Elecraft

K2 PLL Oscillator Range Test failure (barely)

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ne1rd

K2 PLL Oscillator Range Test failure (barely)

On page 60 of the K2 manual the PLL Reference Oscillator Range Test
asks for the Ref. High Freq. and Ref. Low Freq. measurements. I have

HI = 12099.67
LO = 12090.50
DIFF 9.17

which is less than the 9.8 to 15 kHz required by the manual.
Everything else looks good. Any ideas? Any help would be
appreciated. Thanks.

-- Scott (NE1RD)

PS What a beautiful kit. I'm loving it!

B. Scott Andersen | "Magic is real, unless declared integer."
[hidden email] | -- The collected sayings of Wiz Zumwalt
Acton, Massachusetts | Ham: NE1RD, QRP ARCI#11588, FP#-910

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Don Wilhelm-3

Re: K2 PLL Oscillator Range Test failure (barely)

Scott,

Just to check, can you look at what the voltage swing is at U6 pins 1, 2 and
3 when you do the Ref High Freq and Ref Low Freq measurements? Compare to
the voltage table on page 17 of Appendix E in the manual.

If the voltage swings are not correct, you have a likely problem with the
PLL thermistor board, but if the voltage swings are correct, you should look
for the problem in the area of the PLL crystal and varactor diodes. First
check the soldering carefully, and check all components shown in the
scheatic associated with the PLL Reference oscillator area (upper left
corner of RF board sheet 1 of 4).

If you find all is OK soldering and component wise, it may just be that your
crystal is not being pulled far enough. The cure for that is to change L31
to 12 uH instead of the 10 uH that is currently being shipped with the K2
kits. An e-mail to [hidden email] should start a new inductor on its
way to you. I believe Elecraft is still providing this replacement on an
'as needed' basis, free of charge.

73,
Don W3FPR

----- Original Message -----

> On page 60 of the K2 manual the PLL Reference Oscillator Range Test
> asks for the Ref. High Freq. and Ref. Low Freq. measurements. I have
>
> HI = 12099.67
> LO = 12090.50
> DIFF 9.17
>
> which is less than the 9.8 to 15 kHz required by the manual.
> Everything else looks good. Any ideas? Any help would be
> appreciated. Thanks.
>

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ne1rd

Re: K2 PLL Oscillator Range Test failure (barely)

Thanks to all who have responded on, and off, the list!
I'll check these things out tonight and let everybody
know what I discover.

-- Scott

On Jan 3, 2005, at 12:50 PM, W3FPR - Don Wilhelm wrote:

> Scott,
>
> Just to check, can you look at what the voltage swing is at U6 pins 1,
> 2 and 3 when you do the Ref High Freq and Ref Low Freq measurements?
> Compare to the voltage table on page 17 of Appendix E in the manual.
>
> If the voltage swings are not correct, you have a likely problem with
> the PLL thermistor board, but if the voltage swings are correct, you
> should look for the problem in the area of the PLL crystal and
> varactor diodes. First check the soldering carefully, and check all
> components shown in the scheatic associated with the PLL Reference
> oscillator area (upper left corner of RF board sheet 1 of 4).
>
> If you find all is OK soldering and component wise, it may just be
> that your crystal is not being pulled far enough. The cure for that
> is to change L31 to 12 uH instead of the 10 uH that is currently being
> shipped with the K2 kits. An e-mail to [hidden email] should
> start a new inductor on its way to you. I believe Elecraft is still
> providing this replacement on an 'as needed' basis, free of charge.
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
>> On page 60 of the K2 manual the PLL Reference Oscillator Range Test
>> asks for the Ref. High Freq. and Ref. Low Freq. measurements. I have
>>
>> HI = 12099.67
>> LO = 12090.50
>> DIFF 9.17
>>
>> which is less than the 9.8 to 15 kHz required by the manual.
>> Everything else looks good. Any ideas? Any help would be
>> appreciated. Thanks.
>>
>
>
>

B. Scott Andersen | "Magic is real, unless declared integer."
[hidden email] | -- The collected sayings of Wiz Zumwalt
Acton, Massachusetts | Ham: NE1RD, QRP ARCI#11588, FP#-910

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John, KI6WX

Re: K2 PLL Oscillator Range Test failure (barely)

In reply to this post by ne1rd

Scott;
You definitely want the PLL reference to tune at least 9.8 kHz so you don't
compromise the performance on 160 meters. If L31 is 10uH, going to 12uH
will cure the problem without causing any bad side effects. You can ask
Elecraft to send you the different value inductor.

The narrow and wide tuning ranges that sometimes occur on the PLL reference
are due to variations in the Q of the 12 MHz crystal. This is not always
easy to control. Elecraft has implemented a tighter spec with the crystal
vendor so this problem is less than it was in the past.
-John
KI6WX