1
\$\begingroup\$

I have designed and manufactured an antenna that works around 900 MHz. The design includes a ground plane and metallic enclosure that are not strictly necessary, but do affect the performance of the antenna. At the moment I don’t have the ground plane ready, but I would like to test my antenna already. Would a typical, very thin, household aluminium foil be conductive enough to simulate a ground plane at around 900 MHz or should I wait for the actual PCB with copper?

\$\endgroup\$
4
  • 1
    \$\begingroup\$ The problem with Aluminum is it quickly gets covered with a non-conductive oxide film (aluminum oxide) which is also very very hard (they use it to make sandpaper sometimes!) You'll not be able to know if you're making good electrical connections or not. Copper sheet is fantastically easier to solder to, and you can buy it at any craft store (look in the embossing area) \$\endgroup\$
    – Kyle B
    Nov 13, 2021 at 16:24
  • \$\begingroup\$ Thanks! I'm not that worried about the lifetime of this ground plane, I'll just need to do the first testing before I get my hands on the rest of the system. \$\endgroup\$
    – user24368
    Nov 13, 2021 at 16:32
  • \$\begingroup\$ @KyleB, The oxide layer also is very thin. I am not an expert in the subject, but at 900Mhz, it might not matter whether or not there is a good DC connection. Capacitive coupling between the feed and the foil might be all that is needed. (That is, assuming there is some way to make the connection mechanically reliable.) \$\endgroup\$ Nov 13, 2021 at 17:08
  • \$\begingroup\$ @SolomonSlow You're not wrong. I just thought OP should be aware. Not everybody is. \$\endgroup\$
    – Kyle B
    Nov 13, 2021 at 17:19

1 Answer 1

4
\$\begingroup\$

At 900 MHz aluminium foil is good, the skin effect https://en.wikipedia.org/wiki/Skin_effect prevents a thicker plate to give any advantage. The skin depth is about 0,003 millimeters, a 0,01 millimeters thick foil would be in practice as good as much thicker solid aluminium. Tightly layered two 0,005 mm foils would perform as well as one 0,01 mm foil assuming there's no lossy material between them.

One millimeter uneveness of the surface means nothing at 900MHz. You can put it on something stiffer(=wood, iron, plastic, cardboard) to prevent it losing its form due to gravity, wind or a slightest thump. Making a good contact to the feeding line needs some experimenting. There are plenty of aluminium soldering tutorials but I have never tried one.

\$\endgroup\$
4
  • 1
    \$\begingroup\$ I stick a 1 inch square of copper tape to non-solderable ground planes, and solder to that. \$\endgroup\$
    – tomnexus
    Nov 13, 2021 at 17:16
  • \$\begingroup\$ That can well work due the capacitance if the frequency is high enough and the glue as an insulator doesn't cause much loss. Thanks for the idea! \$\endgroup\$
    – user136077
    Nov 13, 2021 at 17:19
  • \$\begingroup\$ You can get good performance from less than a skin depth, it depends only on the conductivity of the layer. In my experience a sub-micron, << skin depth, metal film like a tinted window is still an effective reflector at 900 MHz, though it wouldn't be so good as a groundplane for a monopole. Sure the currents are visible from the other side, but we know a wire mesh works and it has no "separation of sides" at all. \$\endgroup\$
    – tomnexus
    Nov 13, 2021 at 17:30
  • \$\begingroup\$ Some copper tapes come with a conductive glue that works at least until VHF area pretty much equally to a solder connection. This wont, of course, solve the possible oxidation issue. \$\endgroup\$
    – user24368
    Nov 13, 2021 at 18:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.