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Controversy Abound About This One

The Largest Onmidirectional, Ever!

The Shockwave Antenna may be the last ground plane you'll ever buy.  It is 100% hand made in the USA and ready to handle as much as you can throw at it!  It is offered in a 10KW version (S0 239 connector) and a 25KW version (7/16 DIN connector).  This antenna is 3 x the size of a normal aluminum ground plane.  This is definitely, in ground plane terms, a MONSTER! 

This is a very pricey antenna and one needs to utilize information available in being sure they want to drop this kind of money for a ground plane.  A very nice set of beams can be obtained for this kind of cash!  And with a ground plane, no matter how good it is, it'll never match a set of beams. The only thing the Shockwave has over the beam is the fact it is an omidirectional which eliminates the need for a rotor.  However, it's your money and if this is your cup of tea, have at it.  

But, for instance, a set of Maco 6 elements are just slightly more expensive than this ground plane. And there are at least 8 other beams less expensive than this one ground plane above.  

(Maco 6 Element/ 11 Meter Base Antenna "Maximum Beam", Boom Length: 31' Adjustable Ga. - $389.99)

Prices (OUCH!)
10KW - $349.99 plus shipping
25KW - $374.99 plus shipping 
(Also Shipped Internationally)
Click on the link below for more information. 

Please call 270-590-0216 to order. 
If your mast pipe is larger than 1.5" OD (outside diameter), and you will need an adapter plate to fit pipe up to 3" (see on their page).

Posted HODCB 10/29/15 


Article from May 1, 2017 Archived. 

The following is about antennas in general. This includes omni's and yagi's. This is just going to be a simple description that hopefully everyone can understand. I'm not going to get into Lambda and any difficult calculations here. I'm just going to keep it simple.

"An antenna LENGTH is based on its FREQUENCY." Read it again! Get this in your brain! The frequency determines the length! This is physics and not theory. This is a fact!

A full wave signal at 11-meters is 36'. Therefore, a half-wave signal would be 18' approximately. This is just the approximate size of the radiated electromagnetic signal. A 5/8 wave would be (36 x .625) 22.5'. And for those with a .64 hard-on, it would be (36' x .640) 23'.

Now lets talk about this 5/8 vs .64 bullshit...I mean, STUFF for a minute. Back in 1934 (or so) a couple of broadcast engineers were trying to maximize their antenna pattern (gain) for their AM broadcast station. Through much experimentation, they found that if you extended the radiator to .64 wavelength, you could maximize your gain from a ground mounted monopole antenna. Remember, for the AM broadcast band, the tower IS the antenna. Its mounted on the ground and ground radials are buried and shoot out from the base. This is the important part...if the antenna went longer than .64 wavelength, the whole pattern would implode and all the gain would go away! Its like blowing up a balloon and then it pops! This is why you don't see 3/4 wave and full wave monopole antennas! So, .64 is the magic number for maximum gain of a ground mounted monopole!

As you remember, the length of the antenna is based on the frequency and as the frequency goes up or down, the length goes down or up respectively. When I say length, I'm speaking of the ELECTRICAL LENGTH of the radiator or antenna. The antenna gets shorter as you go up in frequency (or longer as you go down in frequency). So lets say I had a perfect .64 wave antenna on channel 6. When I went to channel 40, my antenna would be ELECTRICALLY LONGER than .64 wave and my signal would implode because as I go up in frequency, my antenna needs to get shorter to remain at .64 wave. If you don't understand this, ask me and I'll try to explain it better.

So lets say I had a perfect .64 wave on channel 40. On channel 6 I would only have a 5/8 (.625) wave antenna. On 26.915 I'd have something between a 1/2 wave and a 5/8 wave. You see, the frequency changed, but the electrical length of the antenna did not! With the antenna staying at the same length, as I went down in frequency the electrical length of the antenna effectively got shorter.

So what's the difference between 5/8 (.625) wave and .640 wave. The answer is .015 wave or 6". Its not even worth arguing about. If you set your antenna for 5/8 wave on channel 20, it will be .64 wave on 27.555 (approx) or less than 5/8 wave on channel 6. Whoop-di-do! When people start frothing at the mouth about their .64 wave antenna being better than a 5/8 (.625) wave antenna, I roll my eyes and ask, ".64 at what frequency?" All I get is deer-in-the-headlights because they have no idea what I just asked!

