Al, Thanks for the good idea, that would certainly have saved me a bit of
work:-), but the switch box inserted in the coax line with the counter input
set to high impedance performs the same function, straight through
connection with the option to switch in a 50 ohm shunt resistor, and it's
Nigel,
Set your counter to high impedance. Then install a T connector on the
input. Then you can install or remove a 50 ohm terminator on the T while
plotting the results. Then you can see how fast the frequency shift is
depending on the load.
AL, k9si
Switching the impedance at the
My bet is interaction of the load current and power supply with the EFC
and/or OCXO
-
Well, I haven't started probing the hardware yet, I was hoping I might get
some confirmation first as to whether what I I'm seeing is an anomaly for
this one or just par for the course with the
My bet is interaction of the load current and power supply with the EFC and/or
OCXO.
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and
> Before I start probing any deeper I'd be interested to hear if anyone
> else come across this with the Thunderbolt E.
Is it thermal? Can you measure the frequency shift before it has time to
warm up?
Switching the impedance at the counter itself resets any plot
Please note that this question refers to the branded "Thunderbolt E"
GPSDO, in a silver coloured case with blue label and using a single 24V
supply,
and not the gold coloured "Thunderbolt" that is often found marked "Rev E".
Whilst testing a Thunderbolt E I've observed that the
> I'm familiar with the concept of frequency pulling in oscillators but
> would have expected the Thunderbolt E output to be better buffered than
> this, it's certainly not something I've experienced with the gold cased
> Thunderbolts.
> Before I start probing any deeper I'd be interested
