Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
My Hobby Website:
The Navigation Satellite Timing and Ranging Global Positioning System (NAVSTAR GPS)
has been operational, incredibly, for almost three decades. The first satellite
in the originally planned 24-member constellation was launched on July 14, 1974.
A total of 11 Block I satellites (built by Rockwell) were launched into 10,900 nautical
mile orbits between 1978 and 1985 on the Atlas-Centaur booster rocket. In 1982,
the DoD decided due to budget cuts to reduce the constellation number from 24 to
18, but by 1988, the number was back to 21 plus three orbiting spares. In 1989,
the first of the Block II NAVSTAR satellites was launched. 28 were scheduled for
construction and launch because of attrition from old technology and malfunction.
By 1991, 24 satellites were in orbit and commissioned. Mission accomplished.
Until 1997, the most accurate GPS signal, the L2, was made available to the
public only on a sporadic basis. The L2 signal was closely guarded by the military
for use in their critical aircraft, spacecraft and munitions guidance systems. Advances
in technology that most people outside the highly classified DoD community will
never know about, and pressure brought on by civilian groups to make the L2 signal
available full-time are credited for the policy change. Since that occasion, GPS
devices and products that incorporate GPS have grown exponentially.
GPS really got its launch (no pun intended) during the first Gulf War, when concerned
parents and spouses bought GPS units by the caseload to send to their husbands and
children in the deserts of Iraq. In those days, the GPS receivers and computational
engines were the size of a cigarette pack, often took minutes to acquire and compute
signals, and drew large amounts of current. Since only the less accurate L1 signal
was available for these units and many had only a couple receiver channels, the
accuracy was limited to around 10-20 meters (good enough for a desert in a sand
storm). The military was enjoying accuracies as good as 5 meters with the L2 signal
and many channels. Block III satellites will generate a new
L5 signal, a higher power (roughly 4x), modified version of the
L2 intended for civilian use to provide better coverage with less sensitive receivers.
Now, GPS receivers are integrated onto a single slab of silicon and routinely provide
12 to 16 channels and achieve positional accuracies unfathomable in the early 1990s.
Their current draw is measured in tens of milliamps.
Today, GPS receivers
can and are integrated into just about any kind of device that is not bolted down
(and some that are): cell phones, automobiles, boats, watches, vending machines,
shopping carts, full-size airplanes and model airplanes, and even the new
Gizmondo, GameBoy-like controller (for location-based gaming).
Map software can be had that, when combined with a solid state magnetic compass
Nokia 5140 phone), provides the operator with directions that are detailed enough
to allow navigation instructions like, “Go straight ahead for 200 feet and turn
left at Main Street, then proceed 50 feet to the Starbucks on the right.” “Real”
GPS devices like those available from Trimble, Garmin and Magellan provide even
more amazing features.
GPS is now a technology that the folks at Aerospace
Corporation, when beginning their study in 1963 on the development of a space system
as the basis for a navigation system for vehicles moving rapidly in three dimensions
(leading directly to the concept of GPS), could never have dreamed would be at such
an advanced state of maturity forty years later. Those who are still around can
take pride in the system to which they gave birth. Why, without their foresight,
for instance, the people involved in the frontier-advancing concept of GPS art would
never have been able to indulge in their craft. What is GPS art, you might ask?
It is the process of using a GPS tracking program to record an operator's path along
the ground (or in the air or water) in a shape that results in an outline of a pre-planned,
recognizable object. As you might expect, there are websites dedicated to chronicling
the ample talent out there. One of such websites is
you will find not only a large collection of GPS art that includes tic-tac-toe games,
pictures of whales and text messages, but also instructions on how to generate such
masterpieces yourself. Isn't technology wonderful?