Endfeed vertical halfvawe antenna
 

Togethere wih a fellow amateur I am trying to design an endfeed halfvawe
vertical antenna for 50 MHz.

We have encountered som problems regarding the impedance match in the
feedpoint. I have surveyed the ARRL Antenna Book and Antennebuch (a German
antenna book very popular in Europe). The properties of the antenna and its
impedance is well understood. The missing point is how to realise the
matching network

In order to avoid reinventing the whee: Does anybody have some good links to
study practical realisations of the matching network?

vy 73

Joergen, OZ7TA

Endfeed vertical halfvawe antenna
 

J. Kragh wrote:
In order to avoid reinventing the whee: Does anybody have some good links to
study practical realisations of the matching network?

How about 1.3 meter (4.3 feet) of 450 ohm ladder-line
as a series-section-transformer?
--
73, Cecil http://www.w5dxp.com

Endfeed vertical halfvawe antenna
 

Go back to the ARRL antenna handbooks from the 1970's or 1980's... Look
in the chapter for HF antennas for 160 and 80 meters... Somewhere in
there will be the diagram for an end fed long wire using a parallel
tank circuit - an inductor and a variable capacitor in parallel...
This will work just the same for your end fed half wave vertical on 6
meters...
The bottom end of the tank circuit goes to your ground/radials... And
the top end goes to the bottom end of your half wave vertical wire...
Your transmitter coax has the braid going to the bottom end of the tank
circuit and the center feed of the coax is tapped up a few turns from
the bottom of the coil to match 50 ohms.. Use a few turns of the coax
as a choke for common mode currents on the outside of the braid...
Obviously you will not be using components with as much inductance and
capacitance as you would for 160 meters... As a guess I would say that
for 50 mhz you will be tapping up roughly between 3/4 turn to one and
a half turns from the bottom to get a match... This of course depends
on the form factor of your coil, i.e. short/fat versus long/skinney..
Trying this on your work bench is the best way.. Make up a coil from
#14 AWG solid house wiring and a variable capacitor, use a length of
the house wiring for the radials and vertical and experiment...
Another method is the J Pole matching system.. Look in chapter 18 of
the current ARRL Antenna Handbook...


cheers denny / k8do

Endfeed vertical halfvawe antenna
 

"J. Kragh" wrote in
k:

Togethere wih a fellow amateur I am trying to design an endfeed
halfvawe vertical antenna for 50 MHz.

We have encountered som problems regarding the impedance match in the
feedpoint. I have surveyed the ARRL Antenna Book and Antennebuch (a
German antenna book very popular in Europe). The properties of the
antenna and its impedance is well understood. The missing point is how
to realise the matching network

In order to avoid reinventing the whee: Does anybody have some good
links to study practical realisations of the matching network?

vy 73

Joergen, OZ7TA



An endfed halfwave has inductive reactance, ISTR. If you add another 1/8
wave to it, you reverse the sign of the reactance, thereby allowing an
inductance to tune out the reactance. Ground one end of the inductor and
tap down with the coax center conductor for a 50 ohm match--Voila! A 5/8
wave vertical!

Jeff

Endfeed vertical halfvawe antenna
 

"J. Kragh" wrote in message
k...
Togethere wih a fellow amateur I am trying to design an endfeed halfvawe
vertical antenna for 50 MHz.

How about a zepp antenna fed with open wire, with the antenna running
vertically.

Endfeed vertical halfvawe antenna
 

We have encountered som problems regarding the impedance match in the
feedpoint. I have surveyed the ARRL Antenna Book and Antennebuch (a
German antenna book very popular in Europe). The properties of the antenna
and its impedance is well understood. The missing point is how to realise
the matching network

In order to avoid reinventing the whee: Does anybody have some good links
to study practical realisations of the matching network?

vy 73

Joergen, OZ7TA

Google WB6BLD. Or just go to http://tonnesoftware.com/piel.html Jim has
design software of both Pi and L networks that will perfectly match the
anticipated impedance to 50 Ohms. Other interesting Amateur Radio associated
software as well and free student versions.

W4ZCB

Endfeed vertical halfvawe antenna
 

On Sat, 16 Sep 2006 14:25:35 +0200, "J. Kragh"
wrote:
In order to avoid reinventing the whee: Does anybody have some good links to
study practical realisations of the matching network?

Hi Joergen,

http://www.70mhz.org/halfwav.htm
http://www.qsl.net/dk7zb/6m/Vertical.htm
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=13226 (duplicate)

73's
Richard Clark, KB7QHC

Endfeed vertical halfvawe antenna
 

The simplest fed is a L network with the C at the transmitter end
and the antenna at the unterminated inductor end. Works best
in the radiator is slightly capacitive looking.