If you want to be a hard ass, then pick your highest frequency you run, and using a field strength meter, adjust your antenna until you get maximum field strength at that frequency. If you go longer and you see the field strength go down, that's your signal imploding! Make it shorter until you get a maximum reading. Now you have a .64 wave at THAT FREQUENCY ONLY! As you go down the channels, the antenna will be electrically shorter than .64, but at least your signal will not be imploding! So can we finally put all this .64 bullshit to rest please?!

So lets talk about antennas! Since we know that the frequency determines the length of the signal and therefore the length of the antenna, lets talk about the physical antenna elements. A piece of wire or tubing will have a specific electrical length based on it's diameter. I'm going to illustrate this by using round numbers to make it easier to understand. Don't come back to me later and say my measurements are wrong; I know they are wrong! This is for illustration only!

A 12-gauge wire for 11 meters is physically 18' long for an electrical half-wave. A 1/2" metal tube would be 17' 6" to be the same electrical length as the 12-gauge wire. A 1" metal tube would only be 17' long. So all three elements have the same "electrical length", but their physical length is different because of their different diameters. This is important to understand when we build antennas using different size tubing. We call these "STEPS"!

So Jay makes the I-10K and his bottom tube 1.25" diameter at 6' long. That first tube has a specific electrical length. Then he slips in a 1.125", then a 1", etc. When he is done, he will have taken the electrical lengths of each "step" until he has an electrical 5/8 wave at 27.205 MHz.

Now here comes Chris. He doesn't want to use 6' tubes because it costs more to ship, so he uses 4' tubes. In order to compensate for the shorter tubes, he decides to go with a 1.5" bottom tube, followed by a 1.375", and a 1.25" and then a 1.125", and then a 1", etc. When he is done, he will also have an electrical 5/8 wave antenna at 27.205 MHz. Since Chris used larger tubes, his antenna will be PHYSICALLY shorter than the I-10K. His steps at 4' are also shorter than 6' steps of the I-10K. BUT ELECTRICALLY, BOTH ANTENNAS ARE IDENTICAL!

Is this clear? The next time I hear some numb-nuts say a Maco V58 is not really a 5/8 wave because its only 21 feet long, I'm going to shoot him! The goal here is the ELECTRICAL LENGTH, not the physical length! If I used 3" tubing all the way up, it might only be 15' long to be the same electrical length of the 18' 12-gauge wire! The antenna designer figured out how long the antenna needs to be to be a 5/8 wave for 11 meters. They took into consideration the diameters of their tubing and their lengths.

When all of this is done, a 5/8 is a 5/8 is a 5/8...electrically speaking. This means the Maco works just as well as the Shockwave or the I-10K ELECTRICALLY!

So what makes the Shockwave or the I-10K better than the Maco? For one, the feedpoint is better and has less loss than the Maco. More signal into the main radiator, the better it will get out. The Shockwave/I-10K both use an elevated feed system (just like the Avanti Sigma 5/8). The Maco and the Super Penetrator do not. There is a capacitive component in the base of these antennas and in order to be resonant, inductance is added to counter act the capacitance. This equals loss. The Shockwave and the I-10K do not suffer from this. So, while a 5/8 is a 5/8 is a 5/8, the more efficient antenna gets more signal in the air.

Now lets talk about the Shockwave specifically. It doesn't come with a manual (which bothers me so I'm writing one). However, through exhaustive testing, Chris and crew determined the proper length of the antenna and made marks. They set all the overlaps at 6" and tuned the tip to get an electrical 5/8 wave on channel 20 (assuming). They could have set them at 7" which would have only made the tip longer. Avanti set their overlaps at 4", which made their tip shorter. The reason for the 6" is purely mechanical. 6" is stronger than 4". If you want, you can set yours at 8", but you will have to experiment with a field strength meter to get the tip right. It will be longer than the original marks.

I know the testing Jay did on the I-10K and I KNOW the calculations he gives in his manual are good for his antenna. Unfortunately, since the Shockwave uses different diameters and lengths of tubing, those calculations are useless for the Shockwave. Is this starting to make sense now?!

