[ARC5] R-25 dial nonlinearities

[D C _Mac_ Macdonald]

One thing that is critical is to start with the tuning capacitor fully meshed at the low end of the dial scale.  The owner manual SHOULD advise on this.  It has been a long time since I did this stuff, but I seem to remember that you are supposed to start at that point and adjust the coil slug for correct frequency there.  Then you adjust the trimmer cap for the high frequency end.  From what you have written below, I believe you are starting from the wrong point.  I believe that will result in your chasing an ever increasing error out to forever.


Rewiring/modifying to correctly add a trimmer to the high end probably could not hurt, either!


Good luck, Wayne.


* * * * * * * * * * *
* 73 - Mac, K2GKK/5 *
* (Since 30 Nov 53) *
* Oklahoma City, OK *
* USAF, Ret'd 61-81 *
** FAA, Ret'd 94-10 *
* * * * * * * * * * *





________________________________
From: ARC5 <arc5-bounces at mailman.qth.net> on behalf of Robert Eleazer <releazer at earthlink.net>
Sent: Sunday, January 8, 2017 13:33
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] R-25 dial nonlinearities

I've been trying to align a National NC-270 and I'm having a dial nonlinearity problem.  I get the frequency set on the top end of each band and the bottom ends are always off.  The receiver has a sliding dial so you can align it as required by using the 100 KHZ marker signal.  But the amount it is off can be beyond the ability of the dial to slide.  You set the coils for the top end of each band, but there is only one trimmer cap for all the bands.  I plan to add some individual trimmer caps for each band and see if that helps.

Wayne
WB5WSV
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