"Make a half wave vertical and simply run a wire to the nearest ground
and presto", you have a very high impedance antenna that will not match
to 50 ohms and is very bad advice. Make it a quarter wavelength vertical
radiator and ground the coax to something substantial, that would be
better advice. On the half wave dipole, it doesn’t matter if the element
connected to the center of the coax points up or down, the antenna
doesn’t know any different and it works the same.
Bob



Zombie Wolf wrote:
Make a Half - wave vertical with pipe. If the wall is dry wood, you can
simply clamp it in place on the wall. You figure out the length of this
antenna by the following formula

468 / freq (in MHZ)

Hook the center conductor of the coax to the antenna, and then simply
run a wire from the shield braid of the coax to a nearby ground. Presto.
You now have a half - wave vertical.

A l;ittle note on dipoles. the bands you want to listen to are primarily
vertical in nature. so if you made a diplole, you would want to mount
the thing vertically, not horizontally. The side of the diplole with the
center conductor connection would go at the top.

the sides of this antenna can be figured out by the following formula

234 / freq (in MHZ)

this gives you one side of the dipole. shield to one side, center
conductor to the other. I would use the copper wire for this.

Another antenna is the loop. the entire length of this antenna is
figured out by the following

1005 / freq (in MHZ)

this is a loop of wire, and is usually tacked onto the wall. the hookup
is made at the side of the loop for vertical polarization. Once again,
the copper wire is best suited for this antenna. the only trouble with
this antenna is that it is slightly directional, recieving best at a 90
degree angle to the plane of the loop in both directions. The loop is
usually formed into a circle or a square on the wall. (square is the
usual case).


all of the answers in these equations give the answer in feet and
fractions of a foot. simply multiply the fractional part by 12 to get
inches. rounding to the nearest inch is fine.

naturally, this mounting info is based on an indoor environment, outside
mountings need to be dealt with a bit differently. also, we are
assumiong that the building does not have metal siding, which will tend
to block radio waves. These do make excellent attic mounted antennas in
the house, by the way. Just mount the antenna on the end wall of the
attic, straight up. If you feel you must insulate the antenna, then
electric fence insulators are a quick and easy way to do this. simply
tap the nails into a convenient stud to mount the antenna. The half wave
vertical can also be made from the copper wire, by the way, and it will
work well. The half wave does not require radials , by the way. That is
why we simply run a ground wire from the braid to ground on this antenna.

for the coax connection points, a piece of thick plexiglass makes a good
terminal block. just drill a couple holes in the block, close together,
and put an extra washer and nut on the screws. walla ! you have a place
to hook the wires up. Screw spacing ? 1/2 inch or so works pretty well....



"Paul Monaghan" wrote in message
...
Hi folks, new here.

I have been in need of a weather radio, but when shopping for one this
week it seemed such a waste to receive only 7 frequencies when I could
be receiving thousands. So I ended up with a scanner, just like that.

Wow! Instant hobby! Big mistake! I'm a serial compulsive, so now it's
time to start making antennas...

The scanner is one of those closeout RS Pro-2052s. With the stock
antenna I can receive the local police at around 39 and some
frequencies in the 100s, around 125 and 150, including civilian air.
Maybe more, but I'll concentrate on these for now.

Would like to build a simple half-wave dipole to start with. In my
garage I have a roll of 10ga solid copper, some solid aluminum wire
maybe twice as thick (don't know what it is, is left over from a
satellite TV system), and some galvanized 1-inch steel pipe.

Antenna would be mounted inside a detached garage so weather/weight
are not significant factors.

Reading the archives I can't tell whether to go with the copper
because it is a better conductor than the others, with the aluminum
because it is thicker than the copper, or with the galv pipe because
it is much thicker than the copper though somewhat lossy.

Any thoughts appreciated.

Thank you,
Paul