Inductance

[Mark-VA]

If the connectors are identical and the pin ohm out the same will a coil work?
In other words if pin 1-2 read 22 ohms and pin 3-4 read 5 ohms will it work eventhough the coils might be made for different machines?

[Davor]

In case both rigs are designed to operate within the same octave, and you tweak the capacitors to make it so - why not!
In case these coils are not supposed to work within the same octave you might need to do something to balance your new coil for operation in a new frequency range. It can be done, and is easier than you think.

First find out the inductances of the original setup, and the new coil. Then find out the configuration of your rig's front end so that you can calculate the capacitors and see if any tweaking is necessary.

[Henrikras]

I don't know if this is a bad way to do it, but I used a tone generator and the scope and one resistor at 1K ohm. (Detector turned OFF)
With the plug in the detector and the 1 k ohm at hot wire from the generator, And the scope prope at the plug, I could could see the resonance at coil 1 and then coil 2. If they got same resonance, everything seem to me thats they should work.
If there where some different I could finetune with a small capacity, but only If the coil was to high at resonance.
Doing this I had in mind what Freq. the Detector was runing, and was happy If the resonance allso was the same as the Freq.
Sorry my bad english, I hope you understand. Otherwise Maybee a Guru can explain, If this is a good idea to do it.
Henrik.

[mikebg]

Henrik, if this is your test circuit, you should increase resistance more than 10K.
Resistance 1 kohm is too low. It operates as damping resistor.

[Davor]

You do not need to achieve exactly the same Tx frequency. Plus or minus 30% is fine.
As for Rx, you have to find out what exactly is in the front end. There may be a few options. You didn't say what machine or a coil you are talking about. In case the schematic diagram of the machine is known you will fix this easily.

[Henrikras]

Thanks Mike and Davor.
In my case I will change to a 10 k ohm, next time. At my Teroso 14,(x) khz, the TX had the same resonans, but the RX was some of.
At my Bliss both the TX and the RX got 8,10 KHZ as the detector is working at. And last on my Vista Gold the TX was 25 khz, but the RX got amplifirer in the seachcoil, so couldn't Be measured like this.
Measuring the coil and the Detector together with the plug in the detector, you have the capacity built in the Detector in play allso.
To Markg...If you got time, please tell how your project goes.
Henrik

[mikebg]

Despite inner preamp, the resonance frequency of RX tank circuit can be measured by inductive absorption.
Radio amateurs use a device called "dip meter", dipmeter, or just dipper. It measures the energy absorption at given frequency by inductively coupled nearby tank circuit. The dipper contains a tunable generator whose current changes when the RX tank circuit in the vicinity is in resonance. The generator is tuned for maximum energy absorption or dip reading in an indicator. The coil Ld serves as inductive coupling to the measured LC resonant circuit. It should have diameter almost those of the measured RX coil. For correct measurement, the TX coil L1 is shorted. This has little influence for measurement because L1A and L1B form induction balance with RX coil L2.

[Davor]

Not all Rx-es have a parallel capacitor though...

[mikebg]

Not all Rx-es have a parallel capacitor though...

However each Rx has a resonance frequency thouph ...

[Davor]

Not if series tank is terminated with high impedance. In such configurations the only resonance you may measure is a self-resonance of the coil, and that is not the one you are after.

Hence, a coil resonance works in situ only if there is a parallel resonance with Q well over 0.5.

OK, most detectors qualify.