Re: 5/8th Wave Antennas Why does the 5/8th have gain, and how much gain does it have?
Greg - KO6TH
Good info, Jef. I am running a 5/8 wave J-pole for my packet station, and it works pretty well.toggle quoted messageShow quoted text
A follow-up to the satellite question.. One generally wants some sort of gain, such as a small beam. Satellites are relatively weak, since they're hundreds to thousands of miles a way (line of sight), and generally don't have much by way of transmit power. The exception is the International Space Station, which is in a fairly low orbit, and has a transmitter with some oomph behind it (up to 25 w, but they probably run at a bit lower power). SO-50 is one of the weaker ones at 250mw, and many of the "cubesats" aren't running much more.
All that said, one of the better antennas can be a simple 2m 1/4 wave ground plane antenna, operated in dual-band mode. On it's 3rd harmonic fro 70cm, it turns out to have some gain upwards from the horizontal, which helps with satellite work. It's still not wonderful, but a LOT better than an HT's antenna, and can sometimes be better than a high gain omni antenna, where the pattern is aimed at the horizon.
http://aprs.org/aprs-satellite-igate-antennas.html (Old satellite and product info, but physics still works.)
Jef - N5JEF wrote: