Vehicle antenna tester

A vehicle antenna tester utilizes a transformer having three secondary windings, two of which operate a pair of incandescent lamps, the third of which being capable of operating a neon lamp. The first of the pair of lamps is energized by completing a circuit involving a pair of clamps, one of which is attached to chassis ground of the vehicle, while the other is attached to the shielding conductor at selective locations therealong, of the lead cable feeding the antenna to be tested. The other lamp is energized when a circuit is completed between selective locations along the length of the antenna and the isolated conductor feeding it and the third clamp of the present invention. The neon lamp will glow upon the presence of leakage resistance or a short circuit between the antenna and its associated isolated conductor and the shielding conductor or chassis ground. The apparatus is particularly useful in testing antenna and lead wire assemblies before and after installation to the vehicle, determining faulty grounding of the shielding conductor, breaks in the continuity of the lead wire and antenna proper and leakage paths between the antenna and the isolated conductor to chassis ground or the shielding conductor.

BACKGROUND OF THE INVENTION 
1. The Field of the Invention 
This invention relates to continuity and insulation breakdown testing 
devices and more particularly to that class adapted to evaluate two 
terminal devices, one of which is grounded to a chassis of a vehicle. 
2. Description of the Prior Art 
The prior art abounds with continuity and voltage breakdown devices. My 
Canadian Pat. No. 992,611 dated July 6, 1976 discloses a car antenna 
tester utilizing a pair of clamps, one of which is adapted for connection 
to an antenna shield, the other of which is adapted for connection to an 
antenna. Three battery supplies are electrically interconnected to a 
triple pole single throw switch, each pole of which being individually 
connected to a pair of incandescent lamps and a neon lamp. An antenna jack 
is provided which is electrically connected to a plug fitted at one end of 
the lead wire coupled to the antenna. When the switch is closed, the 
continuity of the shield wire may be evaluated by judicious selective 
attachment of one of the clamps to the shielding conductor. In similar 
fashion, the other clamp determines the electrical continuity of the 
isolated conductor in the lead wire feeding the antenna. However, the 
device as disclosed, may constitute a shock hazard when the neon lamp 
interconnected with its individual high voltage battery supply to the pair 
of clamps, ionizes. Furthermore, the apparatus fails to provide a suitable 
arrangement for bench testing an antenna connected to a lead cable before 
installation in the vehicle, and fails to provide for the installed 
testing of an antenna and lead wire wherein the shielding conductor of the 
lead wire is not grounded as part of a normal installation. 
U.S. Pat. No. 2,229,927 issued on Jan. 28, 1941 to J. A. Kamper teaches 
three indicating lamps, two of which are connected in a series electrical 
circuit terminating across a pair of electrical clamps. The third lamp 
bridges the electrical clamps. A probe wire is electrically connected at 
the junction of the pair of lamps in the series circuit. This device, 
devoid of internal source of energy is particularly useful in checking the 
electrical systems of motor vehicles and the like, utilizing the battery 
supply of the vehicle as a power source for illuminating the test lamps so 
as to dynamically present visual indications of the status of the 
electrical circuitry of the motor vehicle, in regard to the continuity and 
the shorting between the electrical elements thereof. 
SUMMARY OF THE INVENTION 
A primary object of the present invention is to provide an electrical 
testing apparatus which evaluates the continuity between selected points 
along the length of an antenna and its associated lead wire to the 
terminal end of the lead wire and the electrical breakdown resistance 
thereinbetween. 
Another object of the present invention is to provide an antenna and lead 
wire tester suitable for bench testing use or for use on the apparatus to 
be tested when installed on a motor vehicle. 
Still another object of the present invention is to provide an antenna and 
an antenna tester capable of viably testing antenna cable installations 
wherein the antenna cable is grounded solely at the end thereof connected 
to the electronic apparatus coupled to the antenna. 
Yet another object of the present invention is to provide an antenna and an 
antenna tester capable of viably testing antenna cable installations 
wherein the points along the shielding conductor thereof to the chassis of 
a motor vehicle, thereby facilitating evaluation of the faulty or 
intermittent grounding of the shielding conductor. 
A further object of the present invention is to provide an antenna and lead 
wire tester which indicates the presence of harmful leakage resistance or 
short circuits between the antenna and the shielding conductor circuits 
coupled thereto. 
A still further object of the present invention is to provide an antenna 
and lead wire tester which may be operated from household utility current, 
thereby allowing for greater reliability in the leakage resistance testing 
of the lead cable. 
