K3EXREF Questions

[Julian, G4ILO]

1. Will the K3EXREF work straight from the output of an Efratom LPRO-101 or does it need a TTL square wave output or something else requiring extra circuitry between the LPRO and the K3?

2. If the K3EXREF is installed, will the K3 still work as normal if the frequency standard is not turned on? To maximize life of the rubidium lamp in the frequency standard I wouldn't want to leave it on all the time and for a lot of amateur operation the frequency accuracy it provides isn't needed anyway.

Julian, G4ILO

[P.B. Christensen]

> 1. Will the K3EXREF work straight from the output of an Efratom LPRO-101
> or
> does it need a TTL square wave output or something else requiring extra
> circuitry between the LPRO and the K3?

A 10 MHz sine wave output from the Efratom is fine (+4 dBm to +16 dBm).

> 2. If the K3EXREF is installed, will the K3 still work as normal if the
> frequency standard is not turned on?

Yes.

Also, an asterisk (*) in the K3's menu will blink when K3EXREF recognizes a
valid reference signal.

Paul,  W9AC

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[Matt Zilmer]

On Sat, 16 Apr 2011 07:07:25 -0700 (PDT), you wrote:

The K3EXREF will use either a sine wave input at 4 to 16 dBm (2 to
3.3V), or a TTL signal.  The manual advises using a 50 ohm series
resistor for 5V TTL to drop the voltage level into the proper range.
>1. Will the K3EXREF work straight from the output of an Efratom LPRO-101 or
>does it need a TTL square wave output or something else requiring extra
>circuitry between the LPRO and the K3?
>
Yes.  In this case, the K3 reverts to the stored REF CAL value.  The
way I've set this up is to let the K3 make the compensation approach a
final value by running for a few hours on the external reference, then
programming the REF CAL shown while on the ref into the CONFIG menu
parameter.  Testing later shows this produces precision of a few Hz,
even with a 5C of temperature change, at 50 MHz and using the 5 PPM
TCXO in the K3.
>2. If the K3EXREF is installed, will the K3 still work as normal if the
>frequency standard is not turned on? To maximize life of the rubidium lamp
>in the frequency standard I wouldn't want to leave it on all the time and
>for a lot of amateur operation the frequency accuracy it provides isn't
>needed anyway.
>
Another good choice is the Trimble Thunderbolt receiver.  There are a
lot of these refurbished units available on eBay or elsewhere for
under $100.  You can leave this receiver on full-time if necessary (I
do).  The Thunderbolt outputs a sine wave at 12.5 dBm.

I used an Rb standard borrowed from work for a few days, and found
that the Thunderbolt and Rb produced about the same amount of
precision.  The Rb is noisier though (in the time domain), looking at
its output on a spectrum analyzer.  You can't beat an OCXO for
cleanliness....


73,
Matt W6NIA
=.=

>Julian, G4ILO
>
>-----
>Julian, G4ILO. K2 #392  K3 #222.
>* G4ILO's Shack - http://www.g4ilo.com
>* KComm - http://www.g4ilo.com/kcomm.html
>* KTune - http://www.g4ilo.com/ktune.html
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[AC7AC]

CONTENTS DELETED

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[David Pratt]

Ron - Shouldn't the asterisk be blinking if the K3 is being controlled
by and external reference?  The presence of an asterisk merely indicates
that it has at some time been controlled by a reference since the last
power-up.

73 de David G4DMP

In a recent message, Ron D'Eau Claire <[hidden email]> writes
>
>I can answer 2, Julian. It is yes. If there is no external 10 MHz signal,
>the K3 reference oscillator reverts to its normal operation. An asterisk
>(splat, whatever one wants to call it) appears on the LCD when there's an
>external signal detected, so you know at a glance whether the K3 is being
>controlled by the external signal.
--
 + - - - - - - - - - - - - - - - - +
 | David M Pratt, Kippax, Leeds.   |
 | Website: http://www.g4dmp.co.uk |
 + - - - - - - - - - - - - - - - - +



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[P.B. Christensen]

The slow flash of the asterisk changes to a steady asterisk upon loss of the
external reference, and presumably when the external reference falls
reasonably outside of level and frequency tolerances.  One can confirm the
operation of K3EXREF by unplugging the precision reference and noting a
steady asterisk on the LCD display while in menu mode.  Upon re-connection
of the external reference, the asterisk will again start flashing.  It is
definitely confirmation that a precision external reference is active and
present.

