Finding the Correct Dipole Length

We have discussed the standard formula for cutting a dipole to length [L = 468/f(MHz)]. First, you may wonder why 468 is used instead of the free-space factor of 492 for a half wavelength. This is a good question: If our dipole was in free space and with no feed line, the length would be greater than that obtained from the 468 factor. The end effects of the insulators and guy lines, plus antenna proximity to trees, the earth and other influences, causes the antenna to have stray-capacitance effects that tune it lower in frequency. 

You may think of the dipole as an inductance, and stray capacit- ance appears in parallel with it, just like in other tuned circuits. These effects are compensated for by changing the length factor from 492 to 468.

Let's assume that you have cut your dipole wires in accordance with 468/f, as discussed earlier. How can you be certain that this is the correct length (antenna installed) for your chosen frequency of operation, say, 3.7 MHz?

 First, you need to know that the lowest SWR occurs at the resonant frequency of your antenna. It may not be the ideal 1:1 ratio we seek. Rather, it may be 1.5:1 or even 2.3:1. If the SWR is high at the reson- ant frequency of the dipole, you will know that the feed line is not matched to the antenna feed point. The SWR will rise either side of the resonant frequency as you change the operatYou will need an SWR indicator or bridge, as they are called, in order to check your antenna resonance and SWR. 

The SWR indicator must be designed for the impedance of your feed line, such as a 50-ohm bridge for 50-ohm coaxial line. The SWR instrument is installed between your transmitter and the feed line. 

Next, check across the amateur band for which your dipole is cut, observing the SWR reading every 25 kHz or so. Note the frequency at which you obtain the lowest SWR reading (minimum reflected power). 

This will occur at the resonant frequency of the antenna. If the lowest SWR occurs lower in the band than your design calls for, remove small amounts of wire from the ends of the dipole until the lowest SWR is noted at the preferred antenna resonance point. If the lowest SWR reading is observed higher than your chosen frequency, you must add a small amount of wire to the ends of the dipole. Continue this process until the lowest SWR occurs at the chosen operating frequency.

You may use a dip meter for checking the resonance of your antenna. You may do this by connecting a three- or four-turn small coil between the shield braid and inner conductor of your coaxial cable (antenna erected, and feed line attached). A solid-state or tube type of dipper may be used. Insert the dip-meter coil into the small coupling coil on the feeder. Adjust the dipper through its range and locate the frequency at which a deep dip is noted on the meter. Listen to the dip- meter operating frequency by means of your receiver, and note the frequency. Adjust the dipole length until the dip meter indicates resonance at your preferred operating frequency.

We will discuss methods for mismatch correction, later in in this notebook. A minor mismatch (1.5:1 SWR or less) is not of concern to us for routine operation, provided the trans- mitter is designed to deliver normal output power at low values of SWR.

source : Novice Antenna Notebook by DeMaw, Doug

The Folded Dipole

A folded dipole has two conductors in parallel, as you can see in Fig-3. This antenna has a high feed impedance (300 ohms). You may use a 4:1 balun transformer (see later chapter on baluns) to convert the 300-ohm balanced line to 75-ohm coaxial cable. A folded dipole may be used in the same manner as the single-wire dipoles in article Building and using Dipole Antennas .

The advantage of a folded dipole is that it provides slightuiy greater bandwidth between the 2:1 SWR points (most modern transmitters have a protective circuit that reduces the power as the SWR increases) than is characteristic of a single-wire dipole. For example, an 80-meter single wire dipole might have an SWR bandwidth (2:1 SWR boundries) of 75 kHz. 

A folded dipole for the same frequency may have an SWR bandwidth of 100 kHz. Apart from this consideration there is nothing to be gained from choosing a folded dipole. I have included it in this chapter for your enlightenment.

Example of a folded-dipole antenna. The characteristic feed impedance is 300 ohms. A 4:1 balun transformer converts the balanced feeder to a 75-ohm unbalanced line (RG-11 cable). This antenna may be fabricated from 300-ohm TV ribbon line or 450-ohm ladder line. The outer ends of the dipole are shorted as shown by the dots near the end insulators.

source : Novice Antenna Notebook

               by DeMaw, Doug

BUILDING AND USING DIPOLE ANTENNAS

Perhaps the most common amateur antenna in use today is the dipole. It is inexpensive to construct, and it provides good results for local and DX communications if it is erected high above ground. 