Transceiver antennae and receiving antennae are most often vertically 
polarized whip devices when in use on motor vehicles. The electrical cable 
coupled to such antennae usually utilizes a co-axial cable whose central 
isolated conductor is electrically coupled to the whip antenna and whose 
shielding conductor may or may not be connected electrically to the 
chassis of the vehicle at one or more points other than the end of the 
cable electrically connected to the electronic device used on conjunction 
with the antenna. The present invention is capable of evaluating the 
continuity of the entire length or portions thereof, of the shielding 
conductor for both types of installations as well as when the antenna and 
lead wire is bench tested. Furthermore, the present invention is capable 
of checking the continuity along the circuit path comprising the entire 
length of the antenna and the isolated conductor feeding it, or selected 
portions thereof. The present invention is also capable of evaluating the 
presence of disastrous leakage resistance, or electrical shorts, between 
the antenna when coupled to the isolated conductor, and the shielding 
conductor, or the chassis of the vehicle. 
These objects as well as other objects of the present invention, will 
become more readily apparent, after reading the following description of 
the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The structure and method of fabrication of the present invention is 
applicable to a vehicle antenna and lead wire tester having three output 
voltages available from a transformer energized by household utility 
current. This arrangement provides electrical output voltage at the 
terminals of the secondary windings of the transformer being substantially 
constant, dependent only upon the constancy of the input supply voltage to 
the primary of the transformer. The apparatus includes three electrical 
clamps, each connected to a flexible conductor having two of them 
electrically connected, each to a pair of individual incandescent lamps. 
Each of the individual lamps are electrically connected to separate low 
voltage secondary windings of the transformer. The third secondary winding 
produces a high voltage, preferably about 150 volts a/c, and is connected 
to a neon glow lamp or any glow emitting discharge device which may 
operate with low currents. The series circuit, comprising the high voltage 
secondary winding and the neon lamp, is connected across the circuits 
including the incandescent lamps, such that the neon lamp will glow, when 
a leakage path exists between the circuits coupled to the pair of clamps. 
A third clamp is provided which may be electrically connected to chassis 
ground, completing an electrical circuit including one of the low voltage 
secondary windings, one incandescent lamp, and one of the pair of clamps. 
A jack, of the variety similar to that utilized to electrically connect 
the transceiver or receiver end of the plug fitted at the end of the 
antenna cable, opposite the end to which the antenna is connected, or, a 
pair of terminals of any suitable variety, are connected to the 
aforementioned series circuit and to the other low voltage secondary 
winding. This arrangement facilitates the continuity testing of the 
shielding conductor by placement of the pair of clamps associated with 
this low voltage winding, at two separate points along the length of the 
shielding conductor, or if grounding of the shielding conductor testing is 
desired, by placing one clamp on chassis ground and the other clamp 
electrically contacting any desired point along the length of the 
shielding conductor. 
The primary of the transformer is provided with a manually operated 
operating switch, such as a single pole single throw switch, which when 
closed enables the primary winding of the transformer to be energized. A 
fuse is also provided in series with the switch. 
The neon lamp is provided with a series resistance to minimize the shock 
hazard which may occur when the neon lamp ionizes. The value of the 
resistance is not determinative of the breakdown voltage which the neon 
lamp must experience to ionize. The choice of the size of the resistance 
limits the conductor current passing through the ionized neon lamp and 
also limits the amount of voltage which may be experienced by the clamp to 
which it is electrically coupled. 
More than one jack or electrical plug connector may be wired in parallel so 
as to facilitate the evaluation of more than one antenna at one time, or 
to permit antenna lead wires having different plugs affixed thereto, or 
none at all, to be tested with great facility. 
Now referring to the Figure showing the present invention 10 comprising 
transformer 12 having a primary winding 14 and secondary windings 16, 18 
and 20. Electrical plug 22, suitable for operation with household utility 
voltage is electrically connected at one end of cable 23, having a ground 
connection 24 suitable for attachment to the housing, not shown, enclosing 
the apparatus comprising the present invention, exclusive of the terminals 
and external cables and wires thereof. Conductors 26 and 28 provide 
electrical energy of the alternating current variety, to manually operated 
operating switch 30 in series circuit with fuse 32 and terminals 34 and 
36, attached to ends of winding 14. Secondary winding 16 is provided with 
terminals 38 and 40. Terminal 38 is coupled to terminal 44 of incandescent 
lamp 42. Terminal 46 of incandescent lamp 42 is coupled to electrical 
clamp 48. Terminal 40 of winding 16, is electrically connected to contacts 
50 and 52 of electrical receptacles 54 and 56 respectively. 
