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43WR144-Pee Wee

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About 43WR144-Pee Wee

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    Pee-Wee Dxer
  • Birthday 11/09/1958

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    43WR144

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  1. good hook up yesterday pete,we had some well overdue good short distance props.

    73

    criag

    1. 43WR144-Pee Wee

      43WR144-Pee Wee

      Thanks Craig, it was great to get in contact again. I had a good 4+ hours of QLD only props, from Brissy up to Townsville and all in between. Started around 12.15pm & I closed the shack around 4.45pm.

      73s

      Pete.

  2. Thanks for the clue Pete

    kind regards

    Peter

  3. Antenna Design Calculators

    http://www.dxzone.com/catalog/Antennas/Antenna_Calculators/
  4. 43WR144 - 40 Years Of Radio

    until

    Just got a couple of weeks to go, then off to the 'Log Dump' for 4 days. Damn, I'm lookin' forward to it. Bring on the props.
  5. Where's all the DX gone?? Getting bad DX withdrawl symptons.

  6. 43WR144 - 40 Years Of Radio

    until

    Sorry, forgot to mention that the times are for Eastern Australian Daylight Time.
  7. Antenna Design Information & Software

    http://www.hamuniverse.com/antennas.html THE N4UJW ANTENNA PROJECTS DESIGN LAB THE BEST HAM RADIO OPERATORS HAVE GOOD ANTENNAS! You can't work them if you can't hear them! Design or build your antenna here! Antenna project contributions are from all over the world! HF, Vhf, Uhf antenna projects and lots more! Most are designed for ease of construction and expense! All projects have been offered by their authors and builders to share their antenna ideas and fun with all hams worldwide! Some of the antenna projects below will take you away from our site, so click your back button to return.
  8. Balun Construction & Calculators

    Some hints/tips on how to assemble nice COAX TRAPS ! http://www.qsl.net/on7eq/projects/coaxtraps.htm Before we start to assemble our traps, here some general info as introduction : Coax traps are cheap, easy to assemble in a reproducible manner, very rugged, perfect for portable or permanent operation, on dipoles, inverted-V's etc. If made with RG-58 C/U coax, can handle easily up to 500w PEP (750w max) .... or 1.000w PEP (1.5 kW max if carefully constructed) if made from RG-400 with TEFLON dielectric, which withstands heat very well. Coax traps do not exhibit a very high Q-factor - W8NX Al Buxton did some valuable measurements at different frequencies and comparisons for 2 types coax cables - see below. So they are definitelymore 'lossy' than air wound coils with high quality capacitors, but: High-Q coils are not suitable for high power operation: due to the high Q, very high voltages will be produced, with the risk of arcing, and the need for special capacitors (able to withstand high voltages and currents). In fact, if you intend to operate with high power (> 200w), do not aim for a high-Q trap ! A dual-band dipole with the 'best traps of the world' has about 0,3 dB total loss due to traps, this on both bands (so either in pass-through or blocking mode, loss seems quite the same) Same dipole antenna with coax traps would have about 0,6 dB total loss - the double, but a negligible difference on the S-meter of your DX correspondent! The exact resonance frequency of the trap is important to define by construction. If you operate the trap at it's effective resonance frequency, you will have more losses, about 1,6 dB total loss for same dipole antenna. Again, this is not a dramatic figure thinking of our S-meter, but will definitely cause problems at high power, because all losses are dissipated as heat in the traps: at 500 W 0,6 dB = 37w in each trap, but 1,6 dB = 110 W (note : the undersigned has tested this and melted a trap under these conditions HI). So NEVER adjust your trap on a frequency in the middle of the band it was designed for ! I tested my traps with 500w continuous power during 10 minutes, they get 'hand-warm', but do not melt any more ... By mistuning slightly the trap, you have no significant degradation of antenna performance or more critical tuning (narrower bandwidth or so ...). Coax traps have the effect of shortening the antenna length of all subsequent portions of the antenna, therefore narrowing the bandwidth of these. Should this be a problem, it can be compensated easily by adding 'capacity hats' at the end of these sections, even consisting of 2 small wires of 20 cm mounted in 'T'. If you are using high power (500w or more), do not use any hardware which is subject to magnetic fields (like zinc anodized iron), but use metal which is A-magnetic, like stainless steel, brass or copper. This because the trap will cause a very intense magnetic field while resonating, and induce stray currents in surrounding (lossy) magnetic metals, enough to heat them up to such extent that they will melt through the PVC tube. Pee Wee Edit - much more info on website for baluns for different bands.
  9. Free Yagi Antenna Designs for Ham Radio

    Gamma Match The Gamma match is the most used matching device used for yagi beams. What it does is: A Yagi almost never has an impedance of 50 ohms. In other chapters i told that Gain, bandwith, F/B etc. all relate to eachother these figures are never all high at one point. A well designed yagi has for that reson an impedance around 20..25 ohms. A Gamma-match can match impedance below 50 ohms right up to that 50 ohms wich your tranceiver wants to see. The thickness of the rod should be around 1/2 part of the radiating element, The lenght in the order of 0.05 wavelenght long. The desgribed Gamma-match is used for 11 meter Yagi's with an aluminim element thickness around 25mm !!!!!!!! i am however convident that with slight adjustments it will work for other diameters. For the dimensions I took the outside diamter of the radiating element (F) in the order of 2,5 CM. F is an aluminum plate and should be about 0,5 cm thick and wide enough to hold a N-connector female or the equivelent PL version. Preferbly in an L version so you can attach it to one of the U-bolts holding the radiating element to the boom. The hart of the connector should be 10 cm from the hart of the radiating element A the N- connector female or the PL version !!! is between the two aluminium tubes B and C must be NON-electrical guiding material for example: the “plastic” used in coax-cable. The length of it must be a bit longer then the lenght given “G” !!! C The long aluminum tube about 1,3 cm thick and 70 cm long. D An aluminium plate drilled with three holes 1) the driving element 2) the tube D 3) on top a screw to hold it in place. The holes should be from center to center 10 cm seperated E the radiating element also called driven element. B Aluminum tube with a lenght of 13,5 CM diameter 1,8 CM (C and D goes into it) By adjusting the aluminum plate left or right, you should be able to get a low SWR. This Gamma-match can handle upto a couple KW’s.
  10. CB Antenna Tuning Instructions