A dipole antenna is a 1/2-wavelength conductor that is fed at the electrical center. Gain types of directional antennas, such as the log periodic dipole array consists of a group of dipoles. In other words we can combine a number of dipoles to form a wideband log-periodic beam antenna.

A single dipole antenna has no gain, but it does exhibit a bidirectional radiation pattern if it is a half wavelength or greater above ground, and if it is erected for horizontal polarization (parallel to the earth). The radiation pattern for this type of dipole resembles a figure below. Maximum radiation is off the broad side of the antenna.

We learned that a dipole antenna loses its direct-ional characteristics when it is placed close to ground (less than approximately 0.5 wavelength). The resultant radiation pattern for a dipole that is, say, 1/20 wavelength above ground (e.g., 53 feet for 3.7 MHz), is pretty much circular. In other words, the signal is radiated almost equally in all directions. Also, the radiation angle will be very high, which is not ideal for long-distance communications.

Dipoles may be erected horizontally or vertically. They may also be configured as inverted Vs. This is a popular format because only one tall support pole or tower is needed. The center of the dipole is held aloft by the tall supporting structure, and the halves of the dipole droop toward ground at approximately 45 degrees. You may also use your dipole as a sloper (sloping dipole). In this example , see figure 1, we tie one end of the dipole to a tall mast or tower and slope the entire antenna toward ground at approximately 45 degrees. The lower end of the antenna (as with an inverted V) is just a few feet above ground-in a typical case where the tower or mast height is 50-60 feet.

Radiation angles and patterns vary in accordance with the manner in which we erect our dipole antennas. A vertical dipole, for example, has an omnidirectional radiation pattern, and it exhibits a relatively low radiation angle. Sloping dipoles and inverted Vs with an enclosed angle of 90 to 100 degrees will also radiate a vertically polarized signal. The sloper will have a unidirectional pattern off the slope of the antenna (directivity rather than gain) if it is supported by a metal Mast or tower: 

the metal support device acts somewhat as a reflector, If the sloper is supported on a wooden pole, the radiation pattern will be omnidirectional. 

Inverted-V antennas also have an omnidirectional pattern if they are erected in a symmetrical manner, respective to the tower and placement of the antenna legs.

Fig 1. Examples of how half-wave dipoles may be erected. A figure-8 radiation pattern results from the arrangement at A, Antenna B has an omni- directional pattern and vertical polarization. Antennas C and D also have vertical polarization and omnidirectional patterns assuming the enclosed angle at C is 90-100 degrees, and when antenna D slopes approximately 45 degrees toward ground from a nonconductive mast

The feed impedance of the antennas in above figure, ranges from approximately 35 to 75 ohms. The actual value is dependent upon the height above ground, and in the case of antennas C and D, the angle of the wires respective to mast. 

For most amateur operation you may use 50-ohm coaxial cable to feed these antennas, provided the feeder length is 100 feet or less. The losses from the moderate SWR (standing-wave ratio) at high frequency will be minimal if quality cable is used, such as RG-8 line. 

The antennas in Figure 1 are for single band use when coaxial feed line is employed. Multiband operation is possible if you use tuned feed line and a Transmatch.

See Figure 2  for this hookup. If you wish to take advantage of the multiband concept with your dipole, you should cut it to length for the lowest operating frequency of interest. By way of illustration, your dipole should be dimensioned for 80 meters if you plan to use it from 80 through 10 meters. 

The formula for half-wave dipoles is given in Fig 1. Thus, a dipole for 3.7 MHz will be roughly 126 feet, 6 inches long, overall. I said "approximately" because the final length is determined by the installation. Height above ground and nearby conductive objects will affect the initial 468/f(MHz) dimension somewhat. You may need to cut a few inches of wire off the ends of the dipole halves in order to obtain minimum SWR An SWR bridge is used when making the final adjustments.

Fig 2- Example of a multiband dipole that has balanced, tuned feeders. The feed-line impedance is not critical provided it is between 300 and 600 ohms. TV ribbon line may be used, or the line may be 450-ohm ladder type. Homemade open-wire feed line is the best in the interest of minimum RF power loss. The Transmatch (transmitter to feed-line matcher) should be designed for balanced feed line. If not, a 4:1 balun transformer must be used between the balanced feeder and the Transmatch. The SWR is adjust- ed for a 1:1 condition while observing the SWR meter (minimum reflected power) for each frequency of operation,

source : Novice Antenna Notebook

               by DeMaw, Doug

Your's Antenna Personality

Some newcomers are confused about the proper type of conductors to use for antennas. I have been asked, for example, "Can I use wire that has plastic insulation?" Another common inquiry is, "What is the best wire gauge or diameter for my dipole?"
Still another question is, "Which is best? Stranded or solid wire?"

