Earl Andrews VE3AB - busy today Sept 21-08 building and working on my SHORT
VERTICAL ANTENNAS. I want to use a home brew short vertical antenna in my back yard
for 160, 80 and 40 meters (swl and Broadcast band listening as well!!!!)
--Testing the antennas is being done on my truck with a magnetic mount and on a tin
roof of my 10 by 10 shed. I hope to develop something that works well and I would
ideally like to invent a better short antenna. (perhaps a short vertical dipole..who
knows????)
I also like to listen to the LOW FREQUENCIES and broadcast band from time to time. I
want my antenna to be capable of being adjusted to those frequencies as well. A coil
loading system (adjustable) for a short vertical antenna is what I will be working on.
VERTICAL ANTENNAS. I want to use a home brew short vertical antenna in my back yard
for 160, 80 and 40 meters (swl and Broadcast band listening as well!!!!)
--Testing the antennas is being done on my truck with a magnetic mount and on a tin
roof of my 10 by 10 shed. I hope to develop something that works well and I would
ideally like to invent a better short antenna. (perhaps a short vertical dipole..who
knows????)
I also like to listen to the LOW FREQUENCIES and broadcast band from time to time. I
want my antenna to be capable of being adjusted to those frequencies as well. A coil
loading system (adjustable) for a short vertical antenna is what I will be working on.
I picked up some old Hustler coils (without the
windings) at a ham radio flea market several
years ago.
Here I took an old 80 meter resonator and
soldered on an airwound coil I had in my
junkbox. It resonates at around 5.5 mhz or so
with the hustler mast on my truck. A starting
point.
windings) at a ham radio flea market several
years ago.
Here I took an old 80 meter resonator and
soldered on an airwound coil I had in my
junkbox. It resonates at around 5.5 mhz or so
with the hustler mast on my truck. A starting
point.
HERE is the airwound coil with a
top hat I quickly soldered up. The
top hat assembly consists of
copper plumbing strap that I
wound around the hustler coil
upper section. I found this small
top hat had a profound influence
on the frequency of resonance. It
lowered it significantly.
-- Perhaps a top hat that can be
moved up and down could make
for a broad band antenna.
Another option would be to have
a tweaker coil at the base with a
powdered iron core which could
adjust the Fr of the antenna to
allow full band coverage.
top hat I quickly soldered up. The
top hat assembly consists of
copper plumbing strap that I
wound around the hustler coil
upper section. I found this small
top hat had a profound influence
on the frequency of resonance. It
lowered it significantly.
-- Perhaps a top hat that can be
moved up and down could make
for a broad band antenna.
Another option would be to have
a tweaker coil at the base with a
powdered iron core which could
adjust the Fr of the antenna to
allow full band coverage.
Here is the magnetic
mount that I am
experimenting with.
Unfortunately..this
assembly is giving me
problems. It seems to
have some sort of
intermittent problem and
I am going to rebuild it.
I used copper foil to
surround a magnet and
then I homebrewed a
circuit board on top for
the connections to the
antenna and ground.
IT seems to work fine for
awhile then the epoxy
heats up in the sun and
the SWR goes crazy.
I am going to abandon
this unit.
mount that I am
experimenting with.
Unfortunately..this
assembly is giving me
problems. It seems to
have some sort of
intermittent problem and
I am going to rebuild it.
I used copper foil to
surround a magnet and
then I homebrewed a
circuit board on top for
the connections to the
antenna and ground.
IT seems to work fine for
awhile then the epoxy
heats up in the sun and
the SWR goes crazy.
I am going to abandon
this unit.
The conventional hustler
coil and resonator is
visible in this picture.
Also visible is my little
TGM MINI BEAM which is
just over the peak of the
roof in this picture.
A problem (or possible
problem) with phenolic
or epoxy is its tendency
to absorb moisture.
I have some fiberglass
poles and pieces to use
instead for coil forms
and supports.
coil and resonator is
visible in this picture.
Also visible is my little
TGM MINI BEAM which is
just over the peak of the
roof in this picture.
A problem (or possible
problem) with phenolic
or epoxy is its tendency
to absorb moisture.
I have some fiberglass
poles and pieces to use
instead for coil forms
and supports.
I have quite a few hollow
telescoping fiberglass quad
spreaders in my collection of stuff
that I have gathered over the years
(some of it from a commercial quad
assembly).
When I do put up my quad (later on
when the sunspot cycle gets good
(3 years from now)..It will be a cut
down version for 10 and 6.