    So, you've wrestled your CB radio into the dashboard and you’ve got your antenna mounted on a space with decent ground plane. Everything is connected and ready to go, right? Wrong. It’s vital that you tune your antenna before using your new CB radio. If you’re not familiar with the concept behind SWR or the necessity of adjusting it, let us give you fair warning: improper tuning of your antenna has the potential to cause much worse than a weak broadcast signal – it can end the life of your radio before you get a chance to enjoy it. The good news is that this article will walk you through the process of properly tuning your antenna (a.k.a., adjusting the SWR). It’s not a terribly difficult process, as long as you can follow directions and are patient enough for a little trial-and-error. Assuming that everything else in your system is properly installed, the only additional equipment necessary is a short length of coaxial cable (known as a jumper lead), an SWR meter, and something on which to record your readings. The first thing you need to do is find a suitable location to park your vehicle. There should be no obstructions, such as trees or buildings, within 10 to 15 meters of your antenna. Neither you nor your buddies should be hanging out around the car, either. Make sure that you’re inside with the doors and windows closed to ensure an accurate reading. The next step is to hook up the SWR meter. First, disconnect the coaxial cable from the back of the radio. Reconnect this end of the cable, which is going to the antenna, to the SWR meter in the connector marked “antenna” or “ANT.” Next, use the jumper lead to connect your radio and the SWR meter through the connection marked “transmitter” or “XMIT.” Now you are ready to measure the SWR on a few different channels. Remember, throughout this process it's important to keep the microphone the same distance from the meter for each test. Set the switch on the SWR meter to “FWD.” Turn the radio to channel 1. Key the microphone (depress the button and hold it). Turn the knob on the SWR meter labeled “SET” or “ADJUST” until the needle reaches the setting position at the end of its range. While still keying the microphone, flip the switch on the SWR meter to the “REF” or “SWR” position. Quickly record the reading given by your SWR meter and release the transmit key on your microphone. You are now going to repeat this process for channel 40. Follow steps 4 through 9. The objective behind tuning your antenna is to make these two readings as close as possible. Getting down to a 1.5:1 ratio or below makes for a passable broadcast signal. There are two basic points to understand before adjusting the length of your antenna: If the SWR on channel 40 is higher than that on channel 1, your antenna is too long. If the SWR on channel 1 is higher than that on channel 40, your antenna is too short. If your antenna is too long, it is necessary to reduce its physical length. There are several methods for shortening an antenna which vary by manufacturer. Consult your owner’s manual for detailed instructions on how to shorten your antenna. While many antennas feature a “tunable tip” that uses a small screw, some antennas may need to be cut to be shortened. Do so in 1/4" increments and then get new readings to determine your progress. If your antenna is too short, it is necessary to increase its physical length. Most instances where the antenna length is too short are caused by a lack of ground plane. In modern antennas, there's usually a method for adding length built in to the antenna. Other options, such as adding a spring, are also legitimate. Dual antenna installations: If you're tuning dual antennas, you'll want to adjust both antennas the same amount each time. As a starting point, it's best to put the tuning screw either all the way in or out, so each antenna is the same length. Then, based on your SWR readings, length or shorten BOTH antennas the same amount each time. Re-measure SWR and continue to re-adjust as with a single antenna, making sure to make incremental changes that are as close as possible to both antennas. Readings on both channels that are less than 2.0 mean that your radio is safe to operate, but transmission may not be optimal. If readings on these channels are in the red zone on your SWR meter or above 3.0, do not attempt to use your radio. This problem must be remedied before attempting to use your radio. Let’s review the most common problems that cause your SWR meter to register danger on all channels: poor grounds, a short in the coaxial connectors, or an improperly installed mounting stud. A large percentage of high SWR readings are caused by ground plane problems. It's a good idea to run ground straps from the body of your vehicle to the frame, doors, trunk -- everything except your dog. Running the shortest possible ground strap from the antenna to the chassis or your vehicle is generally a good solution for ground plane problems. Simply put, grounding everything that can be ground together will improve ground plane. It is essential that your mount is properly grounded. Most improperly grounded mounts are connected to places on your vehicle that themselves are not thoroughly grounded. Any part of your vehicle that has a plastic or nylon bushing separating it from the chassis is probably not grounded. Also, chassis paint can often prevent a mount from being properly grounded. You can check the grounding of suspect parts with a voltage meter. A short in the coaxial connectors may also be the culprit behind abnormally high SWR readings. Issues with the coaxial cables are often identifiable by eye, such as severe bends or pinches. You should know that it's essential to use 50-ohm coax for single antennas and 75-ohm for dual. When all else fails, sometimes it's necessary to replace the coax cable because there's a failure inside the line. By following the steps outlined in this article, you should be able to successfully tune your antenna for optimal performance and transmission.
  11. Antenna Types - Hybrid

