Teardown of LaBarge IDCP - 1970s tech! - Page 1
Forum section: electronics / projects

author: TheMG
author_rank: Frequent Contributor
timestamp: January 11, 2021, 09:10:22 pm
content: I found this unit in a dark dusty forgotten corner of a storage room (modern archaeology!). It is a LaBarge Interrogated Data Platform model IDCP_1287 manufactured august 1977.What exactly is an interrogated data collection platform? It works together with the GOES (Geostationary Operational Environmental Satellite) satellites to collect and relay data from various ground locations back to a central point. This includes (but not limited to) various kinds of telemetry such as weather, climate and environmental data, etc, from field locations where other forms of communication are not available. Remember this is long before the internet, cellular networks, etc were even a thing. As the name suggests, each data collection platform has its own unique address and doesn't transmit anything until it is "interrogated" (polled) by the satellite. Frequency of operation is in the 400MHz band, using helical antennas.This particular unit is one of the first models (maybe even the first?), operating at a blazing fast 100 baud on 1.5kHz wide channels. FSK modulation I think but can't be certain, it's hard to find specific information on the 100 baud system.The GOES DCS service is still very active, as there are still large numbers of systems in geographical locations with no other cost-effective means of communication. Although other satellite-based data communication methods exist, it is still not cost effective for small amounts of data so the GOES DCS system still has its place. The 100 baud data rate has been discontinued in favor of 300 or 1200 baud only.More information can be found here:https://www.noaasis.noaa.gov/GOES/GOES_DCS/goes_dcs.htmlAnyways, enough with the history lessons and on to the teardown...Pulling the lid off the barrel, all the "guts" come out as one easily serviceable unit. A nice arrangement of cards slotted in to backplane connectors.The backplane wiring. All hand soldered, PTFE insulated wiring (no expenses spared!).more to come (can't fit all attachments in a single post)...

author: TheMG
author_rank: Frequent Contributor
timestamp: January 11, 2021, 09:32:53 pm
content: A1 card. This is clearly the transmitter, as it is connected to the TX port of the duplexer, and contains a Motorola SHW151 hybrid RF amplifier module. Considering the age, it's not surprising to find that there is no PLL or frequency synthesizer, the transmit frequency is set by the crystal oscillator, with what looks like a rather large number of multiplier stages.A2 card, apparently some linear voltage regulators. I'm not sure what the 40xx series logic ICs to the right hand side are for, could be for some type of self-diagnostics, "power good" signal, or something to that effect. Note the SCR crowbar near the center (again, no expenses spared!).A3, the "brains" of the operation! Based on a C4040 processor, which as far as I can tell is an upgraded version of the C4004, the first ever CPU manufactured by Intel. The C4289 as far as I can find contains SRAM, address decoding logic, and a few other supporting functions. There is also what appears to be a discrete switching DC-DC converter. The address associated with the unit is "programmed" using the diodes inserted into chip sockets.more to come...

author: TheMG
author_rank: Frequent Contributor
timestamp: January 11, 2021, 09:43:33 pm
content: On the A4 card, some more addressing logic and what appears to be more voltage regulators.A6 card appears to contain the IF, LO, and demodulation portions of the receiver. Once again, the receive frequency is crystal-controlled and you can see the alternate frequency crystal in its storage location at the top of the card.A7 connects to the RX port of duplexer, it appears to contain the RF receiver front-end circuitry and 1st mixer. Some amplification and a lot of discrete L-C bandpass filters. Come to think of it, I don't see any crystal filters or ceramic resonators anywhere in the receiver cards, so that kind of explains the metric ton of discrete L-C filters to obtain the required narrow bandwidth!more to come...

author: TheMG
author_rank: Frequent Contributor
timestamp: January 11, 2021, 09:54:45 pm
content: The A9 card... this one I'm not sure about. Definitely something to do with I/O as most of the connections to the "outside world" seem to go to it. The presence of multiple opamps would suggest some analog capability however I can't find an ADC anywhere. Maybe the opamps form some sort of discrete ADC? I could be way off, and they might serve some other purpose entirely.Last but not least, the RF duplexer, made by Sinclair.Nothing really special in there, just coaxial line sections and stubs.That's it! Hope you found this old piece of technology interesting. I would love to find more info on this, but given its age, that's pretty unlikely.