73 Earl VE3AB
Maybe the toughest part of any project ..is either making the parts or finding the
The coil I used in my 12 foot copper pipe version of the screwdriver antenna was
made by an Ottawa amateur..Ernie VE3EJJ. We were both planning on building
these antennas back in the late 90s and I still had this real nice coil. It is made on a
lathe with nr 16 guage solid plated wire. It looks like bus wire to me.
In the other picture, you can see a second coil which is a bit smaller in diameter
but is made in much the same manner. This one I bought as an entire antenna from
the old master builder Ted Ve3DXG. This one was fairly corroded but it gave me
the assemblies I needed. I actually took the old corroded wire off and rewound the
coil by hand using new wire. I still have the coil and plan to use it in another
homebrew project in the near future.
|Above the SKIL Twist cordless screwdriver from the old mobile antenna I bought second hand. The builder left the entire unit intact and inserted it into the mast.
The hand operated on/off/forward/reverse switch was removed (see the rectangular shaped open hole. IF you look to the left of this rectangular open hole you will
see the hole where the retaining pin goes through the screwdriver handle and the pin keeps the motor from spining ..thus forces the threaded rod to spin and the
coil moves up and down. NOTICE ..the small cotter pin in the screwdriver bit holder and through the threaded rod.
I did not use this method. I used a screwdriver bit that I chopped down with a grinder and a shaft coupling. I used some tape to keep everything together (at least
for now during the testing stages). I have bought some LOCTITE fastener glue to apply to the joints at a later date to make sure they hold together.
|The "inner assembly" of my backyard screwdriver
vertical is made of two pieces of fiberglass rod.
They nest together and I adjusted the length by trial
and error to allow proper operation.
Its is important to note that this project is now
operational. I can use it to make qsos and I can
remotely tune the antenna from my basement shack.
I have to look out the basement window and kinda
eyeball the antenna from a distance of about 40 feet
or so. Then I have to fine tune adjust it with the MFJ
analyser to where I want to operate.
I merely use a variable power supply and I connect
the wires with clip leads. This system is somewhat
cumbersome and slow but I plan to make it much
I will be going on the internet to the Yahoo Groups
site for screwdriver antenna users and snoop
around for ideas from there and other web spots.
The two pieces of fiberglass rod are from a Lightning
Bolt Quad that I bought about 10 years ago. I never
put the quad up and I have used a couple of the
spreader arms for homebrew antennas like this one.
What I plan to do with the rest of the Lightning Bolt
Quad parts is build a smaller version quad for 6, 10
and 12 meters. We are in a sunspot maximum period
now and I want to have some fun on the upper
bands with a good directional antenna.
Below is a sketch of the antenna I made using the simple art work program for windows. ---->> This antenna could be scaled for other bands. For example.. a 33 foot
piple with a large coil and say 6 or 8 foot stinger whip or small diameter aluminum tube at the top could work 2 bands with one settiing. Actually..probably 3 bands
with one setting. The 33 foot pipe would work on 40 meters and 15 meters and 75 meters or maybe 160 or even 60 meters. In my case..(small city lot with nearby
hydro wires leading to the house) I cannot easily put up this large an antenna.
|link back to my home start page www.hamelectronicsmagazine.com
73 de..earl ve3ab (( PS..this article is still being worked on)) -- the antenna is still being
worked on from time to time as well and I will add more pics and info later.
Tools and parts above pictured. A heavy duty soldering iron or gun ( I used both). Good
snips for cutting the fingerstock to the correct length. Tools to hold the fingerstock in
place while it is being soldered. I used forceps that worked well. Nut driver for the hose
clamps. I use plenty of stainless steel hose clamps and plenty of electrical tape. Emery
cloth for cleaning metal surfaces. The copper pipe 2 inch coupling is shown. The pipe
coupling will have the finger stock soldered to it and will be at the top of the 12 foot copper
pipe. It can be detached for cleaning or replacement with a better updated fingerstock sub
assembly (if warranted) at a later time. The solder and you can see at the top of the
coil..them temporary 3 ft small diamerter aluminum tube. I plan to replace that with a
standard mobile threaded bushing which will allow me to attached various lengths of
stainless steel whips or even mobile coils or other hardware.
If there is a 160 meter special event or contest..I can get on 160 by using another coil in
series with the sliding coil. NO DOUBT..the tuning will be very sharp but I will be able to
operate TOP BAND and at least participate in the contest and hand out some points.
