A&S Company, World's Leading Supplier of Metal Detectors and Accessories
Super Low Prices, We Ship Nationwide
|
A&S Company
|
Phone: (408)248-1233
|
|
3209 Benton St.
|
fax: (408)241-7304
|
|
Santa Clara, CA 95051
|
|
|
http://www.detection.com
|
email: Here
|
Some History
In the late 1920's, Dr. Gerhard Fisher, the founder of Fisher Research Laboratory was commissioned as a research engineer with the Federal Telegraph Co. and Western Air Express to develop airborne direction finding equipment. He was awarded some of the first patents issued in the field of airborne direction finding by means of radio. In the course of his work, he encountered some strange errors and once he solved these problems, he had the foresight to apply the solution to a completely unrelated field, that of metal and mineral detection. Now, an explanation of what a radio direction finder (RDF) is.
In any system making use of radio, there must be a signal source (or transmitter) and a receiver, operating at the same frequency. In the early days of RDF development, the transmitting tower of a local radio station provided an ideal transmitter. Its permanent location was precisely known and so was the frequency of its transmission. An aircraft approaching a city through fog or clouds could home in on a local radio transmitter by using a radio receiver equipped with a directional loop antenna.
To quickly examine these components: the transmitter signal is sent by cable to the antenna tower, which radiates energy in all directions. The radio station's program is beamed into the entire surrounding area. The loop antenna of the aircraft's receiver however, has the peculiarity of being very directional with respect to the transmitter.
The best or loudest reception is obtained when the plane of the receiver loop is parallel with a line toward the transmitting antenna. No signal at all is received when the loop is perpendicular to the line toward the transmitter. This No Signal position is very sharp and has always been used to obtain accurate bearings. Most table and transmitter radios have loop antennas and your reception will be very dependent on how you turn the radio. If you have a loop antenna on your receiver and this loop with its edge is pointing directly to the transmitter, you may also say it is parallel to a line toward the transmitter. You will then receive maximum signal. Turning the receiver 90 degrees results in a minimum signal or the zero induction position. Remember, this is the most important point in our basic theory.
Discovery
This zero induction effect at aright angle is in very simple terms, the basic operating principle of an RDF. If the location of the transmitter is known, your direction becomes known when you obtain the zero induction effect from your receiver loop. For example, if a plane was flying into an airport through fog, he would set his receiver loop antenna at 90 degrees angle from the transmitter which would give him a zero signal. If he flew off course he would get a signal which would tell him he had to correct his direction until he received a zero reading. Some peculiar effects were observed during early research with airborne RDFs. Using the same radio tower as a transmitter, different pilots flying in separate planes at varying times would always encounter bearing errors in certain areas even though they were on proper compass reading as established before or afterwards with their RDF. Research revealed that these same areas over which interferences occurred were either highly mineralized or had major metallic surface features such as the large steel roof of a factory. Theses errors may be explained as follows:
If the signal emitted from the transmitter (radio tower) has sufficient strength, some energy will be introduced or induced into any substance which has good conductive properties. It is easy to imagine that a strong signal, such as transmitted from a high power radio station, will readily be induced in good conductors such as metallic ore body or a sheet metal roof, and set up strong current flow which in turn will rebroadcast the original signal at much reduced strength. This re-broadcast signal, even through weaker, is enough to be picked up by sensitive receiver. Remember that your receiver loop must have in aright angle to the transmitter to obtain the zero induction effect by which you navigate, however, with the presence of a metal object like the metallic roof you now have a second transmitter which unlike your radio tower is no longer at this all-important right angle relationship. This explains the error. With radio direction finding you can compensate for this effect, but Dr. Fisher recognized quickly that this effect could be utilized for underground metal detection.
