Antenna tuning with swr 430. How to set up an antenna, what you need to set up an antenna. Antenna tuning - step by step
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Description
*SWR-430 measures power and SWR. - a device that measures the standing wave ratio and is actively used to tune a variety of radio stations. The presence of an SWR meter will allow you to optimally tune the antenna of your radio station and achieve....
Characteristics
- a device that measures the standing wave ratio and is actively used to tune a variety of radio stations.
The presence of an SWR meter will allow you to optimally tune the antenna of your radio station and achieve maximum efficiency of the radio.
Range 24-30 MHz
Resistance - 50 Ohm
Measurement error - 5%.
Power measurement limits 10 and 100 W
Connectors PL (UHF)
Setting up the car radio antenna. After installation, the antenna must be tuned to the minimum SWR value in the middle of the operating frequency section, or if it is intended to operate on only one frequency, to the minimum SWR value at that frequency. SWR is the standing wave ratio - a measure of the matching of the antenna-feeder path. It shows the percentage of power loss in the antenna. Power losses at various SWR values are shown in the table
| SWR | 1 | 1,3 | 1,5 | 1,7 | 2 | 3 | 4 | 10 |
| % loss | 0 | 2 | 3 | 6 | 11 | 25 | 38 | 70 |
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Licenses and certificates
1. To the nest" ANT" connect a 50 ohm load or an antenna.2. To the nest" RTX"Plug in the radio.
3. Set the switch to the required measuring range ( 10W or 100W).
PWR".
5. Turn on the radio for transmission.
6. On the scale, read the transmitter power.
P.S. AM and FM modes will have different values for the same radio station.
How to measure SWR:
1. To the nest" ANT" connect the antenna.2. To the nest" RTX"Plug in the radio.
3. Tune the radio to the operating frequency.
4. Set the switch to " SWR".
5. Set the switch to " FWD" (direct signal).
6. Turn on the radio station for transmission and handle " CAL"set the pointer to the extreme right position of the scale.
7. Release the radio button.
8. Set the switch to position " REF"(reflected signal).
9. Turn on the radio station for transmission and read the SWR on the scale.
10. Change the radio's tuning frequency and repeat the measurements. The SWR will change. Take SWR measurements at different frequencies. The minimum SWR will be at the frequency your antenna is tuned to.
10. Shorten the antenna (usually car antennas are tuned to a lower frequency). Again, take SWR measurements at different frequencies. The minimum SWR will be obtained at a different frequency. So by the method of successive approximation, you can tune the antenna to resonance at the operating frequency.
RULE: the shorter the antenna, the greater the frequency (the greater the channel and grid number).
P.S.
SWR changes little within the same frequency grid.
The best SWR = 1 (the signal from the antenna does not return to the radio station), the worst is infinity (the signal does not go to the antenna, the antenna or cable may be broken, there is no contact, etc.). SWR \u003d 1.5 you can still work, but not all the energy goes into the antenna and the transmitter works in heavy mode (may fail).
Many people are concerned about the accuracy of SWR meters sold in our radio markets and in radio equipment stores. This article has an answer to this question. Tested and benchmarked against two of the most popular SWR meters, SWR-420 and SWR-430.
On the pages of the magazine, I have repeatedly written that the “devices” popular among the people for determining the standing wave coefficient do not provide sufficient accuracy to obtain an adequate picture of the state of the AFU, which, however, does not mean that they cannot be used for initial antenna tuning.
Materials and methods
In this test, 5 SWR-430 SWR meters and 5 SWR-420 SWR meters from a well-known manufacturer, whose name we will not name :), took part. However, based on practice, the picture is repeated from manufacturer to manufacturer, since the design does not fundamentally change, but is simply copied, and the data obtained can be used to correct the readings of other SWR meters of a similar design. The SWR meters were randomly selected to maximize scatter, if any. All data obtained during the measurement were averaged and summarized in a common table. The readings were compared with the RigExpert AA-600 antenna analyzer, the data of which were taken as a standard.