I'm not sure how Chris got his lengths or if they are even right because I don't know what he did. All I can do is take his word for it until I get a chance to take a field strength meter and test it myself. With Jay's antenna, I can calculate 5/8 wave, .64 wave, .605 wave, etc. I can't do this with the Shockwave. All I got is those damn marks.

Trombones! What do they do and how do they do it? The trombone system was not invented by Jay and he would be the first person to tell you that. What Jay did was per-fect it! Since you can only tune antennas in 1/4 wave increments, we need another 1/8 wave to get the antenna to 3/4 wave (5/8 + 1/8 = 6/8 or 3/4). But wait, if we go past .64 wave, our signal implodes! This is why the vertical element is electrically 5/8 long and the top trombone is horizontal and out of phase of the main radiator. Brilliant! The top trombone fine tunes your frequency without changing your main radiator! Push it in and it gets electrically shorter, or better on higher frequencies. If you are using your analyzer, look at the "X= " change as you push and pull the trombone in and out. Use the dial to find where X=0. If that reading is on too high of a frequency, pull the trombone out and check again. Don't worry about your SWR at this point. Just get X=0 on your desired frequency. For me its 27.205. Now, adjust your bottom trombone until you get R=50. Your SWR is now perfect! But go back and check for X again as it has moved. Just go back and forth adjusting the top then the bottom trombone until you get X=0 and R=50 on your desired frequency. DONE!

Everything else with these antennas is mechanical. Make the ground plane elements all the same size. What's important on these antennas is the EXPOSED LENGTHS! The overlap is not seen by the signal. If all the tubes are 4' and we want 6" overlap, make the exposed lengths 42" If one tube is 1/8" shorter because of the saw blade thickness, then make your overlap 5 7/8" instead of 6". Make your exposed lengths the same! This is more important on the ground radials since there are 4 matching elements. Its not the end of the world if you are off a 1/8" so don't go bat shit crazy trying to get it perfect,

I got more to say on the subject but I'll save it.

Solarcon I-MAX 2000 CB/Ham Radio Base Station Vertical Antenna - 24'

Solarcon IMAX-2000 24' Omni-Directional Fiberglass Base Station Antenna - 5000 Watts. Handles 5000 Watts. Full 5/8 Wave Antenna. 24 Antenna in Three 8 Easy to Assemble Sections. 5.1dBI Gain. Heavy Duty Mounting Plate withstands Greater Wind Loads. SWR Tuning. Broad Bandwidth that Covers Far Above and Below the Traditional CB Channels. DC Grounded. Insulated up to 14 500 Volts. Can be Used for Export Commercial and 10 Meter Ham.


The IMAX 2000 antenna has been a big seller for a while now, but seems that not all of those accolades are worthy of praising this antenna's performance.  For instance, here are some nagging things that my IMAX gave me after installation:

The IMAX does not like a lot of power.  I also have the VSWR to 1:3 to 1:5 across the band. I can run 60W DK and swing to 130 W all day long, but anything more than that and I'm having to back off after about 20 minutes or less due to garbling.  I think it is still going to come down off my tower/pole combo and up with the old A99 that can take the power. Also, there are certain people I cannot hear on the IMAX that I hear on my Antron, which is very confusing. However, this antenna will kick a** on a barefoot radio, without question!   7/3/2017

Ok, brand new coax and great grounding system.  It is a moody antenna for sure.  I don't like moody antennas. Great SWR and all, the A99 will replace it as it has given zero trouble for the last 23 years.  If the A99 breaks, I'll just get another one.  A good antenna should never have to even be checked unless it's after a storm. Just put it up and forget it.  

While I am very aggravated at this antenna's performance, I will say it talks great but there are some real weird things in its performance, one being able to not receive people I talk to everyday, while at the same time others are giving me great reports. Go figure.   I did notice that this antenna should be at least 18' from any metal objects. Since I live in a mobile home, this may be the problem and it will be checked.  The SWR is nearing 2.5 when raining, another problem.  

I will more than likely take this antenna down since it's taken way too much of my time, and I like an antenna that you don't even give it a second thought when you're using it. You turn on the radio and know it works great, like an A99 (in my opinion). I won't say that the IMAX 2000 is not a good antenna, at least not until I've had a chance to do more investigating of the antenna.  1 out of 10, I give it a 6. 

