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Questions tagged [coaxial-cable]

Questions about coaxial cables, including different types of cable, connectors, adapters, and other topics.

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18 views

Using LMR400 and RG8x in the same feedline

I am putting a run together from my shack to a new 2 meter antenna I've built. I'm blessed to have many trees on my property and I'll be placing the new antenna about 90 ft from the ground by hanging ...
4
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3answers
91 views

Testing for 'Bad' Coax

I have a lot of 'donated' coax that has been given to me with unknown provenance. I'm wondering what things I can do that can determine whether I keep it or send to the tip? Some of the things I have ...
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2answers
78 views

What is Electrical length in RF and how to electrically cut and measure the RF cable in degree?

What is electrical length in detail? Why is it so that 1/4 wave , 1/2 wave dipole antenna works properly and not a full wave antenna? What is the role of electrical lengths in degree?
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2answers
84 views

It it really useful to terminate unused 75Ω outputs on a coax splitter?

When discussing improvements to my home HDTV Antenna/distribution system a colleague brought up the need to terminate all coax, even unused splitter ports. My understanding of the way terminator ...
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2answers
61 views

What are the effects of different feed-line incidence angles?

Consider a dipole antenna fed by a coax (say, longer than the antenna) with a signal reasonably close to the dipole's resonant frequency. Various sources say that the feed-line should approach the ...
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1answer
78 views

Suspected Damage in Coax Cable

I suspect that the "white residue" between the coax cable jacket and connector is the result of environmental damage but I could not confirm it yet. Did anyone have a similar issue and if so what was ...
4
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1answer
60 views

Why is the insertion loss of my coax cable higher than expected?

I am testing a long cable run (about 90m). This cable has been used outside and inside, for temporary setups. I've set up my VNA with the correct values (velocity factor,...) and the distance to ...
2
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1answer
93 views

Current flow in a coaxial cable

I was wondering how the current flows in a coaxial cable. Say for instance that the inner conductor transfers the signal, so there flows a current. How will in the outer conductor(shield), flow a ...
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1answer
35 views

For air coax calculation, what is correct diameter metric vis-à-vis tube stock thickness?

I am interested in creating a square outer-conductor with round inner-conductor air coax post for a hex beam antenna. I found the extremely useful information at: How do I design a round or square ...
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1answer
179 views

How terminate RG8 coaxial cable using PL259 (UHF) - screw - gasket - solder type?

Today I came across a problem in terminating RG8 cable using this PL259 plug. I have never had this type and it arrived in a pile of parts; I have tried to puzzle it together but without positive ...
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2answers
76 views

Is a “shorted” coax feedline ok for a G5RV type antenna?

I have "inherited" what I believe to be a G5RV antenna with two 51 foot wire centerfed radiators. If I remember correctly from measuring 2 months ago, there is about 31 feet of 450 ohm ladderline ...
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2answers
288 views

Impedance effect of using 75 ohm coax between transmitter and an EFHW antenna

I have been given several hundred feet of very high quality 75 ohm coax. I need a run of about 36' from my QRP transmitter (FT-817 with elecraft T1 tuner) to an EFHW antenna (about 75' long). Running ...
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5answers
145 views

Coax cable as antenna for 5 watt handy

For a normal 5 watt handy working in VHF or UHF freq with 50 ohm antenna , is it possible to use a same length coax cable instead of a stub antenna, so as to work like a crude antenna. Will this only ...
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3answers
207 views

Is RF current always confined to the inner diameter of a braided outer conductor of coaxial cable?

Prompted by a previous question found at Using a balun with a resonant dipole -- an answer there included the following text: "For transmission lines (twin-lead or coax) to not radiate, each ...
2
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1answer
287 views

Feedline and balun for 80m horizontal delta loop

I am new to HF. I'd like to put up an 80m delta loop. Due to aesthetic considerations I need to use coax to the shack. If tuned for 3.55MHz, I anticipate having a good SWR on 80m, 40m, and 20m. The ...
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1answer
835 views

How does an SWR meter really work?