    Directional Antennas An antenna is known as "directional" if its pattern strongly favors a certain direction. A directional works by concentrating the signal in one direction at the expense of other directions. Also known as the "Beam" antenna. Read the section on Yagi antennas if you are not familiar with directional ("beam") antennas and how they work. Also, you must read the section on Cubical Quads because hybrids are simply a combination of the two. Hybrids Yagi's and Quads are the two main types of beam antennas. There is one other known as the "Log Periodic". It is used mainly for TV antennas because its bandwidth is really wide. It its not a really high gain antenna. The next important category of beams is the hybrid. This simple means combining parts of the Yagi and Quad on the same antenna (some people call them Quagis (QUAd-yAGIS). Lets jump right to a figure so we can see what I mean, check out figure 1. This should look familiar to most CBers, it is the holy Moonraker 4. The Moonraker 4 uses a quad element for the reflector element. They could have actually made the directors quad elements too. I suspect they chose the quad element for the reflector because of the advantages I listed above about the quad parasitic elements (that they respond to all polarization's, so it should better block all signal polarization's that come in from the rear of the antenna, as opposed to just blocking horizontal and vertical). There is no magic to combining the quad and yagi on one boom that makes this antenna have higher gain than just a plain yagi or quad. The gain of the antenna depends on whether the driven element is a dipole or quad loop, where if its a quad loop, it will have 2db more gain than the dipole driven antenna. Figure 1 - The Moonraker 4 (and Shooting Star) is a hybrid consisting of yagi (dipole) driven and director elements with a quad type reflector element. Benefits are discussed in the text. Looking at figure 1, we can classify each element like this. The reflector element is a Quad loop. The driven elements are Yagi type (crossed dipoles), as are the two directors elements. You could actually make any combination of element types that you wanted. Important Note For Moonraker,Shooting Star, PDL2 Etc. Users I was kicking around the idea where to put this note for Moonraker users. One of the main things I wanted to accomplish with this web page was dispel common misconception. One of the biggest I see involves the Moonraker 4. Most operators think they can hop up their (hot-rod if you will) antennas like you can a Chevy Camaro (an American muscle car). Take my advice, you can not hop up a Moonraker (or most antennas) by by adding stuff on it (except for adding more director elements on beams). Most people come up with ideas to make money! The absolute worst mistake you can make on your Moonraker is adding the "rejection" kit that Copper Electronics' (and others) sell. Figure 2 shows the Moonraker 4 with the "rejection" wire in place. Figure 2 - "Rejection" Kit. This kit adds extra wires to the reflector element. Read text for explanation why this is VERY BAD. If you have been reading along (I hope you have) you already have a good idea how a beam antenna works. We said in the "Yagi" section that beams operate by utilizing different element lengths and spacings to achieve a directional effect. Also, you should remember that Reflector elements are 5% longer (which in the case of the quad - each side is 2 1/2%) than the driven element. The director elements are 5 % shorter than the driven element. What have you just done by adding those smaller wires? You have made that element into a DIRECTOR element (because they are shorter than the driven element)! Talk about confusion for the beam, you have a reflector and a director mounted on the same element. Friends, this will result in a lower gain, F/S and F/B ratio. Some people swear by these things...unfornately it is a rip-off. Any Antenna Engineer could tell you this. If you have it on your beam, I seriously suggest you remove it. It's snake oil!
  12. Antenna Types - Cubical Quad

