New answers tagged

0

A garage door opener chipset :D they are making them for something like 40 years now… in one common implementation they handle 4 bits so you send 4 buttons and receive 4 relays or 2 bistable relays. The old ones only did the bitstream handling: the RF section is separate (they where also used for infrared, ultrasound and so on). Most commonly they are used ...


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You can find finished units for about $20 on the big electrical part supplier sites. Search for "RF remote module". They usually have a logic level output that's active high or low, so you'll probably need a transistor to drive the relay, but depending on the load you might be able to get away with using a bigger transistor that can power your ...


1

Drive the screens for full output. Replace the modulation circuit with a modulation transformer in series with the B+ Use plate modulation and modulate the 807s with a 50 Watt audio amp connected to the modulation transformer


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It is known that a coaxial cable needs a balun to provide an optimal supply of a dipole antenna, because of the common mode current that comes back to the transmitter through the external surface of the shield I will get back to this Can we apply the same logic applied for the coaxial cable analysis? Yes, but the situations are not quite identical, as we ...


1

To me, a plug has male contacts (pins). In the specification table for that connector, the "Backend type" line indicates that "40M" is the manufacturer's code for that style of PCB-mounting connector. Somewhere in the catalog there may be a description of how the connector part number is created - what all the bits of the number mean. I ...


1

There are two specs for microwave maximum input power. Thermally safe limits : typ 20 dBm. 1dB compression P1DB ~ 0dBm +/- design types. Ultralinear +5dBm REF


3

If downconverting is not that cost-expensive (Uhm, presumably. I have little knowledge in RF signal processing) and preserves the information, then why doesn't every RF systems in this world use one? There's many other things that can influence that choice. Sometimes your signal of interest is too low in frequency to be transmitted easily or filtered and ...


0

The current in the inner conductor is equal to the total current in the shield. If it's correctly terminated it will be equal and opposite. The last one, because of skin effect, flows mainly on the shield surface, so it goes partially in the inner side and partially in the outer side of the shield. No, because of the magnetic effects of the inner ...


1

The current in the inner conductor is equal to the total current in the shield. One might think so, but it is not necessarily the case. it goes partially in the inner side and partially in the outer side of the shield. Both current have the same direction, as the current that flows any conductor surface at RF. Again, they current on the outside of the ...


0

The signal from the transmitter comes along the insulation layer between the shield and the center wire. Conductive metal has some induced current - it's needed to make the wave able to propagate in the insulation layer. The induced current exists on the inner surface of the shield and the outer surface of the center conductor. When the wave meets the end of ...


1

The issue with CM filters is that both the source impedance and the load impedance are somewhat unknown. All manufacturers give curves for 50:50 ohm, since that is what the VNA gives without extra fixturing. Good manufactures also give 1:100 and 100:1 ohm curves since they are more representative of the common environment the filter will be used in. As for ...


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Junction C5 and C6 connects to the base of transistor Q2 who does double duty as oscillator and audio stage. That would explain C4 and C10, which are impractically low for discrete components.. really? lol I have .5pf and 1 pf in my junk box... 2pf (2.2pf) is a very common value used in UHF and microwave circuitry. John


6

I like to use this sort of BNC to scope probe adapter, which frequently is included in the accessory kit you get with the probe. You put it on the tip of your oscilloscope probe, then plug it into a perfectly ordinary BNC connector. Since the probe has a high resistance (9 MΩ for a 10x probe) positioned right at the tip, there's minimal loading from this ...


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You might consider adding an attenuator probe to your PCB consisting of a single series resistor. The 50-ohm coax cable to your oscilloscope can be any length - the oscilloscope input at the far end of this cable must be 50-ohm-terminated, not left to its default 1MEG simulate this circuit – Schematic created using CircuitLab The series resistor Rs ...


0

The U.FL is a 50 ohm connector and has no attenuation or compensation (scope probes usually have). If your scope has 50 ohm input or you use a feed termination you have a 50 ohm system and everything is fine. However, you are putting a 50 ohm load on your circuit, and it can't necessarily handle it. If you need an high-impedance probe, you could use an U.FL-...


1

Just thought I'd chuck in that the average speed of the electrons flowing through a copper wire due to the electric field is only about 1 mile per hour - but they effectively push each other along. Signals don't propagate at the speed of light in a vacuum (i.e. c = 300,000,000 m/s) of course. If you're thinking about optical fibres then the light particles (...


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You can sign up for CENOS 3D Antenna Design Simulation software Beta version for free here: https://www.cenos-platform.com/antenna-design Disclosure: I am Head of Marketing at CENOS.


