Chris -- yeah, my mistake, the SWR is 1.5:1. Could the 156.8 be either an average or tuned freq? The actual receiver runs on either 161.975 or 162.025. But the antenna spec was sent to me by a Scripps lab that does AIS development, so I'm guessing they know what they're doing with recommending this particular antenna.
This is actually the antenna:
http://shakespeare-marine.com/antennas.asp?antenna=396-1-AIS
If you've seen both 161.975 and 162.025 listed in your docs then they are the transmit and receive frequencies. Tranceivers on repeater systems normally run on one frequency to receive, then jump to an offset (plus or minus) frequency to transmit. The 0.05 difference between the freqs you listed is the giveaway, as that is the common offset.
Chances are there is also a channel programmed into the radio that's set to the base frequency but has no offset. That's for direct-transmission communications (keying up the unit without activating the repeater). This is used a lot when you have units in the field who need to talk directly, but are out of repeater range or don't want to clutter up the airwaves with non-critical communication.
Dunno why they are telling you to tune the antenna for 156.8. For optimal performance the stick should be tweaked for max SWR at the xceiver's transmit frequency. Is there another repeater or radio that will be on the same stick?
Like Chris said, there are some good crimp connectors as well. I'm just old school - I want a hard soldered connection for everything so there is zero chance of corrosion at the wire/connector interface becoming a problem. He's also right that the self-vulcanizing weather wrap is a good idea. I forgot this will be a stationary unit so it would be a better idea to seal the entire connector. (Completely wrapped connections are a gooey headache on mobil antennas, most of which get removed regularly for any number of reasons).
Brad
