The antenna vibrator (wire 2.7 m long) ends - through an insulator - with a hook, this hook either clings to a bent young tree, and then is released; or you hook a rope with a pebble (nut, etc.) to the hook, and throw it onto a branch of a large tree.
The vibrator as a result should be installed vertically upwards.
Also in the design of the antenna there are 3 wire counterweights 2.7 m long, each of which ends with an insulator connected to a metal peg (it is stuck into the ground).
Ideally, the counterweights should be at an angle of 40-45 degrees to the mental continuation downwards of the vibrator. If some direction is predominant, then the counterweights in the horizontal plane are shifted in the direction where the communication range should be greatest.
The kit comes with a feeder (cable 3.6 m long) to make it more convenient to work with the antenna.
Available with TNC antenna connector. If you have a walkie-talkie with a BNC connector, you will need a BNC-TNC adapter.
It should be borne in mind that such antennas work effectively if the height of the structure above the ground is 3 m or more.
marchingmobile antenna "STERKH"
for CB - range (27 MHz)
Idea
After our stormy experiments with portable and basic antennas, the task arose to do something in the middle in terms of efficiency. A portable pin of 40 cm has a good performance limit of up to 7-8 km. Carrying a second Owl with you through the forest is hardly convenient, and deploying it in a desert area without a mast is generally unrealistic. In addition, not all “dummies” from the oar can competently solder the SU.
I wanted to make the antenna as simple as possible, from a couple of wires, and I calculated the Zabredun dipole, from which I intended to dance. However, it turned out to be worse than expected: narrow-band, with SWR on the verge of good, and negative gain. Most likely, the dipole was considered in MMANA , which does not know how to work with low-hanging antennas and overestimates dbi . In addition, the radiation goes mainly upwards!...
The same garbage as the first version of the "Owl". If you calculate the antenna taking into account the thinnest insulation, the SWR will become completely sour ... That is, this dipole, of course, is better than the regular pin, but only due to the height of the suspension and the length of the canvases. Take a look at the results:
Z = 78.417 + j 64.474 SWR (50+ j 0)= 2.92
Max Gain : -1.02dBi at azimuth : 222deg
Max Gain: -0.12dBi at elevation 79deg
In fairness: on the test, the dipole showed an SWR of about 2. But this design still does not suit us, like everyone elsecommon "forest" analogues of radio amateurs - dipoles, rays, inverted V , classic GP etc. - they are either ugly long, or "shoot" up, or require at least one suspension point, and quite high.Making a mini-analogue of the "Owl" is also an undertaking, a matching device will kill the entire efficiency of the antenna. And in general, the “owl” place is at the base! Put and smoke bamboo. A group or person leaving the camp will want to take something more comfortable with them in a sweep (RU3DKW considered the option of a plumb-bob with a capacitive load, but it didn’t come to a specific simulation, although we may still think about this option).
In short, the new antenna must be portable enough to be carried, and at the same time not much inferior to the Owl in terms of efficiency, and most importantly, it must be deployed by one person in any terrain and cover at least 15 km with a "good" rating.
Sergey turned out to be very busy, so I had to think over the geometry, material, and study the necessary programs; after which I modeled and calculated a design that vaguely resembles a paper crane. So, our “birds” arrived in the regiment! ...
Theory
USTERKHA rigid vibrator made of duralumin tubes, bent in the upper part at a right angle, and two counterweights:
The antenna has a simple geometry, no matching device, no rations, no feeder. The hardest part here is splicing the down tube and BNC -mom. The tubes must fit into each other TIGHTLY, be even at the joints and smooth. The most complex element is a 90-degree bent pipe.
Antenna has V -polarization and good bandwidth (~1460 kHz at SWR<=1,5 и ~2890 <=2.0). СТЕРХ рассчитывался условно на середине СиБи диапазона (27,605 мгц), с реальной землей средней плешивости.
The antenna turned out to be directional and has a gain ** ~ 1.5 dbi at a small angle to the horizon, which is very good for such a small and mundane structure. The direction of STERKh radiation is concentrated from the center of the open corner of the counterweights. You must take the correspondent "in pincers" with counterweights. Given that the angle is wide enough, it can be conditionally directed to the side of the world where the interlocutor is.
In the classical case, the vertical part of the vibrator is built as 210 cm, and the "beak" = 40 cm. In this case, counterweights = 282-286 cm, and their lower ends should be ~ 30-40 cm above the ground. The length of the "beak" can vary from 24 to 40 cm, without compromising matching, but the total length of the antenna must remain 250 cm.
As you can see, the lobe of the diagram is well pressed to the horizon, which cannot but please the eye. C with any insulated wire, the antenna has an SWR of no more than 1.2 (in all programs). Taking into account that STERKH counterweights are in isolation, the first dimensions had to be corrected taking into account the radii of the “skins”, but I was satisfied with the results:
Vibrator - made from duralumin tubes with a diameter 6 mm (wall thickness 0.6) and is divided into segments. A greater number of segments is dictated solely by the portability of the antenna.
The tubes fit into each other according to the principle of tent racks, a 2 mm elastic band is stretched inside the vibrator, which is sold in any fishing store. The lowest tube is rigidly fixed in the desoldering box, where it is screwed BNC - connector, or otherwise,
The lowest point of the vibrator should be located 160-170 cm from the ground (theoretically, this is the height of the walkie-talkie connector that an adult holds in his hand during a conversation). The position of the "beak" does not matter.
When using a tube with a cross section 10 mm gain over the horizon will reach ~2 decibels. When using iron, the bandwidth increases, but the matching worsens (you need to adjust the dimensions) and decreases dbi (almost twice). In addition, the vibrator becomes heavier, so you should not use stainless steel.
Counterweights - you can use any copper insulated wire 0.5-1.5 mm in diameter. They must be attached with a clamp or soldering to the "ground" of the antenna connector.
When buying an audio cable in silicone, you should pay attention to the one in which the thickness of the “skin” is no more than the diameter of the vein, and, preferably, of a round shape. A thick “peel” is capable of crushing up to half a decibel, which we already have sparsely ...
