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PA2SNK > MODS 10.01.13 22:02l 55 Lines 2019 Bytes #999 (0) @ WW
BID : 19447_CB9SNK
Read: GAST
Subj: President Lincoln fm RX fix
Path: DBO595<DOK346<BBS645<NL3CAT<NL3PRC<CB9SNK
Sent: 130108/2154Z @:CB9SNK.FRL.NLD.EU #:19447 [Sneek] Sneek $:19447_CB9SNK
From: PA2SNK@CB9SNK.FRL.NLD.EU
To : MODS@WW
Message created on dinsdag, 8 januari 2013 at 22:53:34
FSG WinFBB Message Editor v1.2 (c)1998 FSG's JO1HDV
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President Lincoln
DG2IAQ Modification notes 20-Jul-2003, rev. 29. Jul. 2009 / p. 1
FM detector fix
Some users reported a bad FM signal detection on weaker signals.
This is also what I recognized at all my 3 Lincolns I owned in the
past years.
The reason and the fix are simple.
The input of the FM detector stage is wired from L104 through a serial resistor of 10k
(R1 in the schematic) toward the FM detector IC. But the schematic says ?1k? instead.
With 10k the FM input signal is attenuated so strong, that the detection below S5 gets
more and more worse. You hear more FM-noise than the FM-signal itself, meaning the
S/N ratio gets worse.
The fix is easy:
1. Just replace R1 (10k) with its correct value of 1k.
2. Check and possibly re-align L104 (only !!!) for maximum signal. Use a plastic
screwdriver only.
DG2IAQ Modification notes 20-Jul-2003, rev. 29. Jul. 2009 / p. 2
Another possibility would be, to wire the new 1k resistor on the downside and use the
(unused) middle pin of L115 instead. Check and possibly re-align L115 for maximum
signal level.
Both versions work great on all my modded Lincolns and those from friends and I cannot
tell you any difference on either the L104 or L115 version.
Finally your President Lincoln receives and detects weak FM signals in the same great
way like any common CB transceivers.
73's Danny
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