Abstract:
A surge suppressor configured to receive signals from a coaxial line having a signal carrying inner conductor and a grounded outer conductor. The surge suppressor includes an inner conductor exhibiting capacitance and configured to connect to the coaxial line inner conductor, an outer conductor configured to connect to the coaxial line outer conductor and to ground, and an inductor formed of a wire encapsulated in an encapsulating material electrically coupling the inner conductor and the outer conductor. RF signals in the surge suppressor&#39;s operating bandwidth pass through the surge suppressor relatively unimpeded while electrical surges will be diverted through the inductor to the outer conductor, and therefore to ground, and possible residual pulses will be blocked from passing through the surge suppressor by the capacitance.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to the field of surge suppressors for the protection of sensitive electronic equipment from an electrical surge. More specifically, the present invention relates to L-C filter type surge suppressors serially connected between transmission lines and protected electronic equipment.  
       BACKGROUND OF THE INVENTION  
       [0002]     Surge suppression devices are well known in the art for protecting sensitive electronic devices from electrical surges due to power line fluctuations and lightning, for example. In particular, electronic devices that receive RF signals from antennas or transmission lines (which are typically coaxial cable) are particularly susceptible to electrical surges, because a) transmission lines often carry electrical power signals as well as information signals; and b) transmission lines are typically suspended above the ground, attached to poles or other structures for long distances where they are susceptible to lightning strikes and power interruptions due to broken lines. Lightning strikes are known to reach potentials of 5 to 20 million volts with currents of thousands of amps and thus pose a significant threat to downstream electronic equipment.  
         [0003]     Several types of surge suppressors have been proposed. Gas type surge suppressors contain gas that is ionized by the increase in voltage due to the electric surge and the ionized gas conducts the excessive electricity to ground. Metal Oxide Varistor (MOV) surge suppressors contain voltage sensitive semiconductors that shunt the excessive electricity to ground. Inductor-capacitor or L-C type surge suppressors typically include a capacitive element connected in series with the signal conductor, and an inductor coupled between the signal conductor and ground, typically through a housing that is connected to the outer conductor of the transmission line. The capacitance value of the capacitive element is selected so as to allow the desired RF signals to pass relatively unimpeded, but to block electrical surges which typically occur well below RF frequencies (e.g. between DC and 30 KHz in the case of lightning). In contrast, the value of the inductor is selected so as-to conduct the electrical surges to ground while blocking the RF signal. The combination of the capacitive element and inductor forms an L-C filter, which must be tuned to achieve the desired input impedance over the operating frequency range for low VSWR (Voltage Standing Wave Ratio) and insertion loss.  
         [0004]     U.S. Publication 2004/0042149 discloses an L-C type surge suppressor for serial in-line connection with a coaxial cable to protect electronic equipment from electrical surges, particularly due to lightning. The surge suppressor of U.S. &#39;149 includes an inner conductor comprised of two conductive portions shaped as plates, mechanically coupled together through a dielectric material to form a capacitor, an outer conductor electrically insulated from the inner conductor and an inductor coupling the inner conductor to the outer conductor. The capacitor and inductor values are selected so as to form an L-C filter properly tuned for the bandwidth of operation. The surge suppressor further has an input port shaped and configured as a coaxial connector and a protected output port also shaped and configured as a coaxial connector. Electrical surges that enter the input port are blocked by the capacitor and coupled by the inductor to the outer conductor and, thus, to ground.  
         [0005]     For the purported ease of manufacture, the inductor of U.S. &#39;149 is mechanically and-electrically coupled to the outer conductor by staking and is mechanically and electrically coupled to the inner conductor through a restorative force created by a bent portion of the inductor. As such, the inductor is coupled to the inner and outer conductors via solderless connections. These types of connections, however, cause the passive L-C components to act non-linearly, thus significantly reducing the current handling capability and degrading the passive intermodulation performance of the surge suppressor. Additionally, the solderless connections and physical configuration of the inductor make it susceptible to deformation by electromagnetic forces created by the high pulse currents associated with a lightning surge. Deformation of the inductor will change the frequency response characteristics and eventually lead to failure of the surge suppressor to properly conduct the electrical surge to ground, thereby damaging the device and possibly downstream electronic components.  
