# Tag Info

### 5V DC over Coax

A "better" way is to send 12 V (or more) over the coax and have local regulation to 5V at each RaPi outlet. You can use cheap buck regulators available on Ebay (a few GBP or dollars) to take the 12 V ...
• 465k

### Why do cables specify 75 Ω impedance when impedance is a two-dimensional quantity?

The 75-ohm impedance associated with a transmission line is a so-called characteristic impedance, and it describes the behavior of high speed effects on the line. In particular, if you transmit a ...
• 20.2k

### Are TV coaxial cables compatible with WiFi antennas?

So you want to transport that 2.5 GHz (or even 5 GHz ?) Wifi signal over TV COAX cable ? Indeed to the non-RF people you'd just think that would work. And it does BUT there will be almost no signal ...
• 81.1k

### Can I use a coaxial cable as a DC power cable (without using it as a signal cable)?

Yes, this should work fine. Even in its original application, the coax was probably carrying a DC bias to power the LNB on the satellite dish. Assuming it's RG-6 cable, it should be good for at ...
• 6,184
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### Are there types of standard coaxial cable with a propagation velocity of 0.9c? What would be the application?

Air lines still exist, with velocity factor very close to 1.0. These are AFAIK mainly used in old-fashioned VSWR measurements. The advantages are that the dielectric constant of air is fairly stable ...
• 132k

### Why do cables specify 75 Ω impedance when impedance is a two-dimensional quantity?

Why do cables specify 75 ohm impedance when impedance is a 2 dimensional quantity? Cable characteristic impedance is a big subject When a coax cable is specified as being 50 Ω or 75 Ω it relates to ...
• 465k

### What's the difference between coax cable and regular electric wire?

The thing about coaxial cable is .. it's coaxial. That means there is a core conductor running inside a shield. The shield is usually connected to ground. The filler material inside the cable keeps ...
• 46.9k

### Can I use a coaxial cable as a DC power cable (without using it as a signal cable)?

RG-6 coax has a 18-gauge center conductor, and exhibits a resistance of 6.385mOhm per foot. Its insulation is suitable for a max of around 10A, but it may get too hot before that. Typical satellite TV ...
Accepted

### Is there ever a good reason to ground a coax cable on one side only?

Current through the center conductor of a coaxial cable needs to return to its source (possibly via capacitance, i.e. displacement current). If it does not return via the coax outer conductor, it must ...
• 25.4k
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### Why don't oscilloscope probes use twisted pairs?

If that's the case, why are most oscilloscope probe cables made using coaxial cables? Unless you have a specialist differential probe fitted on your o-scope input terminal, the input to the bare ...
• 465k

### Coax cable - capacitive load

how does my signal source see the whole cable? The characteristic impedance ($Z_0$) of any transmission line be it coax or twisted pair (screened or unscreened) is determined by: - Z_0 = \sqrt{\...
• 465k
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### Modeling bidirectional communication across a coax?

This arrangement is missing the termination which is typically seen in a transmission line circuit -- when terminated, both sides drive their respective ends of the transmission line with voltage ...
• 20.2k

### Are TV coaxial cables compatible with WiFi antennas?

You must use coaxial cable of the proper impedance. The most common impedance for coax cable is 50 ohms or 75 ohms. If the cable you want to use matches the impedance of the interface AND the antenna,...
• 14.5k
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### Why do I have 2 coaxial cables?

If it looks anything like the one in this image, it is likely just for historical reasons. At least here in Belguim, they are pretty much always just wired in parallel internally. When everything ...
• 12.6k

### How does Internet communication work on a coaxial cable?

Energy moves through the cable in both directions simultaneously. Just as different video signals are modulated on different channel frequencies, incoming and outgoing data streams are modulated on ...
• 21.6k
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### What is this metal box with BNC connectors for?

This is an attenuator with coax inputs, no input match, and an output impedance of approximately 50 ohms. Based on the coax inputs and 50-ohm output impedance, it looks like it might be designed for ...
• 20.2k

### Why do cables specify 75 Ω impedance when impedance is a two-dimensional quantity?

Speakers and cables are different beasts: Yes, a reasonable cable has a purely real wave impedance: The imaginary part is the loss. With speakers it's a bit more complicated, but the moment you feed ...
• 97.5k

### Is propagation delay in coax cable a function of signal frequency?

Propagation velocity in an ideal transmission line, i.e. one which satisfies "The Telegrapher's" (i.e Heaviside's) equation(s), is frequency dependant (unless LG = RC). This posed ...
• 25.4k
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### My sourcemeter lets me do a four probe connection using banana connectors or tri-ax. What do the extra lines on the tri-ax do?

The triaxial cables are for low-current, high-precision measurements in the nanoamp range. From the 2450 datasheet: The real-panel diagram shows how the conductors are connected. The second (middle) ...
• 22.2k

### 5V DC over Coax

The splitter in your link is for distributing RF cable TV signals - it will seriously attenuate your DC power, if it passes DC at all. If you are only using the coax to distribute DC (or low voltage ...
• 60.1k

### Are there types of standard coaxial cable with a propagation velocity of 0.9c? What would be the application?

The high propagation velocity would be a "side effect" of more desirable property - signal loss/dissipation along a cable. Losses are dependent on properties of isolation material. If you already ...
• 41.3k

### Connecting microwave oven magnetron with coaxial cable (for a simple plasma torch)

it's not possible. You need to couple out the wave from the cavity, through an appropriately shaped waveguide. You can then convert that waveguide to whatever shape you want as long as you maintain ...
• 97.5k

### Can I use a coaxial cable as a DC power cable (without using it as a signal cable)?

Yes, you can. In fact, using coaxial cables to deliver power to small-scale electronics is a common engineering practice, with all corresponding approvals (EA, UL, etc). You can combine DC on coax ...
• 41.3k

### 5V DC over Coax

I am aware that more length = more resistance so I am wondering if I am good with slightly increasing the voltage on the source side and measuring on the output until I have an exact 5V. NONONONONO! ...
• 6,220
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### Why is the bunny-ears TV antenna normally connected to 300 ohm twin lead?

"Bunny-ears" antenna is a non-technical term for a dipole antenna. At its resonant frequency, a dipole has about 70 ohms impedance at its feed-point. To avoid signal loss and reflections, a matching ...
• 26.8k
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### Can I use Ethernet UTP instead of COAX for satellite TV

No, it would not work over CAT cabling. If it did, everyone would already use CAT cabling for that. CAT cabling cannot pass the frequencies needed for satellite signals which is why coax is used to ...
• 160k

### Modeling bidirectional communication across a coax?

You need hybrids at each end - something that can separate the waves travelling in each direction, something like: (V1 and V2 are the signals from each end) simulate this circuit – Schematic ...
• 3,431