user:kurser:ham_vt2023_l7
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| user:kurser:ham_vt2023_l7 [2026/03/02 17:18] – loka | user:kurser:ham_vt2023_l7 [2026/03/22 18:34] (current) – Updated Swedish glossary. loka | ||
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| - | **Recommended reading: KonCEPT page 191-229 (chapter 7 + 8) ** | + | **Recommended reading: KonCEPT |
| Start with transmission line (TL), the most difficult component. | Start with transmission line (TL), the most difficult component. | ||
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| characterized by: Characteristic impedance, Z_0, a geometry and material parameter. Length and the speed of light in the transmission line. Two metal conductors that guide the fields. | characterized by: Characteristic impedance, Z_0, a geometry and material parameter. Length and the speed of light in the transmission line. Two metal conductors that guide the fields. | ||
| - | Used for high frequency signals. | + | Used for high frequency signals. |
| Waves propagate along transmission lines. Reflections along a TL are similar to light in a glass/ | Waves propagate along transmission lines. Reflections along a TL are similar to light in a glass/ | ||
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| Balanced/ | Balanced/ | ||
| - | balanced TL folded out -> dipole antenna! Nice SWR achieved. L = lambda/2 = 300/(2*f) ~=(0,96*lambda/2) | + | balanced TL folded out -> dipole antenna! Nice SWR achieved. L = λ/2 = 300/(2*f) ~=(0,96*λ/2) |
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| \\ de SA6KRZ | \\ de SA6KRZ | ||
| - | Updated | + | Last updated |
| In this segment, possible exam questions have been marked // | In this segment, possible exam questions have been marked // | ||
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| ==Antenna types== | ==Antenna types== | ||
| - | There are many different types of antennas, since different antenna designs are optimised for solving different problems. There is no antenna that is perfect for every single operational situation. However, the opposite is true; there are indeed antennas | + | There are many different types of antennas, since different antenna designs are optimised for solving different problems. There is no antenna that is perfect for every single operational situation. However, the opposite is true; it is easy to make an antenna |
| A selection of different antenna types, roughly in order of most common -> least common | A selection of different antenna types, roughly in order of most common -> least common | ||
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| ... however, in practice there is nothing prohibiting an antenna array from being built using any antenna type. | ... however, in practice there is nothing prohibiting an antenna array from being built using any antenna type. | ||
| - | Very often, specific antennas are are combination of other antenna types. For example, the very common Yagi-Uda antenna, is usually built using a combination of three (or more) dipole antennas, and one magnetic loop antenna. | + | Very often, specific antennas are are combination of other antenna types. For example, the very common Yagi-Uda antenna, is usually built using a combination of three (or more) dipole antennas, and an additional " |
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| * Directivity, | * Directivity, | ||
| * Antenna gain | * Antenna gain | ||
| - | * Far-field distance = d_f > 2*D^2/λ, given d_f >> | + | * Far-field distance = d_f > 2·(L_D)²/λ, given d_f >> |
| * Radiation efficiency, η | * Radiation efficiency, η | ||
| * Radiation pattern, E & H patterns | * Radiation pattern, E & H patterns | ||
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| These elements are often mounted to a frame of sorts, like a large metal bar that supports all elements. This bar is known as the //boom// (SE: bom). | These elements are often mounted to a frame of sorts, like a large metal bar that supports all elements. This bar is known as the //boom// (SE: bom). | ||
| - | Often, antennas are shielded from the evil world of rain, snow, pidgeons | + | Often, antennas are shielded from the evil world of rain, snow, pigeons |
| \\ | \\ | ||
| ==Direction== | ==Direction== | ||
| - | The most ideal antenna is a single charge floating in free space, radiating as a sphere equally strongly in all directions. Such a single charge is known academically as an //isotropic radiator//. Practically, | + | The most ideal antenna is a single charge floating in free space, radiating as a sphere equally strongly in all directions. Such a single charge is known academically as an //isotropic radiator//. Practically, |
| How small that illuminated segment of the sphere is as opposed to size the entire sphere, is known as the //antenna directivity// | How small that illuminated segment of the sphere is as opposed to size the entire sphere, is known as the //antenna directivity// | ||
| - | A higher directivity means that more of the emitted/recieved | + | A higher directivity means that more of the emitted/received |
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| Practically, | Practically, | ||
| - | A dipole antenna is -2.15 dB less " | + | A dipole antenna is -2.15 dB less " |
| \\ | \\ | ||
| //dBd = directivity in dB with respect to an ideal dipole antenna.// | //dBd = directivity in dB with respect to an ideal dipole antenna.// | ||
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| ==Shaping the lobes + Terminology 2== | ==Shaping the lobes + Terminology 2== | ||
| - | The EM wave that we wish to transmit/recieve | + | The EM wave that we wish to transmit/receive |
| The resulting lobe pattern from the driven element, is then by-design usually deformed using other elements that are in fact not connected to the cable that fed the antenna. All elements on the antenna that are not driving the EM wave, are known as parasitic elements (SE: parasitelement). | The resulting lobe pattern from the driven element, is then by-design usually deformed using other elements that are in fact not connected to the cable that fed the antenna. All elements on the antenna that are not driving the EM wave, are known as parasitic elements (SE: parasitelement). | ||