Winding 20 terminates in terminals 58 and 60. Winding 18 terminates in 
terminals 62 and 64. Terminals 64 and 58 are interconnected and connected 
to contacts 66 and 68 of receptacles 54 and 56 respectively. It should be 
specifically understood that receptacles 54 and 56 are depicted 
schematically so as to represent in customary fashion, a receptacle 
adapted to receive co-axial plugs. Such receptacles may be of diverse 
shapes, sizes and functions, each including a pair of contacts for 
electrical connection to the conductors at one end of an antenna cable 
opposite the end to which the antenna is connected. 
Terminal 60 of winding 20 is connected to terminal 70 of incandescent lamp 
72. Terminal 74 is connected to electrical clamp 76. Clamp 78 is 
electrically connected to terminals 64 and 58. 
Neon lamp 80 has terminal 82 thereof electrically connected to terminal 62 
of winding 18. Terminal 84 of neon lamp 80 is electrically connected to 
one end of resistor 86. The other end of resistor 86 is electrically 
connected to clamp 48. 
In bench testing use, the present invention is utilized in the following 
fashion: 
Clamp 76 is connected to a selected location on the shielding conductor of 
the cable feeding the antenna. The cable is electrically connected with 
the shielding conductor applied to contacts 66 or 68 and the isolated 
antenna feeding wire connected to contacts 50 or 52. Upon the energization 
of transformer 12, lamp 72 will illuminate indicating a continuity between 
contacts 66 or 68 and the point of application of clamp 76. Alternatively, 
the continuity of the shielding conductor may be tested without connecting 
the shielding conductor to contacts 66 or 68 by applying clamps 78 and 76 
to two points along the length of the conductor. Lamp 72 will illuminate 
only when continuity exists between the points to which clamps 76 and 78 
have been applied. Continuity of the isolated antenna feeding conductor is 
determined by applying clamp 48 to a point along the length of the antenna 
or along the length of the isolated conductor connected to it. Neon lamp 
80 will illuminate when either clamp 78, clamp 76 or contacts 66 or 68 are 
in electrical engagement with the shielding conductor, and clamp 48 is in 
electrical engagement with the antenna or the isolated conductor, and a 
sufficiently low leakage resistance or short circuit exists between the 
shielding conductor and the isolated conductor or the antenna. 
It is to be noted that the bench use of the present invention is totally 
and wholly independent of the ground circuitry to be employed when the 
antenna cable and antenna is installed within a motor vehicle. 
The present invention may be utilized in evaluating all of the facets of 
continuity and leakage resistance or shorts described above, when the 
present invention is utilized testing an antenna and associated cable when 
installed in a motor vehicle by using the procedures herein above 
described. A further use of the apparatus of the present invention, used 
in conjunction with an antenna installed in a motor vehicle, is in the 
detection and the location of faulty grounding, when such grounding is 
desired, or to detect the presence of such grounding when such grounding 
is not desired. This is accomplished by applying clamp 78 to the chassis 
ground of the vehicle and clamp 76 to the shielding conductor. Lamp 72 
will illuminate only when the shielding conductor is in electrical 
engagement with chassis ground. During such testing, electrical connection 
to receptacles 54 or 56 should be disconnected, accompanied by shaking or 
vibrating the antenna cable and antenna, simulating the vibration 
experienced by the motor vehicle when in use. 
One of the advantages of the present invention is an antenna and lead wire 
tester which may be operated from household utility current, thereby 
allowing for greater reliability in the leakage resistance testing of the 
lead cable. 
Another advantage of the present invention is a electrical testing 
apparatus which evaluates the continuity between selected points along the 
length of an antenna and its associated lead wire to the terminal end of 
the lead wire and the electrical breakdown resistance there-in-between. 
Still another advantage of the present invention is an antenna and lead 
wire tester suitable for bench testing use or for use on the apparatus to 
be tested when installed on a motor vehicle. 
A further advantage of the present invention is an antenna and an antenna 
tester capable of viably testing antenna cable installations wherein the 
antenna cable is grounded solely at the end thereof connected to the 
electronic apparatus coupled to the antenna. 
A still further advantage of the present invention is an antenna and an 
antenna tester capable of viably testing antenna cable installations 
wherein points along the shielding conductor thereof to the chassis of a 
motor vehicle facilitate evaluation of the faulty or intermittent 
grounding of the shielding conductor. 
Yet another advantage of the present invention is an antenna and lead wire 
tester which indicates the presence of harmful leakage resistance or short 
circuits between the antenna and the shielding conductor circuits coupled 
thereto. 
Thus there is disclosed in the above description and in the drawing, an 
embodiment of the invention which fully and effectively accomplishes the 
objects thereof. However, it will become apparent to those skilled in the 
art, how to make variations and modifications to the instant invention. 
Therefore, this invention is to be limited, not by the specific disclosure 
herein, but only by the appending claims.