The counterweights must be exactly 90 degrees apart from each other. A slight narrowing of the angle is allowed, but not widening! The lower end of each counterweight must be in ~ 30 cm from the ground, and the upper one - 160-170 cm. The ideal plumb angle with respect to the ground is 45 degrees.
The stretching of the plumb lines lies entirely with the operator, since the upper attachment point is the walkie-talkie, which he holds in his hand. The plumb lines are actively involved in the diagram, and should not sag or be misplaced in space.
In order to correctly stretch the counterweights, first spread them at a right angle on the ground, stick in the pegs, and then raise the radio and pull it. At each counterweight at the end it is necessary to make a rope guy, and at its end - a loop for a peg.
Naturally, both counterweights must be made of the same wires and be of the same length. It is desirable to avoid breaks and rations - in STERKh these are radiating elements.
Construction
Nikolai from FMK *** made two sets of pipes in a few hours, since they have everything: pipes, machines and rich experience in working with aluminum. Unfortunately, the 6 mm pipe is too thin to work with bushings, and it had to be bored to fit the “neighbor”, so several unplanned thickenings appeared on the vibrator at the joints.
Example of a travel kit:
Vertical part: 10+40+40+40+40+ 40 cm + 6 cm bent pipe = 216 cm
Horizontal part: 34 cm of bent pipe ("beak").
216+34= 250 cm total length. When making pipes, remember that each joint "eats" 2 cm! Therefore, each tube should be made 2 cm longer.
You can attach the vibrator to the walkie-talkie in different ways. I decided to attach it to the "legs" from the old 50-ohm "telescopes" that were lying around at home idle. It is not difficult to do this, since the copper vein from the coil is already soldered, it remains to cut off the desired piece, clean it with a needle file and screw it onto the tube. A small groove was machined on aluminum for this:
Do not forget about the problem of contact between different metals. If you just solder or wind a copper wire from the connector core onto an aluminum pipe (as I did for the test), after a while we can have an antagonist war in the form of oxide, and, as a result, non-contact. Therefore, it is better to connect them through an iron "intermediary" in the form of a self-tapping screw or something else.
And now the first STERKH is ready!
Folded STERKH next to Berkut
This is what STERKH looks like on Alan:
I designed two antennas, with different thicknesses of counterweights (in silicone), one of which was sent to the Pushkin region for a joint test.
Consider "my" version with counterweights with a cross section of a copper vein 0,75 mm and length 282 see each. Vibrator Height = 216 cm, "beak" length = 34 cm. Length of rope guys of counterweights = 95 cm .
Measurements on the street with radio stations "Berkut-803A" and "601m2T" showed that the calculation of partsturned out to be true:
Real SWR indicators at frequencies 28 805-705: B601 = 1.1, at B803 = 1.2. You can't drink skill! ... J The design hit the mark.
The height of the suspension of the lower ends of the plumb lines during the measurement was about 30 cm, and the height of the antenna suspension (in fact, eye level) varied from 160 to 170 cm from the ground, while the SWR remained stable.
Tests
A strong snowstorm during the tests has already become a good tradition. But the angrier in learning, the easier it is for the birds in battle! ... J
Chil and Seryoga climbed out into the yard in their Pravda, and I habitually crawled to the Mytishchi field, about a hundred meters from the house, unfolded the “Owl” in the snowdrifts and prepared STERKh. The initial plan was as follows: if we do not break through the initial 20 km between the two STERKHs, then the guys get into the car and reduce the distance until a signal appears.
However, the very first relationship between Siberian Crane showed the relationship almost perfect = 5.8 –5.9! Moreover, “Owl” was heard a little “worse”. Either the polarizations of the fry did not match, or the gain of the new antenna beat even the five-meter vibrator of the competitor, whose gain is close to zero, by the way.
Inspired by the results, the men drove another 8 km, and then another 2. The road wanders a lot in the forest, so there is enough vegetation. In total, the maximum distance for that day was exactly 30 km (point on GPS between Balabanovo and Khlopenevo). It’s not enough, but I got stuck in the wind and the test was stopped. In terms of signal strength, STERKH has a power reserve for a longer distance (at least 40 km).
The connection was basically 5.7-5.8-5.9. Sometimes (after 20 km) it went down to 4.8. Very strong interference in my area. For this reason, Pravda always heard me a score better than I heard them. However, the signal is good and clear, intelligibility is almost 100%.
I worked in 6 and 5 watts. At 28 km, the guys connected the B601m2 on batteries (2 watts), and I heard them normally, although the signal became worse (4.7) - I had to listen through the interference. Total: it is clear that after 20 km walkie-talkies from 4 or more watts steer, however, communication with a low-power one is also possible. The problem was mainly in the strong QRM , if it weren’t for interference, the connection to the “two-grip” even at a long distance would have become 4.9, at least. It can be concluded that in places with a clear ether, the antenna will work well with any power. And the weak signals of STERKH, according to Chil, are “pressing”, so a distant dispatcher somewhere on Kola will not interfere with conversations. Despite the terrible terrestrial noise, STERKH allowed us to conduct a test on only two channels, which once again confirms the thesis: happiness is not in the number of channels, but in the efficiency of the antenna. J
Since I did not manage to take a picture of myself, I am attaching a drawing with a conditional little man. Here's how it all looks schematically (the antenna is directed at the correspondent - at you):
Results
STERx belongs to the class of “mobile” antennas that I invented - a cross between a basic and portable antenna for traveling communications. Gain in the direction of the correspondent ~ 1.5 dB. Great job on the crossroads. The operating range of the STERKh is determined by the landscape and, under conditions of pure air, it can, I think, reach 50 km.
What do we have in comparison with "Owl-2"?
