Stupid question on twin feedline (air)
 

I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from
migrating...will small wire "stays" modify feedline characteristics?

This is all about feedline to simple dipole or inverted V.

Thanks,

a new (old) ham

jawod aka john

Stupid question on twin feedline (air)
 

John wrote:
"---how to keep spacers from migrating..."

My 1970 edition of the ARRL Antenna Book shows how to construct open
wire line. The insulating spacers have holes near their ends and their
ends are also grooved for the line conductors.

A small tiewire is run through the hole and its ends are tightly wrapped
around the transmission line conductors to hold everything in place.

Best regards, Richard Harrison, KB5WZI

Stupid question on twin feedline (air)
 

buy it already built. Why wear yourself out building stuff available on
the shelf?


Richard Harrison wrote:
John wrote:
"---how to keep spacers from migrating..."

My 1970 edition of the ARRL Antenna Book shows how to construct open
wire line. The insulating spacers have holes near their ends and their
ends are also grooved for the line conductors.

A small tiewire is run through the hole and its ends are tightly wrapped
around the transmission line conductors to hold everything in place.

Best regards, Richard Harrison, KB5WZI

Stupid question on twin feedline (air)
 

"jawod" wrote in message
...
I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from migrating...will
small wire "stays" modify feedline characteristics?

This is all about feedline to simple dipole or inverted V.

Thanks,

a new (old) ham

jawod aka john

I bought 600 ohm feedline (and dipole) from W7**.
He uses pieces of PVC pipe with notches in the ends
and insulated wires. The notches provide a friction fit on
the wires. Note that you need to be certain that the
PVC has very high resistance at RF frequencies. I
have been told that some do not. You can tell if you
run higher power and the insulators heat up.

You can also buy "ladderline" with 450 or 300 ohm
impedances from a number of sources.

If you can support the center of the dipole, weight is not
as much concern as if you cannot support it. With too heavy
a ladder line, your dipole may resemble a Y.

Regards,
Ed, N5EI

Stupid question on twin feedline (air)
 

On Wed, 04 Jan 2006 23:14:45 -0500, jawod wrote:

I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from
migrating...will small wire "stays" modify feedline characteristics?

This is all about feedline to simple dipole or inverted V.

Thanks,

a new (old) ham

jawod aka john

already-made 600 ohm line is available at www.w7fg.com

bob
k5qwg

Stupid question on twin feedline (air)
 

jawod wrote:

I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from
migrating...will small wire "stays" modify feedline characteristics?

For all-HF-band operation with relatively high SWRs, the
spacing doesn't much matter. 2"-6" is a practical range.
Spacer spacing depends upon wind conditions. Two foot
spacing seems reasonable at my QTH. Some spacers pinch
the insulation on the feedline and thus stay in place.
Very small tie wraps could also be used.
--
73, Cecil, http://www.qsl.net/w5dxp

Stupid question on twin feedline (air)
 

Butch Magee wrote:
buy it already built. Why wear yourself out building stuff available on
the shelf?

Heaven forbid that hams build anything anymore. :-)
--
73, Cecil, http://www.qsl.net/w5dxp

Stupid question on twin feedline (air)
 

On Thu, 05 Jan 2006 15:30:56 GMT, Cecil Moore wrote:

jawod wrote:

I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from
migrating...will small wire "stays" modify feedline characteristics?

For all-HF-band operation with relatively high SWRs, the
spacing doesn't much matter. 2"-6" is a practical range.
Spacer spacing depends upon wind conditions. Two foot
spacing seems reasonable at my QTH. Some spacers pinch

Did you really mean two foot spacing. This imperial measurement system
can be a bit tricky sometimes.

the insulation on the feedline and thus stay in place.
Very small tie wraps could also be used.
--

Stupid question on twin feedline (air)
 

Owen Duffy wrote:
Did you really mean two foot spacing?

