[Elecraft] K3EXREF Questions

[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