As a load, a Lemm AT-2001 Turbo antenna embedded in the roof of a Chevrolet Lacetti (sedan) was used.
Yosan Excalibur served as a signal source at different frequencies for studying SWR meters.
For the measurement, 15 frequencies were selected corresponding to the 20th channel of the selected grid, which is quite enough to obtain an accurate picture of the dependence of readings on frequency.
results
As a result, the picture turned out as follows. The SWR-420 and SWR-430 columns indicate the SWR value at the corresponding frequency.
The Err 420 and Err 430 columns indicate the difference in the SWR meter reading relative to the analyzer, which must be added to the SWR meter reading to obtain the true SWR value. I would like to draw your attention to the fact that these values are not absolute, and may vary depending on the measurement conditions, AFU resistance values, the parameters of the SWR meters themselves, which also have some variation in readings from instance to instance (about 5-10%), however, the general dependence should be preserved.
As can be seen from the table and graph, factory SWR meters not only underestimate the SWR value in the studied frequency range, but also smear the readings somewhat. Although, in general, these devices, especially the SWR-430, are quite suitable for initial antenna tuning and the simplest AFU diagnostics. SWR-420, in my opinion, is less successful in terms of choice, but as an alternative, it is also quite suitable for use. In short, in order to find the minimum SWR and draw a conclusion in which direction to tune the antenna, both devices are quite suitable. For accurate measurements, it is necessary to calibrate each individual instrument by comparing its readings with a reference impedance meter and calculating for each frequency under study the correction that will need to be taken into account in the measurement.
Outcome
In general, SWR-420 and SWR-430 are quite suitable for use as a primitive device for diagnostics and initial adjustment of antenna-feeder devices. SWR-430 proved to be better than SWR-420 and gave more accurate results in the frequency range declared by the manufacturer, therefore, in my opinion, it is more promising in terms of use. Plus, the SWR-430 has a function to measure the output power of the radio transmitter. However, one should not forget that in order to obtain correct results, such measurements must be carried out on a load dummy, and not on an antenna !!!
The article is written for beginners, those who are going to set up the antenna for the first time to work on the channel (frequency) they need. Those who have already repeatedly tuned antennas are unlikely to find something useful for themselves in the article.
The article describes the main points of tuning simple single-band antennas - car mortise, on a magnetic base, basic 1/4 GP, 1/2 (half-wave), 5/8 (five-eighths).
What you need to tune the antenna
SWR meterA device that shows the ratio of the direct (coming from the radio station to the antenna) and the reverse (reflecting from the antenna) waves in the cable.
Indirectly, this device shows that the output impedance of the radio station is equal to the cable impedance, and it is equal to the antenna impedance. You can read about what wave resistance is and how it differs from that shown by a conventional tester in the article:.
An SWR meter (SWR meter) can be purchased (the issue price is about 1000 rubles) or you can temporarily ask someone you know who has one.
radio station
The SWR meter does not work without a radio.
The more "grids" there are in the radio station, the wider the frequency range the radio station can be tuned, the easier it will be to tune the antenna to the desired frequency (channel).
With a radio station with 40 channels at 27 MHz, it is possible to tune the antenna, but it is very difficult, with a radio station that has 400 or 600 channels, this is much easier to do.
Roulette or ruler
It will be required to measure the antenna web and determine how many centimeters to shorten or lengthen.
In principle, you can do without a tape measure or ruler and perform the adjustment simply step by step, slightly shortening or lengthening the antenna web.
Fundamentals of Antenna Tuning
The antenna must be adjusted in the place where it will then stand.That is, the antenna must be tuned in the conditions in which it will continue to be used, especially if at a distance closer than 2-3 wavelengths (wavelength = 300 / frequency in MHz (for 27 MHz, the wavelength is about 11 meters)) there are some conductive objects parallel to the antenna web.
If this is a basic antenna, then you already need to prepare a mast for it, which allows you to remove and install the antenna, raise and lower it all for setup and maintenance.
