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Lincoln 2 receive overload

codeman

Recovering Crackerhead
Jul 10, 2011
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1,078
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I have a President Lincoln2 that i like as as far as features and transmit goes....however the receive on this radio is way too sensitive. Powerful stations on sideband sound distorted. I get way too much bleed over on sideband even from AM frequencies far from the ones I am using. Is this problem fixable? I will keep the radio due to the small size that i am planning on installing in my dash, but i really would like to get the receive cooled down, because it is too hot the way it is now.
 

codeman

Recovering Crackerhead
Jul 10, 2011
685
1,078
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Oh yeah. I have tried that it helps a little. But the receive is still too hot
 

Martian

Well-Known Member
Jul 3, 2018
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Sounds like a repair to me.
There are a few reasons the RX could be distorted.
AGC could be fubar. Filter failed. Something in the AF section....
 

Handy Andy

Do Your Research First, Then Decide...
Apr 23, 2018
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Hmm...IF RF gain offers little - there may be front end damage - as a blown protection system. They use a PIN diode biasing scheme - I don't know much about LINCOLN 2's but is possible that the radio could have suffered static overload and has suffered blown parts - can even be from EMP from a close lightning strike.

The AGC controls the PIN diodes while RF Gain controls the RF amp...

IF AGC is gone - you'd find a "dead" receiver or VERY DISTORTED receive.

RF gain - if one PIN diode blew open - or a cap has failed - you'd have a LOT of receive even when RF gain is turned down 1/2 way. Because you have lost the ability to attenuate the noise at the antenna before it arrives to the RF amp - AGC would try to reduce gain - but it only can do so much "clamping" the rest has to be done by how the RF gain interacts with AGC.

So if RF gain works it's letting AGC work with it ... which to me indicates front end damage or a failed part - at least a good inspection is in order.

IF AGC is gone, the only way you'd understand anyone is to turn down the RF Gain because AGC won't try to average out the signal level to make it understandable even with signals that don't go up to full scale on a normal meter.

IF parts controlled by the AGC - a cap failed as an example would immediately overload any signal into the receiver...

IF parts controlled by RF gain failed - you'd be able to recover some of the signal from all the noise...

So in either case - you need to have that radio looked at...even overpeaking can cause distortion issues but that is a tune-up issue...
 
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codeman

Recovering Crackerhead
Jul 10, 2011
685
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It has always had the problem. I will probably get my normal CB shop look at it.
 

Handy Andy

Do Your Research First, Then Decide...
Apr 23, 2018
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Long time ago, Lou Franklin had mods for the Galaxy radios that used the Quad-324 Op-amp chip - cap changes mostly to lessen the aggressive tendencies of AGC attack, detect and decay rates due to SSB modes - but to have a general overall effect so poorly on a generational platform radio to the newer technology. Looks like a conversion failure by the engineering staff to take the discrete version and properly translate it to the SMD - sounds like they didn't test this very well.

Why I love the discrete, you can nip this in the bud directly on the older platforms using the corrected values - but not so easy to work with on the newer platforms which are multi function and digital switch styles.
 

Handy Andy

Do Your Research First, Then Decide...
Apr 23, 2018
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Indeed...

hmm reminds me of the president Jackson

Don't know if this could help those whom have perished their monies into the newer Lincolns - but for those whom waited along the shoreline....
LouFranklinAGCsupport.jpg

Sorry for the big pic, but I wanted to ensure credit goes to whom it belongs...

If any of you caught the reference to Galaxies, Lou pretty much used the above to prove his point about their RX problems back then.
 
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