Paul, W9AC

----- Original Message -----
From: "David Pratt" <[hidden email]>
To: "Ron D'Eau Claire" <[hidden email]>
Cc: "'Julian, G4ILO'" <[hidden email]>; <[hidden email]>
Sent: Saturday, April 16, 2011 1:21 PM
Subject: Re: [Elecraft] K3EXREF Questions

> Ron - Shouldn't the asterisk be blinking if the K3 is being controlled
> by and external reference?  The presence of an asterisk merely indicates
> that it has at some time been controlled by a reference since the last
> power-up.
>
> 73 de David G4DMP
>
> In a recent message, Ron D'Eau Claire <[hidden email]> writes
>>
>>I can answer 2, Julian. It is yes. If there is no external 10 MHz signal,
>>the K3 reference oscillator reverts to its normal operation. An asterisk
>>(splat, whatever one wants to call it) appears on the LCD when there's an
>>external signal detected, so you know at a glance whether the K3 is being
>>controlled by the external signal.
> --
> + - - - - - - - - - - - - - - - - +
> | David M Pratt, Kippax, Leeds.   |
> | Website: http://www.g4dmp.co.uk |
> + - - - - - - - - - - - - - - - - +
>
>
>
> ______________________________________________________________
> Elecraft mailing list
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[AC7AC]

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[wayne burdick]

This is correct. The asterisk indicates that at some point, an  
external reference was connected and did a REF CAL update. The K3 uses  
this value even if you turn the external reference off, on the theory  
that it is more accurate than the manually entered value of REF CAL.

If you turn the K3 off and back on with the reference disconnected,  
REF CAL will revert to its manually entered value and the asterisk  
will not appear.

Wayne
N6KR

On Apr 16, 2011, at 11:05 AM, Ron D'Eau Claire wrote:

> That's right David, my memory is failing me today.
>
> If you apply an external reference signal the asterisk will appear.
>
> The asterisk will flash as long as the external source is  
> controlling the
> K3's reference oscillator.
>
> If you disconnect the external source the flashing stops but the  
> asterisk
> remains.
>
> If you disconnect the external source and re-start the K3 (power off/
> on)
> there will be no asterisk until the external signal is applied again.
>
> At least that's how my prototype works.
>
> Ron AC7AC
>
> -----Original Message-----
> From: David Pratt [mailto:[hidden email]]
> Sent: Saturday, April 16, 2011 10:21 AM
> To: Ron D'Eau Claire
> Cc: 'Julian, G4ILO'; [hidden email]
> Subject: Re: [Elecraft] K3EXREF Questions
>
> Ron - Shouldn't the asterisk be blinking if the K3 is being controlled
> by and external reference?  The presence of an asterisk merely  
> indicates
> that it has at some time been controlled by a reference since the last
> power-up.
>
> 73 de David G4DMP
>
> In a recent message, Ron D'Eau Claire <[hidden email]> writes
>>
>> I can answer 2, Julian. It is yes. If there is no external 10 MHz  
>> signal,
>> the K3 reference oscillator reverts to its normal operation. An  
>> asterisk
>> (splat, whatever one wants to call it) appears on the LCD when  
>> there's an
>> external signal detected, so you know at a glance whether the K3 is  
>> being
>> controlled by the external signal.
> --
> + - - - - - - - - - - - - - - - - +
> | David M Pratt, Kippax, Leeds.   |
> | Website: http://www.g4dmp.co.uk |
> + - - - - - - - - - - - - - - - - +
>
>
>
> ______________________________________________________________
> Elecraft mailing list
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> Post: mailto:[hidden email]
>
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[Edward R Cole]

And if you want to save about $50, there are several OCXO on e-bay
for $40-50 (with many offering free shipping).  All you do is hook
them to 12vdc and coax to the K3EXREF, as most run at +10 dBm.  The
waveform may not be a perfect sine wave.

--and no satellites were harmed in locking your K3! ;-)

My Russian surplus OCXO is rated +/- 5E-12 (phase noise = -150 dBc/Hz
at 1-KHz) and runs full time.  I also have a Rb, but reserve its use
for critical freq. measurements.

Phase noise is not an issue when running the K3EXREF as that is
established by the K3 TCXO.  The external reference serves only to
correct TCXO freq. drift every 4-seconds or so.
---------------------------
Another good choice is the Trimble Thunderbolt receiver.  There are a
lot of these refurbished units available on eBay or elsewhere for
under $100.  You can leave this receiver on full-time if necessary (I
do).  The Thunderbolt outputs a sine wave at 12.5 dBm.

I used an Rb standard borrowed from work for a few days, and found
that the Thunderbolt and Rb produced about the same amount of
precision.  The Rb is noisier though (in the time domain), looking at
its output on a spectrum analyzer.  You can't beat an OCXO for
cleanliness....


73,
Matt W6NIA



73, Ed - KL7UW, WD2XSH/45
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