B&K Cap Meter has feet of clay

Finally tried the W0XI Tidbit for a Varactor cap for AM radio.  I poked through my bag of diodes and found a 1SV149 which is meant for AM radio use.  The Toshiba datasheet:

source: https://www.alldatasheet.com/datasheet-pdf/pdf/29858/TOSHIBA/1SV149.html

Here is the circuit again from W0XI:

source: https://wb9kzy.blogspot.com/2024/02/w0xi-circuit-tidbits.html

I tried measuring the capacitance at the voltage limits (I didn't realize that the specs were at 1V and 8V so will have to get that data for another post)  using a shifted oscillator type of LC meter similar to the AADE unit.  I got the following results:

23 pF at 9.2 volts

.

617 pF at zero volts

Then for the heck of it, got out the B&K 810C capacitance meter and tried it.  The results were way off - also it affected the LC meter readings which had been left in the circuit:

both read too high at 9.2 volts

,

similarly the readings are both too high at zero volts

I also disconnected and turned off the LC meter but the B&K was still way off:

  The B&K 810C manual is one page and doesn't mention anything about the measurement method other than it is done at 820 Hz for the 2000 pF range (and is accurate to 1 pF).  Whatever the method is, it doesn't work with varactors that is certain.

Next I'll try the varactor with a crystal set in place of the air variable capacitor - also take some data at more voltages.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm