Wednesday, August 13, 1997

442.400+ WB4IUY Rptr in Zebulon

This repeater was originally built and installed at the old Lizard Lick repeater site in March of 1994, but I have lost all photos of that installation. 

'HI de WB4IUY/r' is the CW ID heard on this repeater every 9.5 minutes. This repeater is located on the old water tower in Zebulon NC, just behind the police department.

The first picture below is the finished product, complete with a 6 cavity Sinclair duplexer on top (light brown enclosure on top of the radio), a pair of homebrew bandpass cavities (gray in color) stacked on top of the duplexer, and the receive preamplifier near the rear of the right-hand bandpass can. The Sinclair duplexer was originally used in the commercial service a few mhz above the 70 cm amateur band. They were repaired and retuned for the input frequency of 447.400 and the output frequency of 442.400. The bandpass cavities were built from a set of scrap 800mhz cell site cavities. The repeater was built from a Motorola Micor mobile radio used by the local power and light company on about 452/457 mhz. 

The controller is mostly homebrew, using a Communications Specialists CW ID'r to handle identification chores. All timing (time-out, COS, tx hang timer, ID front porch timer, etc.) is analog and built from 555 timers and discrete components. Audio processing is also homebrew using LM324 op-amps. All audio mixing and controller circuitry is self-contained within the Motorola Case, making for a compact UHF repeater. A pl of 88.5 is re-encoded on it's output signal during COS activity using Selectone decoders. This is for linking purposes.

The receive preamp is a GaAsFet model by ARR. All jumpers are RG-214. The PA is cooled by a small DC fan running on the main "battery-backed" DC buss in the repeater cabinet. The PA runs at about 30 watts and has performed flawlessly since about 1993.

The repeater occupies a large private enclosure at the site (seen in the photo below). The site houses only amateur repeaters and digi-nodes, and is 100% battery backed. The 442.400 operates on a full-time uninterruptable power source comprised of a bank of 2 100ah batteries kept fully charged by a regulated charging system. Notice the isolation network on the lower edge of the cabinet's door. This keeps the batteries isolated from each other.

The repeater's primary antenna is a Diamond vertical fed through about 200' of 1 5/8" Andrews heliax. Zebulon is about 300 feet above sea level, and has a pretty good radio path to southeast. Note the custom "top-hat" on the tower to support up to 4 antennas. 

This repeater's primary coverage area is Wendell, Zebulon, Rolesville, and Knightdale. It provides a coverage radius of about 20 miles in all directions with considerably more range to the S.E. through the S.W. It is linked full-time to 147.39+ PL 88.5 WB4IUY in Clayton, NC (about 20 miles S) and 147.30+ PL 88.5 WB4IUY in Wilson (about 30 miles E).    

 Dave WB4IUY