These are good questions, and I fault no one for asking them. Consider the first question. After all, insulation is used to confine ac and dc voltage in circuit wiring. This prevents unwanted short circuits, and the insulation protects us from electrical shock. Therefore, it is reasonable for a beginner to assume that RF (radio-frequency) energy cannot be radiated through the insulation. 

Actually, this insulating layer has little effect on the radiation of an antenna. It will, however, slow down the passage of RF energy at the higher frequencies, such as VHF and UHF signals. It introduces what is known as a propagation or velocity factor. When this happens we must shorten the wire slightly to compensate for the velocity factor. At HF (high frequency), the effects of insulation are so minor that we can ignore them.

The thinner the insulating material on wire, the better. This is because insulation adds to the weight of the wire, and we may have a problem supporting an insulated-wire antenna because of its weight. It may sag or cause the support masts to bow or break. It is for this reason that most amateurs use bare stranded no. 14 copper wire for antennas. Others prefer enameled single-conductor wire. The insulation is beneficial because it prevents the copper conductor from becom- ing corroded in the presence of contaminants in the air. This enameled wire will, however, break more readily from flexing in the wind than will stranded copper wire of the same gauge. 

Furthermore, soft-drawn single-conductor copper wire will stretch with time, and this will change the resonant frequency of the antenna (move it lower in frequency). For this reason you should make certain that you purchase hard-drawn copper wire.

A stronger type of wire is available. It is known as Copper- weld (TM), to signify that it has a steel core with a copper coating. It is difficult to work with because it is quite springy and hard to manage. It is very rugged wire, and it should stay aloft for years. You should avoid kinking it during handling. Avoid sharp bends in the wire also. Kinking and radical bending ruptures the copper covering, and this allows moisture and pollutants to reach the steel core. 

This will, in time, cause the wire to break.
Wire gauges 12 and 14 are the most popular among amateurs. These sizes offer good strength, cross-sectional area and acceptable weight. This does not mean that you can't use other gauges of wire. I have used 130-foot spans of no. 26 enameled wire for "invisible" end-fed antennas. 

The systems worked fine, but needed to be replaced frequently from breakage. I have also used no. 8 solid copper wire (heavy!) for dipoles and end-fed antennas. The larger the wire diameter the lower the antenna Q (quality factor). 

This won't degrade the antenna performance. Rather, the lower the Q the greater the antenna bandwidth. For example, an 80-meter dipole made from no. 18 wire might have an SWR bandwidth (frequency between the 2:1 SWR points) of, say, 50 kHz. The same antenna, if made from no. 10 copper wire, might have a 75-kHz SWR bandwidth.

Vinyl-covered electrical house wiring is entirely suitable for building antennas, but it is quite heavy. I do not use it for long horizontal spans. I find that it is OK for use in inverted-V and similar antennas that have drooping elements. The vinyl covering adds strength, and this can be helpful if you live in an area where high wind and ice storms are frequent.

Many types of commonly available wire may be used for building antennas. For example, I have made a variety of antennas from no. 18 insulated speaker wire. I split the two conductors, which can be pulled apart easily.

This gives me twice as many feet of wire per roll than before the separation is done. Electric fence wire is used by a number of amateurs. It is very inexpensive, and comes in no. 18 Copperweld or aluminum materials, Checkwith your area farm-supply store, or Sears, for this and other suitable wire.

Some beam antennas and verticals can be made from common items that may be found locally. Commercial antennas of this kind are fashioned from aluminum tubing of a specified tensile strength and hardness. This material is not only hard to find, but it is expensive. You may prefer to make your small beam antenna or vertical from thin-wall electrical conduit. The antenna will be heavier than if aluminum were used, and it will eventually become rusty unless you paint the metal.

I have made a number of vertical antennas from copper tubins that I purchased at a plumbing-supply store. The 1/2- or 3/4 inch copper tubing may be supported on standoff insulatore that are attached to a wooden mast. I have also employed thin wall electrical conduit for the conductor of a vertical antenne Aluminum downspout (gutter) sections may be joined to form a guyed vertical antenna for 40 meters and higher. I know a ham operator who has access to used irrigation pipe. 

He made a lovely guyed, 80-meter vertical from this stock.