Pros:
1. No complex matching device
2. No need for hanging points: trees, masts, sticks, etc.
3. The presence of real gain at low vibrator height
4. No need for field adjustment: SWR will not go beyond 1.5 anywhere
Minuses:
1. Directionality of the antenna. Still, it is necessary to turn it "face" to the correspondent, at least conditionally
2. Making tubes (requires machines, etc. ***)
3. Tubes are more prone to breakage than soft wire
Despite the fact that tubes are more difficult to manufacture, a hard vibrator distinguishes the antenna from its “soft-bodied” counterparts - it can be used on flat terrain and not run in search of trees, which, by the way, like to distort the diagram and spoil the coordination. Now any landscape: desert, steppe, tundra, bald foothills - everything is in our hands! J
Thickening at the joints did not affect the efficiency of the antenna, so this vibrator manufacturing scheme can be used, but it is necessary to seal the joints - this is a clear minus for the test version.
Elastic , stretched inside the tubes, provides almost lightning-fast assembly of the vibrator. Stretching two counterweights, I think, will also not cause any special difficulties. STERKH fits easily into a deep jacket pocket. Damaged counterweights, in which case, can be easily replaced with new ones - the wires are corny fastened with a clamp to the connector leg. A broken segment can also be healed - when ordering tubes, ask for a spare piece of 5 centimeters, 1 mm wider (or narrower) than the main diameter, for joining “fractures” if you plan to use the antenna hard.
What more i can say?
Everything worked on the first shot! … J The idea and implementation were successful, even exceeding my modest expectations a little. Portable rapid deployment antenna, weighing less than a pack of oil, which hits more than 30 km - a tourist's dream! In fact, this is a day of travel between groups, so communication can be provided without setting up a hospital with stragglers, those who have gone to radials, etc. Of course, it is better to make two such antennas per group at once.
Given that the antenna does not have flimsy radio components, you can connect a 50-ohm transceiver up to 100 watts to it, and then the range will increase even more. The antenna gain will also increase if, for example, you work from a hill, cliff, etc. SWR in this case will be within 1.2 at any height. However, the optimal rise above the ground is about 7-12 meters - the gain above the horizon will be more than 3 dB!
It should be noted that two meters with a “tail” is the maximum height of an aluminum vibrator with a diameter of 6 mm, “standing” directly on the radio; as the length increases, its stable position in the connector will become problematic.
In general, both the guys and I were very pleased with the STERKH, and we decided, when the roads melted, to test it (and along the way the Owl-2) at the maximum range, so, as always, we should continue ... J
A few observations during STERKh tests:
Firstly, the “supreflex” antenna (40 cm) hears the STERKh well at a distance of 20 km even in conditions of interference, but with a counterweight. The guys did not use a regular one, which hit somewhere, but an analogue of the STERKH counterweight - two wires of 286 cm each, with a cross section of 0.75. At the same time, their long ends simply lay on the snow. I even heard snippets of transmission from the "superflex", but the interference clogged everything. When the counterweights were removed, the walkie-talkie with the “superflex” stopped hearing me, if I understood Pravda correctly. So plumb lines help a short pin, as I have repeatedly seen.
Secondly, I came to a very interesting conclusion regarding interference. We contacted twice from the same points, at the same time, but on different days. On a cloudy, blizzard day, the connection was much better than on a completely clear and sunny one. After chatting with my colleagues, I decided that on a clear day, near the centers of civilization, the level of interference increases by 2-3 times. Maybe low cloudiness and snow flakes “crush” (do not let in) weakened interference that arrived from the side, and only “our own” remain. And on a clear day, everything that is not lazy flies into the area - distant radio noise, electrical interference, etc. Perhaps this is stupidity, but the result is obvious ... :)
Along the way, good AA batteries were discovered, which I can recommend for walkie-talkies: Panasonic Xtreme Power. Since January, I have been mothering on them (B803A) and at least henna. Although, perhaps, the economizer built into the new Berkuts also plays its role.Tips
1. Try not to be between the counterweights (inside the corner) when transferring. Stand to the side or back
2. Do not use the antenna during thunderstorms or when there is a real danger of lightning
3. Do not touch handsets during transmission
4. Do not make segments longer than 40 cm - otherwise the antenna will lose its portability.
Many thanks to Chil and Sergey (RU3DKW) for participating in the trials! J As well as the inhabitants of the forum QRZ , for advice on mastering the programs.
Data for the second STERKH: vibrator 255 cm, "beak" 25 cm, feeder 97 cm, length of one counterweight 268 cm, length of one guy 100 cm. SWR: 1.5 SWR (27 805), 1.2 MFJ (27 805), 1.0 MFJ (27505)
An alternative version of the antenna is in the form of a bayda angle. en. We are ready to make tubes for antennas by order. You can refer to me and make an exact copy of the tested kit. When reprinting the material, a link to the article is required
I want to tell you about my method of making a light base CB antenna from a fiberglass fishing rod. In order to place the entire matching circuit inside the fishing rod, let's take the most "compact" circuit from the point of view of the matching coil.
Pay attention to the capacitor C1, its operating voltage must be at least 500 volts, taking into account that we will not use the transmitter power anymore 10 watts.
In principle, you can fasten the fishing rod to the mast with simple nylon ties, but I offer a more reliable method. We weld together a strip of metal and a corner of arbitrarily convenient sizes, as shown in the photo below.
A water pipe will be used as the base of the side extension, to which our corners are welded. Subsequently, this pipe will be inserted into the mast and bolted there.
We assemble the matching scheme by hanging installation. As a radiating element, we will use a thick copper stranded wire.
We fix the assembled structure inside the fishing rod in any way possible. Having previously cut out a window at the base for adjusting the SWR. The rod itself is attached to the stem with the help of car clamps.
To obtain a wider operating bandwidth, a small capacitive load can be attached to the tip of the antenna.
We tune the SWR at an average frequency of 27.200 MHz by compressing and stretching the turns of the coil.
After the final tuning of the antenna, you should seal the "tuning" window with electrical tape and fill it with glue, also fill the joints of the knees with glue.
The installed antenna at a low altitude showed good results when working on long-distance routes.
The proposed antenna is a slightly shortened half-wave dipole fed in the middle, made of available materials, easy to manufacture and tune.
