GPS Antenna Amplifier and Extension I had a small h/h GPS that did not work satisfactorily when placed on the dashof my Land Rover Series 3 - so I made an external antenna for it. GPS signals come in at ± 1500MHz, the wavelength is ±190mm.The receive antenna is an aluminium 'patch'antenna about 130mmx120mm.It has a smaller element about 80x90mm mounted 8mm above this. See theexplanation belowThe coax from the antenna then feeds into a wide band (0-2010 MHz) satellitein-line amplifier with a slope gain of up to 26dB. This amp costs about R50.00and is available from any shop that dabbles in TV/sat etc. The amp is small-about two match boxes in line type size and sits about 200mm from the rxantenna.

• Patch Antenna Wifi

The coax then goes into the Landy and terminates in a simple loop ofwire-1 wavelength long. This effectively 'retransmits' the GPS signalin the vehicle cab. The h/h GPS lies on top of this loop, which sits on my cubbybox/armrest. I get brilliant reception and the system does not tie up the h/hGPS i.e. I can just pick it up and go walkabout.Bruce Molzen E-mail: molzenba(at)sabc.co.zaW1GE Patch Antenna for GPSConstructionWe have chosen to build the antenna using aluminum sheet and an air dielectric with nylon bolts and washers to support the patch.The final dimensions of the patch and its ground plane are shown in the diagrambelow. The critical dimensions are those of the patch and the location of the feed point.

The dimensions of the ground plane are much less critical. Separation of the patch from the ground plane is 5 mm (0.197 in) and is determined by the three No. 8 nylon washers.

The sheetaluminium should be at least 1.27 mm (0.05 in) thick to provide sufficient mechanical strength but the exact thickness is not critical. The bandwidth of the two modes of the patch are 8 and 10% respectively which means the critical dimensions of the patch shouldbe held to within about 3%. Having determined the design dimensions of the patch, we will now turn our attention to its construction.The first step is to cut the aluminium sheet metal pieces needed for the patch and the ground plane. One means of controlling the dimensions of the pieces is to scribe the exact dimensions on thealuminium surface, then cut the piece somewhat larger than the necessary dimensions and grind the edges to obtain the final size.After the aluminium is cut to size, clamp the patch so that it is centered on the ground plane and drill the four 4.76 mm (3/16')corner holes for the #8 nylon bolts as well as the small 1.59 mm(1/16') hole in the patch for the center conductor of the coax at the feed point. Then separate thealuminium pieces and enlarge the ground plane hole at the feed point to 4.59 mm (3/16') diameter (for RG58/U coax).

At this stage round the corners of the patch and theground plane to a radius of about 4 mm.157') and then bolt the patch to the ground plane.The next step is to attach the coaxial cable. Section of RG-58/U will satisfy most applications.Since soldering to aluminium is difficult I attached a 1' square of copper tape to both the top of the patch and the bottom of the ground plane centered at the feed points where the cable should be soldered. The tape that I used has a capacitance of 143 pF or 0.7 Ohms reactance at 1575.42 MHz. A DC connection to thealuminium is not necessary because the capacitive reactance is small enough to be negligible. An alternative to using copper tape to make the solder connections is to use copper or brass rather thanaluminium sheet metal.Harold R. Ward E-Mail: Excerpt from QST Magazine, Oct. 45Building GPSReceiving and Transmitting Antenna and Power SupplyThe basic idea of the system is to use.two.

additional GPS antennas.Antenna #1 is used to receive the GPS signal from the satellites, and is placed wherever it has a good view of the sky. Antenna #2 is used as a.transmitting. antenna, and is connected to antenna #1 via coax cable.