For ham radio operators, the SWR meter is a ubiquitous piece of equipment. There are dozens of standalone models on the market and most modern transceivers and antenna tuners have this functionality ...
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1answer
147 views

Does Coax Limit the Maximum SWR a Transmitter 'Sees'?

A recent discussion about SWR led to the assertion that a length of coax cable will ultimately limit the SWR to which the transmitter will be exposed. By experimenting with an SWR calculation tool ...
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4answers
402 views

Can a common-mode current exist on the inside of a coax shield?

People often say common-mode current flows on the outside of the shield, while the current on the inside of the shield is always opposed by an equal but opposite current on the center conductor. This ...
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3answers
504 views

SMA connector sizes

So, I'm currently tinkering with a RTL SDR dongle and want to put an external antenna in the proper way (i.e. not by soldering a random wire on the included mcx terminated coax) I was about to buy a ...
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6answers
566 views

Use a TV coax and balun for a poor-man's OCFD?

Can I use TV coax and a cheap TV balun to build a poor-man's OCFD? Marginal performance is acceptable if it saves money. If I could listen to 10% of transmitters within a 100 mile radius that would be ...
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3answers
600 views

Will coaxial cable degrade over time?

I have a 40' section of RG-8 that is about 35 years old. One end was terminated with a standard PL-259 and the other was soldered directly to an antenna. When I removed the connector from the one ...
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3answers
2k views

How do I connect an antenna with coax output to my stereo?

I want to buy a radio antenna for my stereo in order to pick up a few farther-away stations clearly. The outputs from the antennae that I'm seeing are to coax cables, and the input to my stereo has 75 ...
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2answers
729 views

How much does the quality of coax cable matter?

I am using a bit of coax cable as an antenna (with the shielding off at the last 17.3 cm). However it is cheap Chinese cables and the shielding does not contain that many copper wires (the "web" isn't ...
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3answers
234 views

Why is coax loss logarithmic?

With DC hookup wire, losses are directly proportional to length. If the resistance of 100m of wire is 10 ohms then the resistance of 200m of wire will be 20 ohms. But we measure coax loss in decibels ...
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2answers
4k views

How the Coaxial Collinear Antenna Works?

A length of coaxial cable radiates negligible amount of RF. Same length, if cut into pieces of length (λ/2 * VF), and these pieces joined again cross-connected (i.e. core of a piece to shield of ...
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1answer
82 views

What effect does a balun have on s-parameter, beam patterns?

I have a dual-dipole antenna with a subreflector slightly above it and a ground plane below it, and attached to the ground plane is a balun. While simulating in CST microwave studios, I didn't include ...
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1answer
2k views

How to calculate single-stub match (general case)?

I'm trying to build a 1/2 wave "Coaxial J-Pole" antenna, similar to what is described here: Coaxial J-Pole http://members.upc.nl/a.vrijswijk/documents/J_Pole_Picture.jpg Such an antenna would be ...
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2answers
1k views

Does a balun need to be made with coax?

The short version My understanding is that one of the main reasons to use a balun with coax is to prevent the outside of the shield from becoming part of your antenna system. If that's the case, won'...
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1answer
134 views

Using coax for DC, good idea?

I know that it is best to twist the wires that supply DC power to a device, as to decrease the "loop" surface area. This diminishes the amount of RF that gets coupled in the wires as well as the ...
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1answer
38 views

What factors determine acceptable turning radius of RF cable operating into few GHz?

I want to understand what factors determine acceptable turning radius of RF cable. are the losses high for low frequency or at high frequency if cable is turned or twisted ? the cable i am referring ...
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2answers
1k views

Why isn't twisted pair used for feedlines?

My son was asking about some Ethernet cable (Cat 5 unshielded twisted pair), and since he recently passed his Technician exam and we both have "radio stuff" on our minds, I tried to make the analogy ...
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1answer
204 views

how does slotted coax Balun eliminate common current?

how does slotted coax Balun eliminate common current? why the length of the slot should be quarter wavelength?
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1answer
290 views

What do we mean by “RF in the shack”?

