Analog Target Indicator for VLF

[Nandor]

Hello friends
I hope everybody has a great time!
Not many days ago I have found an interesting little schematic, it's a VDI VCO.
Here is the VDI schematic, it has some errors but the pcb lay file is ok!

best regards!

[Melbeta]

I know this is an old posting, but back in the Compass Coin Magnum days of Good/Bad meter, and migrating into the X70 and X80 Challenger, they used the "X" as the reference signal, and compared the other signals to it, to get the triggers for the potted module. I wanted to post the X70 meter circuit, to go along with the X80 meter TID circuit, but was not able to do so. Posting for a computer that runs with an old telephone line, using AOL, has too many restrictions, in comparison to the smaller memory chips in the older computer that I was restricted to, in order to run the other software which I paid for. So I see here now you are finally catching the reasons. The older TR machines, were not like the "phase shift technology", but they used reference signal comparison to trigger the good/bad and TID meters. It is why I am searching for a TID meter to go into the Coin Magnum and replace the older Good/Bad meters in it, and stay with NO MOTION discrimination rather, then have to go along with the damn MOTION DISC of today... I have my reasons which I will not explain.
Melbeta

[scrungy_doolittle]

Well, you *could" use the VDI that is on this sight, and instead of driving the display, use the DAC to drive an analog meter..... The whites works by using a logarithmic opamp for each channel, and then subtracting the results with an opamp. Subtracting two logrithms from each other, is the equivalent of dividing one by the other. So the x and y channel values get their logarithms computed. This is done by a matched pair of transistors, where one transistor is in the feedback of the two opamps. The transistor has a logarithmic voltage response, and generates a log amplifier.