Two foot spacing between spacers, not between wires.
I tried 4 foot spacing at first and it twisted in
the wind so I installed twice as many spacers.
--
73, Cecil, http://www.qsl.net/w5dxp

Stupid question on twin feedline (air)
 

I will assume that balanced (air) feedline is homebrew....
If you can support the center of the dipole, weight is not
as much concern as if you cannot support it. With too heavy
a ladder line, your dipole may resemble a Y.

If the center of the dipole is NOT supported, I've found the worst problem
is the ladderline breaking -- from flexing caused by wind, etc. -- just
below where it is connected to the antenna. My current dipole has a center
support, but I've read that making the last section(s) of ladder-line out
of stranded wire will reduce the flex-breaking problem.
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)

Stupid question on twin feedline (air)
 

Owen Duffy wrote:
On Thu, 05 Jan 2006 15:30:56 GMT, Cecil Moore wrote:


jawod wrote:


I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from
migrating...will small wire "stays" modify feedline characteristics?

For all-HF-band operation with relatively high SWRs, the
spacing doesn't much matter. 2"-6" is a practical range.
Spacer spacing depends upon wind conditions. Two foot
spacing seems reasonable at my QTH. Some spacers pinch


Did you really mean two foot spacing. This imperial measurement system
can be a bit tricky sometimes.

50 cm, then




the insulation on the feedline and thus stay in place.
Very small tie wraps could also be used.

--

Stupid question on twin feedline (air)
 

On Thu, 05 Jan 2006 19:48:55 -0500, Amos Keag
wrote:

Owen Duffy wrote:
On Thu, 05 Jan 2006 15:30:56 GMT, Cecil Moore wrote:


jawod wrote:


I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from
migrating...will small wire "stays" modify feedline characteristics?

For all-HF-band operation with relatively high SWRs, the
spacing doesn't much matter. 2"-6" is a practical range.
Spacer spacing depends upon wind conditions. Two foot
spacing seems reasonable at my QTH. Some spacers pinch


Did you really mean two foot spacing. This imperial measurement system
can be a bit tricky sometimes.

50 cm, then

Well Amos, I misunderstood the two foot spacing to be wire spacing
rather than spacer spacing. Both spacings are discussed in the space
of one paragraph, and it is a little open to misinterpretation. I
thought he may have meant wire spacing and two inches rather than
feet... hence the reference to the measurement system. Cecil did clear
it up.

BTW, two foot is closer to 60cm (60.96cm).

Owen
--

Stupid question on twin feedline (air)
 

Hello Jawod,

I have buit a twin leed for my center feeder dipole with PCV tubes:
http://www.barbaxoops.com/modules/xc...&album=7&pos=2

Tubes are after filled with glue. You can see here the final result (click
on the picture to enlarge it):
http://www.barbaxoops.com/modules/xc...&album=7&pos=4

Spacing is 5 cm
Distance between spacers is 60 cm

It has been installed for 3 years. It has resisted to many strong winds.

Good luck

Regards

Jean-Marc
F4DRH
www.barbaxoops.com







"jawod" a écrit dans le message de news:
...
I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from migrating...will
small wire "stays" modify feedline characteristics?

This is all about feedline to simple dipole or inverted V.

Thanks,

a new (old) ham

jawod aka john

Stupid question on twin feedline (air)
 

"jawod" wrote in message
...
I will assume that balanced (air) feedline is homebrew. What
recommendations are there for spacing between the twin lines? Number of
spacers per foot? If homebrew, how to keep spacers from
migrating...will small wire "stays" modify feedline characteristics?


I've heard some use well-varnished dowels as well as pvc pipe, and pieces of
scrap vinyl siding cut to size and drilled for spacers.
and for stays, I've heard epoxy, super-glue, and hot-melt glue works.

If the pieces of vinyl (siding scraps) were folded into a "V", then drilled
for the wire on each side, the springiness of the vinyl would probably hold
itself in place without glue.

spacing of spacers would depend on the stiffness of the wire. Use common
sense - just need to keep a consistent spacing. It would take more spacers
for flexible, stranded wire than for stiff solid wire. 10 guage solid wire
is stiffer than 20 guage braided stranded wire.