The antenna folds easily and can be quickly deployed in almost any environment. Such an antenna can be made for different bands, but it is especially advantageous to use it on the 27 MHz band.
Channel 19 is not for general conversation. That's essentially 80 channels. He then connected it to his antenna and power supply and pressed the microphone. Apparently some of the circuits have been tampered with internally, so now he has a problem fixing the problem himself or paying for repairs.
This is just one of many examples, so be careful! More expensive radios may include a number of other controls that may or may not be of particular value to individual users. Table below. This is a very dangerous practice due to the dangerous and corrosive chemicals found in car batteries and the danger of releasing dangerous fumes.
The upper arm of the dipole (see figure) is made of stranded copper wire, and the outer surface of the outer conductor section (braid) of the coaxial feeder is used as the lower arm. This section is electrically separated from the rest of the feeder by a coil. The dipole arms are undulated to match a 50 ohm feed. The preservation of this shape is ensured by means of a nylon fishing line (or cord), to which the dipole conductors are attached at several points. The line also serves to hang the antenna. The length of the free end of the fishing line and the length of the feeder part below the reel depend on the required height of the antenna suspension. The last size should not be a multiple of half the wavelength, the best values are 2.6 m or 8 m.
They are widely available and relatively inexpensive. If you think you may need additional hardware and accessories in the future, then more expensive power supplies will be available that can provide more current that may be required.
Use a high quality 50 ohm coaxial cable to connect the antenna to the radio. Higher quality cable has a denser, more efficient braided shield that minimizes signal loss and reduces the chance of interference.
A safe load is tied to the end of the line, which is thrown, for example, over a dry tree, and then the antenna can be pulled up by the end of the line. There should be as much free space around the antenna as possible. On a helicopter or a balloon, the antenna is simply hung down. No counterweight or ground is required for the radio.
The coil is wound with the same continuous cable from which the lower arm of the dipole and the feeder are made. It should have an inductance of about 15 µH and should be protected from water, snow, dirt, etc. between the turns. It is better to use a cable with a stranded inner conductor, for example PK50-2-12 or PK50-2-16. For the upper arm of the dipole, you can use any insulated wire that more or less retains its shape when suspended. The number of "waves" of the wire in the arms of the dipole It is only important to maintain the total length of each arm (B and H) and the lengths of the wires of the arms indicated in brackets in the figure.
It has a half wave radiator section, so it is a full size antenna. Not only is it a very efficient antenna, but it is also made of wire and is very light in weight, making it easy to fix in different positions. a permanent antenna such as a silver rod and then building a wire antenna that can be easily supported on a light telescopic rod can be an ideal alternative.
So, to make a practical antenna. The optimum point must be found through some experimentation - as is the best length for a wire heatsink. The environment will affect the length of the radiator. This indicates the need to adjust the connection point of the coaxial cable to the 450 ladder line. The ladder line is used as an impedance transformer, converting the very high impedance of the half wave transmitter to 50 ohms required by the radio and coaxial feeder cable.
To tune the antenna, it is convenient to use a multi-channel radio station, preferably with several grids (with a wider frequency range), and an SWR meter. By changing the size of the upper arm B (by uniform stretching or compression along the length along the fishing line without changing the length of the wire), the dipole is tuned to resonance at the selected frequency, and then by changing the size of the lower arm H (without changing the length of the cable section in this arm), the minimum SWR is achieved at resonance. In this case, the resonance frequency may change, and you may have to do the whole process several times. After setting, firmly fasten the fishing line with the wires of the shoulders to prevent displacement.
Thus, this connection point affects the impedance of the antenna, the higher the corresponding section, the higher the impedance, and vice versa. At this point, the coax braid is quickly soldered to the opposite side of the ladder line, ensuring that both points are equal distance from the bottom. Once the ideal point has been found, the coaxial cable can be correctly and permanently soldered to the ladder line.
However, testing and tuning took a little longer. Connection point = 5 centimeters from the bottom. But you can use any low-loss 50 ohm coaxial cable. The wired radiator section is connected to the same ladder line conductor as the center conductor of the coaxial cable.
The authors manufactured and tested two copies of the antenna with a coil on a polyethylene cylinder with a diameter of 60 mm and a length of 80 mm, containing 19 turns of cable, and with a coil on a ring 65x40x6 mm made of ferrite brand M55NN-1 - 22 turns of cable. The mass of the antenna without load is about 300 g. Both antennas have almost the same parameters. On a panoramic SWR meter of the R2-73 type, SWR values of no more than 1.5 in the 0.72 MHz band and no more than 2.0 in the 1.32 MHz band at a center frequency of 27.3 MHz were obtained.
For my antenna, mounted on a fiberglass fishing pole, the radiator wire was 85 meters long. Once the antenna is completed and checked and tested, all bare joints must be sealed against the weather with their own amalgamating tape or liquid electrical tape. The coaxial cable must also be attached to the ladder line with a nylon cable tie as a strain relief to prevent the weld joints from breaking.
The antenna consists of one vertical radiator wire connected to the inner conductor of the coaxial cable and three or four ground wires connected to the outer jacket of the coaxial cable. Each wire is one quarter wavelength long.
The calculated efficiency improvement of 16 dB due to the transition from the efficiency=2% of the helical antenna to the efficiency=80% of the dipole is experimentally confirmed. On flat terrain, an additional 10 dB can give an additional effect by increasing the height of the antenna from 1.5 to 5 m. The total gain of 26 dB is equivalent to a power increase of 400 times, which allows you to increase the communication range by about 4.5 times.
Just two quarter wavelength wires, one connected to the inner conductor and the other to the outer shield of the coax feeder cable. At this point, wrap about 10 turns of coax around a small piece of plastic water pipe to create a simple choke balun.
Short Antenna for Portable Radio
The mobile antenna should be placed in the middle of the vehicle roof to make the best use of the ground plane. The more you load the antenna, the shorter it is, and the less the radiation resistance. Lower radiation resistance means less signal output and input. Choose the highest antenna and place it as high as possible.
