I’m curious about antennas and I have a question I’m trying to buy a good antenna and I see one that says “no ground plane”, one that says “quarter wave”, “5/8 wave”, “high gain” etc. can someone tell me what these terms mean? Is one better than the other? Does high gain mean you can hear further with it?
Thanks so much everyone for your help.
Many antennas use the ground plane under them (think: roof of a car, trunk lid, etc) as the 'other half' of the antenna.
"No ground plane" antennas are designed to work without that, however, they work better with one. They can be a solution when mounting locations are limited. You lose some efficiency without the ground plane, hence the "no ground plane" antennas work better with one.
Quarter wave antennas are the simplest antenna. It's a radiator (the metal part of the antenna that radiates the signal) that is one quarter wavelength long. So, on the ham radio 2 meter band, the length of a quarter wave antenna is about 0.5 meters, or about 19 inches. The nice thing about 1/4 wave antennas is their simplicity. At their feed point (where the coax connects) they present as 50Ω, which is what most radios want to see. They also have a nice round radiation pattern. They are generally referenced as a "unity gain" antenna, as they have no gain. In other words, it's the standard that most antennas are compared to.
5/8th's wave antennas are 5/8th's of a wavelength long. They do not show as 50Ω at the feed point, so they'll have an impedance matching coil at the base. The benefit to the 5/8th's wave is the have more "gain" as compared to the 1/4 wave. A 5/8th's wave usually has around 3dB of gain. 3dB of gain is roughly equal to doubling the 'effective radiated power' of the input. It does that by squishing down the antennas radiation pattern. So instead of being a nice round pattern like the 1/4 wave, it's smashed down more into a disc. That focuses more energy at the horizon, and less up above or below the horizon. That's a good option when you are out on the fringes of coverage and the terrain is relatively flat.
"High Gain" doesn't really mean anything on its own. It just means that the antenna focuses more power in one more more directions to increase performance. How much that increase is will depend on the exact design.
There isn't one that is "better" than the other. It's like any tool, each tool has its job. It is up to the guy using the tool to decide which one is right. You'd need to look at the application, install location, system you are trying to reach/hear, and make a decision on the exact antenna needed for the specific application. Anyone telling you a specific antenna design is "better" than the other without qualifying that, is just giving opinion.
There's other things involved:
Quarter wave antennas will have much more usable bandwidth than a 1/2 wave or 5/8th's wave design. Useable bandwidth is the amount of spectrum the antenna will transmit on with SWR remaining below a set point (usually 2:1 SWR). That can be really handy if the radio needs to cover a wide piece of spectrum. I use 1/4 wave antennas on my trucks because I use my radios for work (158MHz range) as well as amateur radio use. Some of the higher gain antennas won't work well over that amount of spectrum.
Higher gain antennas have less useable bandwidth, but can give you more range if you are on the fringes of coverage. That's good if you have a small slice of spectrum to cover, but are on the fringes of coverage.
Other antenna designs can be used, also. A simple vertical is good for mobile use, but in base applications, there's a lot of other options.
If you give us an idea of what your use case is, we can probable make some suggestions.
Picking antennas isn't as simple as buying the one with the highest amount of gain. There are tradeoffs you need to weigh in each application.