Any ideas will be appreciated.  Just email us at this address

[email protected]


Developed to fill the need for top performance and dual polarity operation, the 8 element Shooting Star® has a gain of 14 dB. The design uses a 16’ boom with 6 scientifically spaced elements, plus a Quad reflector, to obtain the best combination of gain and front-to-back ratio. It’s the same design used to bounce signals off the moon! Features 2kW power handling capability. When performance and price are your main consideration, the Shooting Star® is a great option.  Since the Moonraker has been discontinued, this is a great, almost identical antenna to the Moonraker.    So what is the difference between a Moonraker and a Shooting Star Beam?  Virtually Nothing.  One big thing however, the Moonraker has been discontinued while the Shooting Star is still widely available. Bells CB in Florida has the Shooting Star for $349.50.  MACO Antennas in Alabama are only available at the businesses below. This is the 3 closest dealers to Alabama along with their prices.

Full list here



Face it, your setup is only as good as the amount of antenna you put into the air.  With that said, here are some of the best new antennas on the market from Gizmotchy Products, Division of the World Famous Maco Company, Proudly Made In The USA!!   

All Big League Series Antennas will be similar to the original Gizmotchy® design. Featuring both horizontal and vertical options, but with some big changes!

Availability of the Gizmotchy® Big League Series antennas was June 2016.   The first Big League Series antenna being introduced is a BL8. The BL8 will be an eight element antenna mounted on a 28’ long boom made out of 6061-T6 aircraft aluminum tubing. The boom will have a two inch outside diameter and all elements will be larger than the original Gizmotchy elements. The Big League Series antennas will feature the heavy duty 1/2” thick  x 3” OD machined aluminum hubs that you see here.  

As with all other Gizmotchy antennas, the Big League Series will be made at our Illinois factory with American-made components. The gammas options available for the Big League Series antennas will be 2,000, 5000, 10,000, 20,000, and 30,000 watt gammas.  Shortly after the BL8 antenna is on the market we will be introducing the five, six, and seven element Big League Series antennas. The original Gizmotchy design will still be available for two, three, and four element antennas.

HOD 11/1/16



 1.0 to 1.4
The coax and the antenna length match the transmitter's requirement almost perfectly.
1.5 to 2.0
The antenna and cable and transmitter are operating efficiently.
2.0 to 2.5
Antenna, cable, transmitter operating with some losses. An antenna adjustment should be made to improve match.
3.0 + BAD!
Stop! check your system make adjustment to improve efficiency .damage may happen if run at these swr levels!




The optimum distance for CO-phased antennas is 9 feet, 18 feet, and 36 feet between the antennas.  If possible, try and not go under 9 feet too much as this will create a signal overlap .
Basically your antennas will fight with each other.

Leaning Antenna(s) Forward

Tilting the antennas forward to decrease the height, changes the radiation angle of the antennas and is not recommended. If, due to height restrictions this is necessary, do not tilt the antennas more than 15 to 25 degrees to maintain as much vertical polarization as possible.

If the SWR will not go below 2.0:1

Not being able to go below 2.0:1 SWR, after tuning, generally indicates an impedance problem between the coax and the antenna. This can be caused by poor ground, but is generally attributed to reflection in the mounting location. Stacks, mirror,bars, cab, bad grounds, and hinges all can create poor SWR.  You can add a grounding strap .....DO Not ground your antenna from mirror to mirror as it can create a dipole effect and make adjustment impossible.  Always try and set your mounts as far out as possible.

Big Rig Reflection Test

Here is a reflection test. Get your SWR set and open your doors and see if your SWR drops
or increases. If the SWR drops when you open the doors, then you are getting reflection off the cab, stacks, mirrors, air cleaners, hood,etc.  It's a good little test to try and I have seen antennas go from 1.6.1 to 1.2.1 just by opening your doors. Anyway, if you find this happening set your SWR with your doors open all the way.  Close your doors and that's it.  If your SWR jumps when you close your doors, it's a reflective reading and not to worry as you have already set your SWR and it's not changing. but just creating a false reading due to reflection off the cab and other reflective features. I hope this helps and ill bet when you audio in the mic, your SWR goes down also. Another clue: All antennas should be mounted on the top bar of the mirror bracket, if a big rig, and as far out as possible.  Do not mount the antenna on the bottom bar of the mirror, as this is bad, bad, bad, and will cause reflection and interference from the top bar to the coil
and make it impossible to tune.