    Directional Antennas An antenna is known as "directional" if its pattern strongly favors a certain direction. A directional works by concentrating the signal in one direction at the expense of other directions. Also known as the "Beam" antenna. Read the section on Yagi antennas if you are not familiar with directional ("beam") antennas and how they work. Since the Cubical Quad works off the same principles, you must first understand the Yagi antenna. The Cubical Quad The next type of beam is the Cubical Quad, my favorite. This is the type of beam that I use. There really is not any new principles involved here, the quad works on the same principles as the Yagi. However, instead of using the dipole antenna for the driver, director and reflector elements, we are going to use the quad loop antenna. The quad loop was invented by an amateur radio operator by the name of Clarence Moore. He was working for a broadcast station in Quito, Ecuador. It is called a quad loop because most people configure it as a square (quad = 4, 4 sides to a square). The quad loop measures exactly 1/4 of a wavelength on each side. As you can see, this antenna actually is a Full (1) wavelength antenna as compared to the 1/2 Wavelength driven element of the Yagi. The loop is usually made from a 36 foot piece of copper wire. The Quad loop alone has 2 db of gain over the dipole antenna. So, using this as the driver element our antenna already has at least 2 more db gain over a yagi antenna with the same number of elements. Take a look at the quad loop in figure 1. As you can see, each side of the loop is 1/4 wavelength. The total distance around the loop then equals 1 full wavelength or 36 feet. Figure 2 show the quad loop with a common supporting structure. The arms that hold the wire (usually #12 or #14 copper wire) are made from fiberglass, wood or bamboo. Really, anything that is an insulator can be used. Keep in mind, it must be strong. Wire is light, but when the wind starts hitting it or ice builds up on the wire, weak supports will break. Figure 1 - The 1 Wavelength quad loop. Shown without supporting structure. Another point I would like to point out about the quad loop is what it is really made up of. In figure 2 side A and side B can be thought of together as a dipole antenna. You can see if you remove side C and side D you would just have a dipole who's legs (each 1/4 arm) slant up at an angle. Then you can see if we add sides C and D, and join them all together, we really have just hooked two dipoles together! This is equivalent to co-phasing two dipoles. Read the "Co-Phasing" section for more information about what we mean. This arrangement doesn't quite give us the 3db we would expect, but it does up our gain over 1 dipole by 1.8db. Figure 2 - The quad loop shown with a common way to physically support the wire. Figure 3 shows a drawing to scale that compares the sizes of the quad loop element and the dipole. This is just to give you an idea of size requirements. Figure 4 compares the radiation pattern of the dipole antenna to the quad. When you are using the dipole, you can just feed the antenna in the same place (the middle) and rotate the antenna to achieve a different polarization. But since the quad loop is a loop, rotating it would not do you much good. To obtain a certain polarization with a quad it matters where you attach the coax. Figure 5 shows the feedpoints to obtain a certain polarization. Each of these feedpoints have the same impedance. Figure 3 - Size comparison of the quad loop and dipole. Bother antennas are on the same plane (the dipole is actually lying on the quad). Figure 4 - You can see the increased gain of the quad loop compared to the dipole in this polar plot. Figure 5 - Feed points to obtain different polarization's. Unlike the dipole that you can just rotate to obtain horizontal or vertical polarization, you have to move the feedpoint of the quad. The shield of the coax goes to one side of the wire and the center conductor goes to the other. See figure 1 for a close up of how the coax is suppose to attach to the loop. One of the biggest advantages to using the quad loop that it is impervious to rain/sleet/snow/sand static noise. Have you ever had rain static pound your receiver when a rain storm was rolling in? Things such as sand and rain carry an electrical charge that cause a lot of noise on verticals and yagi beams. Surprisingly, the closed loop of the quad does not respond (pick up) to this type of noise. As a matter of fact, in Operation Desert Storm, Yagi beams where unusable because of the sand storms that cause huge static noise problems! The U.S.troops had to use quad antennas to communicate during sand storms. Lets take a look at some 4 element cubical quads. Figure 6 shows a 4 element cubical quad fed for horizontal polarization. The elements create a beam pattern the same way a yagi does (see the "yagi" section). The parasitic elements are closed loops, meaning they are not electrically broke at any point around. All the wire loops must be insulated from the boom. Fiberglass is usually used on durable quads. The reflector element is typically 10 % longer (the distance around the wire loop) than the driven element and the director is typically 10 % shorted than the driven element. Figure 6 - 4 element cubical quad shown fed for horizontal polarization. Another huge advantage of the the quad parasitic element is the fact that it is not polarization sensitive. By this we mean, quad parasitic elements (reflector and director(s)) respond to all types of signal polarization equally well. Compared to the yagi elements, where the element is either in the vertical plane (straight up and down) or the horizontal plane (side to side) . These yagi elements only respond to signals that have the same polarization as their self. All other signals (that do not match their polarization) are reduced by 20db (I mentioned this under the "Antenna Basics" section)! The quads parasitic elements are a continuous (closed) wire loop, that respond equally well to all polarization's. This means they direct or reflect horizontally polarized waves, vertically polarized waves and everything in between (they direct/reflect all signals equally well regardless of its polarization). Keep in mind the driven element is broken where the feedline connects, which means the driven elements IS polarization aware. What this mean is, during DX contacts when signals arrive at your antenna with its polarization changing constantly (this is one reason signals fade and pop back up suddenly), on the quad this effect is reduced because quad parasitic elements still pick up these changing (flip-flopping polarization) signals. Notice I said parasitic elements, the driven element still reduces signal strength by 20db (if the signal doesn't match its polarization)..but the signal is stronger than it would be on the yagi because the yagi parasitic elements would have also reduced the signal by 20db before re-radiating it (for the driven element to then pick up). If you are confused about polarization "flip-flopping" or changing during DX contacts, you need to do some further reading, check out my section of recommended books. You must keep in mind signals bounce off of objects (water towers, radio tower, water, the ionosphere) and their polarization gets rotated somewhere in between horizontal and vertical most of the time. I can not cover every aspect of how signals travel (called "propagation")...I would be writing for ever! Under the "Angle of Radiation" section, you get get an idea of how "skip" (DX) signals travel. Since our antennas are generally set up to receive only one polarization at a time (usually horizontal or vertical), polarization changes due to reflections can cause signal fade (signal strength waving up and down). This fading is reduced on quad elements! Enough said. Lets look at the 4 element cubical quad fed for vertical polarization. See figure 7. Nothing new to really say, but you can see where the coax attaches for vertical polarization. Figure 7 - 4 element cubical quad fed for vertical polarization. You can see it is not as easy to drop the coax straight off the antenna after it connects like you can if you feed it for horizontal polarization (like in figure 6). With these great features comes some disadvantages! First off, remember in antenna basics when I talked about bandwidth and said that it is mainly dependent on the antennas elements outside diameter? Well, as you can see from the pictures, we usually make quads from #12 gauge wire. This is small compared to the tubing you would normally use for a yagi, and as a result the bandwidth of the quad is narrower than the yagi. Generally you can just cover the CB band with a 4 element quad with a 2:1 SWR. If you are the type of operator that is all over the place (even outside the CB band)...this antenna will put a limit on your frequency range! More elements narrows bandwidth on any antenna type (quad or yagi), so a 2 element quad has better bandwidth than the 4 element quad. Secondly, We are familiar that Yagi's can be cross mounted (see figure 8 under the "Yagi" section), one for vertical and one for horizontal on the same boom. Now think, two quad wires, its not so easy, check out figure 8 to see what I am talking about. It is possible to mount to wires side by side, but this is slightly more complicated. A company by the name of Signal Engineering is making quad antennas that deal with this problem effectively. Figure 8 - Dual polarity quad. The parasitic element wires are left off for clarity. You can see the driven element wires must be side-by-side (a few inches). When one loop is being used, the other must be an open circuit for the antenna to function properly. Most coax switch boxes do not work like this, so if you are going to try this arrangement, make sure you keep that in mind. Maco has a few antennas that they call "quads". The V-Quad is a true quad. It actually uses a full wavelength loop for the driven element. If you shape the quads elements like a triangle (three sides instead of four) it is called a "Delta Loop". It uses the exact same principles as the quad and has similar performance. The other antennas they call a quad is the "Y-Quad"...this is actually a hybrid - see the "Hybrid" section. To sum up the Y-Quad, it really is a Yagi antenna (because its driven element is a dipole, not a full wavelength quad loop...I am guessing the "Y" stands for Yagi). JoGunn's V-Series are also the delta loop variety (they falsely state that they are "circular polarized"). New tests show that loop in a quad (4 sides) configuration yields slightly more gain than the delta configuration. The best configuration would be a loop arranged in a a perfect circle (instead of a 4 sided quad, or three sided delta), but that arrangement would be difficult and expensive, so the four sided quad is the closest practical way to form a loop at 27 MHz. Figure 8 - A commercial 4 element quad. As you can see, you can mount this antenna like an X also. You can still see the feedline hooks to the same area on the loop regardless of how you mount the spreader arms. A nice DX antenna! Here are some gain figures for some Cubical quads. Note: This table is typical performance of Quad's with the stated number of elements. Typically, the gain will be within 2 dB of the indicated gain. However, Front-to-back ratio can vary greatly (as much as 25 dB) from the indicated F/B. F/B is much more sensitive to adjustments to the element length and spacing. As you can see, the Cubical Quad antenna has the same gain as a yagi with one more element..because the driven element of the quad has more gain than the Yagi's driven element (2db more). Number of Elements Gain (Over Dipole) Front-to-Back Ratio (F/B Ratio) Comment 2 5 dB 12 dB Reflector element only 2 7 dB Zero Director element only 3 10 dB 15 dB 4 12 dB 25 dB 5 12.1 dB 30 dB 6 12.2 dB 30 dB 7 12.3 dB 32 dB 8 12.4 dB 32 dB
  13. Antenna Types - Yagi