The transmitting antenna is then placed close to the GPS receiver's owninternal antenna, and the GPS signal is coupled into the GPS receiver's antenna through the air.The Receiving AntennaThe receiving antenna needs to provide a good strong signal, since thecoupling between the transmitting antenna and the GPS receiver is not as good as a direct connection. This usually means using an 'activeantenna', with a built-in preamp, as the receiving antenna. The Lowe or Trimble antennas seem to be ideal for most cases, since their internalpreamp has plenty of gain (about 26 dB). The Garmin GA-26 also works pretty well, though its lower gain (13 dB) means that the signal won'tbe quite as strong at the GPS receiver antenna.

I have not tried other active antennas, but I would expect that almost any one would work.Of course, the disadvantage of an active antenna is that it requirespower to operate. Below, I describe how to build a power supply for an active antenna, but this does require an extra 'box' in the system.The Transmitting AntennaThe antenna that 'rebroadcasts' the GPS signal must be a passiveantenna, because passive antennas transmit just as well as they receive. Thus, any passive antenna that works well for receiving willalso work as the transmitting antenna. If you had a spare Garmin GPS-45 antenna lying around, it would work well, but it's far too expensive tobuy one for this purpose.

The W1GE homebuilt patch antenna also works well, but it's a bit awkward for mounting to your GPS (it's about 5inches square).However, all the transmitting antenna needs to do is to couple thesignal into the GPS receiver antenna at close range - it can be taped directly on top of the receiver's antenna if necessary. So thetransmitting antenna really doesn't have to be a very good antenna, and we can give a higher priority to low cost, simplicity of manufacture,and ease of mounting than to actual performance.The best design I've found so far is a simple one-wavelength loopantenna. To build it, start with 190 mm (about 7.5 inches) of stiff copper wire.

I used 12 AWG wire to make the loop really stiff, but anywire thick enough to hold its shape would likely do. You can use insulated or bare wire, but if you use insulated wire strip 1 or 2 mm ofinsulation off each end. Then bend the wire into a loop, bringing the two ends to within a mm or so of each other (but not touching). You canuse a round loop if you like, but a square loop fits on top of the GPS better.

I made mine a square loop with the gap in one corner, butputting the gap at the centre of one side should also work.When the loop is done, find some 50 ohm coaxial cable and strip 2 or 3mm of it. RG-174 is ideal because it is so thin and flexible, but RG-58 will work as well or better electrically. Then solder the centreconductor to one end of the loop, and the shield to the other end. If you think you might ever use the loop outdoors in the rain, seal theentire connection between the coax and the loop with silicone or epoxy, to keep water from getting into the coax. Then install a BNC plug onthe other end of the coax.The Power SupplyAssuming you use an active receiving antenna, you'll have to supplypower to it. Most active GPS antennas want 5 V at 15-25 mA supplied via the coax that also serves as the signal output cable.

If we are goingto use the external antenna 'in the field', the power supply needs to be small and portable.

Patch Antenna Wifi

A few years ago, some friends of mine shed city life for the country, escaping to a small piece of land in the mountains. They were delighted with the clean air and the elbowroom, but being isolated took its toll — out of the blue, so to speak: Because their tract lay in a hollow, television and radio reception was almost nonexistent.The fact that their house was surrounded by hilly terrain, as well as being located 70 to 120 miles from most of the local transmitters, dictated the need for a high-gain, long range antenna capable of picking up signals over that distance. However, the $100 price they were quoted for a commercial unit stopped them in their tracks. So they came to me (I'm an electrical engineer) and asked whether they could build an antenna that would serve the same purpose.After doing some research and subsequent number-crunching, I discovered that not only could they duplicate the performance of the high-buck rig, but — using common hardware and some sections of bamboo that was growing nearby — they could probably do so for about $20!

By this time, I was excited enough to jump right in and give them a hand, so I drew up a plan, and we built the antenna — twice! The first model, you see, was destroyed in a storm, so I took the opportunity to try out some new ideas on a second version — a conduit and plastic-pipe model. The one I'm about to describe incorporates the best features of both these prototypes. Antenna AnatomyAny antenna — TV, radio, or whatever — consists of three parts: the element array, the framework, and the mast. From a performance standpoint the element array is the most important because it picks up the signals, but it's actually nothing more than a metal pattern of the right size and shape to suit a specific purpose.

