I have a 40meter band xmit/recv antenna up with good swr and works great.
Cost me nothing but my time, and a plastic center insulator to strain
releive the zip cord (rather than tie a knot in the cord at the center. Just
rip down 33 ft of zip cord, tie a knot or use the insulator, and cut the
feedlinne section to a integral half wave long (20, 40, 60etc meters long).
If cut to a half wave (use a dip meter) the swr of the dipole will be
translated unaltered to the radio end of your feedline and 70 ohms is OK for
a swr of 1.4 and the xcvr will not care usually.

Great emergency antenna.



"pegge" wrote in message
...
someone tried to feed a type g5rv antenna with ´european´ zip-cord ?
(european meaning double the Volts compared to USA, thus half amps
for the same lamp wattage)
Would yield a simple ant, peel the first say abt 15- 17 meters, splitting
them up to the dipole part and the the rest X meter to a balanced tuner
etc.
sorry if this has been up too many times, search did´nt give a clue!

Tnx for info, 73 Per / sm7aha malmo, sweden

"tjs" wrote in message ...
I have a 40meter band xmit/recv antenna up with good swr and works great.
Cost me nothing but my time, and a plastic center insulator to strain
releive the zip cord (rather than tie a knot in the cord at the center. Just
rip down 33 ft of zip cord, tie a knot or use the insulator, and cut the
feedlinne section to a integral half wave long (20, 40, 60etc meters long).
If cut to a half wave (use a dip meter) the swr of the dipole will be
translated unaltered to the radio end of your feedline and 70 ohms is OK for
a swr of 1.4 and the xcvr will not care usually.

Great emergency antenna.

Why do you think the SWR of the dipole will be unaltered at the radio end of the feedline? You are apparently ignoring the loss in the line that makes the SWR at the radio end less than that at the dipole terminals.

If the zip cord had zero loss the SWR would be the same everywhere along the line, only the terminal impedance at the radio end would be the same as at the dipole.

Without knowing the vf (velocity factor) of the zip cord how do you determine that the length is a half wave?

And last, why would you want the length to be a half wave?

Walt, W2DU


--------------------------------------------------------------------------------

On Wed, 13 Jul 2005 13:50:03 -0400, "Walter Maxwell"
wrote:

This is a multi-part message in MIME format.
Why? Because you are using that POS Outlook Express again! :-(

Why do you think the SWR of the dipole will be unaltered at the radio =
end of the feedline? You are apparently ignoring the loss in the line =
that makes the SWR at the radio end less than that at the dipole =
terminals.

If the zip cord had zero loss the SWR would be the same everywhere =
along the line, only the terminal impedance at the radio end would be =
the same as at the dipole.

Without knowing the vf (velocity factor) of the zip cord how do you =
determine that the length is a half wave?

And last, why would you want the length to be a half wave?=20

Walt, W2DU

And your posting mentions nothing in it that suggests why there is a
GIF attachment which may be infected.

Walt,

This is like running full power deliberately into a 10:1 mismatch:
15 lines of content does not warrant a 156 line posting.

73's
Richard Clark, KB7QHC

"Walter Maxwell" wrote in message
...

"tjs" wrote in message ...
I have a 40meter band xmit/recv antenna up with good swr and works great.
Cost me nothing but my time, and a plastic center insulator to strain
releive the zip cord (rather than tie a knot in the cord at the center.
Just
rip down 33 ft of zip cord, tie a knot or use the insulator, and cut the
feedlinne section to a integral half wave long (20, 40, 60etc meters
long).
If cut to a half wave (use a dip meter) the swr of the dipole will be
translated unaltered to the radio end of your feedline and 70 ohms is OK
for
a swr of 1.4 and the xcvr will not care usually.

Great emergency antenna.

Why do you think the SWR of the dipole will be unaltered at the radio end
of the feedline? You are apparently ignoring the loss in the line that
makes the SWR at the radio end less than that at the dipole terminals.

If the zip cord had zero loss the SWR would be the same everywhere along
the line, only the terminal impedance at the radio end would be the same
as at the dipole.

Without knowing the vf (velocity factor) of the zip cord how do you
determine that the length is a half wave?

