LMS-6 Radiosonde
The LMS-6 Radiosonde is a radiosonde manufactured by Lockheed-Martin Sippican, and used for meteorological sounding.
Overview
There are two models of the LMS-6, a 403MHz model and a 1680MHz model. This article will cover the 403MHz model unless specified.
Specs
- 16 Fixed transmit carrier frequencies (MHz): 400.250, 400.625, 401.000, 401.375, 401.750, 402.125, 402.500, 402.875, 403.250, 403.625, 404.000, 404.375, 404.750, 405.125, 405.500, 405.875
- Frequency tolerance +/-30ppm
- Mean TX Power 70.8mW (18.5dBm)
- Emission Designator 16K8F1D
- FSK with a maximum modulating frequency of 4.8 kHz
- Emission 3dB BW +/-5.0 kHz
- Emission 20dB BW +/-12.7 kHz
- Omnidirectional antenna
- Main beam gain 2dBi
- Horizontal Beamwidth 360 degrees
- Vertical Beamwidth +84 degrees
Photos
Connectors
There are four sensor connectors (SENSN) used for sensor input by the radiosonde. SENS1 is not populated on the 403MHz units. SENS2-4 have leads connected to them, and the sensors are connected to the other end of the leads, outside of the radiosonde housing. Only SENS1 appears to have spacing for a connector; the others have arbitrary lead spacing.
| Pin | Characteristics |
|---|---|
| 1 | +5V (5.47 measured) |
| 2 | GND? |
| 3 | +4.93V (Microcontroller VCC?) |
| 4 | 1 Hz |
| 5 | 1 Hz |
| 6 | 1 Hz |
| 7 | GND? |
Public information shows this header can be used for adding additional analog sensors to the radiosonde.
| Pin | Connection |
|---|---|
| 1 | Sensor pin 1 |
| 2 | Sensor pin 2 |
0.3" spacing. Both lead wires have ferrite beads immediately before connecting to the board.
| Pin | Connection |
|---|---|
| 1 | Sensor pin 1 |
| 2 | Sensor pin 2 |
0.5" spacing.
| Pin | Connection |
|---|---|
| 1 | Sensor pin 1 |
| 2 | Sensor pin 2 |
0.3" spacing. Fine gauge insulated wire run along SENS3 wire and loomed in white heat-shrink tubing.
| Pin Number | Function | Notes / Observations |
|---|---|---|
| 1,2,7,8 | U3 - Vdd | U15 - Pin 4 | |
| 9, 10, 15, 16, 19, 20, 33, 34 | Ground | |
| 2, 8, 18*, 24, 30 | +5VDC | 18 needs more research, may occasionally drop to ground? |
| 3 | U3 - ICCLK | TP33 | U21 - PCLK | |
| 4 | U3 - Vpp/ICCSEL | |
| 5 | U3 - RESET | |
| 6 | U3 - ICCDATA | |
| 11 | J5 - Pin 2 | |
| 12 | 3.3v - 2.5KHz square wave (4msec p/p) | |
| 13 | U3 - SW1.4 | |
| 17 | U3 - SW1.2 | |
| 18 | U3 - SW1.1 | |
| 23 | Rounded-square wave data bursts | |
| 26 | Rounded-square wave data bursts | |
| 31 | BATT POS | |
| 36 | U3 - SW1.3 | |
| 38 | U3 - OCMP1_A / AIN10 / PF4 | Square wave data bursts, 0.2msec per bit |
| 39 | RED WIRE | |
| 40 | Battery voltage | Around 9VDC measured |
| Pin | Wire Color | Use |
|---|---|---|
| 1 | Black | Ground |
| 2 | White | Battery +9 |
| 3 | Red | +9 VDC In |
| 4 | NC | Unknown - goes to
unpopulated CR1 |
J4 - NC - earphone jack? uses SENS3 leads
| Pin | Use |
|---|---|
| 1 | Unknown |
| 2 | Unknown |
| 3 | Unknown |
| 4 | Unknown |
These traces go to U3 (ST microcontroller)
| Pin | Use | Notes/Observations |
|---|---|---|
| 1 | +5VDC | |
| 2 | Unknown | 3V rounded square pulses, 2x per second, 2 different periods avg ~75msec? |
| 3 | +5VDC | |
| 4 | Unknown | 5V, 0.1msec pulse once per second |
| 5 | +5VDC | |
| 6 | Unknown | 5V, 0.1msec pulse once per second |
| 7 | +5VDC | |
| 8 | Unknown | 3V, 250msec pulse once per second |
These traces go to U14 (SPI mem?)
Components
GPS - Trimble 63530-50 s/n 1190122906
https://www.trimble.com/embeddedsystems/copernicus2.aspx
U3 - 72F324J6T6 - ST72324 - Main Microcontroller, ST7 series
U5, U6 - LP2985
U?? - TPS7201Q
U13 - CD4040BPW
U14 - CD74HC4051PWR
U15 - 92JK ZC5 (can't find much on this component)
| U15 Pin | Function | Observations/Notes |
|---|---|---|
| 1 | GND | |
| 2 | 5VDC | |
| 3 | Rounded square wave (maybe sawtooth) alternating between 2msec and 4msec, resting at +3VDC between bursts | |
| 4 | Rounded square wave alternating between 3msec and 5msec, short periods of 0v, resting at +3VDC between bursts | |
| 5 | Data. Square wave. 5V space, 0v mark? Pulses around 250msec per bit. | |
| 6 | More rounded square wave bursts | |
| 7 | 5VDC | |
| 8 | 3.3VDC |
U16 - LMV761
U21 - TI/Chipcon CC1050 (TSSOP 24)
U22 - TPS791
Sens 4 - Capacitive Relative humidity sensor
Notes
U13 Package marking shows CM040B. TI Park marking lookup provides CD4040BPW
U16 Package marking shows C22A. TI Part marking lookup provides LMV761. The SOT-23 footprint appears to match what is on the PCB.
Sens 4 is know to be capacitive since it is listed as such on page 13 of the WMO Common Code Tables Document
Circuits
RF from CC to Ant1 - coming soon
Relative Humidity Circuit
File:Relative Humidity Circuit Schematic.pdf
U16 -Input also has a cap to ground not shown on the sketch.