If this is a car antenna, then the car should be parked so that there is exactly the situation nearby that will be when driving it at the time the radio station is operating, that is, other cars were standing at a distance of about 5-10 meters, but on the other hand, it should not be nearby be the walls of reinforced concrete houses, garages; you cannot stand inside an iron garage or hangar. At the time of measurement, when setting up, the car doors and trunk should be closed. You should not stand next to the car yourself, the human body absorbs radio waves and thereby introduces losses, affects the operation of the antenna.
There should be no moving conductive objects at a distance of 2-3 wavelengths from the antenna.
All instrument connections must be reliable.
You should not keep everything "on weight", pressing with your hands to the contacts somehow stripped pieces of cable that are about to fall out of the connectors or are closed.
Reliable connections are needed so that the readings of the device do not change as they please, do not float and are repeatable. If the readings are not repeatable, then these are no longer instrument readings, but the weather on Mars at the time of eating Snickers, and it is impossible to focus on such readings.
How to use a SWR meter
We connect the cable to the antenna, the other end of the cable to the SWR meter, to the "ANT" connector, the connector of the SWR meter "TRANS" is connected to the antenna connector of the radio station.We turn on the radio station and set the frequency at which we will measure the SWR.
If there is a SWR / PWR switch, we translate it into the SWR position.
SWR meter switch "FWD/REF" to FWD.
We press the transmission on the radio station and set the arrow sticking out of the SWR meter with the regulator to the end of the scale. Let's release the transmission.
Set the "FWD/REF" switch to the REF position.
We press the gear and count the SWR reading on the indicator. On most SWR meters, the less the arrow deviates, the less SWR, if it does not deviate at all, then SWR \u003d 1 or the device is dead. If at all frequencies, in the REF position, the arrow does not deviate, then either you have a good equivalent load connected instead of the antenna, or the device has died, but let's not talk about sad things.
Antenna tuning - step by step
We connect everything to measure the SWR, as mentioned above, the antenna to the working position.- We set the radio station to the highest frequency that the radio station is capable of delivering, for example, grid G channel 40 (more precisely, see the instructions for the radio station).
- We measure the SWR, moving down the frequencies in about 20 channels (200 kHz), remember at what frequency (channel, grid) there was a minimum of SWR and which SWR was at a minimum.
Now there are several options:
The SWR is large everywhere, the device "scales".
Either you use the wrong SWR meter or you have a break in the cable or antenna.
SWR smoothly, as the frequency decreases, but we did not reach the minimum.
Your antenna is too long. Need to be shortened. In shortening, it is worth remembering the golden rule: "measure seven times, cut once." It is impossible to stick a shortened one back in most cases, so we shorten it a little, for CB antennas in the 27 MHz band it is a little about 1 centimeter, for LPD or PMR antennas in the 433-446 MHz band it is a little 2 millimeters.
The SWR increases as the frequency decreases.
Your antenna is too short. The antenna needs to be extended. How exactly - better by 20 percent, and then shorten.
The SWR decreased as the frequency decreased, at a certain frequency it became minimal, and then, as the frequency decreased further, it began to increase again.
This is the most common case.
This behavior means that everything is fine, the antenna is operating in the desired range, it remains only to adjust it to the desired frequency (channel).
If you have this case, then it is advisable to find exactly on which channel the minimum SWR is.
If the frequency at which the minimum SWR was lower than what you need, then the antenna should be slightly shortened, literally 5 millimeters each, if we are talking about the 27 MHz range, after each shortening, look where the minimum SWR is now, and shorten it until the minimum The SWR will not be at the desired frequency.
If the frequency at which the minimum SWR was higher than you need, then the antenna needs to be lengthened.
What to do if the minimum SWR is at the desired frequency, but this minimum value is still large
This suggests that the antenna does not work quite the way the manufacturer intended or the antenna is rubbish, but you don’t need to immediately talk about sad things.If this is a car mortise antenna, then maybe it "does not have enough mass", that is, contact with the mass is poor.
If this is a car antenna on a magnet, then it may also "not have enough mass", for example, the paint layer is too thick.
