[Elecraft] Questions about new crystals

[Rich Lentz]

Ken:

Haven't spent a lot of time collecting "scientific" data but decided to =
get
some data for you. Here is what I observed. =20

When I first turn on the frequency (WWV) is off by about -15 Hz. =
[9999.985]
After 15 minutes frequency (WWV) is off by about -5 Hz. [9999.995]

At this time I simulated a 15 minute QSO (20 seconds of dots @22 WPM, 10
seconds of no signal, repeated for 15 minutes power @ 10 watts. Figured =
this
is at least a 50% duty cycle.)
Frequency of WWV is now at 10000.003

Waited 30 minutes, Frequency of WWV is now 10000.006 and again I =
simulated a
15 minute QSO (As above). =20
Frequency of WWV is now 10000.012

[Readings taken off of MIXW2 and rounded to closest digit.)

Things I did that may have helped drift.

1. After installing the new BFO inductor, L33, rather than just put a =
piece
of tape on it as suggested in the instructions, I placed a one inch =
square
piece of the double sticky foam tape WITH ONLY ONE SIDE OF THE STICKY
EXPOSED on the cover so that the coil would rest on the foam.  Don't =
take
off both protective covers or the cover will stick to the coil.  The =
thought
behind this was to keep the cover at a constant distance from the coil.  =
I
have noted and read discussions on the reflector about the BFO frequency
changing by pressing on the cover, whether the bail is up or down, etc.
Don't know if it helped but it is there.  Possibly someone knows of a
thermally conductive foam that is not electrically conductive. That =
would
work even better. =20

2. The BFO MOD Instructions say wait 10 minutes before performing =
CAL-PLL I
did this.

However, I let the rig warm up for one hour then performed Steve GU3MBS
method of calibrating the clock oscillator.  HOWEVER, I reversed steps 5 =
and
6 in his directions. You must perform CAL-PLL (His step 6) before you
perform CAL-FIL (His step 5) as the CAL FIL uses the frequencies which =
must
be accurate.  I did Steve's Frequency calibration TWICE.  (The second =
time
got WWV within 10 Hz.)  Logic behind this is that it is my understanding
that the MCU only saves voltages, not frequencies, but these voltages =
are
based upon what they should be for that frequency. Therefore, when these
voltages are programmed in the MCU they should be as close as possible =
to
the exact frequency. =20

When you do CAL-FIL don't forget that if you don't change the number (up =
or
down a few digits and then back) then the memory is not refreshed.  That
means that if you just look at it and don't change it the old value is =
left
in the memory.  This old value is the voltage for the frequency that was
incorrect or at least was just re-calibrated.  If you don't run CAL-FIL =
(and
make sure a new value is saved) then it does no good to recalibrate the
clock oscillator.=20

Rich,
KE0X



-----Original Message-----
From: Ken Wagner [mailto:k3iu@arrl.net]=20
Sent: Saturday, December 14, 2002 4:36 PM
To: Rich Lentz
Subject: Re: [Elecraft] Questions about new crystals

Hi Rich:
When you say that the BFOMDKT limited your freq drift to less than 20 =
Hz,
what conditions are you talking about? Cold start warm up? After some =
heavy
transmitting(CW, SSB, PSK?)? The reason I'm asking is that I finished =
this
mod on my older K2/100(#920) and it worse off than before with respect =
to
drift from heat generated while transmitting than before the mod. I'm =
trying
to gather some data before I send email to the Aptos gang. Thanks...
73 and Happy Holidays!
Ken Wagner
K3IU