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57 lines
1.6 KiB
Plaintext
57 lines
1.6 KiB
Plaintext
Objective:
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Reproduce sidebands observed in 200110303 and look for ways to reduce them.
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In particular, examine the effect of the antenna tuning capacitor C16.
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Test setup / changes:
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4 original board, like in 20110303 (noise from WLAN I forgot to turn off)
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4a reflowed some RF vias; cleaning
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4b removed large solder deposits on RF; not cleaned
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4c cleaning after 4b
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4d 0.5 pF at C16; cleaning
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4e 1.0 pF at C16; cleaning
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4f C16 NC; cleaning
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4g resolder pin B1.1; cleaning
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4h replace cracked B1; switched to leaded solder; cleaning
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4i reflowed B1 at higher temperature; cleaning
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4j reflowed C8's balun side; cleaning
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3 original board, like in 20110303
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3a wait 2 h (warm-up; USRP2 freshly booted)
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3b cycle (unplug/plug) atusb
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3c retract shutters (metal)
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-------------------------------------------------------------------------------
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Observations:
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4 behaves as it did in 20110303
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4a no change
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4b no change
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4c no change
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4d no change
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4e no change
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4f major regression
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4g regression persists
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4h regression persists (slight recovery seen in 4h-0 may be due to
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temporary effects)
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4i regression persists
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4j regression persists; giving up
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3 behaves as it did in 20110303; significantly cleaner
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3a sidebands are reduced
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3b sideband reduction persists
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3c ~10 dB drop at lower end of spectrum
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-------------------------------------------------------------------------------
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Conclusions:
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- build quality seems to be principal factor in RF performance variations
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- a warmed up board performs slightly better than a cold board
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- C16 has no noticeable effect
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- reflection characteristics even of distant items in the environment have
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a strong influence on relative signal strength
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