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Stainless steel vs copper for invisible antenna

Discussion in 'Ham Radio Discussions' started by KB7QPS, May 18, 2019.

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  1. N5AL

    N5AL Premium Subscriber QRZ Page

    If your area is subject to ice accumulations and freezing rain during the wintertime, your "invisible" wire antenna might not remain invisible to the neighbors for very long. :)

    antenna5.jpg photo credit: VA3EON webpage, on
    Last edited: May 19, 2019
  2. G0GSR

    G0GSR Ham Member QRZ Page

    Resistivity of stainless steel is around 10x that of copper.

  3. KM9R

    KM9R Ham Member QRZ Page

    but it would be a whole lot better than copper in the house, right?

    I have always used copper wire when utilizing an indoor antenna. Generic speaker wire is an affordable option. A larger diameter will cause less resistance than 1/32. If you can find a clear area in your attic would be best. Even at 10w or less, I had had issues in the past with rf getting into fire alarm systems. While 1000 watts may be possible with separate resonate dipoles, issues may arise if you plan a single multi band antenna like an off center fed dipole or something else similar. As you know you do not want to cause issues with your neighbor in an HOA.
  4. K6LPM

    K6LPM Ham Member QRZ Page

    Using indoors would not be wise above qrp levels for many different reasons.
    One of the more obvious reasons against running thin invisible strands of Stainless Steel indoors is the threat of it becoming a fire hazzard.
    It has been pointed out that S/S has a much higher resistance than conventional copper or aluminum, especially as the the wire gets thinner.
    If it is being used indoors there isnt too big a concern of corrosion or exposure to the elements. So whats wrong with thicker heavier and insulated conductor. It really shouldn't be a big issue.
    However, another issue to consider besides exposure to strong RF currents and the controversial health concerns, is the fact that such indoor installations are likely to not pass electrical code or building codes. Something to think about is possible liabilities well beyond the simple authority of a H.O.A.
    It is a personal choice to consider what possible risk you may or may not subject yourself to.
    But if you are a Condominium, Duplex, Apartment or other muli-family type of dwelling where most H.O.A.'s occur, it is not too rightful to weigh those risks for the others living there and make that decision without their knowledge or consent of what they consider is acceptable.
    I would say you are better off with hidden outdoor antenna/radiator that is properly up and away and a bit less in defiance of building and electrical codes. Or best yet apply for a variance or exception and receive the blessings of your immediate surrounding community.
    But yeah, thin strands of S/S and QRO likely not the best configuration. However, then again,,,,
    A heavier thicker gauge might be ok outdoors. After all they use it for mobile whips in thicker solid configuration?!
  5. N4MTB

    N4MTB Premium Subscriber QRZ Page

    I tried stainless steel mig welding wire, didn't operate as well as copper ans I do not recommend it.
  6. NL7W

    NL7W Premium Subscriber QRZ Page

    I remember there being a problem with copper-clad steel on 160M anyway. Skin-effect depth and resistance and all... haven't looked at that issue in a decade or more -- I don't run 160M. I could be mistaken.
  7. NL7W

    NL7W Premium Subscriber QRZ Page

    Now there's some "skin effect." ;)
    N5AL likes this.
  8. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Well, yes but that's a false dichotomy.

    It shouldn't be a choice of a copper wire antenna indoors vs a stainless steel wire outdoors. It's very easy to make a stealthy outdoor antenna using copper wire.

    In terms of power handling based on wire diameter, for a dipole that's reasonably well tuned and fed with 1000 watts your antenna wire peak current will be in the vicinity of 5 amps. Number 14 wire will handle that easily as it's rated at 4.7 amps for transmission purposes (longer runs) and 32 amps for chassis wiring (shorter runs). That doesn't push the envelope at all but for folks really seeking the stealthiest wire antennas you could go up to 20 gauge or so from an electrical standpoint.

    But from an antenna durability standpoint it's really not the electrical characteristics that will limit you as much as the strength to handle things like wind and ice buildup and the like. Again 14 gauge handles that pretty well but some hams opt for heavier wire if they live in extreme climates and especially for very long antennas like 160m dipoles or full wave loops. I've run 18 gauge antenna wires that held up nicely through Wyoming winters but did stretch a bit over time with the wind and winter loading and required some re-tuning come spring.

    Personally I'd go with stranded THHN in 14, 16 or 18 gauge with gray or white insulation for a stealthy antenna depending on how much you're willing to trade stealth for long term strength and what you can find at a decent price. If you don't want to go with THHN then I'd recommend Wireman's 501 antenna wire which is 18 gauge copper clad steel which is pretty stealthy and pretty strong but not as easy to work with as THHN.
    KB7QPS likes this.

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