Actually you didn't. But you didn't, also, buy a ton of them either, which is smarter...
Ok, You can use that cap as a means to tune - but you also should check the USB side of that 7.8MHz too...
IF you find that you can not "center" the L59 coil properly - it means you have to tweak the other missing half that is forcing you to tune the coil in this fashion.
So, instead of raising the bridge....
...Lower the water - ok, a Jerry Lewis film but hey- eh?
I'm saying try removing CT 2 variap and replace it with this 40pF instead then retry to tune.
Don't focus so much on the L59 and thinking you have something wrong. You need to also look at the 7.8MHz and getting it right. These two work to offset and compliment each other - set up L59 first - set it's slug is close to mid to upper tuning range point (near the top of the slug but not all the way up) - then go tweak the 7.8 MHz side, via CT2 to move L59's audio curve to center slot...
Once L59 is set to it's near peak - go back to CT2 (that varicap) using your new 40pF - and swing for the bleachers - a.k.a. - set it so you get L59 nearly right (without touching L59) - then go back and tweak the best of both to obtain USB center slot.
See C125 - a 5pF? You can change this too. Works with CT 2 to offset it... so you don't have to even swap the CT2 if you wish.
Ok, with everyone in bed, I have a moment to add more...
Look at the snippet I am attaching to this post. There is a reason to work on the CT2 side inclusive. It's not all L59's fault. Well, maybe it is, but you'd have to locate the guy from Uniden that did this...
Ok, L59 note it does not have or use a "DC Block" cap - like L23 or L22 - you can install a cap but I'm not sure you'd like the results - look at the circuit and all the parts involved.
The 11.125 Xtal floats but L59 is used to provide ground for the other half of the Xtal - so in essence - it's the real tuning point and reference for the other two coils of L22 and L23. So before you go chasing down that guy or look elsewhere - look at the schematic and back to that radio - L58 and R146 are also a part of L59 and that tank circuit resonance. They provide the return path for the Xtal thru L59 if the other lines are active or not - they cannot provide a ground reference to the Xtal - L59 is the one that does that to stabilize the circuit.
You can prove this to yourself by fiddling with L59 at the same time you fiddle with the L22 and L23.
So, you can try that cap idea, but I'd look at CT 2 and fixing/replacing that part and retune. IT should help you locate the best balance for you to find center slot for all the modes.
EDITS: L59 on the brain....