Length of coax cable to use.

If you are using less than 500 watts and a single antenna, use  9' 12' 15' or 18' length of RG-58/AU, depending on how much you need. It's 95% shielded, stranded center, with 50 ohms impedance. 

If you are running up to 2000+ watts, then change to the RG-8U or 213U type of the big stuff.


There are many people that say yes and many say no on the coax issue , to each their own. These are you standard length and work well.


Using a good external SWR meter, calibrate on channel 20.  Switch back to SWR and record the readings on three channels; 1, 20, & 40. If the lowest SWR reading occurs on channel 1, the antenna whip is too long and must be shortened. Loosen the two set screws and lower the whip 1/4"-1/2" into the mast. Tighten mast set screw and again read SWR. Repeat until lowest SWR is obtained. If the whip is fully lowered into mast and the SWR is still high, remove the whip from mast. Using a hacksaw, grinder, or bolt cutters, cut 1/4" from the bottom part of the whip. Re-insert the whip into the mast and test again for SWR. Repeat the above procedure until the SWR is below 1.5 of all channels. If the lowest SWR reading occurs on channel 40 the antenna whip is too short and must be raised. Loosen the mast set screws and raise the whip 1/4", re-tighten set screws and test SWR again. Repeat the above procedure until the SWR is below 1.5 of all channels.


SOLARCON, makers of the A99 & IMAX 2000, is only a name and has nothing to do with whom you contact with problems about their products.

Things many CB'ers didn't know about Solarcon.

The makers of the A99 and the infamous IMAX 2000 antennas, as it turns out, has nothing to do with the name of the company that built your antenna.  Solarcon was bought by Tencom Limited. Here is the full story:   

Tencom Limited was incorporated in 1997, beginning as a producer of CB antennas for the truck stop industry. In December 1999, Tencom purchased the assets of Solarcon, also a manufacturer of CB antennas, as well as a pultruder of rods and tubes. In late 2001, Tencom redirected its strategy toward pultrusion while maintaining its position in the antenna market. At the same time, the company purchased the assets of a local pultruder, greatly expanding its customer base, equipment and total capacity for pultruded products. During the following years, additional equipment has been added toward increasing the company's skills in pultrusion, extrusion and value added services such as machining and fabricating capabilities.

So in layman's terms, Tencom has a lot of irons in the fire other than making the A99 and IMAX 2000 antennas. This could account for a lot of the mistakes they've made lately. Here are your contacts for your antenna company and we hope you are satisfied and that we were of help.

Anyone who owns antennas made by Solarcon and has a problem, this is your contact, address, and phone and fax numbers.

Tencom Limited
7134 Railroad Street,
P.O. Box 176, Holland, Ohio 43528
Phone: 419-865-5877 
Toll free: 888-7TENCOM
Fax: 419-865-9449

(HODCBR 6/21/2017)



Originally posted by Heart of Dixie CB Radio Club  7/14/2012 

Since I work in the commercial radio field, I am accustomed to using very high quality components in radio systems. When I am asked to review CB antennas, I always wonder why many are built with such a light-duty purpose in mind. On hilltop commercial radio sites, antennas must work reliably and consistently through 100 MPH+ winds, ice, rain, high heat, etc. Most of the manufacturers of commercial antennas do an exceptional job of designing with this in mind and their products last for years and years without a second thought. The LAST thing the local police dept. wants is for their repeater station antenna to fail in the middle of a rainstorm, right? 

CBers living in windy, snowy or icy winter areas, know that antenna replacement and staying off the air until winter is over has been looked at as ‘part of the territory’. Copper Electronics sells a lot more base station antennas in the winter than any other time of year, likely due to storm damage. All of the commercial quality antennas I have installed skate through the seasons without a second’s thought. The I-10K is the closest thing I have ever seen to a ‘install it and forget it’ commercial quality antenna for the CB band.