Here is my first MOBILE ANTENNA
MAST UNDER CONSTRUCTION.
It sure doesn't look like much right
now!!
The Hose Clamps are temporary.
They keep the 3 lengths of copper
plumbing strap in position while I
get around to soldering the
copper strap bridges (see the
second picture.
The WHOLE THING (when all the
soldering is done) will be taped
with black electrical tape (to
protect the heat shrink where the
solder joints or sharp edges
appear.
A durable heat shrink tubing will
cover the entire assembly.
IT SHOULD LOOK SOMETHING LIKE
A RATHER LARGE HAMSTICK
MOBILE ANTENNA.
THIS MAST OF FIBERGLASS TUBE
AND COPPER PLUMBING STRAP
WILL BE ABOUT 7 FT LONG OR SO
AND WILL BE EASILY REMOVABLE
FROM THE VEHICLE.
I plan to use this set up for
PARKED MOBILE USE MAINLY AND
CAMPING AND STUFF LIKE THAT.
i WILL HAVE MANY MORE PHOTOS
AS THIS PROJECT PROCEEDS.
telescoping fiberglass quad
spreaders in my collection of stuff
that I have gathered over the years
(some of it from a commercial quad
assembly).
When I do put up my quad (later on
when the sunspot cycle gets good
(3 years from now)..It will be a cut
down version for 10 and 6.
Here is my first MOBILE ANTENNA
MAST UNDER CONSTRUCTION.
It sure doesn't look like much right
now!!
The Hose Clamps are temporary.
They keep the 3 lengths of copper
plumbing strap in position while I
get around to soldering the
copper strap bridges (see the
second picture.
The WHOLE THING (when all the
soldering is done) will be taped
with black electrical tape (to
protect the heat shrink where the
solder joints or sharp edges
appear.
A durable heat shrink tubing will
cover the entire assembly.
IT SHOULD LOOK SOMETHING LIKE
A RATHER LARGE HAMSTICK
MOBILE ANTENNA.
THIS MAST OF FIBERGLASS TUBE
AND COPPER PLUMBING STRAP
WILL BE ABOUT 7 FT LONG OR SO
AND WILL BE EASILY REMOVABLE
FROM THE VEHICLE.
I plan to use this set up for
PARKED MOBILE USE MAINLY AND
CAMPING AND STUFF LIKE THAT.
i WILL HAVE MANY MORE PHOTOS
AS THIS PROJECT PROCEEDS.
I found it resonated on about 5.6 mhz with my
hustler mast. I will have to do some work on it
either tapping it down to get it on 40 or adding a
top hat to get it near 80.
hustler mast. I will have to do some work on it
either tapping it down to get it on 40 or adding a
top hat to get it near 80.
MY NEW AND IMPROVED
MAGNETIC MOUNT FOR MY
MOBILE STATION.
MAGNETIC MOUNT FOR MY
MOBILE STATION.
My target frequency for my mobile whip
was 3.755 mhz. This is a very popular
frequency for nets and is close to some
popular ragchew frequencies.
The Hustler whip (without the top hat)
was resonant around 3.860 mhz.
I put on this top hat (made of copper
plumbing strap). The resonant frequency
dropped way down below the 3.5 mhz!
More adjustments were necessary.
was 3.755 mhz. This is a very popular
frequency for nets and is close to some
popular ragchew frequencies.
The Hustler whip (without the top hat)
was resonant around 3.860 mhz.
I put on this top hat (made of copper
plumbing strap). The resonant frequency
dropped way down below the 3.5 mhz!
More adjustments were necessary.
These short vertical antenna pages are currently being worked on (as is the antenna itself).
I want to develop a short efficient (small city lot friendly) antenna system for the low bands
without extensive ground radials and without unsightly wires in the sky.
click here to see page 2 of this presentation.
I want to develop a short efficient (small city lot friendly) antenna system for the low bands
without extensive ground radials and without unsightly wires in the sky.
click here to see page 2 of this presentation.
NOTE of caution!!
This big mechanical
assembly will be
safety strapped to the
vehicle.
This big mechanical
assembly will be
safety strapped to the
vehicle.
early development work in the yard
| This coil is around 75 uh. To get an 8 ft whip on 75 meters you need 120 uh or so. The ARRL handbook has a chart for 8 ft long vertical mobile antennas and the inductances required. I have since, used this coil at the base of my HF2V vertical to get it to resonate on 160. I needed about 65 uh so I tapped it. Worked well. |