I plan on replacing the Xtal Osc. of my HP 5062C with a HP 10811 since I have a few ones with AV less than 1E-12 from 1 to 100 sec. I would like to use the +18 Volt in the unit for heater. Has any one experience with running the 10811 below 20 Volt, any thing I should look out for? Thanks Bert Kehren Miami