by
Pete Mahowald K6TJ
July 2003
In 1987, the university buys the repeater, Telewave duplexer, two 25 section (4 foot long) antennas, an Icom base station for the club shack, 70 feet of 7/8 Heliax, and an ACC 80 controller. Several people from the club install the repeater in the building at the base of the Big Dish. The duplexer is labeled with TX and RX switched, and at first it can't be heard more than several hundred feet away. The cables are swapped and then things work much better. Frequency is 1291.50 with a 20 MHz split. That repeater is intended to be a backbone path supporting 2m nets in the event of an emergency.
In 1988 the repeater is moved to Stanford's Instructional TV site at the top of Black Mountain (2800 feet elevation). We are given one foot of rack space. The site is excellent, and has backup generator power. We choose a spot at the very top of the tower, with the antenna mounted upside down as it's pattern is 4 degrees up from horizontal. The SRI group, also on 1200 MHz, chooses a spot for their identical antenna halfway up the tower. The club is very active in stabilizing the repeater, replacing the power supply, installing a power amp and preamp, and making the antenna mount strong enough that without doesn't twist in the wind. A battery backup is installed. Check-in's for the SPECS net are often taken on this repeater, a practice which continues to this day.
In 1989 during the Loma Prieta earthquake, the repeater goes off the air as a battery is weak, and the site's generator does not start. A new backup battery is installed, and the site's generator is replaced. Ten Icom HT's are brought by individuals at club discount.
In 1992-3 the repeater is not nearly as sensitive as the SRI group's repeater. Also it is on 20 MHz split, and band plan has changed to 12 MHz split. So the repeater is sent back to ICOM for conversion and maintenance. They find 2W (spec is 10W) transmitter output, and crushed receiver coax. The duplexer is retuned to a new coordinated frequency. With the new receiver sensitivity, an extra cavity must be added on the receiver side, again from Telewave. The power amp is removed as it's power supply is left on with no TX power and the current jumps around the little. It is discovered that the antenna has filled with water, and a new higher gain antenna is installed, this time vertically with the appropriate tilt. There seems to be a weak carrier on the receiver input about half the time. This is traced to a 993rd harmonic of the rotation frequency (well actually a modulation sideband) of the synchrotron at SLAC. A new frequency is coordinated, 1282.5, the duplexer retuned, in the repeater sensitivity now appears to be about the same as the SRI repeater.
In 1995 Stanford hires a consultant to find a spurious emitter at the site. Another repeater at the site is powered off momentarily, the spurious emission stops, and powered back on, and the spurious emission begins again. The other repeater no longer uses the power amp either now.
In 1998 (?) the backup battery is changed out.
In 2003 our coordination has elapsed, and new papers are filed. New control operator codes are established.