This design uses a Yagi-enhanced, log-periodic pattern —which, simply put, means that it has broadband capability and can thus cover the very high frequency (VHF, channels 2-13), ultrahigh frequency (UHF, channels 14-83), and frequency modulation (FM) broadcast bands.Commercial elements are usually made of aluminum rod, sometimes anodized to resist corrosion. However, we got by with bare copper-stranded 'radio' wire and some insulated bell wire left over from another project.

Often, depending upon one's geographical location, a fourth component — a rotor — can come in mighty handy for aiming the antenna directly toward different transmitting stations. The store-bought motor-driven models run $50 or $60, but we worked up a simple remote-controlled manual version for no more than the cost of some wire cable and a few pieces of hardware.Sounds easy enough, doesn't it? Well, bear with me and I'll walk you through the construction procedure step by step. Frugal FramingTo start, you'll want to rough out the framework. That'll require one 3/4'-diameter 10' length of EMT, a second 1/2'-diameter piece about 6' long, and a third 1/2' x 40' segment. You'll also need two 10' sections of 3/4' PVC pipe, an 8' length, a 1 ' piece, and two 6' hunks. (If you do have access to bamboo, feel free to use it — but be sure to dry and varnish about twice as many stalks as you think you'll need, because it's brittle and prone to split when being cut or drilled.)The idea is to make a trellis affair like the one shown in our.

Using 1/4' machine bolts, start at the 'point' (which I'll call the front of the frame) and 'pinch' the ends of the three 10' sections between the two 6' plastic stubs, leaving about an inch between the tips (the conduit should be in the center). Then move to the opposite end of the poles and bolt them to the 8' PVC section, keeping the distance between the tips equal.Next, measure 42' from the front of the frame and mark a mounting location for the 40' piece of EMT, then measure 43' back from this point and do likewise for the remaining 6' section. Trim the conduit pieces if necessary, and drill and mount them to the frame on the same side as the 8' crosspiece.Finally, fasten the 12'vertical plastic stalk perpendicularly to the 8' rear section (half above and half below). Pick up the entire frame by its center pole to establish the balance point, mark that spot, and you'll be ready to string the element wires which form the pattern. It's Elementary!It might be easier to envision the element pattern if you imagine the skeleton of a fish, with backbone and ribs. Wire the backbone first, using the heavy bare copper conductor.

Make the terminals at the front by fastening a No. 10 x 1/2' sheet metal screw through each 6' stub on the front, parallel to the 10' frame sections.

With that done, install similar fasteners at each end of the vertical stalk, at the rear tip of the center pole, and on one arm of the rear crosspiece at a point halfway between the two poles.Start at the front and run one continuous length of wire from one terminal to a screw on the vertical stalk, over and down to the head on the rear crosspiece, up to the other fastener on the stalk, and back to the remaining terminal at the front. Pull each section tight as you go, and then wrap the conductor once around each screw. Next, you'll want to make a 'reflector' — another length of the same wire stretched between the bolts at the rear corners of the frame and the screw at the tip of the center pole. (It's best to insulate this wire from the screwhead with tape or tubing to isolate it from the metal pole.)The ribs of the fish — called resonant dipoles in technical terms — are paired short sections of wire which do most of the signal-gathering work.

They spread out from the backbone spans at angles roughly parallel to that of the reflector.To make them, get a measuring tape and a grease pencil, and starting at the front, mark off the following distances on the top and bottom backbone wires and on the outside of the two plastic side poles:7 1/2'. 95 1/4'.106 7/8'.You should now have four sets of 24 marks each, with the marks close together at the front of the frame and farther apart toward the rear. Drill 9/64' pilot holes at the locations indicated in the in both PVC pipes, and thread 48 No. 10 x 1/2' sheet metal screws partially in.Now, set the frame flat with the front pointing away from you and the three long poles on top of the crosspieces.

