Three features of antennas are particularly important, namely their directionality, gain, and bandwidth. Dipoles are very directional : they pick up incoming radio waves traveling at right angles to them. That's why a TV antenna has to be properly mounted on your home, and facing the correct way, if you're going to get a clear picture. The telescopic antenna on an FM radio is less obviously directional, especially if the signal is strong: if you have it pointed straight upward, it will capture good signals from virtually any direction.
The ferrite AM antenna inside a radio is much more directional. Listening to AM, you'll find you need to swivel your radio around until it picks up a really strong signal. Once you've found the best signal, try turning your radio through exactly 90 degrees and notice how the signal often falls off almost to nothing. Although highly directional antennas may seem like a pain, when they're properly aligned, they help to reduce interference from unwanted stations or signals close to the one you're trying to detect.
But directionality isn't always a good thing. Think about your cellphone. You want it to be able to receive calls wherever it is in relation to the nearest phone mast, or pick up messages whichever way it happens to be pointing when it's lying in your bag, so a highly directional antenna isn't much good. Similarly for a GPS receiver that tells you where you are using signals from multiple space satellites. Since the signals come from different satellites, in different places in the sky, it follows that they come from different directions, so, again, a highly directional antenna wouldn't be that helpful.
The gain of an antenna is a very technical measurement but, broadly speaking, boils down to the amount by which it boosts the signal.
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TVs will often pick up a poor, ghostly signal even without an antenna plugged in. That's because the metal case and other components act as a basic antenna, not focused in any particular direction, and pick up some kind of signal by default. Add a proper directional antenna and you'll gain a much better signal. Gain is measured in decibels dB , and as a broad rule of thumb the bigger the gain the better your reception.
In the case of TVs, you get much more gain from a complex outdoor antenna one with, say, 10—12 dipoles in a parallel "array" than from a simple dipole. All outdoor antennas work better than indoor ones, and window and set-mounted antennas have higher gain and work better than built-in ones. An antenna's bandwidth is the range of frequencies or wavelengths, if you prefer over which it works effectively.
The broader the bandwidth, the greater the range of different radio waves you can pick up. That's helpful for something like television, where you might need to pick up many different channels, but much less useful for telephone, cellphone, or satellite communications where all you're interested in is a very specific radio wave transmission on a fairly narrow frequency band.
The circuit inside it has no power source: it gets all its energy from the incoming radio waves. This one works with 2. Artwork: Oliver Lodge's illustration of sending radio waves through space from a transmitter red to a receiver blue some distance away, taken from his patent US , Electric Telegraphy. There's no easy answer to that question because radio evolved into a useful technology through the second half of the 19th century thanks to the work of quite a few different people—both theoretical scientists and practical experimenters.
Who were these pioneers? Scottish physicist James Clerk Maxwell figured out a theory of radio around , and Heinrich Hertz proved that radio waves really did exist about 20 years later they were called Hertzian waves in his honor for some time afterward.
Near-zero metamaterial inspired UHF antenna for nanosatellite communication system
Several years later, at a meeting in Oxford, England on August 14, , English physicist, Oliver Lodge , demonstrated how radio waves could be used for signalling from one room to another in what he later described in his autobiography as "a very infantile kind of radio-telegraphy. None of the original radio experiments used transmitters or receivers that we would instantly recognize today. Hertz and Lodge, for example, used a piece of equipment called a spark-gap oscillator : a couple of zinc balls attached to short lengths of copper wire with an air gap in between them.
Lodge and Marconi both used Branly coherers glass tubes packed with metal filings for detecting the waves they'd transmitted and received, though Marconi found them "too erratic and unreliable" and eventually designed his own detector. Armed with this new equipment, he carried out systematic experiments into how the height of an antenna affected the distance over which he could transmit a signal.
More types of antennas The simplest radio antennas are just long straight rods. Important properties of antennas Three features of antennas are particularly important, namely their directionality, gain, and bandwidth. Directionality Dipoles are very directional : they pick up incoming radio waves traveling at right angles to them. Gain The gain of an antenna is a very technical measurement but, broadly speaking, boils down to the amount by which it boosts the signal.
Bandwidth An antenna's bandwidth is the range of frequencies or wavelengths, if you prefer over which it works effectively. Who invented antennas? And the rest, as they say, is history! Sponsored links. Wiley, A good, general, theoretical introduction aimed at physics and electrical engineering undergraduates.
Not really suitable for beginners—and you will need a decent grasp of math. Volakis et al. McGraw-Hill, A look at the theory and practical design of small antennas for cellphones, RFID, and other applications. Antenna attachment with 2U nanosatellite structure- a simulation and b fabricated. Antenna performance with nanosatellite structure- a reflection coefficient and b total efficiency. Both the radiation patterns are perturbed by nanosatellite structure and increased cross-polarization label with respect to free space condition.