| - | These parasitic elements have different purposes. They could be used to direct the lobe pattern into some wanted direction; such elements are known as // | + | These parasitic elements have different purposes. They could be used to direct the lobe pattern into some wanted direction; such elements are known as // |
| Example: the Yagi-Uda antenna, has one driven element on its boom. To get the signal pointing forwards, three dipole directors are mounted at the front of the antenna. And to get the lobe pattern pointing less backwards, a reflector is mounted at its back. | Example: the Yagi-Uda antenna, has one driven element on its boom. To get the signal pointing forwards, three dipole directors are mounted at the front of the antenna. And to get the lobe pattern pointing less backwards, a reflector is mounted at its back. | ||
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| - | ==Emitted power: p.e.p. and e.i.r.p== | + | ==Emitted power: p.e.p., e.r.p. and e.i.r.p== |
| The HAM radio band plan sets radiation emission limits in terms of power, either as **p.e.p.** or **e.i.r.p.** (peak emitted power, equivalent isotropic radiated power). | The HAM radio band plan sets radiation emission limits in terms of power, either as **p.e.p.** or **e.i.r.p.** (peak emitted power, equivalent isotropic radiated power). | ||
| * The p.e.p. limit defines how much peak power may be fed into your antenna. | * The p.e.p. limit defines how much peak power may be fed into your antenna. | ||
| - | * The e.i.r.p. limit takes antenna gain into account as well, meaning that no lobe may peak above a certain power. | + | * The e.r.p. limit takes antenna gain into account as well, where gain = the best gain you get from that antenna, meaning that no lobe may peak above a certain power. |
| + | * The e.i.r.p. limit assumes that your are using a theoretically perfect isotropic radiator as an antenna. So, from a given limit, divide by the gain you would get from an isotropic radiator -> gives you the maximum power you may feed your antenna. | ||
| + | |||
| + | All power limits allow for subtracting a known loss in the cable, filters etc. before power hits the actual antenna input. | ||
| \\ | \\ | ||
| // | // | ||
| \\ | \\ | ||
| - | In the 5.3515-5.3665 MHz band, a HAM radio operator may at most transmit with 15 W e.i.r.p. Are you allowed to transmit at 5.36 MHz with 10 W using a +3 dB gain directional antenna? | + | In the 5.3515-5.3665 MHz band, a HAM radio operator may at most transmit with 15 W e.r.p. Are you allowed to transmit at 5.36 MHz with 10 W using a +3 dB gain directional antenna? |
| \\ | \\ | ||
| \\ | \\ | ||
| - | Answer: No, this is not allowed. An antenna with +3 dB gain, would make a 10 W radiated emission seem as if we're transmitting with 20 W, which is above the e.i.r.p. limit. | + | Answer: No, this is not allowed. An antenna with +3 dB gain, would make a 10 W radiated emission seem as if we're transmitting with 20 W, which is above the e.r.p. limit. |
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| ==Complicated: | ==Complicated: | ||
| - | Let's imagine an antenna with two transmitting elements. Thus, there are two electric (E) fields to consider. Let's say that one is vertically polarised, and the other one horisontally | + | Let's imagine an antenna with two transmitting elements. Thus, there are two electric (E) fields to consider. Let's say that one is vertically polarised, and the other one horizontally |
| \\ | \\ | ||
| If we stand directly in front of where the antenna is pointing, we can see both the cosine and sine waves like composants in a complex vector. As time progresses, and the E cosine goes up/down while the other E sine goes left/right, that complex vector will thus be spinning around in a circle as time progresses. This type of polarisation is known as a circular polarisation; | If we stand directly in front of where the antenna is pointing, we can see both the cosine and sine waves like composants in a complex vector. As time progresses, and the E cosine goes up/down while the other E sine goes left/right, that complex vector will thus be spinning around in a circle as time progresses. This type of polarisation is known as a circular polarisation; | ||
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| All commonly used formulas related to antennas, assume simplifications that happen once we are standing at a large distance away from the antenna. | All commonly used formulas related to antennas, assume simplifications that happen once we are standing at a large distance away from the antenna. | ||
| \\ | \\ | ||
| - | The far-field distance = d_f > 2*D^2/lambda, given d_f >> | + | The far-field distance = d_f > 2·(L_D²)/λ, given d_f >> |
| Meaning, that for very high frequencies, | Meaning, that for very high frequencies, | ||
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| 2) Space wave (global range) | 2) Space wave (global range) | ||
| * Reflections from the ionosphere' | * Reflections from the ionosphere' | ||
| - | * Reflections affect | + | * Reflections affect |
| * D = 60-90 km height. | * D = 60-90 km height. | ||
| * " | * " | ||
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| ^ English ^Svenska ^ Comment ^ | ^ English ^Svenska ^ Comment ^ | ||
| + | | -3 dB point | Halvvärdesbredd | ||
| + | | Antenna array | Gruppantenn | ||
| + | | Boom | Bom | | | ||
| + | | Design factor | ||
| + | | Directors | ||
| + | | Driven element | ||
| + | | Elements | ||
| + | | Gain | Antennvinst | ||
| + | | Lobe | Strålkägla | ||
| + | | Lobe beamwidth | ||
| + | | Lobe pattern | ||
| + | | Parasitic element | ||
| + | | Radio broadcast | ||
| + | | Radome | ||
| + | | Reflector | ||
| | Resistor | | Resistor | ||
| + | |||
user/kurser/ham_vt2023_l7.1772471919.txt.gz · Last modified: 2026/03/02 17:18 by loka