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I just passed General and purchased a FT-450D with an internal antenna tuner. While my ultimate plan is to use a G5RV, it will be a while before I can get it up. What modifications would I need to make to use a mag mount CB antenna. Would it work for 10m? Others?

It seems like it may work simply by grounding the base. Not sure if I would have to trim it a bit.

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    $\begingroup$ Depending on which band you want to operate, there are a lot better antenna solutions on the quick and easy to put up. I use just a single wire antenna of about 40 feet in length with a ground counterpoise of roughly the same length as a portable in the field antenna a lot and it works pretty good. I would say more but I am traveling right now and have limited Internet access. $\endgroup$ – K7PEH Sep 29 '17 at 2:30
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The CB mag mount can be used on 10 meters by attaching a wire to the the shielding at the base then extending the wire to the side. There is always some length that is resonant on whatever frequency desired. On my particulat CB antenna the side wire was about twice the length of the vertical. Total length will be a bit longer than 8 feet (half-wave).

My very first contact as a ham was the Virgin Islands with this lashup taped on the roof of my motorhome.

Beside adjusting length I later found the up or down angle of the side wire can fine tune the SWR. The signal pattern will be stronger in the semi-circle toward the side wire... Perhaps half as loud as away from the side wire.

If you try to extend the side wire to tune 12 or 15 meters the feedpoint will be considerably off-center. The impedance will likley be over 150 Ohms, too high for your internal tuner to handle.

The down side is that 10 meters is so quiet now that few hams are trying to work that band. I now use a 20 meter version of that side-arm antenna and a 40-20-15-10 meter end-fed antenna for multi-band work.

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  • $\begingroup$ 8 feet is a quarter wave at 10 metres. Also, be aware of the power that the antenna is designed to be used with. A CB transceiver can only usually put out a few watts or power, and so an antenna designed for that use might only handle up to 10W or so. Be aware of this before putting 100W of HF into it. Finally, while 10m might be quiet at the moment, there is almost always some activity on 28.074 USB using the FT8 digital mode - maybe this would be the best mode to use right now, especially since it doesn't require much power $\endgroup$ – Scott Earle Jul 31 '18 at 2:52
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Congratulations on earning your General license!

You may get the antenna to work using the internal antenna tuner. Make sure the antenna is on a large groundplane. Try tuning it up with low power (< 10 watts) at first to see if the ATU can handle the impedance matching. If it doesn't tune up, reducing the length of the vertical element may help. Try chopping off an inch or so off of the bottom at a time. Of course this will render the antenna useless for any future CB activity.

If you do get the antenna working on 10 meters, don't expect much in the way of contacts. The higher frequency band conditions are very poor right now due to the sunspot cycle. You will find most stations have gravitated to lower frequencies or switched to low power digital modes like FT8 in order to make contacts.

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  • $\begingroup$ Great answer. 10 meters is certainly attainable with a tuner, but like you say, @Glenn, it will be a few years before it will work as well as 20. Even 20 is suffering right now. $\endgroup$ – SDsolar Sep 29 '17 at 8:56

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