It is important that you be innovative when selecting material for your homemade antennas. Not only will you save money, you will be able to acquire the components quickly. Although iron is not as ideal a conductor as aluminum or copper, it will perform well for medium- and high-frequency operation.

source : Novis Antenna Notebook by Doug DeMaw, W1FB

DIY Groundplane Antenna

Reliable communications in radio systems depends upon the over-all effectiveness of both the base station and mobile unit antennas. The radiation pattern of the transmitted signal is extremely important since it must be transmitted and received in densely populated areas as well as over long distances. If you are situated in the center of a town or a city, omnidirectional pattern is best suited for you. Omni- pattern is also the best choice when you do not know the exact direction or location of the station you are communicating with. Directive pattern is practical only if you know exactly which direction must the signal be beamed to, in order to maximize the transfer of RF energy. However, antennas with directive patterns are more complex in design and will be discussed later.

Generally, antennas for VHF bands are mounted as high off the ground as practical to overcome the limitations of the so called line-of-sight transmission and reception. An artificial ground must then be used since the antenna is well above the ground in this case. This is not a problem in automobiles since this artificial ground is provided by either the metal roof or body of the car. For tower installations however, some means must be provided to simulate this artificial ground. This is accomplished by the groundplane radials which are usually made of thin metal rods or tubes each cut to quarterwavelength long and mounted at the base of the antenna. The rods sometimes bend downward at an angle of about 45 degrees below the horizontal. This angle is important to maintain the correct impedance match of the system.

Construction 

First of all construct the antenna mount. It is made from a 1/8'' thick aluminum plate cut to 2'' x 6''. Drill a hole in the plate big enough for the SO-239 VHF connector to insert into (about 5/8'' or 15.8 mm). Drill the hole at the point about 1" away from one end (see Figure below).

Next drill four holes at the other end of the plate following Figure below for the proper dimensions. Make sure that the distance between one pair of holes perpendicular to the length of the metal sheet must be the same with the distance of both ends of the U-bolt that will be inserted into it.

Hole dimensions for the U-bolts

Next, drill eight holes (1/8" diameter) around the large hole following Figure below for the proper dimensions.

Hole dimensions for the radial elements around large hole.

Bend the aluminum plate down to a 90° angle (see Figure below). Follow the illustration for the exact point to bend. 

Bending The Aluminum mounting Plate

Insert the SO-239 VHF connector facing downwards into the mounting plate and fix it permanently with its nut (see Figure below). Discard the grounding ring/lug.

Mounting the SO-239 into the plate.

Cut the brass rod to a length of 19" (48.26 cm) and insert one of its end into the center pin of the SO-239 connector (see Figure below). The brass rod may or may not fit into the center pin immediately, so you may need to file away a small portion at the end of the rod to reduce it to a smaller diameter.

Preparing one end of the brass rod to fit inside the SO-239

Cut four aluminum tubes to a length of 20" each and drill two holes (1/8 " diameter) at one end (see Figure below). 

Bend the aluminum tubes to a 45 degree angle at the point 1 inch away for the end with two holes. The direction of the bend must be parallel with the axis of the drilled hole (see Figure below). 

Bending The Tubes

Mount the four aluminum tubes into the angled plate by bolting each element with 1/8" x 3/4" stove bolts (see Figure below). The stove bolts must be made of rust resistant material such as stainless steel, brass or GI. 

Mounting the tubes on the metal plate.

Finally , you can mount the antenna to the mast using the two U-bolts .

Mounting the antenna to the mast

source : Practical Antenna Design VHF-UHF

ANTENNA FEED-POINT IMPEDANCE

An antenna simply hanging up in free space isn’t worth much; we need to get our energy from the transmitter up to the antenna. Of course, we can bend down one end of the an- tenna and bring it into the house—but, except for certain special types, this is not the best idea for several reasons. Some

energy may be wasted because of absorption by nearby objects. Also, the normal radiation pattern of the antenna may be some- what upset.
For these reasons, in most cases, some type of feeder line is used to get the energy from the transmitter to the antenna as Figure. At this point we need to consider another matter: the impedance of the antenna at the point where the feeder must connect. Fortunately, the theoretical input impedance of a half-wave antenna fed in the center is a value which can be matched by a feedline which, in turn, is of a handy impedance value for powering from the common ham transmitter. Such an arrangement is the basis of the first antenna we will consider.

