The Highway Zapper

There has been much discussion on the Highway Zapper issue as of late. To catch everybody up on what has been discussed I am compiling a list of some of the highlights of this discussion from the past month or so from various sources on and off the net.

What is a Highway Zapper?

A Highway Zapper, also known more loosely as a radar activator, is a small garage-door-opener-type of device that, when the button is pressed, sets off radar detectors that some drivers use to attempt to avoid tickets. Naturally, if the other driver thinks that they may be going too fast, will slow down to ånormal¼ speeds. They are generally available for about $50 and run off a 9v battery. There has been some questions about legality of using these devices as well, but it looks good if reasonable power limits are used. There are also some alternative things to think about using for those that want to home-brew their own radar activator.

This is the point where most everybody has an opinion, and the discussion falls into a flame war about speeders. We aren't going to do that - it's been done to death. The basic points to these arguments are 1) speeding is bad 2) stopping people from speeding is bad. 3) You are a pickle-headed moron. 4)You suffer from cranial rectal inversion. Repeat ad nausium. My personal reflection on this is that anybody who publicly flames immediately loses all dignity and respect in the net community no matter what their point.

Contact Info on Highway Zappers:

No longer available. All suppliers have stopped carrying them per the FCC's request.

Other possible sources for those that like to do a little digging:

There was once a magazine construction article which described how to make a small 10.525 GHz transmitter with a strip antenna, which would set off X-band radar detectors within a half-mile or so. Since then a couple of companies have offered kits (preassembled or build [AND **TUNE**] yourself versions). Cruise through electronics and ham magazines for ads from Innotek, Electronic Rainbow ("The Zapper") and JDR Microdevices (a computer parts outfit who are reselling a lot of the Rainbow kits).¾

Other related ideas:

The City of Menlo Park, CA has acquired a bunch of handheld police radar units which it will loan out for a week at a time to private citizens living on streets with speeding problems. The individuals using the radars can write down the license numbers of particularly egregious speeders and the police will send out letters notifying them they've been observed speeding in a residential district and asking them to slow down in the future. I guess there's nothing better to set off a radar detector than a real radar transmitter. For someone who lives on a winding two-lane road having numerous residences, lots of children in them, 17,000 cars/day going past, a 35 mph posted speed limit, an 85th percentile around 48 mph, and absolutely no enforcement, this thread has generated lots of useful ideas.¾

Most x- Band 10 Ghz microwave transmitters work real nice.Check nuts and bolts and you will see some discount 10Ghz microwave for video.¾

I have a couple of surplus dual-tech (PIR/microwave) motion sensors that I'd like to use to "test" radar detectors with :-). By powering them with the specified 12VDC, walking around the room, and watching the indicator lights they both seem to function. The horns are self-contained cast metal assemblies having a cavity with an electrical part (Gunn plexor diode?) stretched across them. One terminal protrudes through the casing and is connected to wire having a positive voltage. There are small screw adjustments, I assume to be used a fine tuners, that are glued in place and intact. Both seem to have a pot used for microwave sensitivity adjustment.¾

I've heard of people getting surplus motion detectors from supermarket sliding doors and hooking them up to do the same thing. They operate at 10.525 GHz - the same as X-Band radar, and are usually 12vdc to boot.

Check out the June 1995 issue of Popular Electronics (not Popular Science). They have an article on how to build a radar gun from scratch or from a $100 kit available from Ramsey Electronics. The kit is highly suggested due to the availability of some parts and the nature of the circuit board. You supply a 12vdc power supply (ie: car battery) and two coffee cans and you can make a radar gun that operates at 2.6 GHz (too low a frequency to set of radar detectors).

Ramsey Electronics
793 Canning Parkway
Victor, NY 14564
(716) 924-4560 or (800) 446-2295

Home Built Units

Electronic Rainbow sold the Zapper II as a kit which is a modified version of the original Zapper. Instead of a single button for zapping, there is a small "test switch" and a code key input for morse code practice or possably remote mounting and control of the unit. It is a small, simple circuit with 3 resistors, a trim pot, a capacitor, and two transistors. You will also need misc. parts for it such as a push button, a LED, and a 9 volt battery snap. The caps and resistors are surface mount parts and thus a little more difficult to come by. You should be able to find them in packs for about 20 to the dollar. Substituting through hole parts is a bad idea since the lead lengths will affect the radio frequency circuit.

If you get the Electronic Rainbow kit book for $15, you could have got the plans for the zapper on page two. There was a layout for making the printed circuit board which is fairly small - 2" by 3/4" - but beware, it must be on .031¾ teflon board. Standard copper clad will not be able to handle those high frequencies according to the guy I talked to at Electronic Rainbow. If you're not much for making a printed circuit board, they did sell one for $13.

The toughest thing to get is one of the transistors. Normal parts places don't carry it. It is a GaAs FET Avantek AFT 26884-STR. Rainbow sold them for $13 each. One of the leads has to be cut off, and another one solders to a trace on the board that needs to be trimmed to the right size to give it the proper frequency. Trimming that strip by 1/64th of an inch will increase the frequency by about 50 MHz. They are very small and sensitive to static damage so a grounding strap and grounded soldering iron are minimum precautions. If these are not used, the GaAs FET could be damaged and fail without warning some time after the unit is built.

Besides the board and GaAs FET mentioned above, you will also need one of each of the following parts. 33 Ohm, 51 Ohm and two 270 Ohm surface mount resistors, .01 uF surface mount capacitor, 1K surface mount variable resistor, LM 317 LZ transistor/voltage regulator, wire for 3 jumps, push button switch, 3.5 mm code key jack, red LED, 9V battery connector, white plastic screw, 1/4" plastic spacer, LED holder, case with front panel, and hook up wire for connecting the switch, LED, and code key jack to the board. Unless you have most of thses parts already, it would be wise to buy a kit with all the parts from Rainbow Electronics.


