23
edits
Changes
Added TX output schematic; instructions on how to disable amplifier.
{| class="wikitable"
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!U15 Pin
!Function
!Observations/Notes
==Circuits==
=== RF from CC to Ant1 - coming soonTransmitter Circuit ===The transmitter RF path contains a filter IC, pi matching network, broadband amplifier, and a few more output filter stages.[[File:LMS6.png|alt=Schematic diagram|center|frameless|1065x1065px|Basic schematic of TX circuit on LMS6]]
<br />
[[File:Relative Humidity Circuit Schematic.pdf|thumb|Relative Humidity Circuit Schematic]]
U16 -Input also has a cap to ground not shown on the sketch.<br />
== Modifications ==
=== Disable amplification ===
When testing, it's important not to transmit on unlicensed frequencies. Emissions can be eliminated by removing the RF amplifier from the chain and terminating the load at the antenna connection. The amplifier is an SOT-89 device just above the "-" terminal of B3. To access this RF chain, the shield housing may need to be temporarily removed. Also remove the bias feed resistor just below the "L104" marking. Then, remove the transmitter antenna from the "ANT1" connections. Use a 50 ohm resistor across the two terminals to provide a terminating load and eliminate any further transmission. Near-field reception is still possible after making these changes.