What does "RF in the shack" mean? How does it interfere with devices around coax?
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1answer
109 views

Feed line direction for Quad antenna

I am currently getting my EE degree, and I'm trying to build my first antenna for a weather balloon. I understand with a dipole, you want the feed line perpendicular to the antenna for at least l/4, ...
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2answers
111 views

Type of coax used inside of a transceiver?

If you have had occasion to open up a transceiver for repair or other reasons, you have seen the thin grey coax that's used to carry signals from one part of the radio to another. What is the ...
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1answer
136 views

RG-174 to pull signal from 1st IF?

I've built a high impedance buffer out of an op amp on a small piece of perf board. I'm going to attach the input to the first IF on an Icom IC-718 and the output will be pulled out to a jack that I'...
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3answers
118 views

Using cable coax rg 11

I am using RG 11 coax connected to receive radio. Center wire to one post shield to other post. Can it be used as a long wire antenna by it's self?
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4answers
1k views

I have 60 feet of coax but only need 20 feet; can I loop up the excess?

I was given about 60 feet of good cable with connections but only need about 20 feet. Can I loop up the end or do I need to cut and put a new connector on?
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1answer
115 views

Amateur Radio shack/antenna considerations during house construction

We are constructing a house on a tiny 30ft by 55ft plot and the construction uses cement bricks and the roof has embedded iron rods. The house has ground + 2 floors and the top floor mostly has two ...
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3answers
2k views

Using inner conductor of a coax feedline as an antenna

Can I use the inside conductor of coax to radiate RF energy? My in-laws have some sort of attic antenna installed many years ago for broadcast reception, which I would love to temporarily co-opt for ...
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2answers
4k views

How is a 1:1 current balun different from a choke?

I have a 10m dipole and am going to feed it with 50 ohm unbalanced feed line (coax). My understanding is the feed point of this style antenna is about 50-75 ohms and since it is a balanced antenna I'...
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2answers
428 views

What chewed my coax

Today I noticed that a piece of RG-58 that's feeding a Beverage antenna for HF was in two pieces. On further inspection it turned out to be cut. On further inspection I think it's actually chewed by ...
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2answers
1k views

Understanding coax radiation and “current on the shield”

I'm having trouble understanding what seems to be the fundamental principle behind baluns (and probably other related topics). Perhaps some of my confusion comes from an audio background, where one ...
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1answer
117 views

Can I use an RG-8X crimper/stripper on LMR-240?

From all my reading online it seems LMR-240 and RG-8X are only about .002 inches apart in diameter and most connectors/tools that support one support the other. I'm looking for a crimper and stripper ...
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1answer
437 views

Why exactly would cable lengths to a duplexer matter?

So a very experienced friend of mine is making a portable suitcase kit with Yaesu FTL-2001 (VHF), Yaesu FTL-7002 (UHF) and DX-720D duplexer* plus power supply and other miscellaneous gear. FTL-2001 ...
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1answer
948 views

Connect Printed Yagi-Uda Dipole Array with Balun to coaxial cable correctly

I am making the Printed Yagi-Uda Dipole Array with Balun (that is the full name). I used Antenna Magus to calculate dimensions. I am not sure how to properly connect it to coaxial cable. Here is what ...
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3answers
1k views

How to feed coax from inside car?

What is the best (or standard) way to get coax from the radio in the car to the outside of the car without smashing it and damaging the line? If I just put it through the door crack, it seems to ...
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3answers
817 views

How to shorten the length 50 ohm characteritic impedance antenna cable

I have two 50 ohm characteristic impedance cables of which I need to shorten their length to compact my design. (put everything in to a box) The cables I need to shorten are the GPS & GSM antenna ...
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3answers
275 views

Weather-proofing antenna connections

Here's a problem: you buy a fancy new vertical for a fair bit of coin, but there's no coax connector on the thing. There are just screw terminals. You need to attach coax to it, but in such a way ...
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1answer
250 views

How to choose a coaxial cable

How do you know which coaxial cable to choose for your application? For instance; I require a cable that has a 50ohm impedance, an operating frequency of 2.4GHz, length of 100mm, and needs to be ...