line. That's
a definite '+' in my book. I like 60 ohms better than 150 ohms.
zeno
The only reason I was considering #10 solid wire was because it
would absolutely hold its shape with a minimum of spacers. Aside
from the fact that it is electrically overkill, you are saying that
even wire that thick could possible flex enough over time to fatique
and fail? Somehow I got it into my head that the best way to go was
homebrew ladder line, and the only way I could see doing it myself
was with this thick wire, all other wires were too messy somehow.
I checked the #554 that you suggested and it is rated for full
power. I didn't realize that #14 wire could handle that (guess I
have AC wiring in mind and not RF). So you have come to the
conclusion that this wire is the best way to go for balanced feed
line all things considered? (weather, dirt, etc.) Maybe I should
just use that and move on from this obsession about making my own
ladder line. I'll tell you that #10 was going to look cool in a
kind of science fiction movie laboratory kind of way..... It is hard
to get off that track, but maybe I am not being very practical...
I see that Radio Works also has this #14 copper-clad for about the
same price, he says that the actual impedance is approx. 390 ohms.
Now I am wondering how I got onto this do it yourself homebrew
ladder line obsession in the first place, I think it was some folks
complaining about how erratic it was with the rainy weather and when
it gets dirty, and stories of oldtimers going out and coating it
with bacon fat etc. yuk.....
So you are predicting eventual unhappiness with #10 bare copper wire
ladder line with cute little gutter spike uv/pvc ferrules as
spacers. Why do all those guys make their own ladder line...is it
because the commercial version is nearly 30 cents a foot? Or is
there some other downside they were trying to avoid?
I was going to order some stuff from Radio Works anyway, so I could
just get a chunk of that #14 ladder line......unless .......
Zeno (can't seem to really get away from this nickname....so maybe
Bill will just have to wait in the wings.....)
Cecil Moore
> So you have come to the
> conclusion that this wire is the best way to go for balanced feed
> line all things considered?
Not the best, but hard to beat for the price and convenience.
> So you are predicting eventual unhappiness with #10 bare copper wire
> ladder line ...
The solid copper wire usually breaks at the antenna where there
is lots of lateral movement. That can probably be cured by a
rigid center support.
zeno
Hi Richard,
You remind me that I do not understand something. Let's say the
characteristic impedance of this 540' loop is in the neighborhood of 140
ohms in free space, or even as you say closer to even 35 ohms in reality.
Your point was, if I understand correctly, that this is in the ballpark
of 50ohm coax and you suggest it can just as easily be fed into the coax.
But I thought that coax is unbalanced and the point was to go with a
balanced feed line?
I guess I am not understanding the relevant differences between balanced
vs. unbalanced feedlines, and getting the impedance of the the
transmission line close to the impedance of the antenna.
I thought the point of my striving to use balanced ladder line was to
somehow gain something that would be compromised by using coax. I thought
that the the ladder line which might be 488 ohms say is still going to be
a better feedline than using the 50ohm coax. The coax would still then
require a balun, correct? (a 1:1 banlun?).
It is sites like this: http://www.cebik.com/par.html that tend to get
one thinking about this whole diy approach.
My reading and gleaning of websites has me of the opinion (at this point)
that the balanced line with this long loop is better (multi band) than to
feed it with coax.
I believe Cecil has already explained this in terms of the wide range of
actual resistance that may be encountered multi band. (hey, I am just now
learning to talk this lingo....just barely know what I am talking
about....operating intuitively, and with the kindness of strangers.......
Zeno (aka Bill) KG6UHM for the moment.....
Richard Clark
>You remind me that I do not understand something. Let's say the
>characteristic impedance of this 540' loop is in the neighborhood of 140
>ohms in free space, or even as you say closer to even 35 ohms in reality.
>Your point was, if I understand correctly, that this is in the ballpark
>of 50ohm coax and you suggest it can just as easily be fed into the coax.
>
>But I thought that coax is unbalanced and the point was to go with a
>balanced feed line?
Hi Bill,
True, but easily answered with a feed line choke (1:1 BalUn) at the
drive point that will render the coax balanced if the load is - being
that close to ground there is every chance that may be debatable.
Again, there is no getting it right the first time out of the box -
you can only put it up and test to see how much you need to change it.
You were planning pulleys right?
>I guess I am not understanding the relevant differences between balanced
>vs. unbalanced feedlines, and getting the impedance of the the
>transmission line close to the impedance of the antenna.
You can build a twin line of 50 Ohms. Takes pretty close spacers, and
you will need a lot if you use bare wire. The wire pairs would be as
close as zip cord. Twisted pair, insulated could do the trick (might
even match the 35 Ohms).