Starting at the rearmost mark on the upper backbone wire, twist and solder the end of your heaviest wire to it, then run it to the rear screw on the right pole section and pull it just enough to take up the slack. Tighten the screw and clip off the rest of the wire.With that done, run another piece of heavy wire from the next mark on the backbone to the second screw on the left frame pole, and secure it at both ends as before. Do this four more times, alternating left and right, and skipping every other screw on each side.At this point, you can use lighter wire if you have it. Just continue the procedure I've described until you reach the last mark on the upper backbone wire. Then turn the whole frame over and do the same thing with the lower backbone strand, attaching wires to all the screws you left vacant when doing the top one. (Remember to use your heavier wire for the rearmost five or six dipole ribs.)While the frame is still upside down, measure and mark the bottom of each side pole at the following distances from the front of the frame: 3 3/4' 4 1/4' 4 3/4' 5 3/8' 6' and 6 3/4'. Drill pilot holes at these marks, and insert twelve more sheet metal screws.

String your heavy wire (if you have any left) between opposite pairs of screws to create 'directors' which will improve reception at the higher-numbered UHF channels.Finally, install the twin lead terminals by fastening two more sheet metal screws into the lower 6' pipe at the front, centered and spaced about 1' apart. Cut two 4' lengths of wire and connect each of these between a backbone and a terminal screw, twisting and soldering the wire splices to assure a good connection. Once the antenna is permanently mounted, you can hook up the 300-ohm twin lead wire that will carry the signal into your home.

Two Beers Before the Mast?The antenna mast mounts to the frame's center pole with a 1 1/4' x 3' U-bolt and some short sections of 1/2' x 1' iron or aluminum channel. Cut the channel to about 4' in length. Then, using the U-bolt as a template, bore matching 1/4' holes through the center of each bar. Two of the channel pieces fit around the center pole at the previously marked balance point; the third presses against the mast perpendicularly, with its flat back against one of the other sections of channel. Position the frame about a foot below one end of a 1' x 10' length of thin-wall conduit and lock it in place with the U-bolt clamp. Check to be sure none of the copper element wires are touching the mast or the U-bolt.Before mounting the antenna, take the time to think about lightning protection. If you already have a tall lightning rod fastened to your roof or chimney, plan on mounting the antenna several feet below that.

If not, you might want to add a mast extension that will — in most cases — provide a 'cone of protection' for the antenna frame. For this 10'-wide frame, 5' of extension will do.

And you can accomplish the task easily by slipping a 1/2' x 5' piece of EMT about 9' or so into the top of the mast tube, cross-bolting it in place with a 1/4' x 1 1/2' cap screw and nut, and sealing the joint and the exposed end with silicone or cored furniture tips. (I'll cover the actual grounding of the mast shortly.)As I mentioned earlier, some kind of rotor device can really improve the strength of a signal, so I'm going to describe how you can build a mast mount, rotor, and ground stake —all in one. (If you don't need 'aiming' capability, simply fasten the mast to your chimney or house with locally available mounting hardware, but be sure to ground it by running a length of 6-gauge wire or the equivalent directly between a clamp on the bottom of the conduit and a metal stake or pipe driven 4' into the ground alongside the foundation.)To begin, study your roof overhangs near the window you plan to feed the twin lead through.

If they're of a conventional length (about 16') you're in luck, but don't count on putting the antenna anywhere near service lines or tall pine trees. The former can pose a real shock hazard, and the latter can actually interfere with reception! (Try, too, to set the frame above the roof's ridgepole; if you don't, the antenna's effectiveness may be reduced.)You'll probably have to add another full length of 1' EMT to the bottom of the mast to accomplish your goal.

