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I have mounted mobile verticals (mag mounts) on my bicycle, but I have learnt that a bike does not have a good RF ground because there is nothing close to a plane.

Without wasting too much more space, what is a better antenna I can use for 2m/ 70cm on my bicycle?

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  • $\begingroup$ A plane is not necessary for "RF ground" (whatever that even means). Simple example: dipole antennas. It is necessary if you want to make a ground plane antenna, like a mag-mount. $\endgroup$ – Phil Frost - W8II Jun 2 '14 at 12:30
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The ground plane for a 2m or 70cm vertical would be sufficiently provided by the bicycle's frame. I however would try to hard-wire the mag mount with a cable to the frame. Even a simple alligator clip would suffice.

For better performance you could try the J-Pole design, which doesn't require the bike to provide it's ground plane. Here is one design for 2m: http://vk2fmdb.blogspot.com.au/2012_08_01_archive.html#6475312433642669543

Once you start operating HF from a bicycle you may need to check out some ground tuned circuits to provide a virtual ground.

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  • $\begingroup$ In what way is a bike a "sufficient" ground plane? Sufficient to make some kind of antenna? Sure. Sufficient to make a vertical with the characteristics we expect from such an antenna, such as an omnidirectional pattern, 36-ish ohm feedpoint impedance, etc? I think not... $\endgroup$ – Phil Frost - W8II Jun 2 '14 at 12:28
  • $\begingroup$ The poster didn't ask how to get 36ohm feedpoint impedance but how to get the best antenna for his bike without wasting much more space. My point was that he has a ground system that is well over a quarter wave radial system for it to be a workable monopole antenna. If I had a ground system in the same proportions and materials for my 40m vertical I would be very very happy.. $\endgroup$ – captcha Jun 2 '14 at 22:08
  • $\begingroup$ Sure, like I said, you can make some kind of antenna, but a bike frame is still not anything near approximating a ground plane, as you write in your answer. Yes, it can be an antenna, but trying to apply anything known about ground plane verticals generally (such as feedpoint impedance) to this bike-monopole antenna is going to be horribly wrong. It's not sufficient, it's not even close. It's an entirely different beast. $\endgroup$ – Phil Frost - W8II Jun 2 '14 at 23:30
  • $\begingroup$ My bad for using the word 'plane', I shouldn't have. And you're right, it will be near impossible to turn a bike into a plane for a vertical antenna. However, I really look forward to any news of the OP's final solution on his attempt to operate mobile. Good luck on him! $\endgroup$ – captcha Jun 3 '14 at 1:45
  • $\begingroup$ You could edit the answer to improve it, if you regret using plane, for example. $\endgroup$ – Phil Frost - W8II Jul 27 '14 at 11:27

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