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I am building a miniature yagi antenna that is made for 2.4ghz. Would a 2.4ghz yagi antenna work for Ham Radio?

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    $\begingroup$ If designed and built properly and used on 2.4GHz, absolutely! :-) $\endgroup$ – captcha Apr 6 '16 at 3:52
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One of the amateur radio bands covers 2390-2450 MHz. A 2.4 GHz antenna should work quite nicely for that band. But it likely wouldn't work on other bands very well, for receiving, and I highly recommend you don't try to transmit on any other band (Except for perhaps with an antenna tuner)!

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  • $\begingroup$ A yagi is optimized for a given frequency, it would not work at any other frequencies than the one it is designed for (2.4GHz). $\endgroup$ – GmodCake Apr 6 '16 at 14:00
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    $\begingroup$ @GmodCake Yagi's are indeed narrow-band antennas, but you'll find in practice that it's not as black-and-white as you say. At 2.4GHz they will happily operate a few MHz above and below the design frequency. Efficiency will drop off the further you go out but I would not agree with you statement that it would not work. $\endgroup$ – captcha Apr 6 '16 at 22:10
  • $\begingroup$ Of course it would work at frequencies nearby, but I'm pretty sure this would not work on, lets say, 2m for exemple. Maybe I said it too literally $\endgroup$ – GmodCake Apr 6 '16 at 22:11
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    $\begingroup$ @GmodCake Also remember that many antennas will work on related harmonics. That's why an antenna for 70cm will work on 2m. But yes, getting a decent signal out on 2m with an antenna designed for 2.4GHz would be very doubtful and if impedances are not matched then possible damage to the transmitter is also a risk. $\endgroup$ – captcha Apr 7 '16 at 22:10
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    $\begingroup$ Please do yourself a huge favor and don't use your transmitter to test an antenna meant for a completely different band. As captcha mentioned, "possible damage to the transmitter" is actually rather likely if it's a very poor match. You'll want to read as much as you can on SWR and on the use of an antenna tuner. If while quickly test-transmitting on low power you find too high an SWR (the tuner can't find a good match), you'll only want to crank up the power and "use it anyway" if you intend to kill your transmitter. ;-) Better use an antenna analyzer or just use the right antenna. $\endgroup$ – user157 Apr 8 '16 at 11:28
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Absolutely yes. You can find plans for a Pringles can antenna, which is a yagi inside a Pringles can. You may have to adjust the size slightly, but it'll work.

An alternative you might consider is a discarded satellite dish. That would give you more gain (and a larger capture area) at the expense if more directivity.

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  • $\begingroup$ 2.4 GHz is around where parabolic reflector antennas start to become practical in terms of physical size. Sure it's possible at lower frequencies too; see for example ON5GS's 70 cm dish setup (scroll down to right near the bottom; house included for size comparison for the 3 m diameter dish!) K5SO has an even bigger 8.6 meter diameter one with a 70 cm feed. $\endgroup$ – a CVn Apr 9 '16 at 22:48

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