KZSU Technical Notes

Our studios are in Memorial Hall on the Stanford campus. There are two control rooms, both using Broadcast Audio Series IV consoles. The consoles are fairly new, having been purchased around 1988 and 1991. Other studio equipment includes Technics SP10 and SP15 turntables, Denon DN-961 CD players, ITC cartridge tape machines, Otari open reel tape decks, Nakamichi cassette decks, and telephone interface gear from Comrex and Symmetrix.

NOTE: We're looking for equipment to replace our aged, creaky cartridge machines; we already know about MD, Arrakis, and 360 Systems hardware. Send us E-mail if there is a system that you know and like.

Our audio chain is relatively pure, compared with typical FM stations. There is no signal processing other than an Optimod 8000A stereo generator, which has a limiter to prevent overmodulation and is configured to perform some light dynamic compression. We do not employ an STL [digital studio/transmitter link], nor do we use the telephone company to carry the signal. Instead, we have dedicated cabling from the studios to the transmitter.

FACTOID: The cable run from our studios to the transmitter uses 10,687 feet of 22 AWG twisted pair telephone cable (50 pair). Other KZSU cables run from Memorial Hall to various major venues on campus, to facilitate coverage of events at those locations; we installed most of these lines ourselves. In addition, a PacTel line runs to Palo Alto City Hall and carries our weekly City Council broadcasts.

Up at the transmitter shack, an equalizer compensates for the cable frequency response and feeds the Optimod stereo generator, which drives a Continental 802B exciter (installed in 1995), which drives our homebrew 250W power amplifier. The power amplifier uses a single 4CX250B tube. The antenna is a Jampro JCP-4 mounted on a 65-foot wooden pole; antenna height is about 520 feet MSL [height above Mean Sea Level]. It is located in the foothills behind the campus near the Big Dish.

[In case you're wondering, the pictures which show rays emanating from Hoover Tower are a romantic fiction which our Publicity Department has shamelessly perpetrated on an unsuspecting public. Well, now you know...]

We have an effective radiated power of 500 watts with both horizontal and vertical polarization. That's actually 500W vertical, 500W horizontal. Note that ERP is the amount of power you'd need to feed into a simple dipole antenna to produce the same field strength, and is rated for the horizontal plane. Stations are permitted to radiate the same energy, or less, on the vertical plane. So KZSU's "500 watts" is figured by

transmitter power = 250W
1/2 power to horizontal = 125W
antenna gain of 4 x 125W = 500W

In case of power failure, both the Memorial Hall facility and the transmitter site are equipped with emergency battery power and standby generators. Additionally, we have a secondary hookup at Stanford's Emergency Operations Center to help disseminate important information in the event of a campus-wide (or larger) emergency. We installed the cabling and equipment for the EOC facility in 1994.