Directional scanner antenna for a hand held ?
 

Is there a directional antenna that can be used with a handheld
scanner ? I'm trying to track down the origin of a signal in my
neighborhood.

Can one be made easily ?

Kip

On Wed, 11 Feb 2004 12:31:53 -0500, evans wrote:

Is there a directional antenna that can be used with a handheld
scanner ? I'm trying to track down the origin of a signal in my
neighborhood.

Can one be made easily ?

Kip
http://www.ramseyelectronics.com/cgi...ction&key=DF1C

Good direction finding system.

JT

ARROW ANTENNAS

evans ...

^ Is there a directional antenna that can be used with a handheld
^ scanner ? I'm trying to track down the origin of a signal in my
^ neighborhood.
^
^ Can one be made easily ?

One can be made easily for VHF and UHF, not as easily for other bands.

If the signal you need to locate the origin of is VHF or UHF then make a Yagi
antenna. Since this will be a receive -only antenna you can skip the matching
transformer (or balun) and you can use a simple half-wave dipole instead of a
folded dipole. A few feet of wire, a plastic or wood pole, and a short piece
of any type of coax are all you will need.

Frank

evans wrote:
: Is there a directional antenna that can be used with a handheld
: scanner ? I'm trying to track down the origin of a signal in my
: neighborhood.

: Can one be made easily ?

You didn't say what freq you want to search on.

BUT there are a number of tricks you can use with what you already have.
FIRST, I assume that you can hear the signal with the stnadard rubber
duck.

The first 'trick' is called "body fade". Hold the radio close to your
chest and listen to the interference. Now, slowly turn around in a 360 deg
circle as you stand in the same spot. At some point in the circle the
signal should either fade, or cut out altogether. When this happens keep
turning and see if it comes up. If so, stop and turn back and try to find
the deepest "null". STOP. The interference is directly behind you.

If you have a map of the area now would be a good time to draw a line on
the map in that direction. But if the source is fairly close it's not
necessary.

Do this a number of times in different locations to see if all the "lines"
point in the same general direction .. if so move toward that location and
repeat the procedure.

If you get so close that you don't hear any "null" when doing this, try
removing the antenna from the radio. If you are so close to the signal
that you can remove the antenna and still hear it, you can keep doing the
procedure without the antenna.

Another 'trick' is useful when getting close ... instead of listening to
the primary freq. (interference is strongest on xxx.xxxx mHz) listen to a
multiple of that freq (harmonic) say 2 times xxx.xxxx or even 3 times
xxx.xxxx if your radio goes up that high. This may not work if the
offending interference is broadband and you can't pin down the freq.

Good luck

Richard in Boston, MA, USA
N1JDU

Thanks to all for some good suggestions. Maybe I'll try this weekend
some outside work if it ever gets above freezing .


On Thu, 12 Feb 2004 02:43:03 +0000 (UTC), Richard G Amirault
wrote:

evans wrote:
: Is there a directional antenna that can be used with a handheld
: scanner ? I'm trying to track down the origin of a signal in my
: neighborhood.

: Can one be made easily ?

You didn't say what freq you want to search on.

BUT there are a number of tricks you can use with what you already have.
FIRST, I assume that you can hear the signal with the stnadard rubber
duck.

The first 'trick' is called "body fade". Hold the radio close to your
chest and listen to the interference. Now, slowly turn around in a 360 deg
circle as you stand in the same spot. At some point in the circle the
signal should either fade, or cut out altogether. When this happens keep
turning and see if it comes up. If so, stop and turn back and try to find
the deepest "null". STOP. The interference is directly behind you.

If you have a map of the area now would be a good time to draw a line on
the map in that direction. But if the source is fairly close it's not
necessary.

Do this a number of times in different locations to see if all the "lines"
point in the same general direction .. if so move toward that location and
repeat the procedure.

If you get so close that you don't hear any "null" when doing this, try
removing the antenna from the radio. If you are so close to the signal
that you can remove the antenna and still hear it, you can keep doing the
procedure without the antenna.

Another 'trick' is useful when getting close ... instead of listening to
the primary freq. (interference is strongest on xxx.xxxx mHz) listen to a
multiple of that freq (harmonic) say 2 times xxx.xxxx or even 3 times
xxx.xxxx if your radio goes up that high. This may not work if the
offending interference is broadband and you can't pin down the freq.

Good luck

Richard in Boston, MA, USA
N1JDU

"evans" wrote in message
...
Is there a directional antenna that can be used with a handheld
scanner ? I'm trying to track down the origin of a signal in my
neighborhood.

Can one be made easily ?

Kip


If the 'signal' radio is at a fixed location, a loop antenna on your
handheld will give you alot of information about where the 'signal' is. A
loop antenna is usually an easy antenna to fabricate.
Direction finding with loops was used extensively during WWII. The
'signal' will be somewhere along a line corresponding with the null of
signal strength. You will need to move the location of your hand held to
two or more locations, as you have already figured out.
The null will be along a line perpendicular to the plane of the loop. The
'signal' will be maximum when the loop is pointed with its edges toward the
'signal'.

A "Google" search using keywords like wildlife tracking, bird tracking and
antennas will yield alot of information on handheld directional antennas ...
both home-built and commercially-purchased.