    Directional Antennas An antenna is known as "directional" if its pattern strongly favors a certain direction. A directional works by concentrating the signal in one direction at the expense of other directions. It is also commonly referred to as the "Beam" antenna. I am going to start with the earliest type of beam discovered, the "Yagi" Beam. This type of beam was discover by Professor Uda but the english translation was done by Hidetsuga Yagi. This design goes back to the 1920s! One would think today there would be better designs. I believe there is, and that's why I am so interested in antennas! The Yagi Beam The yagi is very simple. The basic yagi consists of three elements, as shown in figure 1. The middle element is an antenna you are already familiar with, the simple 1/2 wave dipole antenna. This element is generically called the "driven element". This is because this is the only element that is connected directly to the radio, it actually drives the whole antenna. The other two outer elements are generically called parasitic elements. One is called the Reflector (some CBers call it the "back door") and the other one is called the director element. These elements get their name from the job they do. The reflector reflects RF energy, the director directs RF energy. There is no magic circuit located inside the elements, they are simply straight rods! The reflector element is typically 5 % longer than the driven element and the director is typically 5 % shorted than the driven element. How it works. See figure 1. As signal A comes in it strikes all three elements hence generates a current on each element. Remember we said that current on a wire causes it to radiate? Even though the current is very low, this current induced on the antenna actually re-radiates off the antenna again! Ok, back to the action, the signals are re-radiated by the director and reflector and arrive at the driven element in-phase with one another (the two re-radiated signals and the original signal). This basically means, the signals reinforce each other...and make the incoming signal much stronger coming from direction A. When the signal comes from direction B and C, the same thing happens, except the signals arrive at the driven element out-of-phase with one another which simply means they cancel each other out, significantly reducing signals from direction B and C. This very useful effect (signals arriving in-phase/out-of-phase) is caused by the special spacing and length of the director and reflector element in relation to the driven element. We can even add more directors elements to increase the gain. Adding more reflector elements has NO more effect on the gain of the antenna, however. Typically most 2 element Yagi's use just the reflector element. If you would use just the director on your two element, you would have more forward gain, but you would also not have any rejection of signals coming from direction B, that is why its F/B or Front to Back ratio is zero. The Front to back is the ratio of gain of the forward direction as compared to the reverse direction. So, if we were receiving signal A, and we turned our beam around 180 degrees, how much would the signal be reduced? This ratio is known as Front to Back ratio, and is as important as gain to some. If you have a lot of CB neighbors, getting a beam that has a good F/B will reduce interference from them if you point your beam in opposite directions from them. There is another term, Front-to-Side ratio that works the same way as as the F/B...except it means when you turn you beam to the side (90 degrees away) from the signal how much is it reduce. Typically, Front-to-Side ratios are even higher than the F/B ratio. You can see the deep notches in the radiation pattern in figure 2 that indicate this is where the greatest rejection of signals occurs. It may not be directly at the side of the beam, it is mainly dependent on antenna design (spacing, length). Ok then, we can have variations of this Yagi beam. We can actually still have a beam even if you take off the reflector element or director element and just have a 2 element beam. This beam would have less gain than the three element, but would still be quite directional. It would certainly have more gain than a 5/8 Vertical antenna. As you can see from the table, it gets difficult to get more gain after 4 elements. Not only that the antenna gets huge, the antenna bandwidth goes down, and it is hard to tune! As a quick note, its better to "stack" or "co-phase" beams rather than go with a large number of elements. For instance, its better to go with co-phasing two 4 elements Yagi's rather than using an 8 element beam. Read section the section "Performance Tips", "Co-Phasing". I have seen some monstrous gain figures for the Maco line of beam antennas, especially their 6 and 8 element beams. In my opinion, these gain figures are really exaggerated! Be cautious, and read on. Yagis have a special matching device where the coax connects that looks a small "jumper rod" that connects a few inches out on the driven element. This matching device is called a "Gamma Rod" or "Gamma Match". It is a device that simplifies adjusting the antenna. The gamma match is a type of matching transformer used to match the feedpoint impedance of the antenna (which rarely is 50 Ohm) to the 50 Ohm coax. This is especially necessary on beams with more elements (more than 4) because the impedance at the feedpoint is naturally low (around 20 Ohms). Here is a table for gain figures for some yagi beams. Note: This table is typical performance of Yagi's with the stated number of elements. Typically, the gain will be within 2 dB of the indicated gain. However, Front-to-back ratio can vary greatly (as much as 25 dB) from the indicated F/B. F/B is much more sensitive to adjustments to the element length and spacing. - Number of Elements Gain (Over Dipole) Front-to-Back Ratio (F/B Ratio) Comment 2 5 dB 14 dB Reflector element only 2 7 dB Zero Director element only 3 10 dB 15 dB 4 12 dB 25 dB 5 12.1 dB 26 dB 6 12.2 dB 30 dB 7 12.3 dB 22 dB 8 12.4 dB 32 dB
  14. Antenna Types - Verticals

