[Elecraft] VCO Relationship with 4 MHz Oscillator

[Mike Walkington]

Hi Ron,

Thanks for this explanation.  Is there an implication here that if you had a
more accurate external 4MHz source you could switch it in when you run CAL
PLL to get a more accurate result in the look-up table?

Mike
VK1KCK




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Message: 29
Date: Thu, 25 Nov 2004 20:03:33 -0800
From: "Ron D'Eau Claire" <rondec at easystreet.com>
Subject: RE: [Elecraft] VCO relationship with 4 Mhz ocsillator
To: 'Jean-Fran?ois M?nard' <jfmenard at mac.com>
Cc: 'Elecraft - Maling List' <elecraft at mailman.qth.net>
Message-ID: <000001c4d36c$e8f53810$c5ddfea9 at RONPORTABLE>
Content-Type: text/plain;	charset="iso-8859-1"

That's not the case for the 4 MHz oscillator in the K2, Jean-Frangois.



-------------------------snip--------------------------


When you run CAL PLL, a frequency counter built into the K2 measures the PLL
frequency. The K2 applies a tuning voltage to the PLL reference oscillator
and notes the frequency measured by the counter. This information is
recorded in memory so it can be looked up later. The K2 tunes through the
whole range of frequencies the PLL can cover noting the actual frequency
measured at regular intervals, and then recording the voltage applied to the
reference that will produce the frequency. 

-------------------------snip--------------------------


Notice that the accuracy of the readout depends upon how accurately the
frequencies and tuning voltages were stored when you ran CAL PLL. That's
where the 4 MHz clock and C22 come in. The Control Board 4 MHz clock is the
time base for the frequency counter! So the closer it is to 4 MHz the more
accurately the K2 will measure the K2 PLL frequency and the more accurately
the dial calibration of the K2 will be in use. 


Ron AC7AC