Can I probably transmit using an antenna tuned for ham 420-450mh on GMRS 462-467mh?

Can I probably transmit using an antenna tuned for ham 420-450mh on GMRS 462-467mh
without generating greater than a 2.0 Standing Wave Ratio?

Welcome Regular,

I have tried using an antenna tuned for 70cm (440 MHz) with a GMRS mobile radio putting out around 17W and was getting anywhere from 1.9 - 2.5 SWR across the GMRS channels. I didn’t check the SWR at lower power levels. YMMV

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The VSWR is independent of power - the only reason they sometimes appear different with low power is the meter’s diodes being non-linear over such wide power ranges. Handhelds get stuffed inside coats, pushed against sweaty bodies and worse, so they are generally made pretty bomb proof. The only critical thing is that when an antenna is used outside it’s bandwidth, the performance drops quickly on receive and transmit. It ends up just being a bit of metal in the sky - not really an antenna!

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I tried this recently with a Tram dual band antenna and the SWR was dangerously high on GMRS. I would highly recommend against this. It is possible that you may have better luck with a different antenna as some have wider bandwidth but I would measure it well before using.

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I know someone who regularly transmits and receives GMRS frequencies on a cheap chinese radio using the radio’s included 2-band (ham, 2m & 70cm) antenna. Says it compromises on distance but works around his purposes well enough and that it’s a “throw-away” radio anyway so he doesn’t care. Says he’s been doing it for years. No idea why he wouldn’t get a cheap gmrs antenna, the Nagoya 701G would fit his radio, and be simple to change over, but I guess he feels it works fine enough and isn’t worth the bother. Don’t think he’d risk it on one of his expensive HT’s though. But that’s him.