[Boatanchors] Heathkit HW-100 VFO linearity

[WQ9E at btsnetworks.net]

Jim,

That is a lot!  The only time I ran into one like this was a TS-520 that
 the owner had loaded up with tuner cleaner.  The dielectric constant of
 that is different than air so it really through off the tracking; 
thorough cleaning with an air gun followed by pipe cleaners was the 
cure.

A couple of things to check:

1.  with the tuning cap fully meshed are the rotor plates centered 
within the stator plates?  It is possible the thrust bearing adjustment 
slipped and if these are out of center it throws off the tracking 
linearity.

2.  I don't have my manual handy but does the HW-100 use the entire 
range of the capacitor for the 500 Khz. range or does it just use a 
portion of the rotation?  It is common to just use part of the rotation 
instead of the full 180 degrees and if this is the case then make sure 
the capacitor is properly indexed for the correct starting point.  In many cases full mesh is not used 
as the lower point  frequency but around 85 to 90% of full mesh is used instead.  The construction 
part of the manual will make this clear.

3. Did it ever track properly to your knowledge?  I assume this has a 
capacitor with split rotor plates near the end that could be "knifed" to
 change the tracking.  Maybe this was never done properly.

4.  When tracking is way off on any tuned circuit, I set it for the 
center of the range and set the trimmer capacitor adjustment to half 
mesh and then use the inductance adjustment to adjust it for proper 
frequency at the midway point.  This usually gives you a good starting 
point when the tracking is way off and will save a lot of time in 
iterating to the final correct adjustments.

Good luck!

73,  Rodger WQ9E

----------------------------------------
From: Jaime Gomez <cwdx.hk1n at gmail.com>
Sent: Saturday, October 09, 2010 11:51 AM
To: boatanchors at mailman.qth.net
Subject: [Boatanchors] Heathkit HW-100 VFO linearity 

I am in the final process of aligning my venerable HW-100. All is
going fine, except the VFO linearity. I have 10% offset from end to end, it
means 50 KHz in the 500 KHZ dial span. I have tried by all means with no
luck. Some components may be affecting it, but I wonder which. I will remove
the VFO, but I would like some hints about it. Any one has a clues as to
which ones should I check?
Thank you, 73,

-- 
Jim, HK1N
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