Build A Simple VHF/UHF "Scanner"
Radio Antenna Build a Police Scanner
Antenna for the price of parts!
Here is
a simple VHF/UHF scanner radio antenna you can build using very
inexpensive coaxial cable and a few parts plus some bits of
wire!
It should cover receiving only from the AM
aircraft band up thru the most used UHF frequencies in use by the
average "police" type scanner radio you may have. If you live in a
large metropolitan area, it should work well way beyond the UHF action
frequencies also. It's design is based on a standard "ground plane"
type antenna and the "harmonic" principle of antennas which means
that is was designed for the VHF band but due to the characteristics
of the way antennas work, it will also work well on it's third harmonic of
the design frequency band. The UHF scanner radio
band is approximately 3 times higher in frequency than the
VHF scanner band so it's design will work well there using only one
length rather than several lengths in the vertical portion of the
antenna to cover the VHF/UHF radio bands. This antenna has NO gain on
VHF, but does have a little on UHF due to being operated in the "harmonic"
mode on these frequencies. Many Amateur radio antennas are based on the
exact same design and have been used effectively for many years. Compared
with the commercially produced antennas, with their cost as a big factor,
it does perform well for "pennies" on the dollar!
(Simple VHF/UHF scanner antenna
made from coaxial cable)
This antenna is
designed to be "cheap". So it must be constructed in such a way to be
supported from the top of the vertical "element" of the antenna and also
from the ends of the 3 "radials" that go away from the coaxial cable at
it's junction. One good way to suspend the vertical section is
to make a small loop on the end of the vertical section and suspend
it from a small non-conductive rope, cord or heavy string from something above. Make the length of the cord, rope,
string, etc as long as needed to get the vertical section and the
radials portion at least 3 or 4 feet away from any large metal
surface like house siding, roofing material, etc. DANGER!DO NOT HANG OR MOUNT IT NEAR POWER
LINES!
The antenna must be in the vertical position, meaning that
the tip of the vertical portion away from the coaxial cable must be up
towards the sky.
The 3 radials may be done the same way as the
vertical section. Just make a small loop on the ends of all 3 and tie them
off in 3 equal directions with the angle about
45 degrees down from horizontal, similar to
the simple drawing below:
Material list 1. Coaxial cable.
Should be any usable cable such as TV type or 50 ohm coax. Coaxial cable
comes in many different types, but as a general rule for receive only
functions, the TV type coax will work fine and is easy to find. Some TV
types have an inner foil and the shield, which makes working with it a bit
more difficult. You can not solder to the foil, only the shield! You will
need enough coaxial cable to hang the finished antenna OUTSIDE
and above the roof if possible. It can be used inside with
reduced performance by hanging it from the ceiling near a
window.
2. Wire for the radials. Final length....About 20 inches
each (3 pieces) #12 or #14 works well and is more stiff than smaller
wire size. See hints below!
3. Wire for
the vertical section. Actually, this wire will come from within the
coaxial cable by removing the outer insulation and the shield...see
constructions tips below.
4. Soldering gun or iron, solder
and sealer for the coax radial junction. This keeps the rain out and is
very important.
5. Assorted hand tools, sharp knife for trimming
insulation from coaxial cable.
All of these parts and tools can be found at any hardware shop or
electronic store. However, building this should be easier and cheaper than
repairing a Ford F150, however it shouldn't cost you an arm or a leg
for parts. Click
here for cheap parts for your Ford and possibly
parts for your VHF/UHF antenna.
Construction and tips for building and using
it. In the drawing above, you will see the black
section representing the coaxial cable.
You will also see the vertical section (A) on
top.
You also should see the 3 radials marked
(B) hanging down.
One of the best ways to construct the scanner antenna is to
take your full length of coax and remove the outer insulation AND the
shield for about 21 or 22 inches from one end leaving the inner wire
exposed with it's insulation intact. DO NOT CUT INTO
THE INNER WIRE inside the coaxial cable. If you cut it into, you
will have to start all over! The idea here is to leave about 21 to 22
inches of the center conductor (wire) exposed with it's insulation
intact after you remove the other section containing the outer
insulation and the shield. You also need to leave about 1 inch of the
shield exposed for soldering of the 3 radials to it! Refer to the drawing
above.
Now take a close look at where the black
portion of the coaxial cable ends in the center of the drawing. This is
the point where the 3 radials are physically and electrically
attached to the shield of the coax that has been exposed.
They should be soldered to the shield being
careful not to destroy the insulation for the "center" conductor of
the coaxial cable. These 3 radials in NO WAY should be attached to the
center conductor (wire) that is inside the cable. If this happens, then
the antenna will become useless! See the drawing. Make sure you leave
the insulation on the center wire until after you are done with the
construction OR as an option, you may just leave it on to help protect the
wire inside it from the ravages of moisture, corrosion, etc, but
remember you have to make a loop on it's end for hanging. Leaving the
insulation on will in no way effect the performance of the antenna! The
3 radials need not be soldered in 3 different
places on the coax shield unless you want to go to the trouble of doing
this...here is another way to attach the radials.
Simply just
attach one, by adding enough extra length to it to wrap around the shield
and then solder it to the shield. Then just solder the other 2 to that
single radial close to the shield and then you can spread them out in
3 equal directions from the coaxial cable of the antenna looking down
(Birds eye view) on it from the top. To be technical, each one should
spread out at 120 degrees, but they don't have to be perfect!
So...after you have completed this simple scanner antenna, all you
have to do is hang it suspended from your support, attach the opposite end
to your scanner radio using the correct connector and enjoy!
For more ideas on ways to help make a more
sturdy scanner antenna, just take a look at how Amateur radio operators do
it using PVC! The basic design is the same, just a different way of using
ham radio ingenuity! Click
Here!
If you don't have the skills or just don't
want to build a good scanner antenna, then check out Scanner Master for
all your Scanner antenna and radio needs below.
