Have questions on making a coil

[grayson]

I have a Tesoro Lobo and I am trying to make a new coil for it.
Question 1: 11 thousandths wire has a resistance of 1 ohm at 5 feet.
For an 8 inch coil, I figured that it contains a total of 21.8 ohms of resistance for 109 feet of wire for the transmitter and
for the receiver, I figured that it contains a total of 22.8 ohms of resistance for 114 feet.
I cut a 5 ft. section of 11 thousandths wire and measured the resistance along the wire.

Question 2: Are my readings correct?

Question 3: I have a 2 inch center coil with an 8 inch outer coil, what size capacitor should I use between the coils.

[Carl-NC]

In measuring 1-ohm for 5 feet, you were probably at the resolution limit of your meter. You really need to measure a length that gives, say, 20-50 ohms. Wire tables list 29AWG (~11 mils) as having 8.2 ohms per 100 ft.

Cap value? I have no idea... what's the cap for?

- Carl

[Qiaozhi]

I have a Tesoro Lobo and I am trying to make a new coil for it.
Question 1: 11 thousandths wire has a resistance of 1 ohm at 5 feet.
For an 8 inch coil, I figured that it contains a total of 21.8 ohms of resistance for 109 feet of wire for the transmitter and
for the receiver, I figured that it contains a total of 22.8 ohms of resistance for 114 feet.
I cut a 5 ft. section of 11 thousandths wire and measured the resistance along the wire.

Question 2: Are my readings correct?

Question 3: I have a 2 inch center coil with an 8 inch outer coil, what size capacitor should I use between the coils.

You really need to measure the inductance of the TX and RX coils. If you do not have an LCR meter, then you could try measuring the TX frequency and then calculate the inductance using F = 1 / (2pi * sqrt(L * C)). This is much more important than the resistance value.
However, based on the resistance values you have provided, I would hazard a guess that the Lobo uses the same coil values as most other Tesoro detectors. i.e. TX = 5.9mH and RX = 6.5mH.
There is plenty of information on this forum about Tesoro coils. Do a Forum search for "Bandido" and select "Show Posts".

[montepollock]

making coils

How critical is coil operating Frequency?
My whites detectors and fisher operate at 6.59K,and both have frequency shifts,is there a danger of damaging detector if the coils are interchanged?
Also many of the Garret master hunters operated at 6.59.
Whites no longer makes a DD in 6.59, so would any other 6.59 be interchangeable?Whites and fisher plugs are same but do not know about the wiring.
To be quite Honest sometimes this Site makes Me realize how much I assume,and How little I really Know.

[Qiaozhi]

How critical is coil operating Frequency?
My whites detectors and fisher operate at 6.59K,and both have frequency shifts,is there a danger of damaging detector if the coils are interchanged?
Also many of the Garret master hunters operated at 6.59.
Whites no longer makes a DD in 6.59, so would any other 6.59 be interchangeable?Whites and fisher plugs are same but do not know about the wiring.
To be quite Honest sometimes this Site makes Me realize how much I assume,and How little I really Know.

Even if the two detectors transmit the same frequency, this does not mean that the inductance values of the coils are the same. Different LC combinations can result in the same frequency. Also, some manufacturers put the tuning capacitors in the search head, while others do not. There are also many ways of driving the TX coil (Colpitts, Hartley, etc.) so the coil configuration may even be incompatible. Finally, when you consider that the pin connections are likely be different, then the chances are slim that the coils are interchangeable.

[Max]

How critical is coil operating Frequency?
My whites detectors and fisher operate at 6.59K,and both have frequency shifts,is there a danger of damaging detector if the coils are interchanged?
Also many of the Garret master hunters operated at 6.59.
Whites no longer makes a DD in 6.59, so would any other 6.59 be interchangeable?Whites and fisher plugs are same but do not know about the wiring.
To be quite Honest sometimes this Site makes Me realize how much I assume,and How little I really Know.

Hi montepollock,
as Quiaozhi stated there could be some differences in input stage and tx-oscillator sections.
Another important thing is resistance of coils too. That's because if you exchange coils also with same inductance but with resistance differences you can end-up with bad results and in some cases also damages on circuits.
This is expecially true for pulse induction detectors...where coil resistance is a quite critical factor...but could be also in some vlf machines.
Some input stages are quite delicate...
You need to match inducatance and also impeadance when exchange coils.
If you can...you really can master your hobby from a technical point of view too.

Best regards,
Max

[grayson]

Thanks for all your help. My operating frequency is 22 khz. I've acquired awg31 wire and plan on flat winding it. I have an oscilliscope and a Volt meter. These are the only tools I have and I am very limited in my knowledge regarding building these kind of things.
Any detailed information would be appreciated and I am still trying to make a coil.
Is there any software available for making these coils?
Thanks again...