29.620 - (page 2)
The WB4IUY repeater in Zebulon, NC
On the distant end (the TX site), the UHF link signal is received via another UHF Motorola Micor with an ARR GaAsFet RX preamp. In the picture to the right, the Micor is the radio on the left and on the bottom. The ARR rx preamp has a red sticker and is located just in front of the Micor. The audio is shaped via homebrew mixer and interfaced to the 10 meter exciter. The exciter is another converted Hygain CB with true FM generated by modulating the VCO. The mixer and exciter are housed in the aluminum enclosure bolted to the top of the Micor. The low level RF stages are modified to run full time for stability, and the 1st rf stage after the tx mixer is buffered and keyed to control the final stages of the TX. Much additional heat-sinking was added, and the transistors in the last 3 stages were replaced to improve duty cycle. The exciter produces about 1 watt into a bandpass filter liberated from a RCA series 700 lowband mobile.
The RF then passes through a low-pass filter and into a homebrew solid state intermediate amplifier producing about 15 watts. The intermediate amp is bolted to the top of the aluminum enclosure to the rear, just behind the Motorola remote head. A small muffin fan is attached to it's heatsink for good measure.
The output of this stage is fed into an Ameritron AL80B (hollow-state technology!), driving the 3-500 (at 1700 volts) to about 350 watts output. The beautiful glow of the 3-500 can be seen in the photo to the left. This RF passes through a Drake low-pass filter and up to the 10 meter TX antenna.
The TX site receives the UHF link signal via another eleven element yagi at about 30 feet. The 10 meter TX antenna is an omni-directional Antron 99 antenna at about 150 feet.
Performance for this system was much better than I first expected. Coverage for ground wave 10 watt mobile stations is about 30 miles in all directions, while 100 watt mobiles can work it over 50 miles out. Fixed stations can work it over greater distances, some as far out as 75 miles. I must say I was surprised to find coverage on 10 fm so good. We have a 220 and 440 repeater at the same site, and the 10 meter repeater far exceeds their coverage.
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