Back to Build it yourself
Back to DetectionNet Main Page
Partner websites
www.detection.com
detection.com
www.detect.in
detect.in
www.detection.in
detection.in
www.detection.net
detection.net
www.detectionnet.com
detectionnet.com
www.detector.name
detector.name
www.detectors.name
detectors.name
www.detector.nu
detector.nu
www.detector.in
detector.in
www.detector.cc
detector.cc
www.detector.bz
detector.bz
www.detectors.bz
detectors.bz
www.detectors.nu
detectors.nu
www.detectors.cc
detectors.cc
www.futurewatch.com
futurewatch.com
www.garrett.in
garrett.in
www.garrettace250metaldetector.com
garrettace250metaldetector.com
www.metaldetector.name
metaldetector.name
www.metaldetector.in
metaldetector.in
www.metaldetectors.tv
metaldetectors.tv
www.metaldetectors.in
metaldetectors.in
www.metaldetectors.cc
metaldetectors.cc
www.metaldetectors.name
metaldetectors.name
www.pd6500.com
pd6500.com
www.pd6500i.com
pd6500i.com www.ace150.c0m
ace150.com
www.ACE250.COM
ACE250.COM
www.AMERICAN.TC
AMERICAN.TC
www.ANCIENT.BE
ANCIENT.BE
www.ANCIENT.CC
ANCIENT.CC
DETECTORMART.COM
www.DETECTORMETALICO.COM
DETECTORMETALICO.COM
www.DETECTORNETWORK.COM
DETECTORNETWORK.COM
www.DETECTORPRICES.COM
DETECTORPRICES.COM
www.DETECTORS.CC
DETECTORS.CC
www.DETECTORS.TV
DETECTORS.TV
www.DETECTORS.WS
DETECTORS.WS
www.DETECTORSPECIALS.COM
DETECTORSPECIALS.COM
www.DETECTORWHOLESALE.COM
DETECTORWHOLESALE.COM
www.DOMAINJACKPOTS.COM
DOMAINJACKPOTS.COM
www.DOMAINWAITER.COM
DOMAINWAITER.COM
www.DOMAINWAITRESS.COM
DOMAINWAITRESS.COM
www.DOUSA.NET
DOUSA.NET
www.E-MARY.COM
E-MARY.COM
www.EARNDOLLAR.INFO
EARNDOLLAR.INFO
www.EARNDOLLARS.WS
EARNDOLLARS.WS
www.EASTS.BIZ
EASTS.BIZ
www.EEU.NAME
EEU.NAME
www.EKISS.BIZ
EKISS.BIZ
www.ELOVE.BE
ELOVE.BE
www.EMAILACCOUNTS.NAME
EMAILACCOUNTS.NAME
www.EMOTHER.NET
EMOTHER.NET
www.ENGINEOPTIMIZATION.NET
ENGINEOPTIMIZATION.NET
www.ENTDECKER.US
ENTDECKER.US
www.ESHGHAM.COM
ESHGHAM.COM
www.ESTELA.NAME
ESTELA.NAME
www.EUEURO.INFO
EUEURO.INFO
www.EUEURO.NET
EUEURO.NET
www.EUROSTORES.INFO
EUROSTORES.INFO
www.EUSA.BE
EUSA.BE
www.EUSA.WS
EUSA.WS
www.EUSTORE.BIZ
EUSTORE.BIZ
www.EUSTORE.INFO
EUSTORE.INFO
www.EUSTORE.NET
EUSTORE.NET
www.EUSTORES.NET
EUSTORES.NET
www.EXPANDDOMAINS.COM
EXPANDDOMAINS.COM
www.EXPRESSNEWS.US
EXPRESSNEWS.US
www.F-75.COM
F-75.COM
www.FFAENGINE.COM
FFAENGINE.COM
www.FFAS.INFO
FFAS.INFO
www.FFAS.US
FFAS.US
www.FFASEARCH.COM
FFASEARCH.COM
www.FINLAND.TC
FINLAND.TC
www.FISHER.TC
FISHER.TC
www.FISHERDETECTOR.COM
FISHERDETECTOR.COM
www.FRENCH.NU
FRENCH.NU
www.GARRETT.NU
GARRETT.NU
www.GARRETTACE250.COM
GARRETTACE250.COM
www.GARRETTDISCOUNTS.COM
GARRETTDISCOUNTS.COM
www.GARRETTFORUM.COM
GARRETTFORUM.COM
www.GARRETTMD.COM
GARRETTMD.COM
www.GARRETTMETALDETECTORS.NET
GARRETTMETALDETECTORS.NET
www.GIFTSTREASURE.COM
GIFTSTREASURE.COM
www.GIRLFRIEND.NAME
GIRLFRIEND.NAME
www.GOJOHNNY.NET
GOJOHNNY.NET
www.GOJOHNY.COM
GOJOHNY.COM
www.GOLDCOIN.BE
GOLDCOIN.BE
www.GOLDCOINS.BE
GOLDCOINS.BE
www.GOLDCOINS.WS
GOLDCOINS.WS
www.GOLDDETECTION.COM
GOLDDETECTION.COM
www.GOLDNUGGET.WS