>I thought the point of my striving to use balanced ladder line was to
>somehow gain something that would be compromised by using coax. I thought
>that the the ladder line which might be 488 ohms say is still going to be
>a better feedline than using the 50ohm coax.
Well.... Only if you use this as a monobander. As a multibander it
will ALWAYS have SWR, the point of big wire twin lead is that the loss
will be less than if you used the same antenna with coax feeding it.
Coax with big center wire is HUGE and COSTLY for the same loss figures
at the same SWRs met by multiband use.
For 160M band, I would REALLY look for the Archer and put my effort
into that prospect. A low loop is the pits - hi Z, lo Z, balanced,
unbalanced, SWR, no SWR hardly counts for diddly.
>The coax would still then
>require a balun, correct? (a 1:1 banlun?).
ibid.
>It is sites like this: http://www.cebik.com/par.html that tend to get
>one thinking about this whole diy approach.
>
>My reading and gleaning of websites has me of the opinion (at this point)
>that the balanced line with this long loop is better (multi band) than to
>feed it with coax.
True enough. I simply responded to you describing it as a 160M loop.
If it was a dedicated monobander, twin lead is extravagant and forces
unnecessary SWR into the picture.
>I believe Cecil has already explained this in terms of the wide range of
>actual resistance that may be encountered multi band. (hey, I am just now
>learning to talk this lingo....just barely know what I am talking
>about....operating intuitively, and with the kindness of strangers.......
Stella! (Oops, wrong "Streetcar").
zeno
Richard Clark wrote:
You were planning pulleys right?
yes indeed, lots of pulleys, I only want to be putting up these masts once.
>
> For 160M band, I would REALLY look for the Archer and put my effort
> into that prospect. A low loop is the pits - hi Z, lo Z, balanced,
> unbalanced, SWR, no SWR hardly counts for diddly.
>
I am going to meet the archer this weekend at the hamfest in Sonoma. Another
friend is giving me a homebuilt house trailer (quaint gypsy wagon) which I
can park out in the back 40 as an alt. shack which will be close to the
antenna up in the <200' Eucalyptus tree. It is not that I am particularly
excited about 160m (although good to be able to operate there when necessary
I guess), but HEIGHT is everything, right?
>
> >I believe Cecil has already explained this in terms of the wide range of
> >actual resistance that may be encountered multi band. (hey, I am just now
> >learning to talk this lingo....just barely know what I am talking
> >about....operating intuitively, and with the kindness of strangers.......
>
> Stella! (Oops, wrong "Streetcar").
>
Wow, a cinematically (literary) erudite ham, cool....I feel like I am
home.....
Zeno (aka Bill) KG6UHM (until further notice.....)
zeno
Richard Clark wrote:
For 160M band, I would REALLY look for the Archer and put my effort
> into that prospect. A low loop is the pits - hi Z, lo Z, balanced,
> unbalanced, SWR, no SWR hardly counts for diddly.
OK, the 540' loop will be up as high as I can get it with these telescoping
masts, somewhere between 45-55 feet at each corner. How will this be for
bands other than 160m (either with the Johnson or my Kenwood ATU (+current
type balun)? As mentioned I have the real estate to try several antennas
here. I am curious to find out how the loop will work. I only call it 160m
because of the length of the wire. There were a handful of websites
expressing enthusiasm about this antenna.
Another plan is some kind of antenna on a rotator. Any ideas of how to
engineer some kind of beam (light-weight) or something similar atop one of
these 50' telescoping tv masts? If I am to telescope 4 - ten foot sections,
the antenna and rotator would have to be light. I would have to engineer this
with a crew of buddies holding the guy ropes as the stong person is up ten
feet trying to push up this whole thing into the air a section at a time.
Anyone done this? The motivation here is 1) I have the 50 mast, so economy is
a factor, and 2) the result will look more like some kind of elaborate tv
antenna. A tower out in the front yard might be a bit much in the
neighborhood at this point. I need to test these waters first.
Richard Clark
>OK, the 540' loop will be up as high as I can get it with these telescoping
>masts, somewhere between 45-55 feet at each corner. How will this be for
>bands other than 160m (either with the Johnson or my Kenwood ATU (+current
>type balun)? As mentioned I have the real estate to try several antennas
>here.
Hi Bill,
Above 80M it should be gangbusters. However, you may wish to look
into Rhombic designs given the vast footprint available to you to
experiment with. This will be more directional, more gain for the 30M
bands and above, so you will want to investigate what direction that
should be (don't guess using a flat map either). It would be roughly
the same shape, only more diamond than haphazard square. Such a
design shouldn't hurt your 160M loop prospects, but would optimize the
higher bands (where formerly you were just going to take what came
with the turf).