If so, join the two sections with a center core of 3/4' Schedule 40 pipe at least half a foot long and threaded at both ends. Make sure it extends an equal distance into both tubes, then cross-drill each half and install 1/4' x 1 1/2' lock bolts to hold the joint together.Now, stand the mast up and, with the help of a friend, hold it upright and about an inch from the edge of the roof, gutter, or what have you. Mark the spot on the ground where the mast stands, then carefully lay the mast aside and remove a core of earth at least two feet deep at that spot, using a post-hole digger. Cap a 4' length of 1 1/4' iron pipe and hammer it firmly — cap first — into the center of this hole. Tamp the earth in place around the pipe, then slip the conduit mast into the iron opening.Straighten the mast once more, and mark spots for two supports: one at or near the roof soffit, and one at waist level. You can use two 18' or 20' lengths of 1 x 4 with 1 1/4' holes bored through their ends to hold the mast, and 6' shelf brackets and lag screws to fasten the supports, depending on your situation.

Don't actually mount the supports until they're around the conduit. And you might want to strengthen the edge of the boards by trimming them with a nailed-on strip of sheet metal surround. (A cut-out tennis ball can be used to seal the bottom pivot mount opening if you wish.)Your antenna will now pivot, but you'll need an indoor control to make it do so.

Simply bend a piece of 1/2' x 20' steel rod into a crank shape and slip the shaft into a 9/16' hole bored through the thickness of a 1 x 6 cut to fit the width of your windowsill (a cotter-pin lock on each side of the wood will prevent the crank from 'walking').Close the window on the crank board, then drive some thread-cutting screws into the exposed metal shaft about 6' apart. Do the same thing on the antenna mast (at a point level with the crank) and mount a pair of 1/8' x 1' pulley blocks on the house siding in line with the conduit.Finally, fasten some 3/32' wire cable to one of the screws on the mast and feed it around the pole about five times. Do the same at the other screw, but wrap it in the opposite direction without unreeling the first group of coils.

Repeat this procedure on the crankshaft, making sure the cables are threaded through the pulley blocks and are fairly taut.This windlass setup should be a big help in fine-tuning reception; however, it could also provide an alternate path for electricity if a direct lightning strike should choose to follow the control cable rather than seek the more immediate ground connection. A 1/2' x 16' plastic-pipe 'insulator' section spliced into each cable should interrupt that conduction route.

Get Your Signals StraightBy this time, a strong blend of TV and FM signals should be clamoring to flow into your living room. All that's left to do, then, is to connect an appropriate length of 300-ohm twin lead to the terminals at the front of the antenna, guide that wire down to window level by using some antenna-wire standoffs (be certain to leave enough slack at that point to allow for one complete rotation of the pole) and pass the lead beneath the window sash.Once it's inside, you can use a $4.00 signal splitter to run a second TV set or an FM receiver —but remember that the more equipment you add, the weaker the signal will be that each receives. And one more thing: Despite the precautions you took in grounding your mast, an electrical charge — from static buildup or in the form of peripheral energy from a lightning strike — could still find its way into your TV set. You can safeguard against this fairly effectively by installing an inexpensive static discharge unit (sometimes called a lightning arrester by optimists) on the lead-in line. This part should be connected to your ground pipe with a separate wire.That about wraps it up. Believe me, it's harder to explain than to actually accomplish, so don't be afraid to jump right in. If you have to buy every component new I'm sure you'll end up spending more than the $20 that we did, but some no-nonsense scrounging will probably put you right in the ball park, even if you purchase the plastic pipe and conduit.

The important thing is that you'll be catching the signals thrown your way. And you'll be doing it with some very basic aerial anatomy. 50 Years of Money-Saving Tips!At MOTHER EARTH NEWS for 50 years and counting, we are dedicated to conserving our planet's natural resources while helping you conserve your financial resources. You'll find tips for slashing heating bills, growing fresh, natural produce at home, and more. That's why we want you to save money and trees by subscribing through our earth-friendly automatic renewal savings plan.

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