Above..the coupling to the screwdriver motor. I plan to use a
type of "LOC TITE" BRAND liquid to the screws and the coupling
so that these mechanical joints and fasteners don't work them-
selves loose over time. For NOW>. I merely used electrical tape
to keep everything bound together. I am still working on the
antenna and developing ideas to make it better.
The 4 by 4 post in the ground with a cement base (1 bag of reddi
mix concrete was sufficient). NOt shown at the top of the 4 by 4 is
a metal bracket which clamps to the vertical antenna element.
The 4 by 4 mast is about 6 ft high.
I used it previously with my HF2V vertical. The article is available
at my web site www.hamelectronicsmagazine.com
I have other vertical elements I can swap into place over this
I have a full length 32 foot vertical that I plan to try with my PAR
antenna match box in order to have a 1/2 wave end fed vertical.
MY ORDER to PAR (LNR PRECISION) should come in by the end of
Oct and I will be trying the antenna out around then.
I will be featuring that on my web pages as well.
NOTE: RIGHT NOW..first part of Novemeber..My Par/lnr Precision
20 meter end fed half wire antenna has come in and I put it up as
a sloper off the tower.
Maybe in the spring..I may try it out as a half wave vertical.
Winter and cold weather are soon to arrive here and my outdoor
antenna work will soon be minimal. I will then turn my attention to
the many projects I have waiting on my work bench: ie..Ten Tec
Argonaut DDS experiment, FT301 Digital Display from AADE,
several radios that I have to repair. Several kits..including the
New England QRP club SCAF filter..and many more.
And then there is always organizing all the little transistors,
capacitors, coils, toroids and semiconductors and ICs and trying
to catalogue them. I SELL PARTS and I have several radios I have
parted out and I sell to raise money for this web site and supplies
I buy. I REALLY AM ENJOYING MY EARLY RETIREMENT.
My email address is email@example.com ...or
firstname.lastname@example.org if you care to drop an email or you need a few
parts. Guest articles and photos for this web site/magazine..are
certainly MORE THAN WELCOME!
There are quite a few commercial manufacturers of
these types of screw driver mobile antennas.
They can be adapted to backyard use.
This one on NORMs car looks like it would work well in
the back yard.
>> Perhaps a person could buy a second hand
screwdriver mobile antenna and rebuild it. The
threaded rod is readily available at hardware stores.
The bus wire can be used to rewind the coil if need be.
|This pin above goes through the
screwdriver handle and the
antenna pipe to hold the motor
assembly in place and it also
keeps the motor from spinning.
IN my case...I did things a bit
differently. My lower antenna
section below the coil is about 12
feet of 2 inch copper pipe. An
adjustable length of fiberglass
tubing runs to the bottom and out
the bottom a wee bit and it is there
that the whole inner assembly is
held in place..not with a retaining
pin (such as above pictured)..but I
merely used electrical tape to
secure the fiberglass piece to the
bottom of the copper pipe.
It is a bit of a lash-up at this
point..but Im only experimenting
with the antenna and a more
permanent method is being
Im thinking of building a base
insultator out of 2 inch solid plastic
rod with a hole to accomodate the
fiberglass masting and perhaps a
retaining pin that can be removed
for when I want to work on the
antennas inner assembly.
The antenna is fairly easy to take down and put back up again. Here
I take it down for a bit of maintenance. A nice fall day in northern
Ontario 16th of October. The 4 by 4 post with the top clamp
(something I bought at a yard sale is in the background.
On the ground is an aluminum 24 foot vertical that I want to try on
10 meters. This weekend is the QRP ARCI Fall QSO Party. I heard 10
meters was pretty good today and so I put up a 3/4 wave vertical for
10. (It also functions as a full quarter wave on 10 mhz band with a bit
of an adjustment. The nice thing about verticals is their small foot
print. My back yard and front yard does not have the proper layout
for much in the way of wire antennas and I dont really like the looks
of too many wires around. With this system I have..I can have some
vertical radiators on storage hooks against the wooden fence and
can swap in various vertical elements at will.
I have just ordered a PAR (LNR Precision) 20 meter end fed half
wave. I plan to use my 33 foot vertical that I have with the PAR
matchbox as a full 1/2 wave vertical elevated up above the ground
a bit..say 3 or 4 feet. Just one of the many configurations possible
with this small exerimental set up.
Above: the antenna with a wee bit of condensation. One possible enemy I will have to
deal with!! The coil is at the 40 meter position. At the 40 meter position ..the lower 12 feet
seems to resonate on 18mhz with a nice broad curve due to the large diameter of the
pipe. I have not tried the antenna on 17 meters yet.