Compared with metamaterial-less without metamaterial antenna, the pattern is more spherical and provide more coverage of area of interest. Moreover, the realized gain obtained by without and with metamaterial antenna is 0. Normalized radiation pattern of the proposed antenna with nanosatellite structure- a without metamaterial and b with metamaterial.
It is seen from Fig. Though both results ensure operating frequency, the resonant frequency discrepancy is acceptable considering fabrication and assembly tolerance. Measured and simulated reflection coefficient of the proposed antenna with nanosatellite structure. The Free Space Path Loss FSPL using variable attenuation has been conducted to estimate the maximum signal propagation of the proposed antenna with active nanosatellite. The free space path loss has been calculated using the Friis transmission equation 29 and represented in equation Where d is the distance between receiver and transmitter end, f is the operating frequency, G Tx is the transmitter antenna gain and G Rx is receiver antenna gain.
The signal modulation system is shown in Fig. The receiving antenna Rx is positioned in the Horizontal orientation and connected to the Receiver through a variable attenuator. Attenuation increased gradually until the demodulation of the transmitted signal is no longer possible. The maximum attenuation value at which the receiver can demodulate the signal represents the signal strength of the transmitter antenna, which can address the maximum path loss. The attenuation level of the proposed antenna has been compared with conventional wire monopole antenna.
From Fig. FSPL performance investigation of the nanosatellite using proposed antenna, a measurement layout and b Signal demodulation. The contributions of the proposed antenna are highlighted in this section. RF failures in nanosatellite antenna have been reported by several incidents that have been occurred due to unsuccessful antenna deployment 6 , The established deployment mechanism is burn-wire method, but it is quite sophisticated to test in laboratory environment. The antenna addresses the frequency shifting issue that happens frequently in nanosatellite patch antenna and makes the mission risky Moreover, the lab prototype of the antenna has undergone a vibration test while embedded with nanosatellite structure that proves the robustness of the antenna.
In this paper, an EMNZ metamaterial has been developed and integrated on the conventional meander line antenna ground plane to reduce the coupling effect with external auxiliary elements. The computational analysis of EMNZ metamaterial properties has been investigated for both unit cell and array configurations. The free space path loss analysis has been performed to verify the feasibility of the proposed antenna for nanosatellite communication system. This work is supported by the research university grant of Universiti Kebangsaan Malaysia.
The antenna design and analysis were performed by Touhidul Alam. Prototype fabrication, characterization experiment and antenna performance characterization were conducted by Touhidul Alam, and Mohammad Tariqul Islam. The experimental set-up for nanosatellite structure was established by Mengu Cho. The project was supervised by Mohammad Tariqul Islam.
Touhidul Alam, Email: ym. Mohammad Tariqul Islam, Email: ym.
Automotive Antenna Design and Applications - PDF Free Download
Supplementary information accompanies this paper at National Center for Biotechnology Information , U. Sci Rep. Published online Mar 5. Author information Article notes Copyright and License information Disclaimer. Corresponding author. Received Jul 27; Accepted Feb 8. Associated Data Supplementary Materials Article file in pdf format. Introduction Over the last decade, nanosatellite missions have increased vividly for low earth orbit space missions. Antenna Design Methodology The meander-line antenna concept is to fold the conductors back and forth to reduce antenna physical size.
Open in a separate window. Figure 1. Figure 2. Figure 3.
Small Antenna Handbook
Investigation on reflection coefficient at the different design stages. Table 1 Optimized antenna design parameter. Parameter Value mm Parameter Value mm L 80 l Figure 6. Figure 4. Figure 5. Figure 7. Table 2 EMNZ frequency region of the retrieved effective parameters. Figure 8. Figure 9. Figure Antenna performance with Nanosatellite Structure The antenna has been integrated with 2U nanosatellite structure, illustrated in Fig.
Table 4 A summary of the antennas mounted on nanosatellite structure. Maximum FSPL analysis using the proposed antenna and wire monopole antenna. Discussion The contributions of the proposed antenna are highlighted in this section.
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Table 5 A comparison of the presented antenna with different UHF nanosatellite antennas. Deployment complexity free RF failures in nanosatellite antenna have been reported by several incidents that have been occurred due to unsuccessful antenna deployment 6 , Conclusion In this paper, an EMNZ metamaterial has been developed and integrated on the conventional meander line antenna ground plane to reduce the coupling effect with external auxiliary elements. Supplementary information Article file in pdf format 1.
Author Contributions The antenna design and analysis were performed by Touhidul Alam. Notes Competing Interests The authors declare no competing interests. Thus kilowatt grounded-grid amplifiers, like the Heathkit SB, when driven by watt exciters could only run watts input if the operator wished to comply with FCC rules.