    Omnidirectional Antennas "Omnidirectional" is generic term for an antenna that radiates equally well in all directions. There are several antennas that are considered omnidirectional. 1/2 Wavelength Vertical Most folks lump all vertical omni-directional antennas into the same category and call them "Ground Planes". A ground plane antenna is actually an antenna similar to the vertical dipole.It's important to understand the difference - especially if you're looking to invest in a certain type. Whether you're after antennas or Mobile Broadband deals, misinterpretations usually end badly. Shown in figure 1, you can see the hollow tubing is now instead brought out at a 45 degree angle (and split into 3 sections) out from where it is on the vertical dipole. These rods are usually called "radials". This type of antenna is really not a very high gain antenna. A Ground Plane Antenna. A much better type of antenna that has more gain is the 1/2 wavelength vertical. We know that the impedance of the 1/2 dipole is 70 Ohms when we attach the coax in the middle, but what if we were to attach our coax directly to the end? The impedance at this point is high, very high, so we must make a matching device to match the antennas impedance to the 50 Ohm coax. What would happen if we did not use this matching device? Well if you have been reading along, you would know that this would result in a very very high SWR. There are several commercial 1/2 vertical antennas available, the two that I can think of most easily is the Solarcon A99 and the Shakespeare Big Stick. They provide slightly higher gain than the vertical dipole antenna.The bandwidth of these antennas are good, they can easily span all the CB channels and more with a low SWR. 5/8 Wavelength Vertical A higher gain antenna than the 1/2 vertical antenna is the 5/8 vertical antenna. As we can figure from the 5/8 wavelength rating the antenna is about 22 feet long (5/8 of 36 feet). This antenna is similar to the 1/2, it needs a matching device at the base to match it to the coax, it cannot be attached directly. This antenna has about 1.2 db gain over the dipole antenna and 1/2 vertical. Figure 2 shows both a 1/2 Wave vertical and a 5/8 Wave vertical antenna. It achieves this extra gain by concentrating its pattern out more at right angles from the antenna instead of wasting signal at high angles. Even if you do not know the manufacture or anything about the antenna you are looking at, you can tell if the antenna is a 1/2 or 5/8 wave by its length, again 1/2 is about 18 feet and 5/8 wave is about 22 feet (at CB frequencies).
  15. Coax cable info chart

