You can see the location here;
KBK610 (HAWAII, COUNTY OF) FCC Callsign Details
It's up on the slope of Hualalai.
Right now I've got 154.830 on hold and the squelch wide open. I do hear very faint Kona Police traffic. I'm going to try to get this antenna I got off ebay into a better location to see if I can get better reception on 154.830 so that I can also monitor the north side traffic. Is there such thing as a directional antenna that can be used with a scanner?
Ok checked out the map at the link you provided. Also got more detailed info via PM from RR member ****tacy. Looks like the repeater is located around the 3000 foot level.
Here is a little more detailed info on Moanuiahea:
http://www.lat-long.com/Latitude-Longitude-362360-Hawaii-Moanuiahea.html
So correct me if I am wrong, but because FM is very line of sight, this means that you are located kinda "around the curve of the mountain". Or basically, the slopes of Hualalai (e.g. above Kailua town/Holualoa) is kinda blocking the signal from the repeater to where you are. Does that seem accurate to you? Whats your elevation?
This may give us a bit more info. Try input the Kona Tower frequency (Kona Tower 120.300 AM). It looks like the airport is directly west of the police repeater so if you can't snag the tower, getting the police repeater is going to be....harder. Even if the airport is at sea level and the repeater is probably higher power (??)....
So to answer your question, yes there are directional scanner antennas. I don't have much exposure to them so maybe someone else can help you out with this one.
But I think that a standard ground plane 1/4 wave mounted as high up as possible (e.g. on roof) may be worth a shot. And to help boost the signal, you can also get a preamp like the ICE 133B listed on this web page. There are other inexpensive preamps but the 133B is solid and very well built.
Receive Only Processing Equipment
And don't forget to unplug any external antennas from your scanner as we get hit with these two storms heading our way! Heck we on the east side of the big island will get hit first so we can let you folks know how it is. Be safe everyone in Hawaii!!
Aloha,
HS