[time-nuts] Thunderbolt no usable sats.

[Arthur Dent]

WarrenS-".....As long as the Dac out (OSC EFC input) is > than a 
couple of volts above the neg supply (or the EFC is positive)  all 
worked fine at any Neg supply down to -3 volts.
This is because most RS232 receivers don't need their input to swing 
negative. 
Your -7 volts statement agrees well with my test. You can go even lower 
on the neg supply with no ill effects IF you do not need the DAC output 
to go all the way to neg -5Volts....."
++++++++++++++++
A previous thread concerning the Fluke.l monitor (Tbolt LCD Monitor - 
No DAC reading) also supports this. A few T-Bolt/monitor owners had 
problems with the DAC voltage displaying 0.0000 when it was actually 
slightly negative, around -0.1000 VDC. I've had about 50 T-Bolts and 
although I never recorded the DAC voltage displayed with Lady Heather, 
I believe they were all positive and less than 1 volt. The fact that only a 
few T-Bolt/monitor owners report this problem of displaying negative 
DAC voltages may support my guess that the DAC voltage needed 
for EFC is more likely to be positive than negative. If this is the case 
then perhaps you might be able to go less than -3 (or technically 
greater than-toward zero volts) on many T-Bolt units but I wouldn't 
recommend it.

  -Arthur