Antenna 144/430 MHz
The antenna is made in a plastic case (a fiberglass telescopic rod is very suitable), inside it is placed a sheet of pieces of copper wire, interconnected by coils L1, L2, L3 on plastic frames. A similar coil L4 is also located at the point of connection of the antenna web with counterweights. The antenna is powered through a tuning capacitor C1 (with an air dielectric) to the second turn of the coil L4 from the top.
The lower end of this coil is connected by counterweights to the cable screen. Pieces of foam rubber are put on the antenna canvas so that the whole household does not hang out inside the plastic "fishing rod".
Make sure that each side of your coaxial cable feed lines is the same length, down to a fraction of an inch, but be sure to avoid an exact 11 meter half wave for your phased hanger. Install antennas on both sides of your vehicle. The best performance will be at the front and rear of the vehicle, with small zeros on each side of the vehicle.
Raise the whip as high as you can on your vehicle. Why send half your signal up to the sky when it could do more good near the horizon? You can locate these antennas easily with a disposable whip and a gray or stainless steel loading coil at the base.
Element. Length
mm. Diameter
mm
H1 387 2.5
H2 424 2.5
H3 367 2.5
H4 564 2.5
H5 514 4.0* -
3 counterweights
Coil. Quantity
turns. Length
winding. External
diameter Diameter
wires
L1 12.5 63 11.5 2.5
L2 64 280 11.0 1.5
L3 7 32 14.0 2.5
L4 6 18 13.0 1.5
DISC-CONE ANTENNA
Compared to a coaxial antenna, a disk-cone antenna, which also has a circular radiation pattern and the same power supply, has a significantly larger bandwidth. Compared to a conventional dipole, the gain of this antenna is -3dB. This decrease in gain should not come as a surprise, since a disk-cone antenna has a correct radiation pattern over a very large bandwidth. The design of the disk-cone antenna, shown in Fig. 11-40, subject to the specified dimensions and direct power supply over a coaxial cable with a characteristic impedance of 60 ohms, has a bandwidth of 85 to 500 MHz.
It is about 20 inches tall with a sealed phased coil in the center and offers increased gain over a small 611 spike. A car with one mounted on the roof will generally still fit in a residential garage.
Because of this competitive market, companies are always trying to release a better product at a lower price. However, you may want to try your hand at building an antenna. The driven element receives the transmission energy from the drilling rig. Rope enough for the guy to be radial, depending on the height of the antenna.
The cone is made in the form of a horn from a sheet of copper or some other material that is easy to solder. The power cable is laid inside the cone and its outer braid is soldered to the cone, and the cleaned segment of the inner core 100 mm long is soldered to the metal disk. The disc is held horizontally
COLINEAR ANTENNA
Recently, the situation on the VHF amateur radio market has changed for the better, for us, radio amateurs, side. Today FM radio station on the 2-meter range has become available to everyone. In view of this, the question is, which antenna to choose for a radio amateur who is mastering this interesting range for the first time? You can hear a lot of answers, but today we will focus on an omnidirectional whip antenna, the appearance of which resembles the English letter J. This is an antenna for a beginner, for giving, for local communications on VHF.
We will not consider the principles of operation of this antenna in detail. We only note that the antenna is matched to the transmission line using a quarter-wave loop, which is equivalent to an inductor and capacitance coil.
Silicone sealant to cover the coaxial connection. The inner conductor of the coaxial cable is connected to the aluminum pipe with a screw at the bottom of the pipe. Detailed drawing on this page. Cover this connection with sealant or tape to protect it from corrosion. All vertical antennas must be grounded in some way. This is called the ground plane of the antenna.
The braided wire that forms the outer conductor of the coaxial cable is soldered to all four radial wires. Remember that the inner conductor and the outer braid of the coaxial cable must not touch each other, and the rays do not come into contact with the driven element. The radionats are tilted down at 45 degrees in different directions and tied to insulators. Rope or nylon cord is then tied to the insulators and used to hold the radii. They can be attached in any convenient place; trees, fence, house, etc.
Using the formulas shown in Figure 1, we obtain the dimensions of the antenna A, B, C and D.
For a frequency of 145.5 MHz:
A = 148.29 (cm)
B = 49.19 (cm)
C \u003d 4.63 (cm) (for Rfeeder \u003d 50 Ohm)
Material - copper or aluminum, tube or wire. What is at hand. I used aluminum wire of round section with a diameter of 9 mm. The only thing to remember is the shortening factor k, which relates the electrical length of the antenna web to its geometric length. The thicker the conductor, the greater this difference. In order not to miscalculate the length of the antenna, it is recommended to make the size B a little larger, and then bite off the excess during the tuning process.
It should be below 2 and ideally below 5 or. We've been talking to stations within a 40 mile radius using this about 30 foot high antenna using a mobile base setup. After removing the outer jacket, start grouping the screen down with the coax cable from the end. Now that the outer sheath and shield match, separate the shield braid to expose the inner conductor through the hole in the braid. Pull the entire inner conductor and pull it and the braid out. Be careful not to isolate the case from the inner conductor.
The antenna was tuned using an SWR meter or field indicator.
We attach the central core of the cable on the crocodiles to the long element (A), and the braid to the short one (B). And we begin to alternately turn on the transmission, looking at the SWR meter and moving the crocodiles, achieving a minimum SWR at the operating frequency. They turned it on, looked at the SWR meter, turned it off, moved the crocodiles. In the region of 4-6 centimeters from the jumper, there should be a minimum SWR. If it is not possible to achieve an SWR close to 1.1-1.2, then it is worth playing around with length B, biting off a few millimeters. During measurements, it is recommended to place the antenna between the two backs of chairs, away from the floor, surrounding objects, and especially metal.
Now attach the antenna insulator to the end of the inner conductor. Cut it off about 106 inches and attach the antenna insulator to the end. The total length of the inner and outer conductors should be approximately 17 feet. You can raise it to any height you want with a cord or rope attached to the insulator on the center conductor. It's a good idea to cover the end of the coax where it separates with some sort of waterproof sealant.
