July 2000               sPARCGAP                PAGE 7

experiment. Stan Rohrer, W9FQN, at the PARC Field Day site simply "transmitted" a mirror flash to Gonsett, who was on Boucher Hill at Palomar
Mountain.
"Flashing this 12.7 mile optical path confirmed that there were no trees,
bushes or buildings in the way--constant problems in optical work," Gonsett
said. Hams have conducted laser communication over paths of 100 miles or so, he noted, so the distance was not record-breaking. The PARC experiment
showed that laser communication can be accomplished with simple, inexpensive
gear.
Equipment involved two full-duplex voice-modulated laser units constructed
by Kerry Banke, N6IZW, and Chuck Houghton, WB6IGP, using PVC pipe housings. Each uses an ordinary 0.5 mW red "pointer" laser costing less than $3 apiece as a transmitter. The lasers were mounted outside the PVC tubes. "Because a laser beam is very narrow, the apparatus is aimed with the aid of a rifle telescope," Gonsett explained. Precise positioning was accomplished using
two micrometers salvaged from microwave tubes.
At the transmitting end, a "stock" pointer laser is powered by a 35-kHz
oscillator. A microphone frequency modulates the 35-kHz oscillator at 5 kHz
deviation. At the receiving end, the incoming red laser light hits a plastic
Fresnel lens that focuses the light onto a photo detector. Out of the photo
detector comes the 35-kHz FM signal. That signal is mixed with a 145.000 MHz local oscillator, producing a signal on 145.035 MHz. That signal is run
through coax to a ham radio H-T tuned to 145.035 MHz--the H-T serving as the
FM demodulator/receiver. The system is full-duplex.

Gonsett said observers at the PARC Field Day site were "blown away" by the
brilliance of the one-half milliwatt red laser beam coming from the distant
mountain. "While the beam shimmered with atmospheric turbulence, voice
communications were clear and steady with only a hint of rumble, thanks to
the use of FM," he reports.

Reprinted from the ARRL News Letter.

Anyone ELSE want to try this? KC7PDI

Our new President needs watching! He claims broad powers. He has stated that he can give awards like this to anyone he wishes without the prior approval of the board of directors. So be forewarned! If you do something he thinks is worthy of praise. He may just call you up before the members at one of our Club meetings at give YOU one of these.
I know I was supprised. Thanks Neal and to all the Club members it was a pleasure to serve you. 

Chuck Parker KC7PDI

CALIFORNIA GROUP ADDS LASER MODE TO FIELD DAY REPERTOIRE
Participants at the Palomar Amateur Radio Club ARRL Field Day site in Valley Center, California, this year completed a two-way voice contact via laser
beam. In typical ham radio tradition, communicating over the nearly 13-mile
path on a beam of light involved minimal cost and readily-available parts.
"The first step in establishing a laser QSO is determining that a clear
optical path exists," says Bob Gonsett, W6VR, one of those involved in the