Specificallly check the article "feeding the EDZ" as that
talks about the problem at hand.



Allison


Not really, the capacitor goes on the end of the coil closest to the higher
impedance. I'm certain his half wave will be appreciably above 50 Ohms.
Mine's about 2600 Ohms.

W4ZCB

Endfeed vertical halfvawe antenna
 

Endfeed vertical halfvawe antenna
 

How do all these various matching schemes affect bandwidth?
73,
Tom Donaly, KA6RUH

For the "L", it depends on the Q of the "L" network. You're not in charge
of that, you have to take the Q that the transform gives you. With a
constant inductor value, I can get pretty close to 1:1 clear across the band
just by varying the capacitor value for the frequency. Of course, if you
don't have any adjustable "C", YMMV. I'd think you need to get to a pretty
high frequency before you didn't have to add "C" to whatever exists, but the
big advantage of Voltage feed is that the current to the "Ground" is
minimal. When you don't know that your ground is zero Ohms, you're better
off putting as little current into it as possible.

W4ZCB

Endfeed vertical halfvawe antenna
 

How do all these various matching schemes affect bandwidth?
73,
Tom Donaly, KA6RUH

For the "L", it depends on the Q of the "L" network. You're not in charge
of that, you have to take the Q that the transform gives you. With a
constant inductor value, I can get pretty close to 1:1 clear across the band
just by varying the capacitor value for the frequency. Of course, if you
don't have any adjustable "C", YMMV. I'd think you need to get to a pretty
high frequency before you didn't have to add "C" to whatever exists, but the
big advantage of Voltage feed is that the current to the "Ground" is
minimal. When you don't know that your ground is zero Ohms, you're better
off putting as little current into it as possible.

W4ZCB

Endfeed vertical halfvawe antenna
 

J. Kragh wrote:

Togethere wih a fellow amateur I am trying to design an endfeed halfvawe
vertical antenna for 50 MHz.

We have encountered som problems regarding the impedance match in the
feedpoint. I have surveyed the ARRL Antenna Book and Antennebuch (a German
antenna book very popular in Europe). The properties of the antenna and its
impedance is well understood. The missing point is how to realise the
matching network

In order to avoid reinventing the whee: Does anybody have some good links to
study practical realisations of the matching network?

vy 73

Joergen, OZ7TA



I am curious as to what the expected use will be. I am not familiar
with 6m in Europe, but 50 megahertz vertical in the US is not something
you will work much on.

If you are looking to work SSB on 6m, you will be better off with a
horizontal antenna. There are many easily built 6m beam plans available.

tom
K0TAR

Endfeed vertical halfvawe antenna
 

Tom Ring wrote:

I am curious as to what the expected use will be. I am not familiar
with 6m in Europe, but 50 megahertz vertical in the US is not something
you will work much on.

If you are looking to work SSB on 6m, you will be better off with a
horizontal antenna. There are many easily built 6m beam plans available.

tom
K0TAR

Respond if you'd like some.

tom
K0TAR

Endfeed vertical halfvawe antenna
 

wrote in message
...
On Sat, 16 Sep 2006 14:25:35 +0200, "J. Kragh"
wrote:

Togethere wih a fellow amateur I am trying to design an endfeed halfvawe
vertical antenna for 50 MHz.

snip

Look at a J-pole antenna. Its really a stub section feeding a halfwave
antenna.

The impedence transformation has to go from coax (60-75 ohms) to
a much higher and possibly reactive load in the range of
1500-3000j(+/-)0-100 depending on dimensions of the halfwave antenna
relative to the actual frequency.

Yes. I have built three copper-pipe j-poles for 6 M. The overall length is
about 13 feet (4 meters) long. I made them predominantly from 3/4-inch
copper water pipe, which comes in 10-foot lengths in the US. I used a
reducer and about three feet of 1/2-inch pipe for the top part of the long
section. All of the connections are standard water-pipe fittings and the
soldering is with a propane torch on sanded and fluxed surfaces. These
three are among about twenty j-poles I've made for VHF/UHF. They seem to be
indestructible.

I was able to match about 80 percent of the 6 meter band under 3:1. My best
SWR was about 1.2:1 with a short length of coax and nothing special at the
feed point. A choke consisting of four turns of the coax is recommended for
decoupling.

I am a j-pole lover. I intend to try a flagpole or two at HF, someday.

Endfeed vertical halfvawe antenna
 

Good morning all

I take the opportunity to answer all of you at once.

Thank you for a lot of suggestions. I had thought about the J-pole the
problem however the problem is that we have some glass fibre tubes only
about 25 mm in diameter, so we are somewhat constrained with respect to
realise a J-pole.

