One last comment on this antenna topic I fails to mention in my previous post… Such a “rubber ducky” antenna could also be a “sleeve dipole” created by running the coax feedline through a brass or copper tube of correct length, terminating the shield at the far end of the shield and then extending the center conductor the correct length past the tune. It’s a simple way to create a vertical dipole but the impedance does not match the standard 50-52 ohm coax and transmitters commonly used. As well you’re still feeding a “balanced” antenna with unbalanced feedline which creates problems with the coax shield becoming conducting RF back to the TX and SWR being very sensitive to length and proximity to other components. A well designed sleeve Dipole will have a coil at the bottom often made from the coax itself to improve the impedance difference and diminish the negative effects of feeding a balanced antenna with coax. However on such tiny antenna it’s very difficult to creat the required coil in such a small antenna and most of these small antenna don’t have one (none that I’ve disassembled). As a result much of the TX RF is wasted being reflected along the shield of the feedline coax. Bottom line: very inefficient and poor performance. So perhaps we his antenna is a sleeve dipole and is correctly labeled as “dipole” however much, much better performance (range, quality) will be realized with a cloverleaf, patch, or even a standard dipole (with a BALUN and proper feedline orientation).

Anyhow, apologies for the length and number of posts here but to get good performance it’s important to know for sure what kind of antenna you’re hooking up to your TX so you can use what’s best for you knowing the cost performance tradeoffs. Hope I helped rather than confused!

Cheers,
Wingspinner

Hello,
I’ve seen several advertisements and posts calling the black “rubber ducky” antenna in your photo a “dipole” antenna. While it could be a “vertical dipole” it’s performance will be very poor due to the feedline not being perpendicular to the radiators, in close proximity to one of the radiators and being fed from a coaxial feed line therefore it’s almost certainly an end fed monopole. If it’s a good monopole it may be of the co-linear type which have more gain horizontally but more than likely it’s just a tuned single wire monopole.

What’s the difference? A true dipole has two horizontally opposed radiators one half the frequency wavelength in length (hence the “Di” in dipole) where one side of the feedline is connected to one radiating and the other side is connected to the other radiator. As a dipole is a balanced antenna requires what is called a BALUN if used with coax feedline to work properly. A monopole is simply a single radiator connected to the center conductor of the coax feedline with the braid ideally going to ground (as in a copper rod pounded into the ground or in the case of a vehicle, a “ground plane” made up of the metal in the vehicle. Scientifically a monopole is a very inefficient form of a dipole with ground being the poor replacement for the second radiator but we don’t call the “dipoles” since they really only have one radiator.

If you have at least a quarter wavelength of metal surrounding a dipole to form a good groundplane the can be pretty good antenna with a low radiation angle but usually that’s not the case. If you want to read more about it check this Wikipedia article – en.m.wikipedia.org/wiki/Dipole_antenna