The I-10K is a commercial quality 5/8 wave ground plane style antenna made by Jay in the Mojave that is designed primarily for 10 and 11 meters but can also be retuned for frequencies from HF high band through VHF lowband. The I-10K resembles the Maco V-5/8 (also available at Copper Electronics). Both the I-10K and the Maco V-5/8 are aluminum 5/8 wave antennas with four ¼ wave aluminum ground planes, and both perform about the same. Both use an external aluminum matching system that can handle lots of power. You have to look closer at the I-10K to see the other differences like an extremely overbuilt aluminum radiator and a strip aluminum capacitive top-hat.  The first thing you notice when you get the I-10K box is that it is really heavy! There aren’t just a few pieces of cheap aluminum in the box, there’s a large quantity of thick-wall aluminum material weighing down the box. According to Jay, the I-10K uses aircraft grade aluminum for its entire construction. Aircraft aluminum is a stiffer alloy that has very little bending give and is also slightly heavier than your typical aluminum stock. The I-10K gains even more strength by utilizing double wall tubing in stress points, double wall tubing in the base and at each of the joints in the vertical element. The resulting aluminum radiating element is very, very stiff and does not sway much at all. I should note, all this tubing and added material provides extra strength, but that also means extra construction time and effort, especially compared to the popular A99 and Imax antennas. The I-10K requires some nominal assembly effort. The only part of the I-10K assembly that I would describe as ‘difficult’ is the matching section. The ground planes and radiator go together very easily despite being very parts intensive. The ‘trombone tuning’ takes a little trial and error. I found it easier to slide all the pieces together without fasteners and clamps first to make sure I got things right. Then, I added the clamps and fasteners later. The I-10K instructions are very clear and well illustrated with digital photos and detailed drawings. I had very little trouble figuring it out. Even the double wall sections are very clearly detailed in instruction sheet drawings and should not be a problem to assembled. 


Some tower models are like huge Mecharno sets that can be put together one piece at a time making them the perfect choice when space is at a premium.

Any tower is going to need a good base with the ideal situation being a solid area of concrete that tower can be set directly into or bolted on. This can either be a suitable flat roof that will handle the weight or by laying down a concrete base on available ground.

Even though the tower and antennas combined weight will be kept to a minimum by the use of lightweight materials try to economize on the base and the first heavy winds will happily turn the whole setup into scrap metal very quickly.


Using Amateur Beams

HF beam antennas designed for amateur radio enthusiasts will work at CB frequencies but do require some additional equipment to function properly. Because amateur HF antennas are wide band they will need to be used via a antenna tuner to get the best possible match to your CB radio and help keep that dreaded SWR (Standing Wave Ratio) at a reasonable level and give maximum RF power transfer.

The other problem with using a full HF beam is there is a lot of extra material in the construction of the beam that a typical CB user will never need, this adds to the cost not only of the antenna itself but might push the rotator needed into a higher weight class which is also going to seriously push the price of installing a directional system higher again.

Whole directional setups including antenna, rotator and tower can often by purchased at good prices if you have or can arrange a method of transporting it.


The Price of Serious CB use

A quality constructed basic two element CB radio quad can be bought new for under 300 USD but that is the quad alone without a rotor or the other bits and pieces needed when installing a new antenna system. The same quality higher gain 8 element beast isn’t going to leave you much change from 1000 USD and that’s before you even start mixing concrete for the tower, throw in everything else you need including the time needed to get the whole system up and running and its going to take one dedicated CB radio user to justify it all.  


There are quite a few possible causes for device failures, here are a few of the most important reasons:

MOSFETs have very little tolerance to over-voltage. Damage to devices may result even if the voltage rating is exceeded for as little as a few nanoseconds. MOSFET devices should be rated conservatively for the anticipated voltage levels and careful attention should be paid to suppressing any voltage spikes or ringing.

High average current causes considerable thermal dissipation in MOSFET devices even though the on-resistance is relatively low. If the current is very high and heatsinking is poor, the device can be destroyed by excessive temperature rise. 

MOSFET devices can be paralleled directly to share high load currents.

Massive current overload, even for short duration, can cause progressive damage to the device with little noticeable temperature rise prior to failure.

If the control signals to two opposing MOSFETs overlap, a situation can occur where both MOSFETs are switched on together. This effectively short-circuits the supply and is known as a shoot-through condition. If this occurs, the supply decoupling capacitor is discharged rapidly through both devices every time a switching transition occurs. This results in very short but incredibly intense current pulses through both switching devices.