Regarding a groundplane as suggested by some, the idea is to mount the
antenna on top of a mast much like an ordinary 2 meter or 70 cm vertical
antenna. In these circumstances a ground plane is not feasible.

Tom Ring asked about 6 metres in Europe. In some counties among them Denmark
there are few FM repeaters in operation. A number of amateurs have either
old army radios or modified Land Mobile Radios (LMR), typically salvaged
from taxis, fire engines and so on. All these radios operate in FM. Our idea
was to operate in this segment of 6 meter operation, not to operate in the
DX part of the band. Together with som fellow amateurs we have also tried 6
metre mobile. It actually works!

vy 73 and once again thanks for the responses

Joergen, OZ7TA
"J. Kragh" skrev i en meddelelse
k...
Togethere wih a fellow amateur I am trying to design an endfeed halfvawe
vertical antenna for 50 MHz.

We have encountered som problems regarding the impedance match in the
feedpoint. I have surveyed the ARRL Antenna Book and Antennebuch (a
German antenna book very popular in Europe). The properties of the antenna
and its impedance is well understood. The missing point is how to realise
the matching network

In order to avoid reinventing the whee: Does anybody have some good links
to study practical realisations of the matching network?

vy 73

Joergen, OZ7TA

Endfeed vertical halfvawe antenna
 

"Tom Ring" wrote in message
.. .
Tom Ring wrote:

I am curious as to what the expected use will be. I am not familiar with
6m in Europe, but 50 megahertz vertical in the US is not something you
will work much on.

If you are looking to work SSB on 6m, you will be better off with a
horizontal antenna. There are many easily built 6m beam plans available.

tom
K0TAR

Respond if you'd like some.

tom
K0TAR

If he plans on working Es, Aurora, F2 etc. vertical polarity will work just
as well as horizontal, except for maybe more man made noise p/u on the
vertical.

Dale W4OP

Endfeed vertical halfvawe antenna
 

If he plans on working Es, Aurora, F2 etc. vertical polarity will work
just
as well as horizontal, except for maybe more man made noise p/u on the
vertical.

Dale W4OP

If that's the plan Dale, he really ought to use something besides a half
wave dipole no matter what the polarization!

W4ZCB

Endfeed vertical halfvawe antenna
 

Jeff Caird wrote:
"J. Kragh" wrote in
k:

Togethere wih a fellow amateur I am trying to design an endfeed
halfvawe vertical antenna for 50 MHz.

We have encountered som problems regarding the impedance match in the
feedpoint. I have surveyed the ARRL Antenna Book and Antennebuch (a
German antenna book very popular in Europe). The properties of the
antenna and its impedance is well understood. The missing point is how
to realise the matching network

In order to avoid reinventing the whee: Does anybody have some good
links to study practical realisations of the matching network?

vy 73

Joergen, OZ7TA



An endfed halfwave has inductive reactance, ISTR. If you add another 1/8
wave to it, you reverse the sign of the reactance, thereby allowing an
inductance to tune out the reactance. Ground one end of the inductor and
tap down with the coax center conductor for a 50 ohm match--Voila! A 5/8
wave vertical!

Jeff

I think the 5/8ths is much more practical on 50 than the 1/2
wavelength. You will find the matching unit much easier to build. The
down side is you have to have radials.

Endfeed vertical halfvawe antenna
 

J. Kragh wrote:
Togethere wih a fellow amateur I am trying to design an endfeed halfvawe
vertical antenna for 50 MHz.

We have encountered som problems regarding the impedance match in the
feedpoint. I have surveyed the ARRL Antenna Book and Antennebuch (a German
antenna book very popular in Europe). The properties of the antenna and its
impedance is well understood. The missing point is how to realise the
matching network

In order to avoid reinventing the whee: Does anybody have some good links to
study practical realisations of the matching network?

vy 73

Joergen, OZ7TA

Joergen, I was working along the same lines for a 60M/5MHz antenna
several years ago. I asked the coded Extras on RRAP for suggestions
and got some pretty nasty replies. I hope that you are able to find
the help that you need.

Best of Luck!

bb

Endfeed vertical halfvawe antenna
 

J. Kragh wrote:
Good morning all

snip

Tom Ring asked about 6 metres in Europe.

K8MN, from Africa, managed to snag a bunch of out of band Frenchmen on
6M.

Perhaps he could shed some light on 6M DX Operations.

Endfeed vertical halfvawe antenna
 

Cecil Moore wrote:
J. Kragh wrote:
In order to avoid reinventing the whee: Does anybody have some good links to
study practical realisations of the matching network?

How about 1.3 meter (4.3 feet) of 450 ohm ladder-line
as a series-section-transformer?
--
73, Cecil http://www.w5dxp.com

Hey Cecil, you have a good answer.

If a coil is used, how many turns and what diameter?