KS PLL Reference Oscillator

[John Heaviside]

K2 PLL Reference Oscillator Range.

Further to my previous posting: the problem was not insensitive counter but was in some way connected with the RIT/XIT control.  The low frequency reading BAND- is now stable but is too low.  BAND+ is 12099 and BAND- 12078 giving a range of over 20kHz which is outside specification.

I have checked the circuit and all seems to be OK.
U5 pin7 (U6 pin3) is 4.06 at BAND+ and 0.01at BAND- which seems OK according to the circuit diagram.
U6 pin1 is 7.48 and 0.00.  This again seems OK as U6A has a gain of about 2 with a small -ve bias resulting from the thermistor mod.
D16 and D17 are unbiased at the low end. (They actually self bias from the RF ro a small +ve voltage at R19/C100).  This seems to be bad practice as the capacity will vary widely from component to component and result in widely varying reference oscillator range. Hence my 20kHz range?

Am I mistaken? Is there a fix for this?

John G3NYX
_______________________________________________
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

[Jim Younce]

John:

Have you used a seperate freq counter measure the freq or a general coverage
receiver to listen to the freq at both hi and lo setting to make sure you
dont see a steady signal?...Also can you adjust the votage at R30 to the
value called for in the manual?.... My freq counter transistors amplified
but not enough to drive the input of the counter at the higher freq and the
result was what appeared to be a frequency jumping all over the place.  I
discoveered the PLL was in lock and the freq steady and in range by using a
general coverage receiver to listen to the PLL output.

About the only thing that could cause that is one or two of the Varicap
Diodes of the wrong type installed in the PLL circuit or a wrong capacitor.

73
Jim Younce K4ZM
K2 SN 18


_______________________________________________
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 Heaviside]

Don,

Your first suggestion seems possible.  12 uH is fitted as supplied with the
thermistor mod kit.

All components D16/D17 etc checked and are OK and there are no bad joints or
shorts.

John G3NYX.
----- Original Message -----
From: "W3FPR - Don Wilhelm" <[hidden email]>
To: "John Heaviside" <[hidden email]>
Sent: Wednesday, November 24, 2004 8:54 PM
Subject: Re: [Elecraft] KS PLL Reference Oscillator

> John,
>
> In my experience, you will find one of 3 things wrong.
> 1) The inductor on the bottom of the board below the PLL crystal (L31) is
> too large.  If you have a 12 uH inductor there, request the 10 uH from
> Elecraft.  OTOH, if it is already 10 uH, look elsewhere.  Elecraft is
> currently shipping the 10 uH inductor with the kits which should match the
> PLL crystal supplied.
> 2) There is something unsoldered, poorly soldered, or shorted on the
> thermistor board.
> 3) R19, or parts of RP2 are improperly soldered or have an incorrect

value.
>
> The BAND+/BAND- measurement points are the extremes, and your voltages at
U6
> pin 1 are correct.  Normal operation will not cause the varactor diodes to
> be left at zero volts - this is NOT the cause of your problem.
>
> Be certain you have the correct varactors at D16 and D17 - looking from
the

> top of the board, D17 (1SV149) should be smaller than D16 (MV209)
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
> From: "John Heaviside" <[hidden email]>
> To: "elecraft reflector" <[hidden email]>
> Sent: Wednesday, November 24, 2004 3:09 PM
> Subject: [Elecraft] KS PLL Reference Oscillator
>
>
> K2 PLL Reference Oscillator Range.
>
> Further to my previous posting: the problem was not insensitive counter

but
> was in some way connected with the RIT/XIT control.  The low frequency
> reading BAND- is now stable but is too low.  BAND+ is 12099 and BAND-
12078
> giving a range of over 20kHz which is outside specification.
>
> I have checked the circuit and all seems to be OK.
> U5 pin7 (U6 pin3) is 4.06 at BAND+ and 0.01at BAND- which seems OK
according
> to the circuit diagram.
> U6 pin1 is 7.48 and 0.00.  This again seems OK as U6A has a gain of about
2

> with a small -ve bias resulting from the thermistor mod.
> D16 and D17 are unbiased at the low end. (They actually self bias from the
> RF ro a small +ve voltage at R19/C100).  This seems to be bad practice as
> the capacity will vary widely from component to component and result in
> widely varying reference oscillator range. Hence my 20kHz range?
>
> Am I mistaken? Is there a fix for this?
>
> John G3NYX
> _______________________________________________
> 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