[Elecraft] 4 Mhz oscillator

Sun Dec 29 11:24:00 2002

Hi

Here are the instructions I send with my noise generator kits. It explains
the Spectrogram method:

Using the Noise Generator to Align the K2

If your K2 is not performing up to snuff then get in there and set it up
right. It sure makes the operation nice

It's not that hard to get everything close to perfect if you will spend a
little time with WWV, Spectrogram and your noise generator. This is the
method I use to align a K2:

The first thing is to make sure the K2 is on frequency you can check that by
looking at WWV with Spectrogram looking for the 500 and 600 Hz tones on
alternating minutes (you may need to wait a little, the tones are not on all
minutes of the hour). Use USB or LSB mode. Set up a marker at 500 and 600
Hertz on the Spectrogram display. When you have the tones on the spectrogram
markers, read the VFO frequency and write it down. Connect the frequency
probe to TP3 in FCNTR mode and adjust C22 on the control board to change the
indicated frequency by the amount needed to make the VFO correct. Here is an
example: if the VFO is reading 20 counts high then change the frequency at
TP3 20 counts lower (note: the frequency at TP3 will be around 12 MHz not
the VFO frequency). Move the counter probe to TP1 and select 40 meters and
run CAL PLL. This should put your VFO on frequency. Recheck against WWV and
repeat if necessary.

Then use Spectrogram and your noise generator to set up your filters. Preset
them to the settings in the K2 manual first so you are sure you are on the
right side of the band-pass then adjust the filters with Spectrogram to
center the band-pass on a marker set at your side-tone frequency. The noise
generator connected to the K2 antenna makes it easier to see the band-pass.
You may need to do all of the above more than once to get everything right.
When setting up sideband move the band-pass so the lowest point on the skirt
on the left starts just a little past 0 Hz. Set each filter trying to
duplicate that left hand skirt. You may need to adjust the K2 volume control
for the best display.

If you would like to check out your K2 filters here is a quick way to make
sure you have it right. Set the band to 80 meters and set the VFO to 4000.00
select CW mode and FL1. You should hear the MPU 4.00 MHz clock as a 600 Hz
tone assuming your side tone is set to 600. If not adjust the VFO a little
to zero beat with the spot tone. Now cycle through the filters FL1-FL4. The
frequency should not change at all or very little. Now without touching the
VFO frequency hold the CW REV button to select CW reverse. Again the tone
should not change with the reverse or when cycling through the filters.

Now switch to USB mode and change the VFO to 3999.40 and you should hear the
same note. Cycle through the filters and it should not change. Change to LSB
and set the VFO to 4000.60 and you should hear the same 600 Hz note when
cycling the filters. If it will do all of the above then you have got it set
as good as it gets.
         Don Brown, KD5NDB

----- Original Message -----
From: "Mike McCoy" <[email protected]>
To: <[email protected]>
Sent: Sunday, December 29, 2002 10:13 AM
Subject: Re: [Elecraft] 4 Mhz oscillator

> >
> > You cannot accurately measure the 4.000 MHz oscillator directly with a
> > frequency counter. Most counters have a 1 meg ohm paralleled with about
50
> > Pf on the input plus the added capacitance of the cable and you may have
> > more than 100 pf in capacitance. This loading will upset the frequency
of
> > the oscillator.
>
> Well there ya go (duh... no wonder it was off. ;)
>
> >
> > I prefer using spectrogram to align the 500 and 600 Hz audio tones
> > broadcasted by WWV so they line up with a 500 and 600 marker on the
> > spectrogram display.
>
> I remember reading posts describing this method way long ago (and to make
> sure you are using the proper alternating tone during alignment). Since
I'm
> having a very hard time receiving WWV on 20 Mhz can someone reiterate how
to
> use spectrogram with 'any' WWV using the 500/600 hz audio tones?
>
> Thanks & 73,
> Mike K5PU
>
>
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