As a part of a project I have noticed that some are using this cable for powering a smartphone on the top of a 120 meter mast. This cable goes from the ground all the way to the mast to power the AC/DC adapter of a smartphone in a box.

The cabe is defined as "Industrial Cable Screened". And it has a shield not an earth wire. Although according to its specs it can pass uto 2.5A current, Im not sure whether it is okay to use as a mains cable.

My questions are:

1-) Is it okay to use such cable instead of a 3-wire(phase neutral earth) AC mains power cable outdoors?

2-) The cable in the link has a shield. Does the shield have any advantage to use as an AC mains cable in this case?

Im wondering what were they thinking when using this cable instead of a typical AC mains power cable. Or maybe just a wrong thinking?

(I hesitated to ask here but I thought maybe some has experience on the matter.)

  • The manufacturer datasheet is easier to find at alphawire.com/en/Products/Cable/Alpha-Essentials/… . Unless it is installed in an industrial establishment and used as Type ITC, this product would not be suitable for use connected to a non-power-limited AC supply. This is assuming that this product would be used in an application under the US NEC. Commented Sep 10, 2018 at 21:58
  • Where is that stated that it would not be used? Can you show explicitly? Thanks
    – floppy380
    Commented Sep 11, 2018 at 4:09

2 Answers 2


It depends on your jurisdiction, but it is unlikely that that particular cable meets all of the code requirements for mains wiring.

I would recommend using an isolation transformer for the mains connection, and use a 1A fuse in series with this cable.

There's nothing wrong with using shielded cable per se — it probably brings some benefit in radio applications.

  • The data sheet did not work for me. If the cable is outdoor rated , protected up 8' and voltage rated for your mains voltage it may be possible if fused prior as com cables usually power limited cables.
    – Ed Beal
    Commented Sep 10, 2018 at 18:56
  • How does the isolation transformer help?
    – floppy380
    Commented Sep 11, 2018 at 3:47

The earth is fine, and I'm pretty sure you're going to want shielding for a wire going 400' up a mast. Since it would be laid parallel to antenna signal cables that would have a lot of HF on them.

I agree with Dave Tweed that an isolation transformer and fuse would cure a lot of evils. 800' is a lot of voltage drop for #22 wire, though you are still under 3% at 0.25 amps (30W). While you're at it, you might kick voltage up to 240V if equipment allows, change sockets so they are not NEMA 5 of course, at that point you ought to be able to handle 120W at less than 3%. You could double those if you really had to, 3% isn't written in stone.

I just can't believe you can have a 400' mast, which is a pretty big project, without some sort of government agency having that in their jurisdiction and wanting to tell you exactly which wire to use.

  • How does the isolation transformer help?
    – floppy380
    Commented Sep 11, 2018 at 3:59
  • 1
    It makes the pole-up run an isolated system which means contact bwtween earth/tower and the hot conductor does nothing. Somewhere on the site I have a treatise on this. Commented Sep 11, 2018 at 4:01
  • Can that "contact between earth/tower and the hot" be due to dry weather? I was planning to use SPD device right before the mobile phone.
    – floppy380
    Commented Sep 11, 2018 at 4:03
  • I mean would an SPD replace the need of an isolation transformer?
    – floppy380
    Commented Sep 11, 2018 at 4:07
  • 30W smartphone? That must burn a hole in your pocket. Also the OP appears to be from the UK (assuming he used RS UK for a reason). Assuming standard USB power 2.5W, I would stick with just 12V DC with either a SMPS or a linear regulator at the top the drop it to 5V. Much safer. KISS.
    – Aron
    Commented Sep 14, 2018 at 10:53

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