The Zappers are no longer sold as radar transmitters, but rather code practice transmitters for the radar range of amature radio. These are tuneable by use of a trim pot to shift the frequency to that of a radar detector. The FCC would probably frown on that.

As long as you stay below 100 mw you should be safe. Most Highway Zappers are 10mw or so, but some home built units have been reported to transmit at up to 250mw! Check before you buy a kit to avoid any problems. Also check FCC rules part 15 for specific limitations. Section 15.122 is pretty specific about unlicensed devices and what guidelines they must follow. At radar frequencies this section states that they device must not have a field strength of over 5000 micro-volt meters at 3 meters, plus something about a limiting device to not allow it to transmit for longer than 1 second.

Document FCC 78-326 is an interesting read about a request by the Washington State Traffic Safety Commission requesting a rule change regarding anti-radar detector drones. The state wanted to install many of these devices about every ten miles or so in their area, but was denied for the following reasons:
As our staff has previously advised you, the device has not been type-accepted by the Commission; the intended use is not permissible under the Commissions present rules; it would not qualify as a "field disturbance sensor" under part 15 of the rules; and it most likely would not meet the duty cycle limitations imposed upon other low power devices which may be operated without a license under part 15.

That was in 1978 and probably about more powerful devices than the zappers affixed in permanent positions. More recently the following post was found in support of their legality.
The owner said the FCC did get on him for his Zappers even though they emit power levels below the min necessary for transmitter licensing or type acceptance etc...
He advertises it as a 10ghz ham radio xmitter now which btw also tests radar detectors. He added a CW key input(really) and make the big red button on top a little red button on the side. No price change. $39.95 kit and $49.95 built (if memory serves me correctly). He said that satisfied the FCC and they will be marketed as I mentioned.
His sales were brisk and he was looking for dealers.

X-Band radar (which is what the zappers use) is 10.525 Gigahertz. The upper end of the ham band reportedly stops at 10.500 GHz, 0.025GHz below the Zappers frequency. Ham operators can get in trouble for transmitting in this range.

These are completely different in form and function to radar scramblers and should be inert to police traffic radar. You can check with your local police department to be completely sure. Heck, some police departments own them (or similar devices) and use them on highways to control traffic. I think the following post sums that type of thing up nicely.
However, if you want to jam police radar, you may be falling into other legal areas like obstruction of justice -- definitely more serious. Many radar jammers transmit a signal typically modulated with a square wave to deceive police radar. I've seen a number of police radar units that have a speaker which allows the officer to listen to the Doppler shifts. Low frequency tones are heard when a slow target is detected; high frequency tones are heard when a fast target is detected. A jammer would sound like buzzing. An officer could recognize this as an attempt to jam him. So there is a definite risk of being caught with a jammer - it might not be for speeding but it could be more serious violation.

As for the interference with police radar, I posted that question on a law enforcement board and got this reply among others that generally said that they don't cause any problems with police radar, and if a cop saw one in use, they probably wouldn't have a problem with them because they help them more than anything, assuming that they knew what it was.
Here's some of the replies I got:

I did try that, just to see what would happen. I had one of the Zappers and another unit that was home-brewed and sold by a local resident. Using two of our MPH Industries K-55 units (X-band of course, and one at a time), I transmitted the Zapper and the other unit directly at the radar antenna from various distances. Nothing happened. No speed reading at all, even when the Zapper was 1 inch from the antenna. So, interfering with police radar with one of those types of units isn't a problem for anyone. I have HEARD (not seen) about some units that transmit a much more powerful signal in an attempt to foil traffic radar, but have only had REAL confirmation about one being effective. That was from the 2/95 issue of Corvette Fever, where they did a test of various Radar/laser detectors and other devices that claim to thwart traffic radar or laser. Only one worked, a $500 unit for X-band radar only. You'd have to be a very serious violator, and hope that you don't run into
Kentucky Department of Transportation several years back installed small silver boxes with small windows on them that transmit a carrier signal on radar solely for the purpose to prevent the use of radar detectors on Interstate 75 coming into Cincinnati. They were installed on overpasses and telephone/utility poles about every half mile or so. This situation was made public a few years back and KDOT specifically stated the purpose and advised that in doing so was not in violation of any Federal Law. Of course this provoked a very heated debate with the public. Threats of vandalism were made and the last that was heard was any one caught damaging such devices will be prosecuted for willfully damage or destruction of public property. After many years the motoring public finally accepted that the use of radar detectors in this 5 mile stretch of highway was limited to the "off position" until motorist cross the bridge into Cincinnati.


1. Obviously the single best use of these devices is to slow the guy that just blew past you doing 90mph.
2. You may also be interested in testing the radar detector you plan to purchase (or demonstrate if you are selling them).
3. Activate the unit and see what break lights come on ahead of you, then reel åem in.
4. If there are more than one radar equipped cars, see if you can keep them in a group or single lane as long as possible. As soon as someone pulls out to pass, hit the button again and watch them fall back into line.
5. As a speeders aid - to break up those pesky groups of cars only doing 60 and blocking all the lanes. Chances are one will have a radar detector and slow down, breaking up the pack so you can get by.
6. A code practice transmitter for morse code

Final notes:

Rainbow Kits contacted me about getting their name out of this FAQ, as it was still generating calls. The FCC had them stop making and selling the devices, kits, and plans with the threat of a stiff fine should they persist. They also apparently are owed a large sum of money from The Edge company, to whom they sold a number of the units, but never received payment.

Updated On: 9/99
By: The Staten Island New York Scanner Guide