This places the RF choke at a low-impedance point in the circuit. The Circuit. Uses a microwave oven transformer. Click Here for a proposed power supply schematic. Completely free, without registration free! Amplifiers should not oscillate when used strictly as amplifiers, but sometimes they do if careless design or layout permits output power to sneak back to the input side of the amplifier.
I have build a push pull audio amplifier with two tubes. Sold separately or with RF decks. Class A Operation Class A is the most linear class of amplifier operation. Figure 1 shows a comparison between a screen-driven circuit fig. Since I now had two successful Matrix amps, I decided to do a high power version, using transformer coupling and reasonably high quality parts. However, it would be beneficial to extend that coverage to 40 if at all possible. First, you need to rethink everything.
The is about the last tube I would use in a homebrew linear that I wanted to fit on desktop. Some of the pages are in other languages, particularly German. Schematics Section Here is the forums area for posting interesting radio transmitter and exciter circuits from simple to complex including other various circuits dedicated to this subject.
Copy any of this at your own risk!! The cct is derived from a number of sources but with added innovation. With the bias set as for the s I switched on whilst nervously watching my milliammeter. He has achieved watts out from two tubes on 10 which is a feat that many hams will tell you is impossible. Hoffman Amplifiers, Guitar Tube amp parts and building supplies. Where I don't want to slog through in a half-understood language, I use Google's translation page.
Which by the way, you typically My Home made amp. This is a single-ended triode amp that I built using the transmitting pentode, connected as a triode. A pair of microwave transformers offers a very convenient means of producing a high voltage supply at minimal cost. But don't be offended by the ham telling you that you have a big mouth, because there are some good objective reasons in using such a power. What's most odd is that both the control and screen grid are strapped directly to ground. Any help would be appreciated!
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Thank you. You could probably use it to make a fairly compact CW transmitter. SET direct heated triode tube power amp. The will take 3kV, but you will not find reference to it by the original manufacturer RCA. To get back to this project page just close the schematic window click on X. Sections of this page. This model PA amplifier has outstanding performance in its class and represents truly exception value for money. Hello, I got a pretty old amplifier with 2x tubes in grounded grid.
And each and every parameter is utilized to the maximum - voltage, current, power, heat and so on. That way, I can switch back and forth with the amp, or barefoot, without retuning the SB final. Distributed Load Operation. Radio Transmitters: Ancient and Otherwise. A second was added.
This humungous monster is pushing watts RMS!! The amplifier uses a basic grid-driven circuit, with a link-coupled input tank preceded by a 3 dB attenuator. Proper chargers are usually expensive and cheap chargers supplied with the original equipment often incorrectly charge the cells and dramatically shorten their life.
Another way to produce a smooth sine wave is to use a push-pull configuration. In a conventional amplifier circuit, the screen grid aids in maintaining high current levels, despite fluctuations in the plate voltage, when a constant voltage is applied to it. Does anyone know of a good tested schematic for a push pull tube ultra linear design amp. Instead, I am going to try a little known, but apparently very efficient circuit known as a "bifilar tuned input" circuit.
Direct heated triode power output tubes are really interesting. The first coil is 3" diameter coil with 0. So, the next step seen here is the speech amplifier which I made from solid state kits to take the place of the audio portion of the Ranger. So my thoughts turned to possibly building a reasonably powerful 10 watts amplifier that might weigh under ten pounds 5 kg or so. Supplies 1 amp continuous. The circuit diagram you show for the has no 'tuning'. The power supply will be a separate unit mounted under the main chassis.
In pictures or a copy of the circuit I used. Also named PAD attenuator, this is a tuned network made of variable capacitors forming the arms of a " P" and two parallel inductors forming the top also designed as a "T" network, hence its name. Screen voltage is derived from the input RF and the grid is at DC ground.
It uses a single pentode as the driver a 12HG7 video amp tube , and a solid-state power supply with a microprocessor controller. The amplifier schematic. Jump to. L1 is actually two coils in series. This project turned out pretty well. The single amp shown is designed to cover only 40 thru 10 meters. His input tuning circuit works perfectly. There has been many amplifier articles written over the years in a half a dozen radio magazines and this one is not much different except for some outback engineering and humor in building it.
W6TC bought a used FLB and modified the bias circuit: Fig 5 shows the original arrangement and Fig 6 the modification, incorporating a voltage-doubler configuration to increase the stand-by cut-off bias. Typically, grid-driven amplifiers have more power gain than grounded-grid amplifiers. As a single linear it had allowed me to test acquired tubes. I settled on Lundahl transformers for the audio iron.
In the amplifier shown in the photographs, provision has been made for convenient changing from one mode to another as well as to any of the bands from 80 through 10 meters.