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Aluminum Core PEX Loop Antenna Material

aluminum core pex loop

You can make an aluminum core PEX loop antenna easily. This material is cheap, lightweight and easy to form a permanent loop shape. But hard to find! 

Previously, I have written about different materials for making small magnetic loop antennas. These included wire, copper and aluminum tubes, and metal foil. For my wideband loop project, I decided to try something different.

A few hobbyists have written about making PEX-AL-PEX, or aluminum core PEX loop antennas. Say, what? I must admit that until recently, I had never heard of the stuff.

PEX is cross-linked polyethylene, a very strong plastic. You will find PEX used extensively for domestic water piping, as well as hydronic radiant heating and cooling. Some versions of PEX come with an aluminum core and are used mainly for heating. PEX-AL-PEX is basically two layers of PEX with a thin layer of welded aluminum sandwiched in the middle.

So, I bought some half-inch aluminum core PEX loop material. The dimensions are 0.5″ inner diameter and 0.64″ outer. From my measurements, I estimate the aluminum core is about 0.04″ or 4 mm thick, with a radius of around 14.5 mm.

Is this aluminum thick enough for use as an antenna. Yes. Skin depth of a radio signal at 1 MHz is 0.08 mm. When a radio signal travels through a conductor, most of it stays within five skin depths from the surface, so 4 mm thickness is more than enough.

Aluminum Core PEX Loop Material Sourcing and Use

Hard to find, easy to use. I searched for a supplier of aluminum core PEX loop material in Alberta. The one I found would not sell me a small quantity. Fortunately, I came across HEAT Innovations in Winkler, Manitoba. Sales manager Mike was happy to sell me a fifty foot roll at a good price and ship it to Calgary.

PEX-AL-PEX is very lightweight and easy to form into a 1 meter diameter circular loop. On top of that, I found that it holds the shape well.

To make a mechanical or electric connection to the aluminum, you need to remove some of the PEX outer or inner layer. Given the low melting point of polyethylene compared to aluminum, I just used an old soldering iron to melt away some of the PEX, as shown in the picture above.

One last note. You need to paint the PEX for ultraviolet protection before it goes outside.

 

4 comments

  1. Zaba says:

    Hello John! Just started my loop construction preparations with a Jennings GCS-55 vacuum cap available… Just a note that 0.04″ equals about 1 mm, still enough for the skin depth requirement! Cheers/73, “Zaba” OH1ZAA

    • John VE6EY says:

      Thanks for your comment, Zaba. I have now built four wideband receiving loops with Aluminum Core PEX and remain quite happy with performance. Its light weight also makes these loops quite easy to mount. Cheers and 73.

  2. Zaba says:

    Hello John! We have this material available in various sizes and with the about 1 mm thick aluminium layer. Copper is quite expensive these days. Conductivity of aluminium is 60% of that of copper. My first loop will probably be 30 x 3 mm Alu-strip which is easier to bend than round Alu-tube. The strip is 66 mm circumphere, which equals to a 21 mm tube. For conductivity a 12 mm copper tube would be comparable. With a (Cu-)loop calculator we can see the projected bandwidth, and by measurement we can judge the quality of the construction, i.e. the narrower the bandwidth, the better the efficiency (as for material selection)… Cheers/73, Zaba OH1ZAA

    • Zaba says:

      In order not to confuse other readers I am commenting to myself, that I am building a narrow-band transmit loop, whereas John is describing the wide-band receive loop. The rx-loop is not as critical for material selection, but studies by LZ1AQ show a better sensitivity at low frequencies for a thick loop conductor…. LZ1AQ is doing great work on special antennas. I have built the 4-way X-shaped yagi for 50 and for 70 MHz with 4 mm AlMgSi rods, and I am preparing the
      4-way wire beam design for 14 MHz with tapered Alu-elements. The relay array can be simplified to 2 pcs DPDT— http://www.lz1aq.signacor.com/docs/2-element-single-mast-wire-beam.php — Cheers/73, Zaba OH1ZAA

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