         [0006]     U.S. Pat. No. 6,236,551 discloses a surge suppressor device similar to that of U.S. &#39;149. However, the inductor of U.S. &#39;551 is a spiral inductor. The spiral inductor is comprised of a high tensile strength material to inhibit the above mentioned deformation and to provide increased current carrying capability. However, the design and tuning processes for such spiral inductors are complicated and time consuming, requiring multiple design and manufacturing iterations and testing to achieve the desired input impedance for low VSWR and insertion loss.  
         [0007]     What is needed, therefore, is a surge suppressor for a transmission line capable of handling large amounts of surge current with improved passive intermodulation performance that is relatively easy to design and cost effective to manufacture.  
       SUMMARY OF THE INVENTION  
       [0008]     It is an object of the present invention to overcome the problems of the prior art by providing a surge suppressor that provides significantly increased surge current capabilities, and improved passive intermodulation performance while providing mechanical stability for the inductor and ease of manufacture and tuning. In accordance with one embodiment of the present invention there is provided a surge suppressor configured to receive signals from a coaxial line having a signal carrying inner conductor and a grounded outer conductor, the surge suppressor including an inner conductor exhibiting capacitance and configured to connect to the coaxial line inner conductor for passing desired RF signals therethrough, an outer conductor configured to connect to the coaxial line outer conductor and to ground, and an inductor electrically coupling the inner conductor and the outer conductor, wherein the inductor includes a wire encapsulated in an encapsulating material. Preferably the inductor wire is in the shape of a coil, and the encapsulating material generally defines a cylinder larger than the coil.  
         [0009]     It is also preferred that a first end of the inductor is electrically and mechanically coupled to the inner conductor by soldering and a second end of the inductor is electrically and mechanically coupled to the outer conductor by soldering.  
         [0010]     The surge suppressor of the present invention is easy and economical to manufacture, yet can handle high current pulses without deviation in performance due to the inductor coil being fixed in a mechanically stable medium (i.e., the encapsulating material). In addition, since the ends of the inductor wire are fixed to the inner and outer conductors by soldering, the passive intermodulation performance of the surge suppressor is significantly enhanced.  
         [0011]     In one embodiment, the inner conductor includes a first segment, a second segment and a third segment which are releasably connected along a longitudinal axis, and the second segment carries the inductor and the capacitor.  
         [0012]     In another embodiment, the capacitance is provided in the form of a coaxial capacitor, and the capacitance of the coaxial capacitor is adjusted by adjusting the length of the second segment.  
         [0013]     In another embodiment, the wire of the inductor has a resistance of less than 3 mΩ, and is made of a material selected from the group consisting of beryllium copper, spring bronze, spring steel, standard soft copper, and Hardened oxygen-free copper.  
         [0014]     In another embodiment, the encapsulating material of the inductor exhibits a relative permittivity between 3.0 and 3.5, and is made of a material that is epoxy-based or silicone-based. Preferably the encapsulating material exhibits a hardness between 65 and 70 Shore D to ensure sufficient mechanical strength to withstand the deformation of the inductor wire that results from high current pulses.  
         [0015]     In another embodiment, the inductor has a longitudinal axis that extends generally perpendicular to a longitudinal axis of the inner conductor, and the second segment can be rotated 180° about a longitudinal axis of the inductor without changing an axial position of the inductor with respect to the outer conductor. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     For a full understanding of the nature and objects of the invention, reference should be made to the following detailed description of a preferred mode of practicing the invention, read in connection with the accompanying drawings in which:  
         [0017]      FIG. 1  is a schematic diagram of a surge suppressor circuit in accordance with one embodiment of the present invention;  
         [0018]      FIG. 2  is a cut-away view of an assembled surge suppressor in accordance with one embodiment of the present invention;  
         [0019]      FIG. 3  is a diagram of a disassembled coaxial capacitor in accordance with one embodiment of the present invention;  
         [0020]      FIG. 4  is a diagram of an assembled coaxial capacitor in accordance with one embodiment of the present invention; and  
         [0021]      FIG. 5  is a diagram of an encapsulated inductor in accordance with one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]      FIG. 1  is a schematic drawing of a surge suppressor  100  in accordance with one embodiment of the present invention. Surge suppressor  100  includes capacitive element  103 , inductor  104 , inner conductor  110 , outer conductor  107 , and first  102  and second  105  connectors. First  102  and second  105  connectors couple RF signals into and out of surge suppressor  100 . In the embodiment shown in  FIG. 1 , first connector  102  is on the unprotected side of surge suppressor  100  and second connector  105  is on the protected side. Capacitive element  103  is serially connected between first  102  and second  105  connectors. The value of capacitive element  103  is selected to have a low impedance to RF signals in the desired operating bandwidth thereby allowing those frequencies to pass through surge suppressor  100  relatively unimpeded. The value of capacitive element  103  is further selected to have a high impedance to electrical surges caused by lightning, for example, which typically occur at frequencies well below RF frequencies. Additionally, the capacitive element is designed to withstand high electrical strengths so as not to be damaged in the event of an electrical surge. Accordingly, electrical surges caused by lightning, for example, are effectively blocked from passing through capacitive element  103 . As one example, capacitive element  103  is selected to have a value between 30 and 50 pF. This allows RF signals above 120 MHz to pass through surge suppressor  100  relatively unimpeded. Conversely, RF signals below 120 MHz will be blocked from passing through surge suppressor  100 .  