GOLDNUGGET.WS
www.GOLDNUGGETS.WS
GOLDNUGGETS.WS
www.GOLDPROSPECTINGS.COM
GOLDPROSPECTINGS.COM
www.GOPS.US
GOPS.US
www.GTI1500.COM
GTI1500.COM
www.GTI2500.COM
GTI2500.COM
www.GTP1350.COM
GTP1350.COM
www.HADDOMAINS.COM
HADDOMAINS.COM
www.HIDDENGOLD.NET
HIDDENGOLD.NET
www.HOBBIES.NU
HOBBIES.NU
www.HOBBYDETECTOR.COM
HOBBYDETECTOR.COM
www.HOBBYDETECTORS.COM
HOBBYDETECTORS.COM
www.HOSTDOMAINS.BIZ
HOSTDOMAINS.BIZ
www.HOTLOVE.BIZ
HOTLOVE.BIZ
www.HOWTODATE.US
HOWTODATE.US
www.ICANN.TC
ICANN.TC
www.INDONESIA.TC
INDONESIA.TC
www.INFINIUMLS.COM
INFINIUMLS.COM
www.INTERNETDOMAINREGISTER.NET
INTERNETDOMAINREGISTER.NET
www.INTERNETEXPLORE.BIZ
INTERNETEXPLORE.BIZ
www.INTERNETEXPLORE.US
INTERNETEXPLORE.US
www.INTERNETEXPLORERS.BIZ
INTERNETEXPLORERS.BIZ
www.INTERNETEXPLORERS.INFO
INTERNETEXPLORERS.INFO
www.INTERNETEXPLORERS.US
INTERNETEXPLORERS.US
www.INTERNETEXPLORING.NET
INTERNETEXPLORING.NET
www.INTERNETUTILITY.ORG
INTERNETUTILITY.ORG
www.KISSES.CC
KISSES.CC
www.LABDETECTORS.COM
LABDETECTORS.COM
www.LINKSITES.BIZ
LINKSITES.BIZ
www.LINKUS.BE
LINKUS.BE
www.LOBOSUPERTRAQ.COM
LOBOSUPERTRAQ.COM
www.LOSTTREASURE.INFO
LOSTTREASURE.INFO
www.LOSTTREASURES.BIZ
LOSTTREASURES.BIZ
www.LOVEDOMAINS.BIZ
LOVEDOMAINS.BIZ
www.MAILORDER.NAME
MAILORDER.NAME
www.MAILORDERS.MOBI
MAILORDERS.MOBI
www.MAILORDERS.WS
MAILORDERS.WS
www.MANYDOMAINS.NET
MANYDOMAINS.NET
www.MARKETINTERNET.NET
MARKETINTERNET.NET
www.MARY.TC
MARY.TC
www.METALDETECT.BIZ
METALDETECT.BIZ
www.METALDETECT.US
METALDETECT.US
www.METALDETECT.WS
METALDETECT.WS
www.METALDETECTING.MOBI
METALDETECTING.MOBI
www.METALDETECTOR.NU
METALDETECTOR.NU
www.METALDETECTOR.TC
METALDETECTOR.TC
www.METALDETECTOR.VG
METALDETECTOR.VG
www.METALDETECTORBLOG.COM
METALDETECTORBLOG.COM
www.METALDETECTORDISCOUNT.COM
METALDETECTORDISCOUNT.COM
www.METALDETECTORDISCOUNTS.COM
METALDETECTORDISCOUNTS.COM
www.METALDETECTORDISTRIBUTOR.COM
METALDETECTORDISTRIBUTOR.COM
www.METALDETECTORLINKS.COM
METALDETECTORLINKS.COM
www.METALDETECTORNET.COM
METALDETECTORNET.COM
www.METALDETECTORPRICES.COM
METALDETECTORPRICES.COM
www.METALDETECTORS.BE
METALDETECTORS.BE
www.METALDETECTORS.CC
METALDETECTORS.CC
www.METALDETECTORS.NU
METALDETECTORS.NU
www.METALDETECTORS.TC
METALDETECTORS.TC
www.METALDETECTORS.VG
METALDETECTORS.VG
www.METALDETECTORSPECIALS.COM
METALDETECTORSPECIALS.COM
www.METALLENTDECKER.COM
METALLENTDECKER.COM
www.METALSENSORS.COM
www.MODERNDETECTOR.COM
MODERNDETECTOR.COM
www.MODERNDETECTORS.COM
SUPERDETECTORS.COM
www.SUPERDOMAINS.BIZ
SUPERDOMAINS.BIZ
www.SUPERSALEDOMAIN.COM
www.TREASURE.TC
TREASURE.TC
www.TREASURE.VG
TREASURE.VG
www.TREASURE.bz
TREASURE.bz
www.TREASUREBLAST.COM
TREASUREBLAST.COM
www.TREASUREBLOGGER.COM
TREASUREBLOGGER.COM
www.TREASURECHAT.COM
TREASURECHAT.COM
www.TREASUREPAL.COM
TREASUREPAL.COM
www.TREASUREQUEST.INFO
TREASUREQUEST.INFO
www.TREASURES.BE
TREASURES.BE
www.TREASURETV.BIZ
TREASURETV.BIZ
www.TREASURETV.INFO
TREASURETV.INFO
www.TREASUREV.COM
Maintainer: DetectionNet, Email.
All Rights Reserved.
© Copyright 1996-2007 A&S Company