With a lot more wire (and work), you could get into the Fish Bone
Array, or a wire Log Periodic Array. Both would, again, be fixed
direction so planning ahead is again seen in the XTAL ball.
>I am curious to find out how the loop will work. I only call it 160m
>because of the length of the wire. There were a handful of websites
>expressing enthusiasm about this antenna.
What choice did they have? Such is the fallacy of testimonial. As
the saying goes, if all you have is a hammer, everything looks like a
nail.
>Another plan is some kind of antenna on a rotator. Any ideas of how to
>engineer some kind of beam (light-weight) or something similar atop one of
>these 50' telescoping tv masts?
That would have to be WARC bands and 10M, probably; otherwise you are
dreaming in technicolor and surround-sound.
Cecil Moore
> Another plan is some kind of antenna on a rotator. Any ideas of how to
> engineer some kind of beam (light-weight) or something similar atop one of
> these 50' telescoping tv masts?
Check out Worldradio's SD-20 systems at http://www.wr6wr.com
zeno
> Above 80M it should be gangbusters. However, you may wish to look
> into Rhombic designs given the vast footprint available to you to
> experiment with. This will be more directional, more gain for the 30M
> bands and above, so you will want to investigate what direction that
> should be (don't guess using a flat map either). It would be roughly
> the same shape, only more diamond than haphazard square. Such a
> design shouldn't hurt your 160M loop prospects, but would optimize the
> higher bands (where formerly you were just going to take what came
> with the turf).
>
Although I have the acres (7) there are a lot of buildings (old barns etc.),
trees, etc. My antenna planning has to dodge many many obstacles actually. This
is an old chicken ranch and there are building everywhere, then all the trees.
Are you saying that a rhombic could be put up on the same masts more or less
(only one of the masts is potentially moveable, meaning that it would only be
diamond like at one end of the trapezoid. This rhombic would be instead of the
540' loop?
I will look up rhombic in the books and see what gives.
>
> With a lot more wire (and work), you could get into the Fish Bone
> Array, or a wire Log Periodic Array. Both would, again, be fixed
I will look these up as well. I don't want to get so complex and over my head
that I will be overwhelmed. Now that I have the call sign of choice, I am ready
to rock and roll.....
-Bill (aka Zeno)
Hey I got it!!! I am now K6TAJ, Tango Alpha Juliet. The old bongo drummer morse
code tapper in me is tickled DAH, DI-DAH, DI-DAH-DAH-DAH is so cool for me for
a variety of esoteric reasons, aside from the fact that it is fun to tap out.
My second choice was my 1953 call K6CCG (also fun to tap, but not as fun as
TAJ, the new call is shorter as well), also I like tango alpha juliet more than
charlie charlie golf.....I don't really own any checkered pants.....
I actually found myself listed in an old 1958 call book, which actually was the
year my old Tech ran out.....
Hopefully I can make up for lost time......
73
Bill, K6TAJ
zeno
I apologize for the Beany reference....I am just elated at getting k6taj.
Cecil Moore
> Hey I got it!!! I am now K6TAJ, Tango Alpha Juliet.
Now we will have an endless thread of words to match your
TLA (three letter acronym). Transmitting All Joules?
Richard Clark
>Although I have the acres (7) there are a lot of buildings (old barns etc.),
>trees, etc. My antenna planning has to dodge many many obstacles actually. This
>is an old chicken ranch and there are building everywhere, then all the trees.
>Are you saying that a rhombic could be put up on the same masts more or less
>(only one of the masts is potentially moveable, meaning that it would only be
>diamond like at one end of the trapezoid. This rhombic would be instead of the
>540' loop?
>
>I will look up rhombic in the books and see what gives.
Hi Bill,
No, this time shape matters as it is a function of all angles of
radiation combining to ADD rather than jumble. Again, think in terms
of the supports/mast merely being the outer, irregular perimeter to an
ordered interior antenna shape.
The Rhombic would BE the 540' loop. Normally it is open or terminated
at the end opposite the feed point, but having the shape anticipated
is more the work than this simple change. (It has the same feed
considerations, complete with your expected twin lead.)
Congrats on your desired call.
zeno
and for the hometown crew: Tasty Apricot Jelly or Typical Antique
Junk
zeno
configuration support structure for the specifically ordered interior shape is the
sag the inevitably occurs when wire is a rope and pulley distance away from the
supporting mast. I already see this with the tree supported antenna. The ropes drop
down and the wire is 8' or so lower than anticipated. This seems critical when the
masts are only 50' to begin with. How high, or shouls I say, what is the minimum
height for an acceptable Rhombic?