DIY SWR Bridge , measure antenna SWR from 7 to 435 MHz with this cheap project

For over fifty years I have been matching my home-brew antennas to my radio, using makeshift field-strength-meters, lamps, pencils (arc), or finger (ouch). My solid-state amplifiers have complained about this treatment, however, forcing me to consider methods that really define the matching in terms of standing- wave ratio (swr). The effort resulted in a very simple device that measures swr to better than  1 : 1 in all the bands I am interested in, 7 to 435 MHz, it can be built in a few hours for less than few dollars. The basic method is a stripline-type directional coupler. The operating principle is that a properly terminated line parallel to, and coupled to, the transmission line will pick up energy traveling in one direction. The detected signal from this coupled line will represent either the forward or rcflected energy depending upon which end is terminated  Fig, 1 gives the schematic.

The Circuit

Swr values are determined from the forward and reflected peak- voltage outputs:

V(FWD)+V(RRFL) / V(FWD)-V(REFL)

The outputs can also be calibrated in terms of power. However* the output-voltage sensitivit>' of this type of directional coupler is directly proportional to frequency. As an example, using this particuhir device at 7 MHz, 100 Watts is required to detect an swr of hi, while at 146 MHz, less than 250 mW will make an equivalent measure- ment. This power/frequency relationship is a limitation.
The effect is in the right direction, how- ever. HF higher power is more likely available than at the VHF/UHF frequen- cies. Power-handling ability is also fre- quency related, and it is limited by the cou- pling -striptine terminalion resistors. Exam- ples arc about 4 W at 435 MH/, 35 W at 146 MHz, and 1 kW at 28 MHz, Total power dissipated at maximum power input is les3 than one Watt.
This project has been simplified by using a glue-down stripline technique that I have employed successfully in a number of previous projects. Striplines are cut from double-sided glass-epoxy PC board having the same dimensions that you would choose using the etched-PC board method. One side of the stripline is smeared with glue and pressed firmly against the common-base PC hoard. Changes can be made within minutes by lift- ing the glue-down stripline with a knife and replacing it with one having the altered dimensions. No dc connection is required between the glueline foils.
In this project, two striplines are glued together to effectively double the dielectric thickness. This results in a wider stripline for a given impedance, making fabrication and handling easier.
Matching the directional coupler-line impedance with that of the transmission line is a critical parameter, significant differences resulting in a self-generated swr error. Optimum strip! inc width was calculated using conventional stripline theory. Assuming a 50-Ohm Zo (line impedance), the calculations resulted in a 0.219-inch width when using two sandwiched 0.062-inch thick glass- epoxy PC strips having 1.5-ml foils (net J 18-inch dielectric). A dielectric constant of 4.5 was assumed for the glass-epoxy material. Tests indicate that the lloating center foils have no effect.
The pickup lines, glued to the top of the 50-Ohm conducting stripline, are 0. 125-inch wide, Although their calculated impedance is 69 Ohms, the termination resistance in this special configuration is about 60 Ohms. This resistance is experimentally pruned to null for zero output when the pickup is in a position to detect reflected energy and when the transmission line is terminated with a non-reflective load (50 Ohms). Pruning is accomplished easily using parallel 4-W resistors.
My assembly required four: two 150s, a 330, and a 2.2k-Ohm resistor. The resistor connections are with minimum lead lengths (approximately l/32nd inch). The assembly is reverse-connected in the transmission line to enable the pruning procedure for both pickup lines in an identical manner. Lack of fabricating symmetry will result in slightly different resistor values for the two pickup lines. A large output-readout dynamic range en- hances the usefulness of the device. As an example, only 1.2 V is indicated in the for- ward direction when used with my 7-MHz, 100-W transmitter. This means that to read a 1:1 swr, it is necessarv to detect a reflecitxl voltage of 0.057 V. 1 have found that selected lN34As will reliably meet this requirement. In a typical package often diodes from Radio Shack, over half of them had a back resis- tance of more than 10 Megohm (less than 1 uAat 10 V).
Using these selected diodes in the peak- detection circuit together with a high-im- pedance (10 Megohm) digital voltmeter permits reliable readings down to 0,05 V. The table in Fig. 2 shows input readout characteristics and the correction factors. The required readout sensitivity is a trade* off of how much power is available at a par- ticular frequency and the desired swr- mea- surement accuracy. The usual ham shack VOM- multimeter wilt be adequate for most applications.
Fabrication details are shown in the Fig. 3 layout, and the stripline cross-section draw* ing in Fig, 4. It is best to start by cementing the stripline sandwich and then finish trim- ming the edges to the required width. A file works fine, however — as does a sandpaper block, which will save dulling your file with the glass epoxy material.
The primary stripline width should be held toO.219 inch, ± 0.005 inches, I used calipers to size the striplines, but a ruler would be satisfactory if used with considerable care. Maintaining symmetry through the assembly is important. When mounting the BNC chas- sis connector, use a double nut so that it can be fastened in a position for minimum com- mon-return inductance.
Final alignment is simply pruning the pickup-line termination resistors in the man- ner mentioned earlier (multiple 1/4-W resis- tors). It is best to do this procedure at the highest frequency you intend to use the swr device— 1 used 435 MHz. One thing required is an accurate 50-Ohm termination. I used a fifty -fool section of RG-58/LJ terminated with two 100-Ohm, I /4-W resistors. The 7.5-dB cable loss reduces the estimated worst-case resistor reactance swr from a val- ue of 1.2 to L03
After pruning the lerminations of both pickup striplincs for minimum reflected indi- cation (less than 1 : 1 swr)» the device is ready to measure any swr of less than 10. The calibration results were made by terminating a short s^ection of RG-58/U with various values of 1/4 W resistors,
Inability to null the swr device may be the result of an error in the primary stripline impedance. This could be caused by a differ- ent gla&s-epoxy dielectric constant. Try alter- nate striplines differing in widths of about O.OiO inches.
Spurious responses In the transmitted source can cause a measurement error. As an example, a — 30 dB spurious signal is likely to result in a significant error when making a U swr measurement. Also* reflected signals from a reactive source will result in an error. This error will be particularly evident with large swr values.
Connectors also can be a suspect source of error. For example, I have used RG-59/U connectors {75 Ohm) for RG-8M cable (an RG-8 mini foam), and measurements indicate that they contribute to the swr.
How did my home-brew antennas mea- sure? The 435-MH2, 1 5-elemem antenna swr was 1.2, the 2m 5-element was 1 .4, the 2m J antenna was L4, and the 2Qm flat -top with a tuned antenna coupler ai the transmitter was
1.5. That makes sense, 1 spent more lime matching the UHF antenna.
In summation: You can match antennas adequately without an swr instrument, hut it's a lot easier if you have this simple gadget. Besides. it*s a good way to become acquaint- ed with directional couplers