    Coax Basics Most CB and HAM radio operators use coaxial (coax) cable to feed their antenna. Another name for the cable you use to hook your radio to your antenna is "feed line". Feed line is a generic term for all types of cable including coax. Coax has been around for a long time and became very popular with Radio Amateurs after World War II, when army surplus stores were filled with miles of coax cable. This is one of them main reasons why we use coax today, it became such a trend of sorts. Coax cable consists of two concentric wires, as shown in figure 1. It is important to note that coax cable is unbalanced, no current flows on the outside shield of the cable. This is in comparison other types of feed line that are balanced such as twin-lead, which you may be familiar with from your old TV antenna. Coax has several advantages. You do not have to be careful what type of metal objects you run your coax over like you do twin-lead. It is even possible to bury some types of Coax, if the outer jacket is suitable. Its major disadvantage is that some types of coax have high loss at CB frequencies and get even worse as SWR increases. Usually companies rate their coax in decibels (db) of attenuation per 100 foot lengths. So at a given frequency, if you are using exactly a 100 foot length, you would incur a loss of however many db's the manufacture states. Here is a chart of the losses for the most common types of coax used for CB service: (coax table at bottom of page) As you can see, some coax has high loss. Loss is RF energy that the coax turns into heat or "leaks" instead of passing on to the antenna (or to the receiver from the antenna). The lower the db of attenuation the better the cable is. Think of cable loss as negative gain! The higher the attenuation, the less efficient our antenna system is. Loss is primary dependent on the coax's shield and dielectric. The shield is the outer wire braid that surrounds the inside of the cable. A thick, tight braid results in less loss. Also, the dielectric (usually white), the plastic type material that separates the inside wire from the outside braid has an effect on cable loss. Cables that use foam dielectric, that is where the insulation is mixed with an inert gas, have very low loss. It is important to use quality low loss cable! As you can see from the chart, the losses can be quite high. You must make perfect connections at the coax ends or, even higher losses will occur. It is also important to note that old coax has high loss also. The cables properties break down over time, resulting in very inefficient cable. If you are still using that coax from the 1970s, its time to replace it! New coax is manufactured better than the coax was in the 1970s also, so this newer cable should last a lot longer. Two special cables are listed. One is Belden 9913. Belden is the name of the company that makes the cable and they call it "9913". It is a special coax that has two outside shields! The first is a foil material that is on the outside of the dielectric, then over that is the regular copper braid. As a result, the cable is very efficient (low loss) and also STIFF (though they now make a 9913F that is supposed to be flexible)! With low loss comes cost, this cable is expensive. The other special cable listed is hardline. This cable has a solid aluminum cover on the outside for the shield. It is thick, and very efficient---stiff (can't really bend it) and costly. It is used by cable TV companies. Since they run miles and miles of cable, they need low loss cable. Cable loss is still so bad, they still need to have amplifiers along the cables every few miles or so. You can see hardline on telephone poles if your area has cable. It is usually a silver cable about 3/4 inches in diameter. I said before that loss becomes even worse as SWR increases. These attenuation numbers in the chart are assuming a perfect 1:1 match. If your SWR is over 3:1, cable loss is horrendous no matter what kind of coax it is! Coax Impedance Again, the term impedance in "Coax Impedance" has different meaning...you can not measure it with your trusty Ohm meter. It is determined by the spacing (ratio) of the inner wire and outer braid. In CB service, the two impedance's mainly used are 50 Ohm and 75 Ohms. Velocity Factor Wow, doesn't that sound like a serious high tech term! You can be king nerd of your CB group if you know things like "velocity factor". Ok, ok we said before that waves travel different speed through different materials, if you missed it, its under the "1/2 Wavelength Dipole" Section of "Antenna Basics". Velocity factor is simply a number we use to determine how fast or slow a wave travels through coax. Different coax models have different velocity factors. Lets look at some numbers. Say we want to make a coax that is exactly 1/2 wavelength long (this means when the wave travels through the coax, it makes exactly 1/2 of a cycle while it travels from one end of the coax to the other). If this sounds confusing, better check out the "Antenna Basics" section. We will take our formula for figuring out 1 wavelength and modify it. One Wavelength in coax, in feet = 984 * (Velocity Factor) / Frequency in Megahertz (MHz) Ok, say we want a 1/2 wavelength RG-8/U Foam on channel 40 (27.405) 984 is for a 1 wavelength, so we want a 1/2 wavelength or half of 984, 984 / 2 = 492. Get the Velocity Factor from the table above for RG-8/U Foam, which is .80. Put these numbers into the formula: 1/2 Wavelength, RG-8UFoam, Ch.40 = (492 * .80) / 27.405 1/2 Wavelength, RG-8UFoam, Ch.40 = (393.6) / 27.405 1/2 Wavelength, RG-8UFoam, Ch.40 = 14.362343 feet The length of coax is 14 feet 4 inches! Practice and see if you can get lengths for other coax types with different velocity factors. This will become important if you ever "stack" or co-phase antennas. You must cut certain length coax lines for co-phased antennas to work! Assemble Your Coax Correctly Bad connections cause loss. If you are going to solder connectors on the ends of your coax, be sure to do it right. You must have the right tools. Most Cbers and Ham radio operators think that they can solder on connectors to coax with their 25 Watt pencil tip soldering iron. You can't. You should use a high wattage iron, preferably over 100 watts. You must heat the connector up quick, so you do not damage the coax and connector, and the only way to do this is with a high wattage soldering iron. I am not going to go into detail of soldering on PL-259 connectors to coax but let you look at figure 2. Trim the coax carefully, do not nick the inside when cutting. And I have one big tip you do not want to forget, before soldering the PL-259 plug to the coax, do not forget to slide the PL-259 collar over the coax! I have done this so many times! Soon as you start working just slide that collar on, push it back far down the coax out of the way so it does not slide back off..you will thank me for this! If you solder the connector on without sliding the collar on, you will have to start over (the collar will not fit over the connector once it is soldered on)! After you are done (or to check coax you suspect is shorted or bad) take an Ohm meter and check you coax. When you are done, be sure to waterproof the ends of the cable. Wrap it in quality electrical tape (I like 3M electrical tape) or use a special wrap you can get at radio shack. Water will easily find its way into coax ends. Remember I said old coax has high loss? This is probably the number one way coax is ruined. Why does my coax length affect the SWR of my antenna? How many of you change the length of your coax to tune your antenna? One of my good friends said to me, "I think changing the length of the coax is the same as moving the gamma rod adjustment on my Moonraker 4". Sorry to say, this is not true. As most people will find, varying the length of coax to the antenna will vary the SWR that the SWR meter is reporting. Actually, SWR should remain relatively constant no matter how long the coax is or where it is placed on the line (if its 5 feet down the coax from the radio or 50 feet down the coax from the radio). In most cases, the cause of inconsistant SWR meter readings is from poor SWR meter design or component aging / failure. For the SWR meter to read consistant SWR readings on the coax, the meter has to have an impedance itself of exactly 50 Ohms. Any deviation of the SWR meter's self impedance (from 50 Ohms) from poor design or component aging / error / failure will cause slightly inconsistant SWR readings when the SWR meters position on the coax or length of the coax is varied. In practice, generally you will find varying