Sunday, May 12, 1996

WB4IUY 29.620- 10 Meter Repeater

'Good 'ole southern hospitality from the WB4IUY repeater; Lizard Lick, North Carolina' is heard on the female voice ID of this repeater every 10 minutes when inactive. The voice is actually that of Debbie Sue, AC4QD. The ID was originally recorded back in 1994, when the repeater receiver was located about 3 miles to the west of it's current location. The old voice ID was retained after the move to Zebulon, just for nostalgia. During periods of activity, the CW ID heard on this repeater is 'WB4IUY/r FM05'. This repeater is located in Zebulon NC, in a small town just east of Raleigh NC. This is a split-site repeater; it's receiver and site link transmitter hardware are located Just north of Zebulon NC, while the transmitter and link receiving equipment are located in Zebulon `proper`. Both sites are located within grid square FM05. The repeater output is 29.620 mhz, and the input is 29.520 mhz. It has provision for sub-audible tone access on 114.8 hz, but that is not currently in use. It was originally placed into service on June 20 1994, and operated on 29.680/29.580 for about six months...when it was moved to the 29.620/29.520 frequency pair currently in use.

This is largely a 'homebrew' repeater...The first picture on the right is the repeater receiver and linking hardware. The 10 meter receiver is a converted Hygain CB with a homebrew I.F. discriminator for FM detection and an ARR bipolar RX preamp. 2 additional stages of ceramic I.F. passband filters were installed to improve selectivity. A pulse-type I.F. noise blanker was built and installed, and this was a big help at our sometimes noisy site. Coaxial stubs were cut and installed in the feedline to eliminate interference from local high-powered 27 mhz operations, and can be seen as the coiled cables in the far right of the top picture. The discriminator output is amplified about 10 db and fed into a noise switch and squelch board from a Motorola UHF Micor. I know, as many people have pointed out, it would have been MUCH simpler to grab a low-band commercial rig and make a simple conversion, but improvisation and building are a part of this hobby that I enjoy.

A home brew COS is driven from the noise switch and has about -6db hysteresis. The controller is completely home brew, as is all audio mixing. The ID'r was built from 2 voice storage boards pulled from Hallmark Greeting Cards. The ID'r is in a female (XYL AC4QD) voice during periods
of inactivity, and CW when signals are present on the repeater input. All of the above mentioned hardware is installed in the black enclosure bolted to the top of the UHF Micor (Micor is the bottom piece in the stack). Note the local volume, local squelch, rptr squelch, and repeat inhibit controls on the 'front' of the enclosure. There is a local speaker grill drilled into the upper cover just in front of the RX preamplifier, and an rx S-meter mounted on the side of the enclosure just below the rx preamplifier. That box is FULL! The controller output is interfaced with a UHF Motorola Micor running about 5 watts output. A pl of 88.5 is encoded on the UHF link tx output during COS activity for linking purposes.

The second photo above is a rear view of the 10 meter repeater receive cluster and linking equipment. A small DC cooling fan is seen as well as the full time battery supply.

The 10 meter receive antenna is a vertically polarized, top-mounted, Antron 99 omni-directional antenna up about 150 feet. The 10m rx site is linked via 70cm to the tx site at about 5 watts power through an eleven element UHF yagi at 60 feet. The link and primary 10m antennas are fed through 75 ohm 1/2" hardline. No matching devices are used, and the match is very good. The uhf-to-hardline connectors are all homemade from plumbing fittings and have worked flawlessly for years. The homemade connectors can be seen in the first photo.

This repeater has a full-time 70cm simplex port, as well as linking capability to the 147.39+ Clayton NC, 147.30+ Wilson NC, and 442.400+ Zebulon NC repeaters. This was an especially challenging project with MAJOR CB interference, powerline noise, birdies on 10 meters from everything in the county, mega-STRONG signals from amateurs working 10 khz off of the input frequency on simplex, etc. It all works well now, so all the effort paid off. 

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.