Elecraft

Re: [KX3] Frequency Drift on JT-65

Classic

List

Threaded

2 messages Options

W7GJ, Lance

Re: [KX3] Frequency Drift on JT-65

Hi Fred,

I also found that the KX3 was not stable enough for JT65A on 6m, and am still hopeful
of an eventual solution to this problem, since that is the only reason I invested in
a KX3. I suspect more people will be interested in KX3 frequency stability as the new
narrower JT9 mode of WSJTX becomes popular on the low frequency bands. The more
recent firmware includes a Temperature Compensation program that you can use to
achieve reasonable JT65A frequency stability on 6m, and suitable stability on HF ; I
am not sure if it can render the KX3 stable enough for the newer modes such as JT9.
It will be interesting for low band devotees to determine how the KX3 performs on
this powerful new mode:

http://www.physics.princeton.edu/pulsar/K1JT/WSJT-X_Quick_Start_Guide.pdf

I found that with the addition of finned heat sinks on the PA and the OSC, the KX3
runs much cooler in JT65A mode, and quickly reaches its operating temperature within
the first couple of seconds) and cools down to its receive temperature well before
the next JT65A receive period begins. Here is what I wound up doing with my KX3:

http://www.bigskyspaces.com/w7gj/KX3HeatSinks.htm

Careful examination of the SpecJT waterfall traces above indicate that there still is
a small frequency jump of several Herz at the start of every transmission period,
apparently before the temperature compensation can be applied. This one or two second
delay appears to be due to a physical separation between the OSC and the temperature
sensor in the hardware. It would be interesting to have the firmware immediately set
the temperature value (and invoke the suitable temperature correction value) at a
user-definable increase from the receiving temperature for a user definable period
during the start of a transmission sequence.... In my case, I would select a 2 degree
C temperature jump for the first second. After that, things seem to be relatively
constant, and the temperature compensation routine in the firmware does a pretty good
job of keeping the KX3 transmitting on frequency.

I only use JT65A from WSJT on 6m and am not familiar with JT65-HF. However, I think
the results that I have achieved would work successfully for JT65A on 6m as long as
the receiving station uses the AFC option to receive my JT65A. I don't know if you
have such an option in JT65-HF, but I strongly suspect that it would not be required
for you, since you should be able to achieve viable frequency stability on HF with
the Temperature Compensation routine in the KX3 firmware.

GL and VY 73, Lance

On 11/19/2012 12:28 AM, k5frd wrote:

--
Lance Collister, W7GJ
(ex WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8, E51SIX, 3D2LR, 5W0GJ, E6M)
P.O. Box 73
Frenchtown, MT 59834-0073
USA
TEL: (406) 626-5728
QTH: DN27ub
URL: http://www.bigskyspaces.com/w7gj
Windows Messenger: [hidden email]
Skype: lanceW7GJ
2m DXCC #11/6m DXCC #815

Interested in 6m EME? Ask me about subscribing to the Magic Band EME
email group, or just fill in the request box at the bottom of my web
page (above)!

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Edward R Cole

Re: [KX3] Frequency Drift on JT-65

Lance,

Nice work and good info on running JT65A on 6m. I haven't tried to
interface my KX3 for using JT65, yet. I am hopeful a frequency
correction circuit for use of an ext. reference is forthcoming from
Elecraft. Use of the EXREF on my K3 is very useful on frequencies
into the microwaves as the delta-F of the IF radio is added to the
delta-F of the transverter. MY 432 and 1296 transverters are
phase-locked to the same reference so I get, at most, 3-Hz
error. Drift of the K3 is smaller than the offset by almost an order
of magnitude. Of course I run the 1mw transverter mode with the K3
so the 10w module is not keyed.

On 144 the transverter is xtal controlled but only drifts upward 5-Hz
for a total error of 11-Hz (rest freq is +6 Hz including the offset
of the K3 on 28-MHz).

Since the forthcoming Elecraft 2m module will use 50-MHz as IF it
will benefit from better frequency stability.

73, Ed - KL7UW

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html