Hi Paul:
At 09:00 PM 7/6/2005, you wrote:
I found a reasonable kit for the main guts of a homemade freq. counter at
Almost All Digital http://aade.com/index.html#dfd specifically his DFD4a
http://aade.com/DFD4A/dfd4a.htm I got mine in the assembled version because
it comes with the TCXO already calibrated. You still need to wire it and
provide a suitable enclosure but that's the easy part. Cost ~$80 plus spare
connectors, switches, battery and a box. Used it to align the 4Mhz osc on K2
#4826 which later zero-beat to WWV within 30Hz.
With all due respect, Paul, you can manually zero the K2 to well within
10Hz to 20Hz of WWV for FREE, using the procedure outlined by Wayne Burdick
below:
Subject: 4 MHz oscillator cal method for the K2
Date: Wed, 20 Aug 2003 13:57:44 -0700
From: Wayne Burdick <[EMAIL PROTECTED]>
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
Of course, it's still a good excuse to buy an AADE Freq Counter... which
ARE pretty neat devices... heheh!
73,
Tom Hammond N0SS
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