Just attach the coax connector on the end of the coax cable to your transceiver and you're on the air. The metal pipe serves as a ground connection for the antenna, replacing the space on the car body. Be sure to run a separate ground wire to a proper ground rod for lightning protection.
After setting, clamp the cable onto the bolts with clamps, check if the setting has gone astray, and then cover the contacts with automotive sealant.
Below a few centimeters from the connection point, it is recommended to wind a filter, which is 4-5 turns of the same cable on the frame, for example, from a 10 cc syringe. As a result, the flow of RF currents to the cable sheath will decrease and the likely TV interference will decrease.
This is a simple antenna for assembling and looking for parts. You can use any number of pieces of aluminum pipe as long as they are cut and thick enough not to bend and break in strong winds. The pieces should be gradually smaller, one of them may fit into the next. Cut two 2-inch grooves with a hacksaw into the outer pieces of aluminum and place a hose clamp around them. Now adjust the antenna to 22 ½ feet and tighten the hose clamps to hold it all together.
This board should be treated or painted to protect it from the weather. Place the bolt through a piece of wood a few inches below the vertical element. Here you should secure one end of the 6-foot piece of copper wire or tubing, the outer jacket of the coax cable, and each of the 104-inch stranded wires. These are called ground radions and should be tied with a cord at a 45 degree angle from the bolt. The radial arms and coaxial cable braid can be soldered together or can be crimped together with a crimp connector that fits the bolt.
Any 50 ohm cable can be used. In my case, this is a small piece of 3-4 meters of thin RG-58U from the antenna connection point to the balcony, and then through the connector about 25 meters of thick RG-8. I note that the thicker the cable, the lower its attenuation coefficient, as a rule. The thinner - the greater the loss of the useful signal. The same applies to the length of the cable, the longer the cable from the antenna to the transceiver, the greater the loss of the useful signal. In other words, to reduce cable losses, we try to adhere to the rule "the thicker and shorter the cable, the better."
The other end of the 6" copper wire is bent and secured to the vertical member. The center wire end of the coaxial cable is then twisted so that it slides up or down along the copper wire and is soldered after adjustment. Be sure to completely seal the end of the coaxial cable with hermetic sealant to keep moisture out.
While the following project won't necessarily save you any money, you can give it a try if you're interested in learning more about how fiberglass antennas are marketed. Two plastic insulating washers. First you should get yourself a 6 to 9 foot rod. If you already have an old one lying around, you can wring out the line loops and cut out the handle.
It is recommended for repetition by beginner VHF players, as well as a survey or backup antenna for experienced VHF radio amateurs.
Literature.
1. Karl Rothammel: Antennas. Volume 2. Edition 11. Light Publishing LTD., 2007, p. 10
Short Antenna for Portable Radio
Igor, UA6HJQ
(August 2001)
All portable radios are sold complete with regular shortened antennas, which are popularly called "gum". Some "rubbers" are quite long and if you do not need to communicate over long distances, they just get in the way. I decided to make an even shorter antenna, suitable for everyday use and communication over short distances.
Range 144 - 146 MHz
... for Yaesu VX-1R and C-508
I made this antenna for the VX-1R because it has a small SMA type antenna connector. The total length of the antenna with a connector is 43mm. A wire with a diameter of 0.6 mm is wound coil to coil on a frame with a diameter of 8 mm. A total of 25.5 turns were wound. In this case, the resonance turned out at a frequency of 145.3 MHz and an SWR of 1.1. After winding and checking the resonance, a thermo-tube is put on the antenna and heated. The thermo-shrink fits snugly around the antenna and gives it a "signature" look.
For any r / stations with a SR-50 connector
The total length of the antenna, together with the CP-50 connector, was 69mm. A wire with a diameter of 1.3 mm is wound coil to coil on a frame with a diameter of 10 mm. A total of 22 turns were wound. In this case, the resonance turned out at a frequency of 145.3 MHz and an SWR of 1.1. After winding and checking the resonance, a thermo-tube is put on the antenna and heated.
Range 430 - 440 MHz
The design of the antenna for the 433 MHz range does not differ from the previous design, only the number of coil turns must be reduced. The total length of the antenna with the connector is 42mm. A wire with a diameter of 1.3 mm is wound coil to coil on a frame with a diameter of 8.5 mm. A total of 6 turns were wound. The resonance turned out at a frequency of 435.3 MHz and an SWR of 1.8. After winding and checking the resonance,
Very often now you can see on the Internet ads for the sale of regular antennas of portable radio stations at 2m and 70cm. The prices of these "rubbers" are very high and can be very expensive for such a trifle. too time a simple scheme.
The antenna works on 2m and 70cm bands. Good luck in radiosport!!
C - B radio stations are often used in the country and in the field. Moreover, sometimes a C-B radio station is purchased only in order to provide communication with a summer house, with a fishing place or on a hiking trip. Since the physical dimensions of C-B antennas in the 27-MHz band are relatively small, as a rule, conditions, there are no problems with installing a full-size antenna.
The main criterion, which in this case must be guided by, is the convenience of installing the antenna, and the purposes for which the antenna will be intended. Now let's move on to considering the practical designs of these antennas.
A simple country quarter-wave vertical CB antenna in the 27-MHz range. In my opinion, the best antenna that can be installed in the country is a quarter-wave vertical. Such an antenna has many advantages over other types.
It emits radio waves that are mainly vertically polarized, which is optimal for communication with car and portable radio stations C - B of the 27-MHz band.
The vertical polarization pattern of a vertical whip antenna is circular, so it can provide radio communications in all directions, which is often required of it. For example, Provide radio communication with the city, with the route along which the car drives up to the dacha, with a place for fishing or hunting.
Rice. 1 shows the layout of a quarter-wave vertical C-B antenna. Let us consider in more detail the design of this antenna. It consists of a lambda/4 electrical pin connected to the central core of the coaxial cable and four counterweights. The pin can be 5-40 mm in diameter, the exact length for several pin diameters is indicated in this picture.