         [0023]     Inductor  104  is electrically connected on a first end  106  between first connector  102  and capacitive element  103 , and on a second end  117  to the outer conductor  107  and, therefore, to ground. The value of inductor  104  is selected to have a low impedance to frequencies associated with electrical surges caused by lightning, for example, thereby allowing those frequencies to pass through relatively unimpeded to ground. The value of inductor  104  is further selected to have a high impedance to RF signals in the desired operating bandwidth. Accordingly, RF signals in the desired bandwidth are effectively blocked from passing to ground through inductor  104 . As one example, inductor  104  is selected to have a value between 25 and 45 nH. This blocks RF signals above 330 MHz from passing to ground through inductor  104 . Conversely, signals below 330 MHz will pass relatively unimpeded through inductor  104  to ground.  
         [0024]     In operation, RF signals from an antenna or other source are coupled into first connector  102  of surge suppressor  100  by transmission line  101 . RF signals in the desired bandwidth pass relatively unimpeded through capacitive element  103  and are coupled out of surge suppressor  100  through second connector  105  to cable  108  and to electronic equipment  109 . Electrical surges can be coupled into first connector  102  of surge suppressor  100  by transmission line  101  in the same manner as the desired RF signals. However, electrical surges will be blocked from passing through surge suppressor  100  by capacitive element  103  and will be diverted through inductor  104  to outer conductor  107  and, therefore, to ground as described above in detail.  
         [0025]     The structure of surge suppressor  100  allows electronic equipment  109  to perform two way communications. In other words, electronic equipment  109  will be capable of transmitting as well as receiving RF signals. RF signals transmitted from electronic equipment  109  are coupled into second connector  105  of surge suppressor  100  by cable  108 , pass through capacitive element  103  relatively unimpeded and are coupled out of surge suppressor  100  through first connector  102  to transmission line  101 . Again, the RF signals are not coupled to ground due to the selected value of inductor  104 .  
         [0026]     Referring now to  FIG. 2 , the surge suppressor  200  in accordance with one embodiment of the present invention includes first  202  and second  205  connectors; an inner conductor including inner conductor components  210   a ,  210   b ,  210   c  and  210   d ; capacitive element  203 , inductor  204 ; and an outer conductor including first  207   a  and second  207   b  housing body components. Again first connector  202  is on the unprotected side of surge suppressor  200  and second connector  205  is on the protected side.  
         [0027]     In accordance with a preferred embodiment, capacitive element  203  is a coaxial capacitive element further comprising outer portion  203   a , inner portion  203   b  and dielectric portion  203   c  as can best be seen in  FIG. 3 . Outer portion  203   a  further includes a hole  203   d  for soldering the first end  206  ( FIG. 5 ) of inductor  204  as will be discussed later in more detail. Dielectric portion  203   c  can be comprised of any material that provides electrical insulation between outer portion  203   a  and inner portion  203   b  of capacitive element  203 . Preferably, dielectric portion  203   c  is made of dielectric material that shrinks when heated, to facilitate its positioning on inner portion  203   b . Examples of appropriate materials are polyolefine-based shrink tubes manufactured by the assignee of this application or Kynar manufactured by Raychem of Menlo Park, Calif.  