DIY Field Strength Meter

 

The Circuit 

The circuit in Figure 1 shows how simple the FSM is to build. RF is coupled to Dl and D2, which are configured as a voltage doubler. The developed voltage is seen across the resistors RI and R2. R2 is the sensitivity control. Simple? You bet. So let's get started.

The most expensive part of the whole project is the meter movement. I got mine from Delia Electronics in Atlanta a few years back. Any value of meter from 50 uA(mu ampere) to 1 mA will work. The diodes Dl and D2 are general purpose germanium point contact diodes, 1 N34As or 1 N60s would be just fine, C 1 and C2 are 50-volt ceramic disc capacitors, I got mine in a grab bag at a hamfest Rl is l A watt and R2 is a 10k ohm pot from my junk box. I used a 2" x 3* x 1 1/2 inch plastic box from whereabouts unknown. The size of the box will be determined by the size of the meter that you use.

I mounted all the components on a small piece of perf board, then mounted the perf- board to the three solder lugs on the potentiometer R2. Next, mount the potentiometer in the hole cut for it in the box. Then connect the binding post to C 1 with a small length of hookup wire and connect the meter to the board. That's about all there is to it. Use your imagination to work out your own component mounting schemes. A word of caution: Don't forget to heat-sink the diodes' leads during soldering. Excessive heat can ruin them.

If you want to go to the extra trouble of making a printed circuit board, go ahead. Personally, I thought it was too much trouble for this particular project.

Testing the Meter

Testing is as simple as building the FSM. Just connect a short piece of stiff wire to the binding post and rotate the sensitivity control as you apply a signal to your antenna. It is a good idea to always start with the control all the way to the left to keep the needle from slamming into the stops, While the FSM only gives an indication of relative field strength, it will allow you to check for front-to-back ratio of beam antennas and to make a comparative analysis of different antennas. Get back into building and have fun

source : 73 Amateur Radio

How to pick up good Antenna TV or most for Antennas in General ?

