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I have a mobile mounted CB antenna that has an SWR of 1.5 on channel 20. Is it possible to use it with a 10 meter radio? I do not have enough room on my car for an additional antenna, so if it is possible to use my CB antenna for 10 meters, that would be great. If anyone here has done this before, I'd appreciate your insights on the experience!

My antenna is something like this one, which is described as being designed for 26–30 MHz and having a tuneable 48" (1.2 m) whip on top.

amazon.com stock photo of a vertical mobile antenna with a loading coil at the bottom and a whip on top

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    $\begingroup$ Hello and welcome to ham.stackexchange.com! I edited your question to tweak the title a little and incorporate the important information from the Amazon item you mentioned. Thanks for researching the correct tags, we appreciate that! I have a couple pointers: first, links rot, so it's always a good idea to copy as much relevant information as possible from the linked page to the post. Second, the only reason to put "EDIT:" in the post is if the post evolves significantly over time in a way that might make following an ongoing discussion tricky for readers. Otherwise just skip the "EDIT:". $\endgroup$
    – rclocher3
    Dec 22, 2021 at 19:46
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    $\begingroup$ Bear in mind there's not a lot going on the 10m amateur radio band. It's just not a very useful frequency, antenna requirements too big for mobile use, but frequency too low to get much skywave propogation for long distance contact. $\endgroup$
    – rcx935
    Jan 4, 2022 at 16:36

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The same antenna won't be optimized for CB (~11 meter) and 10 meter ham bands at the same time, though that one appears to be tunable so could likely be used in either band. There are other considerations, though -- first, you shouldn't connect the two radios to the same antenna at the same time; the transmit power of one might damage the receiver in the other (an A-B switch for radio frequency should be sufficient).

Probably the most effective way to do this is to install an antenna matching unit (aka "antenna tuner") between the ham rig and the A-B switch so that you can physically tune the antenna for your CB rig, then when you switch it over to the 10 meter you can (one time, more or less) adjust the matching network to match the antenna to the ham rig's frequency. Then you just need to remember to set the switch to match which radio is powered up (it might also be prudent to build/buy the A-B switch so it can connect the radio not wired to the antenna to a dummy load, to avoid damage if things get crossed up).

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    $\begingroup$ I appreciate a check mark as much as the next guy, but it's usually encouraged to wait 24 hours after posting a new question to accept an answer. Users aren't all on the same time zone, and an accepted answer may discourage someone from posting a potentially better answer. $\endgroup$
    – Zeiss Ikon
    Dec 22, 2021 at 18:58
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Yes, you can use that antenna, but you will likely have to tune it. Typically the top section, above the coil, is held in place with a set-screw, and if you loosen the screw, you can move the element down, into the coil, until your VSWRs are satisfactory where you want to use the antenna. Then just mark the the tow points where you set it for 10M & 11M. You can also get an antenna tuner, but with an antenna like that, I'm guessing you aren't running 4 watts, so if you go the tuner route, it's going to be another appliance in your vehicle.

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