Bill, K6TAJ
Richard Clark
>The problem, as I see it, with using the fixed masts as outside perimeter
>configuration support structure for the specifically ordered interior shape is the
>sag the inevitably occurs when wire is a rope and pulley distance away from the
>supporting mast. I already see this with the tree supported antenna. The ropes drop
>down and the wire is 8' or so lower than anticipated. This seems critical when the
>masts are only 50' to begin with. How high, or shouls I say, what is the minimum
>height for an acceptable Rhombic?
Hi Bill,
Think positively: how high will they be? 40 Feet? 10 Meters? One
quarter wave for 40M? This is not a hardship case. One half wave or
better high for 20M and above? No one's gonna let you cry in your
beer there either. And now for the classic "testimonial": it's gonna
be boomin! (what choice do you have?).
As a cautionary, don't try to pull out the catenary. The tension
rises with the tangent of the of the deflection angle. If you could
achieve perfect flatness, a breeze would snap the line.
emme...@gmail.com
What are the units of distance? Inches? CM? MM?
For 300 ohm ladder line, I get .390.
Thanks
On Tuesday, March 30, 2004 at 8:43:04 PM UTC-5, Tom Bruhns wrote:
> Impedance is about 120*ln(2*D/d) ohms, where ln is the natural
> logarithm, and D is the wire spacing, center to center, and d is the
> wire diameter. Assumes round wires, and air dielectric. You can
> rearrange that: if you want x ohms and have d diameter, D =
> d*exp(x/120)/2, where exp(x/120) is "e to the x/120 power". If you
> don't have a calculator that handles that sort of math, this table
> will probably get you close enough:
>
> D/d impedance, ohms
> 1.9 150
> 2.8 200
> 6.2 300
> 22 450
> 75 600
>
> Construction depends a bit on how much you're making and what you have
> available for materials and tools. People used to use wooden spacers,
> boiled in parafin wax. Someone gave me a bunch of PETE
> tensile-strength test strips that are a good size. You can make
> spacers from PVC pipe. You can thread wires through holes (generally
> not so efficient), or fit wires into notches and secure by with a
> plastic or wire wrap, or by melting the wire into an undersized notch,
> or with various glues. Undoubtedly lots of other ideas, both
> tried-and-true and just waiting to be tried for the first time.
>
> You can drill holes through the glass and install feedthroughs (but
> probably not if it's double-pane!), or drill a couple over-size holes
> through the wall or possibly through a wooden window frame member, or
> install a wood or plastic piece in a partially-open window. You can
> also possibly inductively or capacitively couple through the window.
> If you decide to go through wood or wall materials, plan to make
> oversized holes, lined with decent electrical/RF insulation. What
> strikes your fancy?
>
> Cheers,
> Tom
>
>
> Larry Gagnon <laga...@fakeuniserve.com> wrote in message news:<106jk0i...@corp.supernews.com>...
> > Hello to all. I intend to erect an 80 meter full size dipole and feed
> > it with homebrew open ladder line. Would anyone care to reply as to how
> > to construct ladder line easily and effectively? How does one determine
> > spacing to get X ohms impedance line?
> >
> > Also any ideas on how such line can easily be fed in through a window
> > with a wood frame would be greatly appreciated.
> >
> > Larry Gagnon VE7EA
Ralph Mowery
emme...@gmail.com says...
>
> What are the units of distance? Inches? CM? MM?
> For 300 ohm ladder line, I get .390.
>
> Thanks
>
>
>
> On Tuesday, March 30, 2004 at 8:43:04 PM UTC-5, Tom Bruhns wrote:
> > Impedance is about 120*ln(2*D/d) ohms, where ln is the natural
> > logarithm, and D is the wire spacing, center to center, and d is the
> > wire diameter. Assumes round wires, and air dielectric. You can
> > rearrange that: if you want x ohms and have d diameter, D =
> > d*exp(x/120)/2, where exp(x/120) is "e to the x/120 power". If you
> > don't have a calculator that handles that sort of math, this table
> > will probably get you close enough:
> >
> > D/d impedance, ohms
> > 1.9 150
> > 2.8 200
> > 6.2 300
> > 22 450
> > 75 600
> >
>
>
use the same. Say .1 inches in diameter and 3 inches spacing or 1 foot
in diameter and 30 foot spacing although that is an awful example but
could come into play with VLF or even power line frequencies.
The units cancel each other out and it is just a ratio of diameter and
spacing.