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

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

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?

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

"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

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.

"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.

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

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

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