LMS-6 Radiosonde: Difference between revisions

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''U4 - (Marked Z252)''

'''U5''', '''U6''' - [http://web.archive.org/web/20200206204209/http://www.ti.com/lit/ds/symlink/lp2985.pdf LP2985] - LDO - 2.8V?~~[[File:U?? - TPS7201Q.jpg|none|thumb|TPS7201Q on PCB]]~~

'''U5''', '''U6''' - [http://web.archive.org/web/20200206204209/http://www.ti.com/lit/ds/symlink/lp2985.pdf LP2985] - LDO - 2.8V?

''U7 - (Marked G4/905)''

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''Unot_marked (23/24?) - (Marked W6K/W76) - RF Amp, similar to SKY65013-70LF (No designator; under TX can to bottom-right of U21.)''

'''U25''' - [http://web.archive.org/web/20200123234645/https://www.ti.com/lit/ds/symlink/tps72.pdf TPS7201Q] - Adj. 1.2-9.75V LDO - (Designator silkscreen is hard to read; 8-SOIC on bottom-right)[[File:U?? - TPS7201Q.jpg|none|thumb]]

'''U25''' - [http://web.archive.org/web/20200123234645/https://www.ti.com/lit/ds/symlink/tps72.pdf TPS7201Q] - Adj. 1.2-9.75V LDO - (Designator silkscreen is hard to read; 8-SOIC on bottom-right)[[File:U?? - TPS7201Q.jpg|none|thumb|U25 and general area]]

[[File:Screenshot 20200904-195417.png|thumb|92JK ZC5 chip noted as U15]]

{| class="wikitable"

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===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.

When testing, it's important not to transmit on unlicensed frequencies. Emissions can be eliminated by replacing the RF amplifier with a jumper between pins 1 and 3, and terminating the load at the antenna connection. The amplifier is an SOT-89 device just above the "-" terminal of B3. To access the 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.

[[File:TX circuit modified.jpg|alt=Picture of circuit board|left|thumb|Picture of TX circuit, hilighting components to remove to disable amplifier and a replacement jumper.]]

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@@ Line 276: / Line 276: @@
 ''U4 - (Marked Z252)''
-'''U5''', '''U6''' - [http://web.archive.org/web/20200206204209/http://www.ti.com/lit/ds/symlink/lp2985.pdf LP2985] - LDO - 2.8V?[[File:U?? - TPS7201Q.jpg|none|thumb|TPS7201Q on PCB]]
+'''U5''', '''U6''' - [http://web.archive.org/web/20200206204209/http://www.ti.com/lit/ds/symlink/lp2985.pdf LP2985] - LDO - 2.8V?
 ''U7 - (Marked G4/905)''
@@ Line 311: / Line 312: @@
 ''Unot_marked (23/24?) - (Marked W6K/W76) - RF Amp, similar to SKY65013-70LF (No designator; under TX can to bottom-right of U21.)''
-'''U25''' - [http://web.archive.org/web/20200123234645/https://www.ti.com/lit/ds/symlink/tps72.pdf TPS7201Q] - Adj. 1.2-9.75V LDO - (Designator silkscreen is hard to read; 8-SOIC on bottom-right)[[File:U?? - TPS7201Q.jpg|none|thumb]]
+'''U25''' - [http://web.archive.org/web/20200123234645/https://www.ti.com/lit/ds/symlink/tps72.pdf TPS7201Q] - Adj. 1.2-9.75V LDO - (Designator silkscreen is hard to read; 8-SOIC on bottom-right)[[File:U?? - TPS7201Q.jpg|none|thumb|U25 and general area]]
 [[File:Screenshot 20200904-195417.png|thumb|92JK ZC5 chip noted as U15]]
 {| class="wikitable"
@@ Line 378: / Line 379: @@
 ===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.
+When testing, it's important not to transmit on unlicensed frequencies.  Emissions can be eliminated by replacing the RF amplifier with a jumper between pins 1 and 3, and terminating the load at the antenna connection.  The amplifier is an SOT-89 device just above the "-" terminal of B3.  To access the 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.
+[[File:TX circuit modified.jpg|alt=Picture of circuit board|left|thumb|Picture of TX circuit, hilighting components to remove to disable amplifier and a replacement jumper.]]
+<br />