[Elecraft] K2 frequency drift

[Don Wilhelm]

Dave,

It is not abnormal for electronic equipment to have some warm-up drift, the
K2 is no excpetion, so I would hesitate to call the situation you describe
as a 'problem'.

You can download the K2 Temperature-Compensated PLL Reference Upgrade
document from the Elecraft website - it contains a procedure for adjusting
the ampount of compensation.

Do note that even this procedure calls for letting the K2 warm up for 30
minutes before attempting to measure drift.  The temperature compensation
change is directed toward reducing drift during operating cycles of
alternate transmit/receive conditions rather than attacking the warm-up
drift, but it may assist with warm-up drift, or maybe not - it all depends.
For this reason, you may want to delay making any adjustment until after you
have the KPA100 installed because the temperature differential may be
different with the KPA100 installed.  The KPA100 will not cause any
problems, but the temperature swing inside the case will be greater than
with the QRP K2.  The nominal value for RA works for most environments, but
you may wish to experiment a bit and see if your compensation can be
improved.

The K2 spec is for less than 100 Hz total drift from a cold start (25
degrees C.), so your K2 is operating well within the specs.

73,
Don W3FPR

> -----Original Message-----

>
> Two questions for the group:
> 1. My K2, serial 5120, has worked flawless since I built it last
> fall...except that about a week ago, friends on a 20m net I work
> daily said I was low about 40 Hz in frequency. (Frequency
> calibration checked occasionally against both my external counter
> and WWV had been right on.) I transmitted first maybe 2 minutes
> after turning the rig on. So I dialed up about 40 Hz (.04 kHz) to
> get on frequency. In the next 15 minutes, I had to move the
> indicated frequency down slowly to the exact net freq. Drift was
> the obviously the problem.
> Since then, I've turned the K2 on early and found that by net
> time, it was on the exact frequency on the LCD. However, just
> after turning it on (room temp constand at about 68F), tuning WWV
> on 10 MHz (equalizing the stations's audio tone on USB and LSB)
> shows I'm low by 40-50 Hz, drifting up to indicated freq. in
> 15-20 minutes.
> I know that resistors RA and RD on the thermister board control
> drift rate, and some months ago there were comments here on how
> to compensate, but I didn't retain the thread. Anybody care to
> provide that advice again or new comments?
> 2. I'm currently building a KPA100 internal amplifier kit, and
> I'm wondering if the added heat creates drift or frequency
> calibration problems.
> Dave Martin
>