Elecraft

K2 frequency drift

Classic

List

Threaded

6 messages Options

windwing1@juno.com

K2 frequency drift

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
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Don Wilhelm-3

RE: K2 frequency drift

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
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

John, KI6WX

Re: K2 frequency drift

In reply to this post by windwing1@juno.com

Dave;
I designed the K2 VFO stability mod that is now included in all K2's.
Variations in the crystal stability cause each K2 to drift slightly
differently. That's why I included the instructions on how to adjust the
resistor values to minimize the K2's drift.

I tested my K2 from 15C to 45C in a home built environmental chamber (use
one of those thermoelectric cooler/heaters from WalMart or Target). I
picked the resistor values to produce the minimum drift over an assortment
of crystals that Elecraft sent me. I also adjusted those resistor values to
achieve minimum drift in my K2.

Over that temperature range, my K2 shows a maximum drift rate on its worst
case band of 15m of 1.8 Hz/C. The average drift rate is less than 1 Hz/C.
The K2 warmup internal temperature change is 5C. On 20m, my K2 will show a
warmup drift of about 5 Hz. This shows what you can achieve if you run a
careful set of experiments with different resistor values.

I only know of a few people who have actually adjusted the resistor values.
It is a long time consuming process with very careful data measurement.
However, you can reduce your drift rate following the printed procedure.
-John
KI6WX

----- Original Message -----
From: <[hidden email]>
To: <[hidden email]>
Sent: Wednesday, March 15, 2006 1:58 PM
Subject: [Elecraft] K2 frequency drift

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
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Phil Kane-3

High-Kevel Audio Output for K2

My K2/100 will be bullt for me in the near future, and I remember
seeing a post or two in the last month or so about providing a high
level audio output (not controlled by the VOL control) for data or
recording purposes. I coudn't find it in the archives (too new??).

Can someone be so kind as to repost it (or send it to me off-list)?

WTIA

--
73 de K2ASP - Phil Kane

From a Clearing in the Silicon Forest
Beaverton (Washington County) Oregon

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Don Wilhelm-3

RE: High-Kevel Audio Output for K2

Phil,

I think you may be referring to my K2 Fixed Audio Output. See my website
http://w3fpr.qrpradio.com for details. I no longer have the kits, but I do
have boards available.

Not yet on the website yet, I have successfully mounted the board on the
back of the Control Board in a K2/100 and taken the audio output to an mic
jack pin - this is accomplished by laying the capacitors and resistor flat
on the board rather than the conventional vertical mounting.

73,
Don W3FPR

> -----Original Message-----
>
>
> My K2/100 will be bullt for me in the near future, and I remember
> seeing a post or two in the last month or so about providing a high
> level audio output (not controlled by the VOL control) for data or
> recording purposes. I coudn't find it in the archives (too new??).
>
> Can someone be so kind as to repost it (or send it to me off-list)?
>
> WTIA
>
> --
> 73 de K2ASP - Phil Kane
>

Sverre Holm-2

SV: High-Kevel Audio Output for K2

In reply to this post by Phil Kane-3

> -----Opprinnelig melding-----
> My K2/100 will be bullt for me in the near future, and I remember
> seeing a post or two in the last month or so about providing a high
> level audio output (not controlled by the VOL control) for data or
> recording purposes. I coudn't find it in the archives (too new??).
>

Five different alternatives for a high level output can be found here:

http://www.qslnet.de/member/la3za/K2/mod.html

Then go to 1. General mods and then to Input/Output.

73

Sverre
LA3ZA
http://www.qslnet.de/la3za/

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com