the coax length seemingly effects the SWR reading. Most SWR meters (built into radio and external type meters) and impedance "humps" in coax lines and connectors will cause minor variations in SWR as jumpers and coax length are varied. In reality, the mismatch at the antenna's feedpoint / coax junction is unchanged. Therefore - the actual SWR is unchanged. Another reason SWR could vary is from the situation where the coax is acting as part of the antenna. Not a favorable or normal situation. The signal is traveling back down the outside of the of the coax braid (note power should only be traveling on the inside on the coax braid). Therefore, the coax is part of antenna system and changing the coax length will change the SWR. This situation is more likely to occur in mobile installations. You can try to eliminate this situation (called "Common mode currents") by winding an "RF Choke". Wind about 6ft of RG-213 or RG-8 into a coil (6 to 8 turns). For RG-58 use 4ft with 6 to 8 turns. Wind the coax up, placing each turn right next to one another. Use electrical tape to secure turns together. You should place these as close to the antenna as possible. Right at the antenna coax connection point being optimum. Most times, you can verify that you have common mode currents flowing back down the coax by grabbing hold of the coax while transmitting and moving the coax around. You can watch the SWR waver by moving the coax while transmitting (don't speak into mic!). You have to do this with all the doors closed from inside the vehicle. SWR should waver, if you notice that SWR jumps rapidily between two values, you might have a intermitant (bad) connection in the connectors (PL-259s) on the coax. In most cases of "common mode currents", just grabbing the coax will cause the SWR to change. The "RF choke" described above stops the signal from traveling back down the outside of the coax. The signal inside the coax is * u n a f f e c t e d * by the choke (contrary to what you may have heard about coiling up excess coax). Common mode current kills antenna efficieny. You could have a decent SWR and not realize half your signal is being broadcast into you car (result very poor antenna performance). If your linear amplifier causes serious problems with your car's computer, lights, etc....you may have common mode currents. If moving the coax around the vehicle results in SWR change, this is a good indicator you have common mode currents flowing back down the coax line. This doesn't happen often with base station antennas. Most base antennas have some type of device that will decouple the antenna from the feedline (gamma match, balun, etc.). Make sure you run your feedling (coax) straight down from the antenna, taking care not to run close to antenna to prevent "common mode" currents which could still occur if coax is oriented in a way to pick up strong antenna signal. Coax Length Issues Simplified Question: What is the "correct" length of coax? Answer: The shortest length that makes it from the radio to the antenna. Question: Are there any exceptions to the above rule? Answer: 75 Ohm harnesses for Co-phasing is the only exception. Question: Why do most mobile antenna makers recommend 18 feet of coax? Answer: You got me, they claim you should use 1/2 wavelength multiples of coax. 18 feet isn't even close to being a 1/2 wavelength in any 50 Ohm coax you will find. Check some commonly used coax using the above formulas. RG-58, the most commonly used mobile antenna coax length would have to be 12 feet to be a 1/2 wavelength. RG-8X would need to be 14 feet. Question: Ok, seriously nerd, when I trim my coax it changes my SWR. You can't tell me it's not good to lower my SWR from 1.5 to 1.2 by taking off a few extra feet of coax. Answer: Hey, I'm not a nerd! Go ahead, change your coax length. If you change coax length and it affects your SWR in minute amounts, everything is working fine. If your SWR was 2.5:1 and putting in a 4 foot jumper brought it down to 1.3:1, this large change indicates you have real problems...i.e. common mode currents (see above). Really, you should be changing the antennas length to alter SWR. NO special length of 50 ohm coax is going to fix or lower your SWR signficantly and/or boost performance. Period. Question: I notice when I change coax length, my "modulation" needle jumps more / harder / faster when I talk. I get more watts out of the radio (verified by a watt meter) with certain lengths of coax. Is there a certain length that will allow my radio to put out the most power? Answer: No, there isn't a magic certain length that will do this. Certain lengths of coax will allow your radio to "see" a load that it can couple with better which results in more power out of the radio / amp. Unfortunately, there isn't a good way to determine what length you need to allow the radio to put out the max wattage its capable of. I am only refering to newer solid state radios with transistors. Old tube radios usaually have devices built into them to tune the radios finals impedance to match that of the input end of the coax. If you want to accomplish the same effect with your solid state radio, pick up a device known as a "antenna tuner". The term antenna tuner is misleading because it doesn't actually tune the antenna - or take the place of tuning the antenna - it simply lets the radio couple to the antenna system with better efficiency. Other more appropriate names for the antenna tuner are the transmatch or feedline flattener. If your SWR is low (below 2:1), don't expect to notice a (performance) difference from using an antenna tuner. Question: Why do so many people recommend using 1/2 wave mutiples of coax? Will it really hurt me if I take the time to measure a 1/2 wavelengh multiple of coax? Answer: The idea of using 1/2 wavelength multiples of coax comes from the fact that the antennas feedpoint impedance is "mirrored" at the input of the coax when using the said length. Many operator make / made the assumption that was a good thing because it was just like having the antenna hooked right to the radio / SWR meter. If anything other than a 1/2 wavelength mutiple is used, the impedance the radio / SWR meter sees is the antennas feedpoint impedance transformed to some other value of impedance. So, if your antenna has a feedpoint impedance of 25 Ohms and you use a 1/2 wavelength wave length of coax, the radio will "see" 25 Ohms in the input end of the coax. If you were to use some other length, say a 1/4 wavelength of 50 Ohm coax, the radio would "see" an impedance of 100 Ohm. What consequences does this have? None. Whether the impedance is 25 Ohms or 100 Ohms, the SWR is STILL 2:1. No matter what the 50 ohm line length, the resultant SWR is still 2:1...at the antennas feedpoint, at the input end of the coax and at any and every point along the coax line. Many operators take half the truth of transmission line theory and make up their own rules. If you have been reading my page since its inception, you know I used to be "uneducated" when it came to transmission line theory. Sorry to admit I thought coax length was important. It was drilled into my head by somebody I respect(ed). This isn't the easiest part of CB to wade through. Hopefully I've covered this with enough detail to set everyone straight. Many beginner amateur radio operators and students have misceptions and make false extrapolations in tranmission line theory. There are many conditions that must be stated when simplifying things. I have made one assumption here. I have been assumming the coax loss is negligible. At CB frequencies this is a pretty safe assumption to make. Question: Ok then, why is the length of 75 Ohm coax line important? If coax length doesn't matter, why is 75 Ohm coax different? Answer: I've heard this a question more than once. The fact your radio has a 50 Ohm jack on it is the reason you use 50 Ohm coax. The antenna is designed to have a feedpoint impedance of 50 Ohms. When all the impedances match, maximum power is transfered from the radio, through the coax, out the antenna. Using coax with a (characteristic) impedance of 75 Ohms can potenially transform the antennas feedpoint into another value..another value such that the resultant SWR will vary with line length. This function is handy for matching antennas to the feedline that do not have feedpoint impedances of 50 Ohms. This is beyond the scope of this section, but antenna makers can specify certain lengths (1/4 wave) of 75 Ohm coax to achieve the proper match between radio and antenna. Again, this form of matching is not possible with 50 Ohm coax.
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