A Canned Ham Ham Antenna

If you’d have asked us for odds on whether you could successfully turn a canned ham into an amateur radio antenna, we’d have declined the offer. Now, having seen [Ben Eadie (VE6SFX)]’s “hamtenna” project, we’d look at just about any “Will it antenna?” project with a lot less skepticism than before.

To be painfully and somewhat unnecessarily clear about [Ben]’s antenna, the meat-like product itself is not in the BOM for this build, although he did use it as sustenance. Rather, it was the emptied and cleaned metal can that was the chief component of the build, along with a few 3D printed standoffs and the usual feedline and connectors. This is a slot antenna, a design [Ben] recently experimented with by applying copper foil tape to his car’s sunroof. This time around, the slot was formed by separating the top and bottom of the can using the standoffs and electrically connecting them with a strip of copper tape.

Connected to a stub of coax and a BNC connector, a quick scan with a NanoVNA showed a fantastic 1.26:1 SWR in the center of the 70-cm ham band, and a nearly flat response all the way across the band. Results may vary depending on the size of canned ham you sacrifice for this project; [Ben]’s can measured just about 35 cm around, a happy half-wavelength coincidence. And it actually worked in field tests — he was able to hit a local repeater and got good signal reports. All that and a sandwich? Not too shabby.

29 thoughts on “A Canned Ham Ham Antenna

  1. I am not sure I would call 1.26:1 SWR “fantastic”. Pretty much any piece of wire cut to the approximate length for the wavelength will produce similar results.

    Heck, he even shows the unopened can of spam to have SWR “just under 2” in his video. SWR 1.3 is usually the limit for when an antenna is considered usable because there is so much energy being reflected back to the transmitter that some components could get damaged or an overload protection in the PA will trigger.

    To be fair, he never claimed that this is a good antenna, I am commenting on Dan’s blurb above.

    1. SWR is overrated; an SWR of 1.5:1 results in a reflected power loss of 4%, and a 2:1 SWR produces a reflection loss of 11%. Since it takes a 3 db loss or gain to be noticable on the other end, the difference will not be noticed, and the power reflection will not be enough to damage the transmitter. Anytime you can get an SWR of 1.5:1 or less, you’re good to go. Of more importance is the radiation pattern of the antenna, and this depends on the user’s needs.

    2. That depends a lot on the transmitter or the final amp. Handhelds expect to get a lot of reflection and keep transmitting, because they might have absolutely terrible antennas fitted and they use your body as the other half of the antenna. Even apart from that, sometimes with any radio it’s a valid strategy to just step down the power a bit from the full limits of the components, and let reflection occur rather than try to get a “perfect” SWR. Frankly I suspect this thing is probably fairly lossy, so I’m not impressed by the SWR either, but hey.

    3. You’re confused. The general limit for danger to any amateur or fairly low power transmitter is usually set at 1:3, not 1.3. Look at any SWR meter and the red area starts at 3.
      And as someone else said, at 2 you’ll have just over 10% losses and that’s not something you’re really gonna notice.
      Things might be different for the huge broadcast transmitters, but we’re not talking about those here.

    4. No … 1.3 to 1 is NOT the generally accepted limit. My guess is that less than 5% of antennas in use today by hams have an SWR lower than that even with the use of a tuner. Less than 1.5:1 is generally considered a goal, but most rigs tolerate up to 3:1 and handhelds like the one used in this article are tolerant of much worse.

  2. Fascinating. I suggest that you could stack several of these on a common vertical PVC pipe and devise a feed system for phasing and impedance match. The gain improvement would be proportional to the number of (empty) cans used , ~3dB for 2 and ~6dB for 4 cans. Improvements in construction could make it more weather-worthy.
    Does lettuce, tomato and swiss cheese improve the Sandwich Gain [dBs]?

      1. Yep, no problem, I bet you could come up with a winner.
        Just a few items on the “wish list:
        1) All coax feedines within the pipe. Make a 2:1 or 4:1 power divider. Not too tough for a single band.
        2) Coax Connections within the interior of the can.
        3) Use of a balun ?(maybe a few turns of RG-174/U?) to choke off feedline radiation
        4) Corporate feed. Equal power to each can element for max gain on the horizon.
        5) Weather proof the air gaps with something like clear shipping tape?
        Sorry, it was more than a few. But it could turn into a QST article.
        So, where do we get Big Canned Hams for 144 and 222 MHz?

  3. This might be a cute experiment but a few short pieces of wire arranged as a ground plane antenna would be more efficient and have a better pattern. An SO-239 panel mount connector even makes it trivial to build.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.