         [0028]     To form the capacitive element, dielectric portion  203   c  is placed around inner portion  203   b  and the inner portion  203   b , with the dielectric portion  203   c  placed therearound, is inserted into outer portion  203   a  such that dielectric portion  203   c  capacitively couples outer  203   a  and inner  203   b  portions as is shown in  FIG. 4 . As those skilled in the art can appreciate, this type of coaxial design provides ease of tuning capacitive element  203 , and therefore the frequency response of the surge suppressor  200 , by controlling the depth to which the inner portion  203   b , with the dielectric portion  203   c , is inserted into the outer portion  203   a . As will be discussed later in more detail, insulators  213   a ,  213   b  maintain the relative positions of outer  203   a  and inner  203   b  portions of capacitive element  203  within surge suppressor  200  after assembly, thereby maintaining a constant value of capacitance.  
         [0029]     Inductor  204  is comprised of wire  204   a  and encapsulating material  204   b  as is shown in  FIG. 5 . The wire can be comprised of any material that provides good electrical conductivity and good tensile strength. Preferably, the wire is comprised of a material that exhibits a low resistance to high energy electrical pulses such as from a surge due to lightning. More preferably, wire  204   a  exhibits a small resistance not greater than 3 mΩ, and a tensile strength of at least 200 N/mm2. Examples of appropriate materials are known to those skilled in the art and include BZ 7/4 (spring bronze), X12CrNi177 (spring steel), BeCu (Beryllium Copper), Cu (standard soft copper) and Cu—OF hard (hardened, oxygen-free copper).  
         [0030]     In a preferred embodiment wire  204   a  is encapsulated in encapsulating material  204   b . Encapsulating material  204   b  preferably comprises a material with a low relative permittivity (ε T ) and at the same time provides a high mechanical stability. Relative permittivity is a measure of the ratio of the magnitude of the electric field within the material produced by a given charge to the magnitude of the electric field in a vacuum produced by the same charge. By selecting a material with a low ε T , the inductor&#39;s  204  effect on RF signals passing through surge suppressor  200  is minimized. Preferably the encapsulating material exhibits an ε T  between 3.0 and 3.5.  
         [0031]     The high mechanical stability of encapsulating material  204   b  eliminates the deformation of the inductor wire  204   a  due to electromagnetic forces created by high pulse currents associated with a lightning surge. Preferably, encapsulating material  204   b  exhibits hardness between 65 and 70 Shore D thereby providing a high mechanical stability. Accordingly, inductor  204  comprised of wire  204   a  and encapsulating material  204   b  is capable of handling significantly higher currents than is found in prior art lightning surge suppressors as will be shown later in more detail.  
         [0032]     Returning to  FIG. 2 , surge suppressor  200  further comprises seal  211 , nut  212 , insulators  213   a  and  213   b , ferrule  214 , and contact cap  215 . Seal  211  provides protection for surge suppressor  200  against water intrusion, such as from rain. Nut  212  provides the mechanical connection between surge suppressor  200  and the transmission line (not shown) and also provides the electrical connection between the outer conductor of the transmission line and the outer conductor of the surge suppressor, which includes first  207   a  and second  207   b  housing body components. Insulators  213   a  and  213   b  electrically insulate the inner conductor, which includes inner conductor components  210   a ,  210   b ,  210   c , and  210   d , from outer conductor housing body components  207   a  and  207   b . Contact cap  215  provides ease of assembly for soldering second end  217  of inductor  204  thus establishing the electrical connection between inductor  204  and the outer conductor of surge suppressor  200 . Ferrule  214  is used to assemble the components of the surge suppressor  200  as will now be discussed in more detail.  
         [0033]     To assemble surge suppressor  200 , inner conductor component  210   a  is pressed into insulator  213   a  to form a first subassembly. Similarly, inner conductor component  210   d  is pressed into insulator  213   b  to form a second subassembly. Inner conductor component  210   b  is then screwed onto the first subassembly consisting of inner conductor  210   a  and insulator  213   a , and inner conductor component  210   c  is screwed onto the second subassembly consisting of inner conductor component  210   d  and insulator  213   b.    
         [0034]     The dielectric portion  203   c  of capacitive element  203  is cut to the desired length (e.g., 16 mm), placed over inner portion  203   b  of capacitive element  203  and shrunk by heating, for example, to tightly encompass inner portion  203   b  of capacitive element  203  as is known in the art. First end  206  of inductor wire  204   a  is then soldered into hole  203   d  provided in outer portion  203   a  of capacitive element  203 .  
