dsp@oakhill.UUCP (Generic DSP account) (04/12/88)
I recently purchased a used TI 9900 LORAN-C receiver. I would like to procure the schematics for this beast. Is anyone out there familiar with this receiver?? The thing is not tracking the Loran stations at all....even though the receiver output shows the GRI pulses. A source for schematics or advice would be greatly appreciated. Charlie Thompson (512) 892-6161 Austin, TX
commgrp@silver.bacs.indiana.edu (BACS Data Communications Group) (04/12/88)
>I recently purchased a used TI 9900 LORAN-C receiver. I would like >to procure the schematics for this beast. Is anyone out there familiar >with this receiver?? The thing is not tracking the Loran stations at >all....even though the receiver output shows the GRI pulses. A source >for schematics or advice would be greatly appreciated. > >Charlie Thompson >(512) 892-6161 >Austin, TX There may be nothing wrong with the receiver. LORAN-C works poorly or not at all in most of Texas because of unsuitable geometry relative to transmitting stations, even though signals are strong. A baseline extension (area of ambiguity) of the Southeast Chain runs between Dallas and Austin; my car-mounted Micrologic ML-5000 was totally unusable (would not track) from just south of Dallas to San Antonio; it gave error indications west of Dallas because the repeatable accuracy was greater than 1000 feet (due to very obtuse crossing- angles between lines of position). No other LORAN chains have sufficient signal strength in Texas. I tried the Great Lakes Chain but couldn't get enough signal from Minnesota; it might be worthwhile to experiment with cycle-stepping (a weak-signal technique). New transmitters, due to be operational by 1990, will fill the "mid- continent gap" and provide primary coverage in Texas. Existing LORAN receivers will require ROM upgrades to use the new stations. See _Aviation Week & Space Technology_ magazine, Sept. 28, 1987 p. 120. All LORAN-C stations are on the same frequency, 100.000000 kHz, and transmit their pulses in a sequence precisely controlled by atomic clocks. Stations are grouped into "chains" which are selected by their group repetition interval (GRI). Three stations of a chain (a master and two secondaries) must be received to calculate a unique fix, however, only two stations can establish the receiver's position somewhere on a hyperbolic line of position. LORAN-C transmitting stations are impressive! Output power ranges from 400 kW to 1.2 MW. Antennas are 600 or more feet tall, with many long top-hat radials. Stations are manned by the U.S. Coast Guard, and have diesel generators for emergency power. -- Frank W9MKV @ WA8YVR reid@gold.bacs.indiana.edu BITnet: reid@iubacs
budden@tetra.NOSC.MIL (Rex A. Buddenberg) (04/14/88)
Frank had most of the specs right. 625 foot towers are the most common ones in the US. But we still run a half dozen high power stations (I had Iwo Jima in 1980). 1.8 Mwatts thru a 1250 foot tower. The high power stations still don't have the solid state transmitters -- each push-pull transmitter has 2 first intermediate power amp tubes -- air cooled, about 10 inches tall plus 2 second IPA air cooled tubes about foot and a half tall and 7 pairs of driver tubes which stand about 3 feet tall and are water cooled. The transmitters are walk-in -- we have two at each station side by side with a passageway down the middle. Great excitement when the transmission line shorts out !!-). Rex Buddenberg
johne@hpvcla.HP.COM (John Eaton) (04/16/88)
<<<< < < LORAN-C transmitting stations are impressive! Output power ranges < from 400 kW to 1.2 MW. Antennas are 600 or more feet tall, with many < long top-hat radials. Stations are manned by the U.S. Coast Guard, < and have diesel generators for emergency power. -- How do they compare with OMEGA broadcast sites? You would think they have to do something spectacular to transmit at 10 Khz. John Eaton !hpvcla!johne
henry@utzoo.uucp (Henry Spencer) (04/16/88)
> LORAN-C transmitting stations are impressive! Output power ranges > from 400 kW to 1.2 MW. Antennas are 600 or more feet tall, with many > long top-hat radials... If you want to see impressive, find a diagram of an Omega station. It's just as well that only about a dozen of them are needed to cover the world; they are *enormous*. -- "Noalias must go. This is | Henry Spencer @ U of Toronto Zoology non-negotiable." --DMR | {allegra,ihnp4,decvax,utai}!utzoo!henry