[Elecraft] Re: Help with Birdie (not "tweet tweet!")

Fri Mar 21 00:03:00 2003

Good question! I don't have a birdie at 28.704. I do have one nearby but
it's very weak. "Band noise" - even when the band is dead, covers it up. =
I
must pull the antenna and turn on the preamp to hear it. The only
significant birdies I find on the 10 Meter band are the expected ones =
down
at 28000.=20

The frequency counter is not used in normal K2 operation. It is only =
used
when actually performing CAL FIL or CAL PLL. So it won't mess with =
anything
to change the 4 MHz time base frequency unless you need to re-run CAL =
FIL
and CAL PLL.=20

The frequency display you are seeing on the LCD is a number retrieved =
from
memory that was stored when you ran CAL PLL. It is not being "counted" =
from
the actual oscillator frequency.=20

That all said, there is something odd about that birdie, and I'm not =
sure
you need to go through the hassle of changing your Control Board 4 MHz
oscillator just to get rid of it. Did you try touching C22 (the =
frequency
control trimmer on the Control Board 4 MHz oscillator) and see if that
birdie moved?=20

I only have the SSB, NB, 160 Meter and KPA100 options in my K2, so maybe
there is an oscillator on some other board that you have and I don't =
that is
mixing with something.=20

Ron AC7AC
K2 # 1289
=20
-----Original Message-----
... Looking at the schematics, I see that the 4.000 MHZ oscillator is =
used
as the control frequency for the MCU and appears to provide a basic time
base for the whole of the K2, including the fqy ctr.  I don't have a =
KPA100
so I don't have to worry about that....

Also to give me a birdie at ~28.7 the 4 Mhz oscillator would have to be =
off
by approx 100 Hz !! I have checked and the K2 gives a close "zero beat" =
of
WWVH at 10.000 Mhz (using the AF CW tone set at 600 Mhz, I get an error =
of
approx 50 Hz. Close enough for government work.!

If I eliminate the 4.000 Mhz MCU oscillator, then I'm left
with my original question. i.e What's causing the Birdie at 28.7???

I'm going to check all the option boards - just in case  :-)

I can't remember the Brazilian ventriloquist's name but his "punch line"
fits well here  Quote "Is a problem!!! Unquote.

73

Dave KK7SS
K2 #3003

----- Original Message -----
From: "Ron D'Eau Claire" <[email protected]>
To: "'Elecraft'" <[email protected]>
Sent: Thursday, March 20, 2003 7:11 PM
Subject: RE: [Elecraft] Re: Help with Birdie (not "tweet
tweet!")

It's easy to tell if one of the 4 MHz oscillators is the source. Just =
touch
the frequency adjustment trimmer and see if the birdie shifts. Your =
finger
will add enough capacitance to make it move.

If so, you can move either oscillator with no deleterious effects right =
now.
The frequency of the oscillator on the KPA100 is not critical at any =
time,
according to the Elecraft documentation.

The frequency of the oscillator on the Control Board provides the time =
base
for the frequency counter function that you use when running CAL FIL or =
CAL
PLL, but otherwise it is not critical. So you could move it, provided =
you
remembered to put it back before you run CAL FIL or CAL PLL for some =
reason.

Of course, moving either oscillator down in frequency will put them in =
the
75 meter phone band.

Ron AC7AC
K2 # 1289

-----Original Message-----
Further to my original message (see below) - could it be the 7th =
harmonic of
the 4 Mhz oscillator?? Is so, what exactly does this oscillator do? And,
would it be harmful to move it down to, say, 3.999 - so that any =
harmonics
would fall outside the Ham Bands??

Any replies??

Dave KK7SS
K2 #3003

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_______________________________________________
Elecraft mailing list: [email protected]
You must be a list member to post to the list.=20
Postings must be plain text (no HTML or attachments).=20
See: http://mailman.qth.net/mailman/listinfo/elecraft
Elecraft Web Page: http://www.elecraft.com