For its manufacture, it is convenient to use an aluminum or copper tube. For example, two ski poles that have reliable electrical contact between them work perfectly with copper water pipes, which have recently appeared on sale.
Fig.1. Antenna design 27MHz.
Counterweights can be positioned to the antenna pin at an angle of 90 to 140 degrees. Depending on the angle at which the counterweights are located to the antenna, the input impedance of the antenna depends.
A quarter-wave whip antenna installed at a height of at least 0.3L relative to the ground and equipped with four quarter-wave counterweights has an input impedance of about 20 ohms when the counterweights are located at an angle of 90 degrees to the antenna. Antenna resistance increases to 40 ohms when counterweights are located at an angle of 120 degrees to the antenna, and up to 50 ohms when counterweights are located at an angle of 135 degrees to the antenna (see L.1).
Of course, it is preferable to use counterweights located at an angle of 135 degrees to the antenna pin, in this case the antenna has an input impedance of 50 ohms, which is optimally matched with a coaxial cable with a wave impedance of 50 ohms.
Increasing the height of the antenna installation slightly affects the nature of the input impedance of the antenna. Reducing the installation height of the antenna causes an increase in the input impedance.
This is due to the absorption of the reactive field existing near the antenna by the real earth. As a result, the transmitter energy is spent on heating the earth and is not used for radio communication. A low installation of a vertical antenna should be avoided, otherwise, in order to maintain efficiency, the number of antenna counterweights should be increased to several tens (L.2).
At the end of the coaxial cable, it is desirable to install a high-frequency choke (it is also called a blocking choke), which will prevent high-frequency current from flowing to the outer sheath of the cable. This may be if, for some reason, the resistance of the outer sheath of the coaxial cable is comparable to the resistance of counterweights.
In this case, the outer sheath of the cable will serve as the radiating part of the antenna, which will lead to an increase in the level of interference during the operation of the antenna for transmission and loss of high-frequency energy in objects surrounding the coaxial cable. The simplest design of the blocking choke is 10-30 ferrite rings, tightly put on the end of the coaxial cable, the permeability of the rings does not matter.
Instead of ferrite rings, you can use ferrite tubes that are installed on the cords of computer monitors. When installing ferrite rings on a coaxial cable, the resistance of the section on which the rings are installed for high-frequency currents increases significantly, as a result of which the high-frequency current from the coaxial cable will flow into the antenna elements, and not to the outer sheath of the coaxial cable.
Rice. 2 shows a graph of the input impedance of the antenna shown in fig. 1. Fig. 3 shows the SWR of this antenna with respect to a coaxial cable with a characteristic impedance of 50 ohms, and fig. 4 shows the vertical polarization pattern of this antenna.
The MMANA program shows the antenna radiation pattern in the horizontal plane as a section of the volumetric pattern by the X-Y planes along the angle of maximum radiation. In the vertical plane, the radiation pattern of an antenna is a section by the X-Z plane of its volumetric radiation pattern.
On fig. 1, which depicts a vertical antenna, shows the location of these sectional planes. In the calculations, it was assumed that this antenna is located at a height of 3 meters above the real earth (conductivity is 5 mS/m, permittivity e = 13). These graphs were calculated using the MMANA program (see L.2).
In all cases of calculation, it was assumed that the diameter of the pin is 20 mm, the diameter of the counterweights is 4 mm, and the antenna is made of copper.
Tab. 1 shows the length of the shaft of a vertical antenna mounted 3 meters above the real earth and equipped with four 270 cm counterweights placed at an angle of 135 degrees to the antenna shaft at which it resonates at 27 MHz.
Please note that changing the height of the antenna installation, the number of counterweights, their angle of inclination leads to a change in the resonant frequency of the antenna. The resonant frequency of the antenna will decrease if you use a pin or counterweights in plastic insulation (see L.1).
The antenna can be tuned to the resonant frequency by extending/shortening the antenna pin (some methods of lengthening/shortening the antenna pin are given in L.2), as well as by means of antenna counterweights. Antenna input impedance can be adjusted by changing the angle of inclination of the counterweights relative to the antenna pin.
As can be seen from fig. 3, at SWR in a coaxial cable with a characteristic impedance of 50 ohms
A further increase in the diameter of the rod leads to an expansion of the antenna bandwidth, and a decrease in the diameter of the rod leads to a narrowing of the antenna bandwidth.
Fig.4. The radiation pattern of a homemade antenna is 27 MHz in vertical polarization.
Rice. 5 shows the dependence of the bandwidth of the antenna described above (a pin with a length corresponding to Table 1, 4 counterweights with a diameter of 4 mm located at an angle of 135 degrees to the pin, an installation height above the real earth of 3 meters) for an SWR value in a coaxial cable equal to 1.5: 1 and 2:1.
As can be seen from this figure, even a “thin” antenna with a vibrator 5 mm thick will fully provide acceptable operation on the 27-MHz C-B band, especially if you focus on the SWR in the antenna coaxial cable equal to 2: 1, namely this value SWR can withstand 99% of commercial C-B transceivers.
It is quite possible to manufacture a vertical antenna having a pin consisting of vibrators of different thicknesses, for example, from a ski pole with a diameter of 16 mm and a length of 1.5 meters and a piece of wire from a power transmission line with a thickness of 4-6 mm and an approximate length of 1.2 meters. The MMANA program allows you to calculate the parameters of such so-called "tapered" antennas.
The English word (in this case, it would be more accurate to say American) “tap” here can be translated as “part of an antenna of a different diameter.” In the case of such a combined antenna, it is necessary to use a design that provides reliable electrical contact between the sections. For example, in this case, a vibrator of a smaller diameter riveted into a vibrator of a larger diameter, a vibrator of a smaller diameter is tightly screwed to a vibrator of a larger diameter, or an adapter insert is used between vibrators of different diameters.
To install a whip vertical antenna, you can use natural or artificial elevations. For example, a dry tree or a roof ridge can be used as a mast.
Fig.6. Installing a homemade 27MHz antenna on a roof ridge.
