Posted by
Tom Hammond-3 on
Apr 24, 2006; 2:19pm
URL: http://elecraft.85.s1.nabble.com/Need-help-for-sick-K1-tp389102p389112.html
Douglas:
>I've just completed soldering the K2, and have WWV at 10Mhz tuned
>in. The display shows it at +380 hz high. According to the manual,
>on page 60, the K2 can be calibrated using WWV. Unfortunately I do
>not see the procedure to do this. Is it published ? Could I have a
>link to a a procedure on how to do this
Here's an 'improved' method for zeroing the MCU master Oscillator.
Comes directly from the designer, N6KR:
Subject: 4 MHz oscillator cal method for the K2
Date: Wed, 20 Aug 2003 13:57:44 -0700
From: Wayne Burdick <
[hidden email]>
All of the methods that have been described for
calibrating the K2's 4-MHz oscillator will work. But I use
a different technique that allows C22 on the Control board
to be set to precisely to the correct position, with no
guesswork.
This method relies on the following simple observation. If
you tune in an on-air signal at a known frequency, the
difference between the *measured* VCO and BFO (using CAL
FCTR) *must* equal that frequency, or C22 is not set
correctly. (Actually, this holds for 160-17 m; on 15-10 m
it's the sum, or VCO + BFO, that must equal the signal's
frequency. But it's easier to do the adjustment of C22 on
17 m or lower because you don't have to do any math at
all, as I'll explain below.)
Here's the procedure. It requires revision 2.XX firmware,
and assumes you have already done Alignment and Test, Part
II, at some point. The K2 should also be allowed to come
up to room temperature.
1. Tune in a signal at a known frequency. Use one that's
at an *exact* kHz boundary, so you can easily see when
the VCO and BFO readings match in step 2. (I use WWV at
10, 15, or 20 MHz.) Use USB or LSB mode rather than CW,
so that there will be no CW receive offset. In the case
of a K2 I was calibrating, the VFO read 10000.17 when
the signal was tuned in perfectly. If it had read
10000.00, no further improvement would have been
possible.
TIP: Zero-beat the carrier precisely, or listen to a
voice signal and adjust the VFO for the best quality.
The more accurately you tune in the signal, the more
accurately you'll be able to set C22, below.
2. Run CAL FCTR. Now alternately move the K2's internal
counter probe between TP1 (VCO) and TP2 (BFO),
adjusting C22 in small increments until the kHz and Hz
digits at the two test points match as closely as
possible. In my case, the two readings matched at
14913.60 and 4913.60. The difference is exactly
10000.00--the frequency of the on-air signal.
3. Put the counter probe on TP1 (VCO), switch to 40
meters, and run CAL PLL.
4. Put the probe on TP2 (BFO) and run CAL FIL. For each
operating mode, vary each filter (or BFO) setting up 1
count, then back down, to force the K2 to take a new
BFO measurement for each and store it in EEPROM.
The VFO dial should now be very well calibrated.
If we get a lot of positive feedback on this method, we'll
post it as an application note.
73,
Wayne
N6KR
You might want to hold up on dong anything at this juncture, until
you get everything assembled and tested. It won't HURT to perform it
now, but you might need to re-do it at the end as wel..
73,
Tom Hammond N0SS
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