[R-390] PTO Problems

[David Wise]

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of
> Flowertime01 at wmconnect.com
> Sent: Saturday, November 03, 2007 10:08 AM
> To: r-390 at mailman.qth.net
> Subject: Re: [R-390] PTO Problems
> 
> You touched on adjusting the corrector stack in the VFO.
> Once you get the end points adjusted the VFO is likely to be linear.
> As you look down the adjusting stack it likely has a nice S 
> or C curve.
> The curve is not necessarily symmetrical from end to end.
> But the curve should be nicely done with not sudden jumps.

If your PTO frequency curve has a bow, you may get away
without a corrector stack recal by changing the tank
circuit capacitance.  Beware - the originals were selected
for temperature compensation.  For curiosity's sake, I
replaced the little ones with two trimmers with different
tempco's, and got to where the curve was pretty much a
horizontal line, and the frequency drift was also low.
Don't try this unless you have lots of time on your hands,
and patience too.

Dave Wise