VCO vs. Non-VCO??

[scott-bc]

I am new to this site and quite excited about building the HH PI unit. I keep seeing VCO? What does this stand for and what is most common, VCO or non-VCO. Yes I did a search and nothing come up on this.

Just need a quick simple explanation. Thanks.

Scott

[Carl-NC]

It refers to the audio. VCO is "voltage-controlled oscillator"; VCO audio responds with changes in pitch, whereas non-VCO responds with changes in volume. It's just a matter of preference.

- Carl

[1843]

non-VCO

Carl,

I have finished my third Hammerhead. Their detections are pretty good.
But all of them have a common problem in the output sound:
When an object becomes very close to the coil (less than 6cm for small objects), instead of its noise loudness becomes stronger, mutes (damps)...

What do you think about this problem?

I am sure that problem is after IC8 because when HH detects the object, TP5 rises to +5V.
(When object is near the coil, TP9 has a square waveform)

Regards