MXT Coils for RHAPTOR Project?

[Dixix]

From a friend I got given some old MXT coils.



Can I use these coils for the Rhaptor project or for coil experiments?
What has the connector for pin assignment?



Thanks for the help!
Dirk

[Qiaozhi]

From a friend I got given some old MXT coils.

Can I use these coils for the Rhaptor project or for coil experiments?
What has the connector for pin assignment?

Thanks for the help!
Dirk

Chapter 10 (IB Coil Experiments) of ITMD highlights some of the difficulties of using different coils with the Raptor project. If you have an inductance meter, and a scope, you should be able to figure out whether the MXT coils are compatible or not. If the elliptical coils are the Eclipse type, then I suspect the answer will be "no", as the TX loop is lower than 1mH (around 600uH to 700uH) and the RX is approximately 14mH. I don't know the pin wiring for these coils, but it should be easy to figure out with a combination of a continuity tester and looking at the internal plug wiring.

[Dixix]

Yes, the coil has really a very strange configuration. I have RX and Tx measured. (See photo)
Dirk

[joop]

Don't these MXT coils have capacitors inside of them? This makes them not suitable to use for the raptor...

[Qiaozhi]

Don't these MXT coils have capacitors inside of them? This makes them not suitable to use for the raptor...

Also, the TX oscillator will not function with the inductances shown.

[Davor]

It can be improved so that it does.

[Dixix]

The defective capacitors were totally encapsulated in resin. I have removed it. (I have measured without them).

It can be improved so that it does.

How?

regards
Dirk

[joop]

By adding or removing windings so the inductance matches that of the raptor coil. Make sure you check your TX/RX phase settings when connecting the coil to the raptor electronics.

[Davor]

How?

I'll see to the schematic and suggest some simple changes so that it can accept such low inductances. Many MD oscillators are incapable of starting with low inductances and they may need some improvements so that they do.
Maybe today...

[Davor]

I've checked it in LTspice, as I already had IGSL oscillator that is basically the same configuration.
My suggested change is very simple: replace R1 with 47ohm.

The original Raptor is presented as follows, and it operates with R1=560ohm, L=5.7mH @ Rl=22ohm ...



With MXT coil inductance and series resistance are ~1/10 of Tesoro, so capacitance must go 10 times up, and also tank current goes way up, but don't worry, transistors are capable of handling the extra kick. R1 is the only component that limits the current, and I found that with 47ohm it is just about right. For any case it can be replaced with 100ohm trimmer and reach the perfect value by checking it with a scope. Thing to look for is Ie of PNP transistor not going negative (by observing voltage across R1), while maintaining maximum amplitude on coil. Good estimate is 47ohm.



Spectral purity is the best if Ie current minimum (between two peaks) reaches near zero.

[Dixix]

Davor, thank you for your explanations! And calculations. You're an expert!
It takes me some time until I've finished the circuit. I have only etched the pcb. And the many holes drilled.
But it is good to know that I can use for testing this (MXT) coil.