The chances of shoot-through occurring are minimised by allowing a dead time between switching transitions, during which neither MOSFET is turned on. This allows time for one device to turn off before the opposite device is turned on.

When switching current through any inductive load (such as a Tesla Coil) a back EMF is produced when the current is turned off. It is essential to provide a path for this current to free-wheel in the time when the switching device is not conducting the load current.

This current is usually directed through a free-wheel diode connected anti-parallel with the switching device. When a MOSFET is employed as the switching device, the designer gets the free-wheel diode "for free" in the form of the MOSFETs intrinsic body diode. This solves one problem, but creates a whole new one...

A high Q resonant circuit such as a Tesla Coil is capable of storing considerable energy in its inductance and self capacitance. Under certain tuning conditions, this causes the current to "free-wheel" through the internal body diodes of the MOSFET device. This behaviour is not a problem in itself, but a problem arises due to the slow turn-off (or reverse recovery) of the internal body diode.

MOSFET body diodes generally have a long reverse recovery time compared to the performance of the MOSFET itself. This problem is usually eased by the addition of a high speed (fast recovery) diode. This ensures that the MOSFET body diode is never driven into conduction. The free-wheel current is handled by the fast recovery diode which presents less of a "shoot-through" problem.

If the MOSFET gate is driven with too high a voltage, then the gate oxide insulation can be punctured rendering the device useless. Gate-source voltages in excess of +/- 15 volts are likely to cause damage to the gate insulation and lead to failure. Care should be taken to ensure that the gate drive signal is free from any narrow voltage spikes that could exceed the maximum allowable gate voltage.

MOSFET devices are only capable of switching large amounts of power because they are designed to dissipate minimal power when they are turned on. It is the responsibility of the designer to ensure that the MOSFET device is turned hard on to minimize dissipation during conduction. If the device is not fully turned on then the device will have a high resistance during conduction and will dissipate considerable power as heat. A gate voltage of between 10 and 15 volts ensures full turn-on with most MOSFET devices.

Little energy is dissipated during the steady on and off states, but considerable energy is dissipated during the times of a transition. Therefore it is desirable to switch between states as quickly as possible to minimise power dissipation during switching. Since the MOSFET gate appears capacitive, it requires considerable current pulses in order to charge and discharge the gate in a few tens of nano-seconds. Peak gate currents can be as high as 1 amp.

MOSFETs are capable of switching large amounts of current in incredibly short times. Their inputs are also relatively high impedance, which can lead to stability problems. Under certain conditions high voltage MOSFET devices can oscillate at very high frequencies due to stray inductance and capacitance in the surrounding circuit. (Frequencies usually in the low MHz.) This behaviour is highly undesirable since it occurs due to linear operation, and represents a high dissipation condition.
Spurious oscillation can be prevented by minimising stray inductance and capacitance around the MOSFETs. A low impedance gate-drive circuit should also be used to prevent stray signals from coupling to the gate of the device.

MOSFET devices have considerable "Miller capacitance" between their gate and drain terminals. In low voltage or slow switching applications this gate-drain capacitance is rarely a concern, however it can cause problems when high voltages are switched quickly.

A potential problem occurs when the drain voltage of the bottom device rises very quickly due to turn on of the top MOSFET. This high rate of rise of voltage couples capacitively to the gate of the MOSFET via the Miller capacitance. This can cause the gate voltage of the MOSFET to rise resulting in turn on of this device as well ! A shoot-through condition exists and MOSFET failure is certain if not immediate.
The Miller effect can be minimized by using a low impedance gate drive which clamps the gate voltage to 0 volts when in the off state. This reduces the effect of any spikes coupled from the drain. Further protection can be gained by applying a negative voltage to the gate during the off state. eg. applying -10 volts to the gate would require over 12 volts of noise in order to risk turning on a MOSFET that is meant to be turned off !  Rapid switching of large currents can cause voltage dips and transient spikes on the power supply rails. If one or more supply rails are common to the power and control electronics, then interference can be conducted to the control circuitry.

Good decoupling, and star-point earthing are techniques which should be employed to reduce the effects of conducted interference. The author has also found transformer coupling to drive the MOSFETs very effective at preventing electrical noise from being conducted back to the controller.  *******   Antistatic handling precautions should be used to prevent gate oxide damage when installing MOSFET or IGBT devices.  But are very reliable once they are soldered in place.



