[time-nuts] About HP10544A

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Mar 9 23:09:44 UTC 2009

Esa Heikkinen wrote:
> Hi Bruce,
>> White emitter follower circuit attached.
> Here are the results. First, the circuit draws 33.3 mA at 12 vols. And 
> it's gain is 1:1 as expected with emitter follower - checked that with 
> RF generator as an input just to make sure that I built it correct.
> With HP10544A the output level is below +8 dBm:
> http://www.amigazone.fi/files/gpsdo/544-10.png
> (with 2 meters of RG174 and SMA-connectors between the circuit and SA)
> Now the harmonics look like this:
> http://www.amigazone.fi/files/gpsdo/544-11.png
> And 2nd harmonic level:
> http://www.amigazone.fi/files/gpsdo/544-12.png
> So the spec told that 2nd harmonic should be more than 25 dB down, it is 
> just in spec...
> So the final result looks that the 10544A is OK but it really has this 
> kind of output spectrum?

You can reduce the circuit current by increasing the value of R10.
Try 47 ohms instead of 39 ohms.
The value depends on the difference in forward voltage drop of the LED
and the Vbe of Q5.
Should still get a low distortion output even when the load is a short
to ground.


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