Yesterday..with the coil inserted most of the way in..I could work 15 meters and I got
good results. I worked Spain quite easily during the QRP contest. This antenna seems to
work quite well on 15 for some reason. Not sure..but I think it may be acting like a loaded
3/4 wave antenna or something along those lines.
Lots of room for experimentation. And just like the famous W5GI mystery antenna...one
never knows when something might just happen to work real well and cannot be
modelled with software.
Setting aside the copper pipe screwdriver antenna, for now, and in its place..Im putting up a 24 foot high vertical for 10 meters. It will be a 3/4 wave high. I checked
the swr and it bottoms out around 28.080 with the lowest swr being about 1.3 to 1. Good enough. Below.. the 24 foot vertical antenna for 28 mhz. The base insultator is
a short length of fiberglass tube wrapped in electrical tape. The MAIN SUPPORT for these vertical antennas comes from the metal bracket mount about 6 ft off the
ground. This is a good system. Allows quick lowering of the antenna for maintenance, bad weather, or (in my case) when I want to try another vertical element.
There are only 3 hose clamps to loosen. 1 holds the coax center conductor to the vertical element..lower left picture. 2 more hose clamps are loosened from the
upper support bracket. I often use a tie rope to the bottom of the insulator to the brown colored metal post/pipe in the lower left picture. The whole system works
well. In winter with snow..I use the snowblower to blow snow away from the general area of the vertical and then I use a hand brush and shovel to keep the antenna
feedpoint in the clear.
|18 October 2011 (link to page 3)
-->> I took the screwdriver antenna apart to make some
much needed refinements and changes -- CLICK here to
see pictures and text
|LINK TO PAGE 3 of this construction
|CLICK HERE ON THIS
LINK TO SEND ME AND
73 Earl VE3AB
Elliot Lake, Ontario
|I take donations of parts or old broken rigs to keep in my inventory for helping other
hams fix older gear. I also fix up the older rigs. Solid state rigs from the 70s and 80s
are what I mainly work on ie...Atlas 210x, FT301, FT7, Ten Tec Argonaut and similar
radios. I sell parts for these rigs as well (at a very reasonable price).
|Below pictures: Two coils. One that I got from a fellow ham who machined it on his lathe and the other I got from a second
hand screwdriver vertical antenna I bought that needed repairs. NOTE: the second hand screwdriver vertical had a fair amount
of rust on the threaded rod but the parts were all there and I could see how it was put together. I opted for a departure in
design ..I used alot of electrical tape to secure things together..ie the fiberglass poles to motor interface. ITS ALL WORKING SO
WELL..I'm not going to fix it until it breaks! -- the antenna does freeze up and that needs to be fixed!!! Im going to use a motor
from a cordless drill and that should give design the robust capability to work in all weather conditions (I HOPE!) ..Ive got some
other things up my sleeve for this spring antenna working season (2012 spring)..so stay tuned..I will post the enhancements
here in this article!
|The second hand screwdriver mobile antenna had oxidation not only on
the threaded rod but also on the finger stock.
I kept all the parts that were good..but..I opted for my own kind of design
that works good for a larger base station vertical. Up here..the laws for
mobile operation are changing..hands free is the rule.
Perhaps this is why this
antenna I built will not
work when the
temperature outside is
A stronger motor should
break the ice so to speak.
I have some other plans
for this antenna which will
be modified this summer
winter hits I will be making
changes. Stay tuned to
these pages for more
|I use a 4 by 4 inch wooden post with a special bracket on it to secure the vertical. It acts
as a kind of "guy" up at about the 7 foot from the ground level. I would not want this
antenna to fall down in the wind. It is quite strong. The 11 foot stinger piece of aluminum
tubing above the coil ..does move around in the wind a bit..but it is strong and has stayed
up so far without any problems. This antenna can be tuned to any frequency. I have tuned
it to the new 60 meter band. I want to get it to load on 160 ..so I may take most of the top
stinger off and run a fiberglass pole beside the vertical which will carry a wire and I may
configure this antenna as a type of tunable inverted L. The vertical mast would be about
25 ft high and there would be a 25 ft semi horizontal wire going out to my tower near the
house. I feel with 50 or perhaps a bit more foot radiator ..the inductance in the coil would
then load up on 160 -- I think Im going to try this before next winter.
The feedpoint. Nothing fancy..at least not yet. This antenna is still in
|My tunable inverted L concept is shown in the sketch here
The fiberglass pole (green) is necessary to take the tension
off the wire and to allow enough slack to allow the coil to go
up and down and tune the antenna.
I will be posting actual pictures in the fall when I get around
to trying this out.