What can cable TV coax be used for ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: August 26, 2018, 10:00:41 am
content: I have regular cable TV coax, aswell as coax from off utility poles that phone or cable/internet guys left on the ground.I know its NOT the same as scope probe coaxWhat all else can a hobbyists use it for ?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 26, 2018, 10:03:20 am
content: Anything you want to use 75 ohm cable for. Probably not bad quality, like RG-8 or similar (I don't think it's usually that fat, but something with similar specs... or just look for the bloody label on the stuff, if it has any!).Main downside is, most test equipment (outside of AV) is 50 ohm.Tim

author: HB9EVI
author_rank: Frequent Contributor
timestamp: August 26, 2018, 10:21:42 am
content: Compared to e.g. RG-8 most TV-coax have a steel conductor with copper surface instead of plain copper. That's ok for todays rather high CATV and Sat frequencies but it poses a problem if you wanna use the cable for lower frequencies. Steel is a rather bad conductor and with the decreasing skin effect towards lower frequencies, the resistance of the steel conductor shows its effect.

author: Wolfgang
author_rank: Super Contributor
timestamp: August 26, 2018, 09:30:21 pm
content: Hi,the main differences between TV coax (75Ohms or 60Ohms if it is really old) and measurement grade 50Ohm coax are:- higher losses- more leakage- less power rating- more reflections on (F-type) connectorsIf you are aware of the above and these do not interfere with your intended application, they could be used without problems.What is your frequency range ?

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: August 26, 2018, 09:42:08 pm
content: Cables for old gaming consoles and plug to CRTOr plug you're arduino as a DSO

author: BrianHG
author_rank: Super Contributor
timestamp: August 26, 2018, 10:26:12 pm
content: SDI 1.5ghz and 3ghz for shorter runs digital video.

author: JS
author_rank: Frequent Contributor
timestamp: August 27, 2018, 02:16:17 am
content: You could probably make a resistive probe using a 75Ω load and a 1.5k resistor for a HF ~X20 times probe. More usual to see 1k and 50Ω coax and load but you have a tad higher load for the circuit. The load to archive HF are sensitive to construction, you'll likely want four 300Ω 0805 resistors inside a BNC to get reasonable results.Anyway, a bit tough to work with a thick wire for the load, preferred a skinny wire so it's easier to move around but you could find a use for 1m or 2m of it while you are in a hurry.JS

author: Wolfgang
author_rank: Super Contributor
timestamp: March 10, 2020, 12:16:56 pm
content: Quote from: lordvader88 on August 26, 2018, 10:00:41 amHanging your laundry.Seriously: Its high loss, and the wrong impedance for measurement stuff.Its also low power, and not very durable. Why use this if you have a choice ?

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: March 10, 2020, 02:07:48 pm
content: On my one GPS antenna system I use LMR-400... expensive, good stuff!My other GPS antenna, I use some cable TV drop line (pole to house) FREE. I am seeing good signal there too. Possibly a dB or two lower.Both systems use splitters as well. Typically seeing 7-9 sats in a canyon area.These are 50 foot runs, so not too long.

author: bjbb
author_rank: Contributor
timestamp: March 10, 2020, 03:52:12 pm
content: 20mA current loop communications. Can be driven to MHz, but have too many drops (about 40 sensors) so keep to 10s of kHz. More reliable than (unlicensed lo-pwr) RF, and more BW and much cheaper than LoRa.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: March 10, 2020, 04:17:08 pm
content: I use this stuff when I need low-speed, shielded cables.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 11, 2020, 01:33:44 am
content: Quite a few Hams have used cable TV coax at HF with good results.The problems with steel at HF & MF are real, but I have only really seen them manifested in equipment in the region of tens of kW, & then mainly where someone has inadvertently swapped a cad plated steel screw for a nickel plated brass one.At low power levels, there is obviously a proprtional loss, but it is often ignored, & the cables used."Cable TV coax" can mean many things, from 75 Ohm "hardline", down to plain old RG6.I still have most of a roll of RG6 cable I used to connect the antenna & splitters for my TV set.It is pretty much the standard used for external terrestrial TV antenna work in Oz.The dB/100m loss is better than RG59, but not as good as the old, horribly flimsy semi-air cored coax which was the previous standard.It does have a much heavier shield, is rugged, & the "compression" "f" connectors are light years ahead of the "Belling Lee" & simple "clamp & screw terminal" things we used to use.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: March 11, 2020, 01:39:27 am
content: Use it as a delay line.. very handy to make precise delays of ns to us range.

author: Stray Electron
author_rank: Super Contributor
timestamp: March 11, 2020, 04:47:40 am
content: You can use it to tie up your GF.

author: JohnN1WOM
author_rank: Newbie
timestamp: March 15, 2020, 08:33:37 pm
content: In the past I have used RG-6U coax as 1/4 wave matching sections for loop type HF antennas (Standard loops, Delta loops, etc.) with great success.75 Ohm coax placed side-by-side with the shields connected together at the station end (shorted and connected to the antenna tuner ground connection and to your station ground) make a 150 Ohm shielded twin lead feed-line for folded dipoles. Just make sure that both pieces of coax are the same length and zip tie them together to prevent impedance fluctuations when it moves in a breeze and especially on really windy days. Works just as well as (if not better) than 450 Ohm window line and if the coax is free, then it cost a whole bunch less than the window line.73,John N1WOM

author: Berni
author_rank: Super Contributor
timestamp: March 16, 2020, 07:51:49 am
content: Quote from: SoundTech-LG on March 10, 2020, 02:07:48 pmThe reason it works well with GPS is that the antennas pretty much always have a LNA built in that puts a good 15 to 30dB of gain on the signal before sending it down the cable. With the weak signals that GPS uses this means the LNA noise figure is what becomes the limiting factor in SNR.So when the LNA is sending a strong signal with its own noise mixed in it really doesn't matter if you loose 15dB of the signal along the cable as the resulting signal+noise will still be well above the noise floor of the GPS receiver.But for other uses the loss in the cable can be a problem and the 75 Ohm to 50 Ohm mismatch can make the frequency response look like a rollercoaster. So for lab use its only really usable as a generic shielded cable for sensitive analog signals like an audio cable for example (But is also significantly thicker and stiffer than a typical shileded audio cable).

author: Brumby
author_rank: Unknown
timestamp: March 16, 2020, 08:00:48 am
content: I've got a couple of reels of RG-11 in the garage. It has 4 auxiliary conductors on the side and solid foam dielectric. I was planning on replacing the cheap RG-59 I ran years ago that's suffered attack from a parrot.If I ever get around to it, that will still leave me with at least 150m of the stuff.Suggestions.....?