There are many brands of antennas on the market, all of them promise good quality. This makes us need to determine what parameters help us to choose the right antenna, recommended according to the parameters of a good antenna

Impedance 

Pick 75 Ohm input Antenna ,  meaning , the input Antenna matched with Coaxial 75 Ohm cable Impedance  for TV , as Theory this will make the TV signal transmit/receive  ideally100 % without reflected.

Range

Scientific fact: The Earth is round. (Sorry, flat-earthers.) The curvature of the Earth will block most over-the-air broadcast signals at roughly 70 miles. According to the current laws of physics, it is generally impossible to deliver the 100 and 150-mile range claims some antenna manufacturers boast.

Gain

Indicates how well the antenna focuses energy from a particular direction, in comparison with a standard reference antenna (an antenna with known performance, used to calibrate other or developing antenna technologies). The gain number specified on an antenna is the value in the direction of maximum reception intensity. Example Antenna Gain 6 dB, 9 dB, 14 dB, 18 dB. the greater the antenna gain (in dB) the better the reception

What this means is that the distance measured for an antenna's reception capacity is based on the hypothetical instance where the broadcast transmitters you're trying to receive signals from all line up like points on a single straight line. Also, it is relevant to note that "gain" in this usage doesn't take into account possible dips in reception from what is called "impedance mismatch". In practice, the antenna's performance can be faulty if its impedance is different from that of the cable connected to it.

Model

Antenna model consist of by range criteria  Short Range/Medium Range/Long Range, by location installed Indoor/Outdoor/Attic Antenna ,  by frequency working UHF and UHF/VHF Antenna  and by Style , Wireless , Unidirectional (Directional)  and Multidirectional (Omnidirectional) Antenna

A Short-range digital TV antennas are engineered for distances within 50 miles of the broadcast towers. Their shorter range means they are very powerful and will consistently pick up your local signals.

A Medium-range TV antennas are engineered for distances within 60 miles of the broadcast towers. These high-performance digital antennas can be placed on a tabletop or a wall. For optimal performance and to minimize interference from electronic devices in the home, place the antenna near a window or on a wall facing the broadcast towers. Outdoor HD antennas will perform best when installed in your attic, or preferably on a rooftop or fascia.

A Long-range HD antennas reach further than most other outdoor TV antennas and minimize interference from obstacles such as trees or heavy foliage, providing you with the best possible reception in every scenario.

Indoor Antenna ,  indoor TV antennas are designed with timeless features to blend into sophisticated spaces. These indoor antennas can be painted to match your wall, furniture, or accent color for a custom fit.

Outdoor TV Antennas , Perfect for suburban and rural areas, outdoor TV antennas are the best option overall for receiving long-range signals when installed on a roof or fascia, providing the best line-of-sight to the broadcast towers.

Attic TV Antennas, Installing your antenna in an attic allows you to conceal your antenna when an outdoor antenna is not possible. Our attic TV antennas provide powerful, long-range performance for consistent, reliable reception in the city and in rural areas.

UHF Antennas, UHF HDTV antennas have the power and efficiency normally found in antennas up to 10 times their size.  TV antenna designs are engineered to receive consistent high-gain across the entire UHF TV spectrum. UHF signals are broadcast on channels 14 to 69 and have a higher noise level and greater attenuation, so  high-gain digital antennas are often required.

UHF/VHF Antennas, Over-the-air channels are divided into two bands, UHF and VHF.  High-VHF signals are broadcast on channels 7 to 13 and UHF signals are broadcast on channels 14 to 69. UHF/VHF HDTV antennas represent a breakthrough in long-range performance. They are engineered to be smaller and more powerful across today's DTV spectrum, with dedicated UHF and VHF multi-directional elements that deliver range and reception in less-than-ideal locations

• If your location near Trasmitter locator tower and have Strong TV Signals, pick these Antennas

•  If your location have Moderate TV Signals , Pick Up these Antennas

• If your location have Weak TV Signals , Pick Up these Antennas

Filter

Some Antenna products , included this filter, the main function is to Blocks 4G/5G LTE cellphone and transmitter frequencies that cause pixelation and reception disruption. 

 
How to Get the Best Reception Antenna ?

The actual receivable range may largely depend on your location and distance. Areas with large obstacles, such as terrain, high concrete buildings, trees, valleys or mountains will reduce the effective range.

Also keep away from the high power device that will make interference when you install the antenna.

