Thanks a lot Don. You nailed everything. Now working fine. I have a
20MHz TCXO (1ppm) that I use to cal check my counter. I was also tuning
the K2 to hear it and somehow confused the radio - then me ;)
Re-tweaked C22 again and managed to get within a few Hz.
Thanks again! The rapid response and subsequent fix has lowered my
blood pressure!
On 5/19/2017 2:20, Don Wilhelm wrote:
Woodie,
In addition to your 15 and 17 meter problem (see my prior email), I
have the following questions.
Is that the maximum or minimum frequency?
A few K2s need additional range for the capacitors around the crystal.
If the frequency is too high, it is easy to lower it with a parallel
low value capacitor (try 10pF).
If that drives it in the wrong direction, you will need to reduce the
value of C21 - try 27pF and if that is not enough try 22pF.
Be certain your frequency counter is truly accurate. I can do that
measurement with my frequency counter, but it is accurate to 10exp-9.
If you have any doubt about that counter accuracy, use the N6KR method
when tuned to the highest frequency WWV signal that you can receive.
Details on this method can be seen on my webpage www.w3fpr.com -
article on K2 frequency calibration.
73,
Don W3FPR
On 5/18/2017 8:28 PM, woody wrote:
Took more measurements, Ref the K2 manual (Rev C) Pg 57, 58...
-----------------------------------------------------------------
_4 MHz Osc Cal_:
Setting C22 with well calibrated outboard counter, the counter at TP3
indicated 12,096.62. As close as C22 would adjust was a K2 display of
12,095.89.
_PLL Ref Osc Range Test_
Ref High Freq = 12.104.37
Ref Low Freq = 12.08237
_VCO Test
Voltage readings_ (left end R30) Note (*) that in the table below the
band progression still has 15M and 18M progression *reversed* (see
earlier, below). Also note ZERO volts at 18000 !
3500 - 2.06 volts
7000 - 2.98
10000 - 5.13
14000 - 4.27
* 21000 - 8.22
* 18000 - ZERO (0.02v)
24.800 - 6.82
28000 - 4.74
Hope this is some help. Thanks again, Woody
------------Earlier email is below----------------
On 5/18/2017 20:18, woody wrote:
Hello,
I have an elderly K2 (S/N 02600) that had been working well. After all
these years, it was about 200 Hz off frequency so I proceeded to do an
alignment. Got it pretty close, but the trim cap (C22) would not pull
quite on freq. Close enough maybe...
Proceeded with band by band alignment / peaking. All bands peaked as
expected except 17M, (maybe 15M too).... No change when adjusting C32
& C34 for 17M.
More symptoms:
* Stepping up the bands is normal until going from 20M to 17M. Then:
17M and 15M are reversed from normal progression.
e.g: 160, 80, 40, 30, 20, _*15, 17*_, 12, 10
* System Rx noise is significantly reduced on 17 & 15.
* In CW mode, the Tx freq is OK on all but 15 & 17.
The display reads as expected on 15 & 17 - as VFO is adjusted. But, my
freq counter indicates the actual Tx output freq is different and does
not change when the display freq is changed:
Example... For 17, the Display indicates 18.120, the output is on
18.766+-. For 15, the display indicates 21.265, the output is
21.434+-. It is also receiving on the (actual but wrong) Tx freqs.
Changing the VFO changes the display but does not change the actual TX
or Rx frequency which seems to always be the same.
I am stumped!!! Can you offer any suggestions as to what might be
happening???
Thanks,
Woody, KZ4AK (Formerly WB4QXE)
---
This email has been checked for viruses by AVG.
http://www.avg.com
--
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [email protected]
