Juancho
  • Member for 7 years, 10 months
  • Last seen more than a week ago
  • Montevideo, Uruguay
What kind of antenna has a spiral connected to a reflector like this picture?
Accepted answer
8 votes

This is a helical antenna (Wikipedia link). Configured in axial mode, these are commonly used in microwave satellite communications (below a few GHz) where you need high gain and circular ...

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What is the velocity factor of a wire?
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8 votes

A coaxial cable is a transmission line by itself, and therefore the velocity factor is known. It depends on the dielectric properties, geometry, and conductivity. A single wire is not a transmission ...

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Can two FM radios transmit two separate PL tones at the same time, and be received by two radios with matching PL tones?
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8 votes

Assuming that the two transmitters operate at the same carrier frequency, and that the receivers receive similar power from each transmitter, then the FM signals will suffer destructive interference ...

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Who regulates ham radio satellites?
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6 votes

When all the communications of a satellite qualify as amateur radio satellite communications, then the frequency coordination is carried out by IARU. ITU delegates this function to IARU. The link ...

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How are capital letters sent in Morse code?
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6 votes

There is no upper/lower case differentiation in Morse code; just the alphabet. There is a reference to the military recently approving lowercase letters for navy messaging. Use of uppercase-only ...

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SDR - FM Radio station interference
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6 votes

The interfering harmonics are spaced at around 15.5 kHz. Do you have an old (CRT) TV set nearby? That may be the source, since TV line frequency is 15.625 Hz. If not, look for other interfering ...

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Why needs a carrier signal on receiver (SSB)
5 votes

You need to add a carrier in order to perform envelope detection, which is the standard detector in most applications. If no carrier is added, the signal envelope is centered around 0, so the ...

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What does radiation power mean?
5 votes

This means that the transmitter output power (to the antenna) is 10 dBm (which is $10^{1.0}\, \rm{mW} = 10\, \rm{mW}$). Normally this is valid at the rated output impedance. If the transmission line ...

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Can sub GHZ frequency can be used in space communciation?
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4 votes

Most cubesats communicate in a combination of VHF and UHF for both uplink and downlink. Advantages: Better link budget (lower free-space attenuation). Cheaper ground station (radio equipment, cables,...

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Using two antennas with IC751A — one for transmitting and another for reception
4 votes

According to the user manual published here, page 11, the receiver antenna IN and antenna OUT connectors are located before the TX/RX antenna switching relay. Something like this: Transmitter -------...

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Can one modify footprints in Gpredict?
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3 votes

The footprint calculated by gpredict (and other satellite tracking software) is the area from which the satellite appears above de horizon (or, equivalently, the patch of earth seen from the satellite)...

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2.4GHz wifi parabolic antenna frequency response
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3 votes

The antenna feed is designed for 2.4 GHz, so performance at other frequencies will be not good (unmatched impedance, poor gain). The parabolic reflector is usable at other frequencies as long as the ...

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What would happen if I created this circuit?
3 votes

As a purely logic circuit, it is unstable and has no solution as is noted in your question. In practice, logic gates have a propagation delay and a non-linear transfer characteristic. Delay in CMOS ...

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Command-line satellite tracking software
3 votes

Predict is the option that comes to mind. It is console based (no GUI), and provides a server mode where you can request data via UDP messages to a running predict server. It uses hamlib for rotor ...

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What determines the optimum frequency range for the transmission of signals?
3 votes

Many factors, and since your question is so broad, a broad answer follows: The signal bandwidth (amount of information per second) will determine a minimum carrier frequency. In practice, the ...

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EIRP - Conservation of energy
2 votes

The following statement: The calculated value is equivalent to the power which a isotropic radiator would use to provide the same power of the system. is somewhat confusing. The calculated value for ...

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Why is coax loss logarithmic?
2 votes

In a DC (or low frequency) power line, current is constant and the voltage drop is due mainly to resistive losses. So voltage drop is proportional to wire length. Constant current and voltage drop ...

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Are there receivers and transmitters that can be tuned to multiple frequencies at once?
1 votes

A software-defined radio (SDR) with appropriate programming can transmit and receive multiple signals inside a given band.

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How does the length of a metal sleeve around a (shieled) coax cable affect antenna performance?
1 votes

This is a quarter wave monopole antenna. The current on the inner conductor is fed to the vertical wire, while the current on the (inside surface of the) coax shield is fed to the soda can. The soda ...

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Is it possible to have 2 FM transmitters on the same frequency?
1 votes

If you transmit the same FM signal from 2 locations, the receiver will experience a similar effect as FM multipath (when a single FM transmission arrives at the receiver from different paths, mainly ...

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Theoretical Wifi antenna not working for the expected range
1 votes

Given the size (30cm) and assuming it is omnidirectional, it is probably a collinear array. For this type of antenna, claiming 20dBi gain is quite exaggerated. You would expect something around 6 to ...

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Frequency modulation with gnuradio
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0 votes

The FM modulator in GnuRadio (as well as other modulator blocks) work in baseband: the carrier frequency is 0 Hz. Maybe you should recall that, when working with SDR, you work with complex-valued ...

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Field Strength calculations with known antennas
0 votes

The antenna factor gives, for each frequency, the ratio between electric field strength and voltage at the antenna terminals. In the linked article you'll find the relation between AF and antenna ...

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Why does an "electrically small" antenna have narrow bandwidth?
0 votes

These antennas rely heavily on the associated inductors or capacitors to attain a reasonable impedance match. This matching condition, much like an L-C resonance, has a high Q and therefore works ...

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Reciprocity and SWR
0 votes

High SWR on the transmitter means that less power gets radiated. Received SNR (signal to noise ratio) is degraded. High SWR on the receiver side means that both signal + noise reaching the antenna ...

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