Quick, what are the attributes of a good repeater antenna? Most people will come up with things like durability, low noise floor, high gain, low takeoff angle, etc. All of these are good things to look for in choosing an antenna for your repeater system. But have you ever considered using a J-Pole or Slim Jim antenna for your repeater?
Most repeater designers choose high gain and commercial grade antennas for their repeaters for the simple fact that this antenna will be mounted on a tower several hundred feet in the air. Once the antenna is up there, the last thing you want to worry about is sending someone up the tower to fix a broken antenna.
Repeater systems also exhibit a lot of RF power losses. You really want an antenna with some gain once you consider the amount of energy that is lost by the duplexer, combiner, filters, and feedline.
Still, the 2 meter Slim Jim makes a great antenna for a repeater. The end fed folded dipole design of the Slim Jim gives you about 5.5db of gain and an 8 degree RF takeoff angle. With decent gain and RF energy focused at the horizon, the antenna is a great choice for a repeater. The copper construction is rugged and the antenna can be side mounted on a tower in such a way to deliver years of dependable service.
The standard J-Pole antenna also makes a great choice for a low power, portable, or temporary repeater system. The antenna is lightweight, rugged, and can be quickly deployed in the field. Why mess with a 15 foot antenna for your repeater, when a 5 foot J-Pole will work just as well.
Remember, the key point of any repeater system is solid coverage for the area the repeater serves. A repeater that transmits further than it can hear doesn’t do anyone any good. Choosing the correct antenna can make all the difference from solid signal and no signal.