[Boatanchors] Heathkit LMO Linearity

[Jim Liles]

Hi Mark,

Guess I'm divulging my antiquity.  Sounds like a street gang thing ---  
Knifing a capacitor.

Knifing a capacitor is the process used to bend the outer plates of a VFO 
capacitor to align the 100Kc and 1KC points on the frequency dial.  If you 
look at the tuning capacitor on most VFO's you'll find the outer slotted 
plates in all kinds of disarray.  The outside plates are slotted to enable 
adjustments throughout the tuning range.  Most variable caps have slotted 
end plates which are for this purpose.  A good quality VFO/LMO can be 
adjusted to be right on for the 100Kc and end points and within 1/2 Kc for 
the 1Kc points.  They can also be Temp comped to deliver a 100 cycle range 
for drift.

Knifing a cap is kind a right of passage for a lot of old timers.

I can send a photo of the tool that you'll need to make if you like.

Good luck with that radio.

Kindest regards Jim K9AXN



-----Original Message----- 
From: Mark Johnson
Sent: Saturday, November 21, 2015 8:04 PM
To: Jim Liles
Subject: Re: [Boatanchors] Heathkit LMO Linearity


I'm sorry Jim..knifed?
Sent from my iPad

> On Nov 21, 2015, at 8:51 PM, Jim Liles <hallicrafterssr2000 at k9axn.com> 
> wrote:
>
> The variable capacitor at the rear of the LMO is used to coordinate the 
> end to end frequency points with the dial.  Use the variable cap on the 
> rear to align the end points.  Then verify the 100Kc calibrator is right 
> on.  Then check the 100Kc points from end to end.  If they are not right 
> on you have to knife the main cap to get them there.  Now if the 1Kc 
> points do not align within 2Kc, the variable capacitor will need to be 
> knifed again.
>
> While your in the LMO, note the values of the temp comp caps.
>
> Knifing an LMO cap is not for the impatient or slight of heart.
>
> Kindest regards Jim K9AXN
>