Hey You! 2,000 to 15,000 Watt Amplifier Guys. 

Read This. It may save your life.

If you are a serious CB radio guy or gal, then please read this information on the dangers of RF and its effects on your body. 

This is by far one of the most important articles we've posted on the Heart of Dixie Website. I've been doing CB radio since I was ten years of age, starting in 1969. We never ran any power back then due to the FCC strict polices that were not just a threat, like they are now, but penalties were actually carried out. But the power being used today on CB radios is "off the hook" to use a phrase someone else made popular. However, RF power is a dangerous thing and, if not tempered correctly, can kill the radio operator or make your family very sick. Please read the article below and take it seriously.

Courtesy Kollman Radio:

I have for many years preached on what RF energy will do to you. This all came about when CB'ers were stopping by the old shop showing off the multi-alternator systems, feeding their dual amps in the back of their Suburban’s. The scary output was 5,000 watts or MORE!

The antenna of course was either behind their head or on top of the vehicle. Which is a moot point considering anywhere on the car is too close!  Forget the legalities for a second. I have been at this since I was ten years old, in 1969. I don’t consider it an accident that so many of the operators I used to look up to, at that time, have died of cancer or tumors.  I am not a doctor and don’t play one at all.  Yet I still see and talk to those who are not paying any attention.

There are stations in neighborhoods that are operating at 10,000 watts or MORE. One in particular with their kids sleeping in the attic under the antenna!  Okay so they didn't know you can’t feel it. Somewhere, sometime the light should go on in their head that the antenna is glowing!  What about our neighbors, aren't they glowing too?

This is serious! and since the season is on the way for mobile radio competitions it needs to be brought up.  Saturating your body with extreme RF (radiation) has to be thought out.  There is no filter for that. 

RF exposure is a very serious matter and should not be taken lightly. The FCC has numerous articles and literature regarding the dangers of RF to not only the operator, but also people implanted with pacemakers and defibrillators, etc. Please take the time to keep your radio in perspective. There is nothing more important than your family, and I'd imagine you're pretty important to them also.  

(Provided as a Service to the Radio Public)  Also Courtesy to Kollman Radio.


FCC Proposes to Fine CBer $14,000 for Not Permitting Station Inspection

The FCC continued this month to demonstrate that it's serious about enforcing its rules and regulations, proposing to fine a Florida Citizens Band operator $14,000 for failing to allow FCC agents inspect his station. The Commission issued a Notice of Apparent Liability for Forfeiture (NAL) to Tommie Salter of Jacksonville on August 22. The Commission alleged that Salter earlier this year denied permission for agents from the FCC's Tampa Office to check out his station in the wake of renewed complaints of interference to a neighbor's "home electronic equipment." On March 21, the agents monitored radio transmissions on 27.245 MHz and used radio direction-finding techniques to track the signal's source to Salter's residence.

"The agents told Mr Salter about the radio interference complaint from a neighbor and asked if they could inspect his CB radio station," the FCC NAL recounted. "Mr Salter denied the agents' request. The agents verbally warned Mr Salter that refusing to allow an inspection of his CB radio station violated the [Communications] Act and the [FCC] rules and could result in a forfeiture action, but he again denied the request."

The FCC's Forfeiture Policy Statement and its rules set a base forfeiture amount of $7000 for failure to permit inspection. Salter had previously received a Notice of Violation for refusing an inspection request in 2004, the NAL noted, and he also had been fined for operating with a non-certificated transmitter during restricted hours the Commission had imposed following similar interference complaints.

"Misconduct of this type is serious, exhibits contempt for the Commission's authority, and threatens to compromise the Commission's ability to fully investigate violations of its rules," the FCC said in making an "upward adjustment" of $7000 in the proposed forfeiture. In a footnote, the FCC pointed out that its agents do not have to obtain a search warrant prior to requesting a station inspection.

Salter has 30 days to pay the fine or to seek reduction or cancellation of the proposed forfeiture.

In July the FCC proposed substantial fines for two radio amateurs, alleging deliberate interference with other Amateur Radio communications and failure to properly identify.


Before Restoration    

BELOW:  After Fully Chromed Restoration

Slinger - Pennsylvania

Thanks for sharing the process with us.

One man's trash is another man's treasure