         [0035]     Nut  212  is placed over first housing body component  207   a  and then first  207   a  and second  207   b  housing body components are screwed together with insulator  213   a  captured therebetween. Intervening spaces between the threads of first  207   a  and second  207   b  housing body components are filled with sealant  216  as is known in the art.  
         [0036]     The outer portion  203   a  of coaxial capacitive element  203  and inductor  204  (first end  206  of inductor  204  has been soldered into hole  203   d  of outer portion  203   a  as previously discussed) are positioned in second housing body component  207   b  through threaded opening  219  and pressed together with inner conductor portion  210   b.    
         [0037]     The second subassembly, inner conductor component  210   c , and inner portion  203   b  of capacitive element  203  are placed in second housing body component  207   b  such that inner portion  203   b  of capacitive element  203  aligns with outer portion  203   a  of capacitive element  203  and inner conductor  210   c  aligns with inner portion  203   b  of capacitive element  203 . Ferrule  214  is then pressed into second housing component  207   b  with insulator  213   b  captured between second housing body component  207   b  and ferrule  214 . In this manner inner portion  203   b  of capacitive element  203  is inserted by a predetermined distance into outer portion  203   a  of capacitive element  203  to obtain the desired capacitance value as previously discussed. Additionally, since insulator  213   a  is captured between first  207   a  and second  207   b  housing body components and insulator  213   b  is captured between second housing body component  207   b  and ferrule  214 , the capacitance value of capacitive element  203  is maintained because outer  203   a  and inner  203   b  portions of capacitive element  203  are unable to move relative to each other in a linear direction.  
         [0038]     However, due to the coaxial nature of capacitive element  203  outer portion  203   a  can easily be rotated such that second end  217  of inductor  204  is positioned to extend substantially through the center of threaded opening  219  in second housing body component  207   b . Contact cap  215  is screwed into threaded opening  219  in second housing body component  207   b  such that second end  217  of inductor  204  passes through hole  218  of contact cap  215 . Intervening spaces between threads of second housing body component  207   b  and contact cap  215  are filled with sealant  216  as is known in the art.  
         [0039]     Second end  217  of inductor  204  is then trimmed such that it extends approximately 1 mm beyond hole  218  of contact cap  215  and is soldered to contact cap  215  to complete the assembly process (the inductor  204  is now electrically connected to the outer conductor of surge suppressor  200 ).  
         [0040]     As previously discussed, during assembly inner conductor component  210   b  is screwed onto the first subassembly consisting of inner conductor component  210   a  and insulator  213   a , and inner conductor component  210   c  is screwed onto the second subassembly consisting of inner conductor component  210   d  and insulator  213   b . However, in accordance with another embodiment, it is also possible to screw inner portion  203   b  of capacitive element  203  onto the first subassembly and to screw inner conductor component  210   b  onto the inner conductor component  210   c . In a sense, inner conductor component  210   a  acts as a first fixed segment of the overall inner conductor, inner conductor components  210   c  and  210   d  act as a second fixed segment of the overall inner conductor, and inner conductor component  210   b , along with inner  203   b  and outer  203   a  portions of capacitive element  203  act as a second, reversible segment of the overall inner conductor. Accordingly, when the outer portion  203   a  of coaxial capacitive element  203  and inductor  204  are positioned in second housing body component  207   b  in the opposite direction than previously discussed and pressed together with inner conductor portion  210   b , the configuration of surge suppressor  200  is changed such that first connector  202  is on the protected side of surge suppressor  200  and second connector  205  is on the unprotected side. Therefore, it is easy to manufacture configurations of the surge suppressor to respond to different customer requirements while maintaining simplified logistics and lower production costs.  
         [0041]     As previously discussed, soldering the connections of first  206  and second  217  ends of inductor  204  improves the passive intermodulation performance of surge suppressor  200 . For example, a surge suppressor in which the inductor is coupled to the inner and outer conductors via solderless connections (as disclosed in U.S. &#39;149, for example) typically exhibits a bad passive intermodulation performance up to −71 dBm with two carriers of 43 dBm. In contrast, the surge suppressor of the present invention exhibits a passive intermodulation performance better than −107 dBm with two carriers of 43dBm due to soldering both connections of inductor  204 . Additionally, encapsulating wire  204   a  in encapsulating material  204   b  provides an inductor  204  with a high mechanical stability under high current and voltage conditions (such as in the case of a lightning strike) thereby eliminating the aforementioned deformation of the inductor  204 . Accordingly, the surge suppressor  200  is capable of handling significantly higher currents with improved passive intermodulation performance compared to prior art lightning surge suppressors.  