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My understanding is that signals along a transmission line do not propagate at the speed of light but at some percentage of 'c' depending upon the properties of the line. In the past when using a time domain reflectometer you had to factor in the 'Velocity of Propagation' (VOP) if you wanted an accurate reading of the distance to say a short or open.


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According to Maxwell's laws, there are 2 types of electrical signals: 1 - Conduction current signals The energy of the signal is proportional to the overall kinetic energy of all electrons moving in a host material like Copper or Silicon. 2 - Displacement current signals The energy of the signal is proportional to the overall electrical and magnetic energy (...


4

While a practical design of an RF detector with the Schottky diode use distributed elements (see, for example, the AVAGO Technologies datasheet HSMS-286x Series Surface Mount Microwave Schottky Detector Diodes, Figure 21 5.8 GHz Matching Network for the HSMS-286x Series at 3 µA Bias), and these circuits should be developed using specialized design tools, ...


1

The symbols with the red dots are schottky diodes, as Bimpelrekkie stated in comments. The red dot indicates the unused pin. This device comes in a SOT23-3 package, which has 3 pins, of which only two are used. I don't know why they used a 3-pin model in ADS for this, since you don't do pcb layout in ADS, and don't care about that 3rd pin for RF simulation....


4

But why magnetic materials are rarely used? A few thoughts: - Extra cost Extra losses (eddy current losses especially as frequency rises) An extra process Another variable Changes in permeability with temperature Changes in permeability with frequency Another thought Having a magnetic substrate across the whole PCB will mean extra undesirable properties ...


1

A frequency synthesizer does exactly what its name implies. I synthesizes a frequency. Often these are adjustable so that they can generate a range of frequencies. A mixer, on the other hand takes two signals and produces an output which amounts to the sum of the two and the difference of the two. So this would be useful for your upconverter. If you take ...


0

Of course it depends on where you are, there are FCC standard and EN standard and whatever standard in other countries. The main denominator would be field strength. If you stay in the relevant EN 61000 emission curve you don't really need to use the ISM bands, it's simply considered a 'tolerable unwanted emission'. I can do a 4MHz capacitive sensor, for ...


3

This is a signal line, not a power line, you are asking about right? The resistor does strengthen the effect, however, it is possible to have too much of a good thing. The RC filter is not smart enough to discriminate between transitions due to noise and transitions due to your signal. In this case, it is probably slowing down the edge which reduces ...


4

These bars help you to locate specific components in the schematic and on the PCB. Example: locate R36 In the bar with "R"on the left, find the number "36" then in the schematic R36 is below that "36" (it is connected to the emitter of Tr.6). R => Resistor C => Capacitor S => inductor or transformer It works in an ...


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That scheme is a fast-finder index for the schematic components. Figure 1. Instead of having to search the schematic coils, capacitors and resistors can be quickly located by scanning the index across the top. Two lines are allowed for each component type - but this is barely enough judging by the results. It's a nice system. For a long time now we have ...


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There's a long discussion in comments. Here's some echoes. You use the common series equivalent circuit for the antenna. It's the Thevenin equivalent. If we assume that the equivalent circuit is valid then the radiation resistance can be shown to exist also when an antenna receives and it should re-radiate (=scatter) 50% of the catched power if nothing is ...


1

I think you have a mistake in \$F(s)\$, I get: $$F(s) = \frac{1+sR_2C_2}{sC_2(1+sR_1C_p)}$$


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Chicken dots. Used to allow fine tuning of a design by means of solder bridges to change the geometry. You place them when you are not sure about the design and wish to have the ability to change lengths or widths on the bench.


0

This a daffodils versus yellow flowers problem, all daffodils are yellow flowers, but not all yellow flowers are daffodils. MIMO means 'Multiple Input, Multiple Output', no more than that. Having many antennae can allow you to do various things, assuming you have the additional hardware and software to enable them Spatial Diversity Beamforming Antenna ...


4

clocked at 1MHz As a general rule of thumb when looking into data corruptions on mis-terminated lines anything up to the 10th harmonic would be considered. So if the basic data rate is such that it looks like 1 MHz we might consider 10 MHz to be a good basis for analysis. The wavelength of 10 MHz is 30 metres and, another the rule of thumb is that any ...


1

Theoretically, yes. Practically, you'll have to design a complete NFC frontend to drive a coil that's ca 1m in diameter. NFC isn't really designed with that degree of impedance mismatch in mind, so chances are the tag itself would need to be modified, too. So, not really NFC compliant afterwards. So, no. The N in NFC is for "near".


0

Your title asks for suppression in the ground place. That makes no sense, the field around the stripline induces current in the ground plane, otherwise it wouldn't be a stripline (but a free-hanging wire antenna). I'm hence interpreting you like you think that relatively far away from one strip line, there's field caused by it that interacts with the other ...


