[Hammarlund] Accuracy

[Bill Kirkland]

Don't know if this will make it to the reflector Roy as am using work
email.

Tracking and dial accuracy are of course two different things.  Setting
identical
capacitor values for each section of the tuning cap get you tracking
between the RF stages.  Does help with dial accuracy - thats up to the
LO.

Getting the caps to track should be relatively easy with a cap meter
these days.
Of course you have to eliminate strays in the test leads.  I would
suggest disconnecting
 the RF leads between the tuning cap and the RF unit - leaving the
tuning capacitor
 isolated.  Then it should be easy to make capacitor measurements for
each section.

 It would probably help to have each RF section layed out identically to
eliminate
 stray capacitance effects.


bk

-----Original Message-----
From: hammarlund-bounces at mailman.qth.net
[mailto:hammarlund-bounces at mailman.qth.net] On Behalf Of Roy Morgan
Sent: Wednesday, January 17, 2007 9:35 AM
To: hammarlund at mailman.qth.net
Subject: Re: [Hammarlund] Accuracy


At 11:43 PM 1/12/2007, you wrote:

>In between the top and bottom, all bets are off. The big variable
>capacitor isn't calibrated any more after 30 years. Moreover, you and I

>can't align it. It requires a custom jig that compares one section to
the 
>next and measures the capacitance. We had an email a few years ago from
a 
>lady that actually aligned these capacitors for Hammarlund.

Capacitor Nuts,

I would really like to read that email if anyone can find it.

"Knifing" a tuning cap is a skill, but it seems to me it's not rocket 
science.  Having little experience in it, I won't speculate on how it's
done.)

One trick however, is to align the band tracking a quarter of the way in

from the band edges. This will reduce errors in the middle at the
expense 
of hopefully modest errors at the ends.

>One of these days, maybe I'll sit down with a precision capacitance 
>bridge
>and try my hand at adjusting it, but only if I have a lot of time to
kill . . .

Hooray for the precision cap bridges (I have more than one GR bridge 
here).  But if the goal is to make a radio track right, I'd suggest
using 
the radio itself as part of the experiment.

Roy



- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911   Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-975-6097 roy.morgan at nist.gov --  


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