Koko Head Site Info

Located atop Koko Head (not to be confused with Koko Crater), this site contains a Quantar repeater (on 442.775) which serves East Honolulu (Kahala, Aina Haina, Niu Valley, Hawaii Kai, Kalama Valley etc.) Additionally, it covers the West end of Moloka'i.

Note: The below pictures show a Micor repeater which has been retired and replaced with a Quantar.

TOWER

 

Here's a list of what's all in the rack from top to bottom (frontside):

- Motorola Micor UHF 75 watt repeater station

- Link-Comm RLC-Club Controller

- Behringer MX-882 Mixer/Splitter

- Custom E&M bridge

Antenna:

2x Sinclair SC381-HF2LDF(D06), 6 dBd gain, 6 degree downtilt, 18 deg. beamwidth, 230 MPH wind rating. The main feedline up to the antenna is LDF5-50 7/8" heliax. 1/2" Heliax is used exclusively on all cabling up to the power amplifier and receiver.

This site uses a combiner/multicoupler system because it is a shared antenna system which also has government UHF channels on it. This system uses separate RX and TX antennas due to the number of combined channels. The transmit side insertion loss is pretty high (75 watts input is reduced to about 35 watts on the combiner output). Because of this insertion loss, the antenna having 6 degrees of downtilt (this was done for simulcasting reasons on the government channels) and the lower position of the TX antenna, Koko Head does not have a strong output signal outside of East Honolulu. However, the receiver multicoupler has a pretty hot preamp and we're always amazed at what this site can hear. When using this repeater, the likelihood is that if you're hearing the machine only so-so, you're probably getting in just fine.

On the tower photo, the receive antenna is at the top left of the tower and the transmit antenna is side mounted on the tower facing the camera (it's a bit hidden in all that framework). Find the big dish at top right and look just to the left of that in the mid section of the tower, you'll see the blue fiberglas stick which is identical to the receive antenna.

Linking:

This site is on the main backbone of the microwave system and bridges the gap between Diamond Head and Moloka'i. There are two Intraplex 4 wire audio cards (VF-5B) connected to the repeater at this site (one westbound to Roundtop, one eastbound to Haleakala). Through use of the MX-882 mixer and E&M bridge, Roundtop and Haleakala are connected together and audio/signalling are fed to/from the Koko Head Repeater.

Last Updated 8/29/14