Use Transmitter Locator Software or other software related, will allow you to view the TV transmitters in your area. Using this tool, you will see the radius patterns showing

For example Enter your City name or ZIP Code and Click “Go” or Click “Go To My Locations” for Get DTV Coverage  

Please note:

These predictions are based on a terrain-sensitive propagation model resembling but not identical to the propagation model used when calculating service and interference contours for licensed broadcast television stations. Actual signal strength may vary based on a variety of factors, including, but not limited to, building construction, neighboring buildings and trees, weather, and specific reception hardware. Your signal strength may be significantly lower in extremely hilly areas. Click on a callsign for details about that station's Incentive Auction repacking plans.

Antenna Range False Claim

Antenna products in market claims have the receive signal  more than 100, 150, 200 miles, this is not true. We here to educate this false claims, there is no such antenna like that. 

The truth is TV antenna reception is influenced by the shape of the earth's curvature.

That's why TV stations need a lot of relay stations, to cover places that are far from TV tower stations such as rural areas, valleys behind mountains, and so on.

Curvature of Earth per mile

How large is the curvature of Earth, then? As we don't notice it in our everyday lives, it has to be relatively small. Most sources consider 8 inches per mile as the most accurate estimate. That means that for every mile between you and an object, the curvature will obstruct 8 inches of the object's height.

Scientific fact: The Earth is round. (Sorry, flat-earthers.) The curvature of the Earth will block most over-the-air broadcast signals at roughly 70 miles. According to the current laws of physics, it is generally impossible to deliver the 100 and 150-mile range claims some antenna manufacturers boast. While you may receive signals from farther away in absolutely ideal conditions (a home atop a hill whose broadcast towers are directly on top of another hill with a clear shot between the two and absolutely no obstacles) or you’re inclined to engineer a unique (and probably dangerously tall) setup, then consistent, reliable reception of anything over 70 miles away should not be expected. Range can also be impacted by factors such as location, obstructions in the terrain around you, other buildings, the location of transmitters on the broadcast tower, and other variables

The Channels You'll Receive

You may be thinking that watching TV with an antenna will bring you back to the old days of antennas when only a handful of stations were available. Today, most areas in the United States broadcast 50+ channels over the air. Locations like Los Angeles have as many as 175 channels. We’re talking about over-the-air broadcast television channels -which are transmitted in Full HD 1080p and with 5.1 surround sound- you receive for FREE once you have a TV antenna. In addition to your local NBC, CBS, ABC, CW, and FOX affiliates, you’ll also find a wide variety of specialty programming available on these stations. So much content is available over-the-air that we like to call it “the new basic cable”. Keep in mind, these are network and local channels. You won't receive any pay-TV stations via a TV antenna, ever. We’ve seen antennas claiming this possibility, but it is 100% false. You will not receive ESPN, CNN, or any other such channel with a TV antenna. Period. That said, there are many new streaming options becoming available all the time which combine broadcast TV content with packages available for purchase to watch sports channels, pay-TV subscriptions, and more, all from one streamlined platform.

The 4k TV Antenna

As of writing this, OTA television is not yet broadcast to the general public in 4K. However, that doesn’t stop unscrupulous antenna companies from claiming that (only) their antennas will allow you to watch broadcast TV in 4K. The truth is, once 4K broadcast television becomes available, any antenna will be able to receive it. What you, the TV-watcher, will need in order to view OTA television in 4K is a device which will be capable of decoding the transmissions your antenna receives so that you’re able to watch your shows in the new 4K standard. This can be a TV or a designated TV tuner, for example, a set-top box. We believe that our ClearStream™ HDTV Antennas will deliver the best, most reliable picture quality we’ve always been known for when that day comes, which is why we indicate on our packaging that all our antennas are “4K-Ready”. Until then, 4K-quality picture has become available through mediums such as Blu-Ray® and certain streaming services, but broadcast television viewers will need to wait until the new standard of television arrives on local airwaves in the near future, to view over-the-air television in 4K.

If you’re still unsure or just need guidance choosing the right antenna for your needs, we are here to serve as your beacons of light for all antenna myths you may be grappling with. Our Midwest-based Connection Crew is available 7 days a week to answer questions and help you achieve the best possible over-the-air TV-viewing experience. They’ll help you pick the right antenna for your location, troubleshoot installation, conduct a free home signal analysis, and more. They’re a passionate bunch of real antenna enthusiasts who will help you separate fact from fiction and find success with a TV antenna.

 

Reference :

http://www.Antennasdirect.com

http://www.amazon.com

https://www.fcc.gov/media/engineering/dtvmaps

https://www.omnicalculator.com/physics/earth-curvature#curvature-of-earth-per-mile