Superheterodyne principle in two box and IB metal detectors

[Mashiner]

Old two box detectors used direct amplification in receiver and modulated signal in oscillator. So you could hear signal from osciliator directly in your speaker. We can see so circuits in many projects. For example in ETI549, ETI566 (deep seaking metal locator), GD-348 and many others. Two box Gemini 2 also used this principle. But Gemini 3 as I know built on supeuhet principle. Signal from oscilator in not modulated but receiver has a heterodyne. It solves many problem and produces good sensitivity. In old magazines I read about this configuration but I did not see any circuitry. Some chips already contains almost all parts so circuit. For example TCA440. It would be interesting to built detector on this ciruitry. Maybe someone has any ideas or circuts about this...

[profesor]

Congratulations on a good topic.

[pito]

This is Tx generator, you need to add TC4420 connected to 0.1uF to drive a Tx coil , (serial resonance ) tuned to approximately 200 kHz.

Tx coil 20 cm diameter 30 turns, wire 0.5.
Rx receiver tuned to 200 kHz. First step is making Tx Rx hear the transmitter at distance about 50m then bring them closer to 60 cm distance and adjust Tx Rx antennas.

[Eddy71]

But Gemini 3 as I know built on supeuhet principle.

Do you have a diagram of the Gemini 3 receiver?
I'd really like to see it, but it's been removed from all the websites because the pages are outdated.

:-(

[Qiaozhi]

Do you have a diagram of the Gemini 3 receiver?
I'd really like to see it, but it's been removed from all the websites because the pages are outdated.

:-(

I only have the transmitter.

[kt315]

Do you have a diagram of the Gemini 3 receiver?
I'd really like to see it, but it's been removed from all the websites because the pages are outdated.

:-(

all pics of the boards were got from Koliaj. you may find his in md4u forum. Главная страница • Схемы металлоискателей MD4U •

he is at this photo.