         [0042]     Table 1 shows comparative results of applying incrementally higher current pulses to coils made of different wire materials without encapsulation. As can be seen, hardened oxygen-free copper, which exhibits the lowest resistance to high energy electrical pulses, provides the best current carrying capability, successfully conducting a 20 μsec 8 kA pulse.  
                                   TABLE 1                           Beryllium   Spring   Spring   Standard   Hardened           Copper   Bronze   Steel   Soft   Oxygen-free           ASTM   ASTM   DIN 17224   Copper   Copper           B 196   B 103   ASTM   EN 1652   EN 1652       8/20 μs   C17300   C54400   A 313   Cu-ETP   Cu-DHP                   1 kA   Pass   Pass   Pass   Pass   Pass       2 kA   Pass   Pass   Pass   Pass   Pass       3 kA   Pass   Pass   Fail   Pass   Pass       4 kA   Pass   Fail                 Pass   Pass       5 kA   Pass                               Fail   Pass       6 kA   Pass                                             Pass       7 kA   Fail                                             Pass       8 kA                                                           Pass       9 kA                                                           Fail                  
 
         [0043]     Table 2 shows the comparative results of applying incrementally higher current pulses to a coil comprised of hardened oxygen-free copper encapsulated in materials with different combinations of ε T  and hardness values. As can be seen, the combination of hardened oxygen-free copper and a two part epoxy manufactured by the assignee (which exhibits the lowest ε T ) provides an inductor for a surge suppressor capable of withstanding significantly higher surge currents than prior art surge suppressors (e.g., higher than 25 kA) due to the high mechanical stability of the encapsulating material and the low resistance of the wire material.  
                                   TABLE 2                           Two-Part           Two-Part               Polyurethane       Two-Part epoxy   Polyurethane           based product:       Araldit ®   based product:           Macromelt   Two-Part epoxy   AY 105-1   Macrocast   Two-Part epoxy       8/20 μS   CR6127/CR4300   H + S 92021600   HY 991   CR3127/CR4300   H + S 1043/02                    1 kA   Pass   Pass   Pass   Pass   Pass        2 kA   Pass   Pass   Pass   Pass   Pass        3 kA   Pass   Pass   Pass   Pass   Pass        4 kA   Pass   Pass   Pass   Pass   Pass        5 kA   Pass   Pass   Pass   Pass   Pass        6 kA   Pass   Pass   Pass   Pass   Pass        7 kA   Pass   Pass   Pass   Pass   Pass        8 kA   Pass   Pass   Pass   Pass   Pass        9 kA   Pass   Pass   Pass   Pass   Pass       10 kA   Pass   Pass   Pass   Pass   Pass       11 kA   Pass   Pass   Pass   Pass   Pass       12 kA   Pass   Pass   Pass   Pass   Pass       13 kA   Pass   Pass   Pass   Pass   Pass       14 kA   Pass   Pass   Pass   Pass   Pass       15 kA   Pass   Pass   Pass   Pass   Pass       16 kA   Pass   Pass   Pass   Fail   Pass       17 kA   Pass   Pass   Pass                 Pass       18 kA   Pass   Pass   Pass                 Pass       19 kA   Pass   Pass   Pass                 Pass       20 kA   Pass   Pass   Pass                 Pass       21 kA   Fail   Pass   Pass                 Pass       22 kA                 Pass   Fail                 Pass       23 kA                 Pass                               Pass       24 kA                 Fail                               Pass       25 kA                                                           Pass       26 kA                                                           Pass                  
 
 There has been disclosed herein a surge suppressor that provides significantly increased surge current capabilities while providing ease of manufacture and tuning. It will be understood that various modifications and changes may be made in the present invention by those of ordinary skill in the art who have the benefit of this disclosure. All such changes and modifications fall within the spirit of this invention, the scope of which is measured by the following appended claims.