After a long period of inactivity, I'm in the process of getting all of my repeaters cleaned up, checked out, minor repairs made, and readied for going back on the air. Here's a couple of photos of the 442.400 repeater, online in my work shop. I originally built this back in 1993. I've made a few adjustments, and so far, all is running good. The PA is running at low power (15 watts), and it is carrier access. I do have it set up for a sub-audible tone of 88.5, but that is disabled at the moment. It's running on a test antenna out behind the shop, only about 20 feet off the ground.
This will be going back on in the stack of repeaters: 29.620, 53.07, 147.39, 224.80, & 442.400. I'll post more of the permanent installation, once the antenna work is completed.
This repeater uses a 6 cavity Sinclair duplexer on top (light brown enclosure on top of the radio), a homebrew bandpass cavity (gray in color) stacked on top of the duplexer. 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 cavity was built from a scrap 800mhz analog cell site cavity. The repeater was built from a Motorola Micor mobile radio used by the NC Forestry Service 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 encoders. This is for linking purposes.
Dave WB4IUY
www.WB4IUY.net