-1

The centertap conductor is actually a dielectric such as the gigahertz frequency don't create much of a potential drop in de helical monopole. What i don't know is what kinds of dielectric does it have the bare conductor. Given case the dielectric is very high, the center pole is actually reflecting electrons at the gigahertz frequency.


2

This answer on how the electric field is established in a DC circuit might help you visualize what happens in the initial moments in your imagined circuit. When you close the switch, surface charge that had accumulated at the switch's terminal will start to recombine and redistribute in order to establish the uniform electric field \$E = j/\sigma\$ directed ...


0

You asked: In which direction do electric signals flow? Which I will answer with another question: what's an "electric signal"? Is it an individual electron? The net motion of electrons? Maybe not electrons but some other charged particle? Or is it a wave in the electromagnetic field? Or sometimes "signal" means "the electric ...


4

The signal in a cable is carried by a radiowave which propagates in the space around the wires. Parallel wires or twisted pair have this capability. Coaxial cable also has it, but the wave is limited to the insulation layer between the middle wire and the shield. The wave happens as electric and magnetic fields, it's not inside the metal. The electrons in ...


4

Thanks for including the good photos, and a ruler! The typical "rubber ducky" antenna is a simple monopole. The center conductor may be straight, but often it is coiled to reduce the physical length of the antenna while maintaining resonance. There are also "coaxial dipole" antennas which look somewhat like this. The upper element looks ...


20

If electric signals are the propagation of EM waves at close to c in which direction do these waves travel? In the conventional direction? In the direction of electron flow? In both directions? "Both" directions, as well as an omnidirectional component. The best example might be an Ethernet cable. A bit is represented as a pulse. To transmit this ...


11

signals travel in all directions like waves in a pond, they are a disturbance in the current not necessarily a current themselves.


0

The Y axis on the graph illustrating demodulator threshold settings is labeled "RSSI [dBm]" which suggests the dB value in RegOokFix is relative to some RSSI value, the question is what value? RSSI values go from 0 dBm (RssiValue = 0x00) to -127.5 dBm (RssiValue = 0xFF). The procedure recommended to optimize OokFixedThresh (shown in the flow chart ...


0

Power transmission in a cable: You have a 2 parallel wire cable between the signal source and the load. You can have power meter inserted at some point of the cable (practically it's at the source or the load end of the cable). It gives to you 2 numbers: Power towards the load and power towards the source. The first one can have text label "transmitted&...


4

In distributed element filters the circuit isn't put together of discrete capacitors nor inductors. The visible elements are pieces of transmission lines which are coupled together by joints and couplings where the wave jumps over a gap form one line to another. They are said to be distributed because transmission lines (at least those which work carrying ...


1

Distributed element filters are called that to distinguish them from lumped element filters. In a lumped element filter, assuming it was practically possible to have zero-size components, then in theory you could build the filter in zero size, electrical length is not required for it to function. In a distributed element filter, some, or often all, of the ...


1

In a circuit connected to a DC voltage source, the current direction is from the positive terminal to the negative terminal of the source; therefore, Kirchhoff Current Law requires that the current in the voltage source flows from its negative terminal to its positive terminal. Your simulation measures the current SRC1 through the source (equal to a minus ...


3

but from all of the tutorials and material I've come across online I can't seem to find a way to to transmit data at frequencies around 80 kHz to the surface. As said, you'd modulate your current or your voltage, from a controller. I've been told that using VCO circuits to simply generate a low frequency signal Well, a VCO is a voltage-controlled ...


1

The best is one that you know works. 87kHz SSB AM with a 50m loop antenna, 1200m range REF https://en.wikipedia.org/wiki/Project_Sanguine https://en.wikipedia.org/wiki/Through-the-earth_mine_communications https://en.wikipedia.org/wiki/Tunnel_transmitter http://souterweb.free.fr/boitaoutils/prospection/annexes/bps/nicola.pdf


7

I've been told that using VCO circuits to simply generate a low frequency signal and modulate it with an input signal would be unstable and unreliable There's no evidence to suggest that what you say is true. I'd consider this as a good basis for a decent VCO at 80 kHz: - Picture from this site. Or consider the LM567 from the same site: - Then you'll need ...


1

As @BrianDummond pointed out, Vf is way larger than your test voltage, the diode doesn't conduct at all. Also the capacitance of the diode is maximum 2pF according to the datasheet for the BAS70, which corresponds to 33ohm@2.4GHz. In series with 10pF//50ohm, calculate the output voltage from that and you will probably figure out why you are seeing this ...


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