Or your car antenna stands where it should not be placed - next to the elements of the metal roof rack, next to the additional light that you hung on the trunk, you generally magnetized it to the hood or trunk, bumper or wheel disk.
Maybe you fixed the mortise antenna on the aluminum skids of the trunk that you have on the roof, but the trunk turned out to be not aluminum but plastic or does not have reliable contact with the mass of the car, or is not long and wide enough to act as a mass for the antenna.
If the antenna is on a magnetic base, try to look for another place where to "slap" it, try from the corner of the roof, in the center of the roof, from another angle.
RF currents do not flow exactly like DC, where the tester shows excellent contact, for radio frequency this can be a bottleneck.
If the antenna is mortise, see if you cleaned the paint well from the place where the antenna ground contact is attached.
If you mounted the mortise antenna on the trunk or some kind of fixture on the drain, try to improve contact with the ground. There were times when the author of the article took 2 pieces of wire 0.5 mm thick without insulation, wound it on a bracket on which a mortise antenna was fixed hanging on a drain or trunk, threw them into different corners of the car roof along the drains and the SWR decreased from 3 to 1, then there the antenna began to work perfectly (naturally, the signal on the air also improved).
Throwing extra wires, tearing paint and then pouring sealant or looking for other ways to improve the mass or installation point - it's up to you, it's your antenna and your car.
If you don’t have a car, but a basic version of the antenna, then the treatment here is actually exactly the same, namely: maybe you need more “mass”, or maybe you need to climb into the design of the antenna with a soldering iron.
To begin with, we make sure that there is enough mass - the pipe is the base, it is also the main counterweight, the mass for antennas of the type 5/8 (five-eighths) and 1/2 (half a wave) must be at least 1/4 of the wavelength, that is, for 27 MHz it is about 2 meters 75 centimeters. More is better; less - you have to lengthen the wire thrown over the roof.
Although sometimes it happens that everything is done well, but the antenna does not tune, as it happened with a friend of the author of the article, 1/2 did not want to tune. It seems to be in the frequency, but the SWR is not 1 or even 1.2 or 1.5 - it turned out that someone "climbed into the antenna" before it and cut off the coil coil installed inside the antenna.
It is also very likely that your base antenna is interfering with the nearby stretched optics of your provider or the collective antenna mast.
How much to cut and what is the ruler for?
Antenna dimensions depend linearly on frequency.
If the antenna is full-size, then how much it needs to be shortened or lengthened in order to get to the desired frequency directly depends on the ratio of the current frequency where it resonates and the desired frequency where you would like the antenna to resonate.
Let me explain with an example:
we have a quarter, let it be 267 centimeters long, it resonates (SWR is minimal) turned out to be at a frequency of 27.0 MHz (channel 4 of sect C), we want the antenna to work at 27.275 MHz.
We consider K differences in frequencies:
27.0 / 27.275 = 0.9899175068744271
We multiply by this K the current length of the antenna:
267 * 0.9899175068744271 = 264.3
and we get the length that the antenna must have in order to earn on 27.275.
Calculate how much to cut:
267 - 264 = 3 cm.
However!
It is not necessary to cut exactly 3 cm at once. Do not forget, the antenna is not only a pin, it is also counterweights. Everything affects.
So you can determine the order of the first cut - either 3 cm, or 5 mm.
Next, we proceed step by step.
For the above example, you can cut off 1.5 cm, again find the resonance, and based on the result, move on.
Last but not least, this should have been written first:
Basic rules for installing antennas
The antenna must be placed no closer than one wavelength to other conductive objects, especially those that will be parallel to the antenna.
The higher the antenna is installed, the better.
It is clear that for car antennas at 27 MHz these rules are simply impossible to comply with, therefore car antennas are compromise, so do not demand miracles from them.
If, nevertheless, you have no time, there is no desire to deal with the intricacies of measuring SWR, look for an SWR meter, adjust the antenna yourself and you are in Novosibirsk, you can refer, for example, here:
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