When installing the antenna on a roof ridge, make sure that there are no objects that absorb high-frequency energy under the antenna. Installation of the antenna on the ridge of the roof of the cottage is shown in fig. 6.
To fasten the antenna pin as a home-made support insulator, a strong dry wooden stick, preferably oak, which must first be boiled in paraffin, can be used. This will give this surrogate post insulator electrical strength, moisture insensitivity, and rot protection. The antenna is attached to a wooden stick with two long screws, in extreme cases, it is simply screwed with a thick wire.
Instead of a wooden stick, you can successfully use pieces of plastic water pipes or a plastic ski pole. Instead of these surrogate post insulators, it is quite possible to use commercial post insulators, or post insulators used to install VHF intercom antennas. Post insulators from old decommissioned VHF antennas can be purchased inexpensively on the radio market.
Pay close attention to the antenna installation height. The minimum allowable height for the C - B range can be considered 0.25 * lambda, or 2.75 meters. In this case, the height is measured from the base of the antenna.
As the antenna installation height decreases, the ground begins to absorb high-frequency energy, which, during antenna operation, is created around the counterweights and under the antenna base. In practice, this will be expressed in a drop in antenna gain and in a decrease in radiation at small angles to the horizon, which is exactly what is required for both grassroots (local) and long-distance communications on CBS. The antenna weights will no longer have resonance in the 27-MHz band, and the antenna will only need to be tuned by changing the length of the vibrator.
It is possible to eliminate the effect of antenna gain loss and increase radiation at lower angles to the horizon by increasing the number of counterweights, and in order for the antenna to work efficiently enough, the number of its counterweights can be in the tens (more about the number of counterweights of an antenna located on the ground can be found in L.2). However, in my opinion, on the 27-MHz band it is easier to use a raised whip antenna with 2-4 counterweights than to install dozens of non-resonant counterweights around the antenna on the ground.
To power the quarter-wave vertical antenna shown in fig. 1, a 50-ohm impedance coaxial cable is required. It is desirable that the electrical length of this cable be a multiple of half the wavelength of the 27-MHz CB band, this will immediately eliminate many of the problems that arise during tuning and operation of the antenna.
As mentioned earlier, the input impedance of a quarter-wave vertical antenna depends on many factors, and in practice it can be in the range of 30-70 ohms for an amateur radio vertical quarter-wave antenna mounted on a roof ridge. Using a half-wave segment of a coaxial cable to power the antenna will allow you to “deliver” the input impedance of the antenna without unnecessary transformation directly to the output stage of the transceiver, which, in general, will somewhat increase the efficiency of this antenna-feeder system.
For a cable with polyethylene insulation, the length of the half-wave segment will be 3.63 meters, and for a cable with fluoroplastic insulation, 4.4 meters. Serious attention must be paid to protecting the opening of the coaxial cable from atmospheric influences. The simplest protection can be achieved with a fast curing automotive epoxy putty.
More details about vertical antennas can be found in L.3 and L.4.
A whip antenna installed in a rural area high above the ground, even a small one designed for the 27-MHz CBS band, needs to be protected from atmospheric electricity. Otherwise, the transceiver connected to this antenna may be damaged and the operator may receive an electric shock. Some methods for protecting antennas from atmospheric electricity are described in L.2 and L.Z.
Grigorov I.N. Rk2005, 2.
Literature:
- Grigorov I.N. Antennas. Urban structures. - M.: IP RadioSoft, 2003.
- Grigorov I.N. Antennas. Adjustment and coordination. - M.: IP RadioSoft, 2002.
- Grigorov I.N. Practical antenna designs. -M..DMK, 2000.
- The ARRL Antenna Book. 20-Edinion: published by ARRL, USA, 2003.
Most often, the CB antenna is selected for communication with truckers at a frequency of 27.135 MHz AM- this is the so-called "15th channel", but in Russia and other countries other frequencies of the cb range are also used. This range entered free use in the USA in 1957, and later, in 2006, it was allowed in Russia. The most popular intercoms are the Megajet brand walkie-talkies.
Automotive CB antennas. Fastening types:
- Mortise, it is cut-in or with installation on a bracket. Crashes into the roof or trunk of a car, or mounted on a bracket. Various types of brackets allow you to attach them to the drain, mirror, roof rails and other protruding parts of the car;
- Magnetic. Mounted with a magnetic platform on the roof or trunk of a car. The platform is connected with a pin with a collapsible or non-collapsible connection. The magnetic mount is convenient to use, allows you to avoid cutting holes and quickly remove the pin if necessary, but it can damage the car's paintwork or fall off at high speed from the oncoming air flow if the size of the magnetic base is incorrectly selected.
Mortise antennas can be installed on magnetic bases if they have the same types of connectors. This also works vice versa. The most common connector types are PL-259 (aka UHF-male) and NMO. They are not compatible with each other. The mating part of the bracket mount is a connector with a cable. Usually 4 meters. As a rule, a connector for connecting a cable to a walkie-talkie must be purchased separately, since a 27 MHz mortise antenna requires a fixed cable installation.
Emitter length
The communication range depends on this parameter. The longer the emitter, the better it is. But there are restrictions on the length depending on the type of operation. For example, for a walkie-talkie on a truck that often moves around the city, do not put a long antenna, as it will hook the wires.
The following sizes are commonly used:
- 0.3 - 1m - truckers and motorists for long trips;
- 1 - 1.5m - truckers (highway-city), jeepers, special equipment;
- 1.5 - 2m - taxi, radio amateurs, motorists;
- more than 2m - radio amateurs, often as a base.
The description often contains a power characteristic. It characterizes the maximum signal power that the emitter is capable of transmitting. If you connect a CB radio with a power of 50 W to a 25 W emitter, the station will fail due to the destruction of the insulation of the matching coil and overheating of the transmitter.
The most common brands represented in Moscow and Russia are Sirio, Diamond, Megajet, Optim. They can be bought both in Moscow and St. Petersburg, and with delivery to the regions. It must be remembered that long antennas are twisted into a ring when sent and, upon receipt, they may have to be corrected.