And last, why would you want the length to be a half wave?

Walt, W2DU

I think he was correct about the half-wave length of feedline:
according to the ARRL Antenna Book - 17th edition copyright 1994 - page
24-12 in chapter 24, under the Heading "Special Cases" and under the
sub-heading "The Half-WaveLength Line", it pretty clearly states that
regardless of z, it will be the same on both ends of a half-wave line. and
sections having such length can be added or removed without changing the
load Z. (as long as loss is negligible)

Also - You don't need to know the VF if you use a dip meter (or MFJ 259) -
And he would want the length to be half-wave so as to be able to ignore the
characteristic impedence of the zip line and deal directly with the
impedence of the dipole directly.

On Wed, 13 Jul 2005 17:40:02 -0400, "Hal Rosser"
wrote:


I think he was correct about the half-wave length of feedline:
according to the ARRL Antenna Book - 17th edition copyright 1994 - page
24-12 in chapter 24, under the Heading "Special Cases" and under the
sub-heading "The Half-WaveLength Line", it pretty clearly states that
regardless of z, it will be the same on both ends of a half-wave line. and
sections having such length can be added or removed without changing the
load Z. (as long as loss is negligible)

Also - You don't need to know the VF if you use a dip meter (or MFJ 259) -
And he would want the length to be half-wave so as to be able to ignore the
characteristic impedence of the zip line and deal directly with the
impedence of the dipole directly.

This analysis seems to imply use of the antenna on only one one band.

Ill conceived alternative feed arrangments are the most common reason
why so-called G5RVs performs even poorer than the "genuine" article.

The original question about how well "Euro zip line" will perform will
depend on the characteristics of the line. I hazard a guess that it
will be unlikely to have a characteristic impedance as low as 75 ohms
as suggested by some, more likely 100 ohms or more. It is likely to be
PVC insulated, and lines of that type perform much poorer than a high
z line made of the same conductor, not just because of the dielectric
issue, but because the RF resistance of the conductor increases as the
spacing is reduced for very close spacings (proximity effect).

As to whether it "works" for you, you need to define your criteria for
"works". If "works" means you make some QSOs, then I am sure it
"works", but if "works" meand you want to deliver 80% plus of the
transmitter power to the "G5RV variant" antenna feedpoint on several
bands, then it is unlikely to "work".

For arguments sake, if the feedpoint Z of a 30.5m centre fed dipole
(G5RV length) on 3.6MHz is 10-j340, using the characteristics of US
Zip cord measured by K8ZOA, the loss in 25m of such feeder would be
13dB with a Zin of 563-61, so there would be some small
(insignificant) additional tuner loss. Is this what you mean by
"works"?

Owen
--

"Hal Rosser" wrote in message
...


I think he was correct about the half-wave length of feedline:
according to the ARRL Antenna Book - 17th edition copyright 1994 -
page
24-12 in chapter 24, under the Heading "Special Cases" and under the
sub-heading "The Half-WaveLength Line", it pretty clearly states that
regardless of z, it will be the same on both ends of a half-wave line.
and
sections having such length can be added or removed without changing the
load Z. (as long as loss is negligible)

Also - You don't need to know the VF if you use a dip meter (or MFJ 259) -
And he would want the length to be half-wave so as to be able to ignore
the
characteristic impedence of the zip line and deal directly with the
impedence of the dipole directly.



Exactly

I also have a W6RCA type antenna up...80m dipole in the trees 25-50 feet,
fed by 98 feet of homemade 4" spaced ladder line, and ending outside the
shack wall with a way to add-in lengths of the feed line by 1 foot, 2 foot,
4 feet or 8 feet. This allows tuning the feedline onto any ham band almost
via harmonic relationship of the bands . You endup with a multiple halfwave
feedline and whatever swr the antenna runs shows up at the feedpoint (50
ferrite coax to ladder balun 1:1). Best antenna I have. Always better to
tune the feedline, and translate the antenna characteristic from the remote
locale to the shack wall. There is some loss I guess, but I cant detect it
or measure it, and I dont care because the antenna radiates and receives and
I get 59 reports.

Tim