I have an old coil from fischer that I would like to use again.

[Walter Aster]

The coil has 4.8-4.9 ohms and 38-39 ohms.
Can anyone tell me which detector this coil was originally used for?

Thanks in advance and best regards from South Tyrol, Northern Italy
Walter Aster

[kt315]

some pics of it will give a light, from you, for coil ID.

Anatloy

[Walter Aster]

hello anatoly

this is a kit from Nuova Elletronice, an Italian electronics magazine. A good friend of mine built this device many years ago. But he wasn't particularly satisfied. He found this almost unused coil while cleaning out the cellar and I bought it from him for 20 euros. As the reel has no labeling and I only found out on the internet that it may be a vintage model from fischer, I wanted to ask if anyone could tell me more about it.

Walter

*https://www.worldradiohistory.com/IN...=auto,-462,758

[Carl-NC]

If the coil you have is the same as in the article, then its a 1990s Fisher. Fisher used the same coil housing for several different coil designs. The resistances you list are very close to what I have for a CZ coil, I would need to compare the inductances to be sure.

[Walter Aster]

Thank you very much.
In the meantime I have also done some research here in the forum and found this list:
XLT 9.5”
TX: L=540uH R=1.4 ohms
RX: L=36mH R=122.8 ohms
---
Fisher 1210
Rx 6.48mH / 15.3 ohms
Tx (1.64mH / 7.7Ohms) + (1.62mH / 7.5Ohms)

Fisher 1266
Rx 10-10.4mH / 38.2 - 39.3 Ohm
Tx 2.14-2.2mH / 4.7 - 4.9 Ohm

Fisher Quick Silver
Rx 6.69-6.7mH / 31-32Ohm
Tx 0.945-0.960mH / 3-3.1Ohm

White's Spectrum
Rx 1.2 36mH 123 ohms
Tx 4.5 540uH 1.4 ohms

White's 6B
Rx 1.2 16mH 35 ohms
Tx 4.5 1.7mH 7 ohms

White's DFX concentric
Rx 1.2 13.8mH 36 ohms
Tx 4.5 540uH 2.7 ohms

White's DFX DD
Rx 1.2 14.2mH 55 ohms
Tx 4.5 680uH 3.5 ohms

Tesoro concentric
Rx 3.4 6.2mH 22 ohms
Tx 1.5 5.7mH 22 ohms

Tesoro early Lobo DD
Rx 1.3 1.35mH 12 ohms
Tx 2.4 10mH 55 ohms

Fisher CZ
Rx 1.2 6.8mH 30 ohms
Tx 3.4 1mH 2.8 ohms

[Walter Aster]

Unfortunately, I don't know whether you can trust this information? According to the resistance measurements I carried out myself and the comparisons with this table, it looks very much as if it is the search coil of a fischer 1266. That would be very important to me, because I am working on a replica (a slightly modified SMD version) of this 1266 machine. All the professionals here in the forum will laugh at this because the effort involved is far too great)..... but it's also a very personal bet between me and my son.

P.S. Thanks again for the welcome to the forum. Thank you!
Walter

[pito]

I don't know whether you can trust this information = as you can see the numbers are varying that's mean they are not critical, most of the coils have 80 turns for Tx and double of that for Rx, wire diameter 0.5mm Tx , 0.25 mm for Rx.
I would like to use again. = Are you going to build a detector?

[Walter Aster]

Hello Pito,
yes, I would like to build “a detector”. It's actually already finished. The problem is not really the coil. It's the detector and the coil together. The detector has a quartz oscillator and the square wave signal is transferred to the TX coil via a level converter. The resonant frequency must therefore be just as correct as the winding resistance. +/- a few 100 milliohms. Otherwise the power / the current... is missing or the signal is distorted.
However, I have now simulated both oscillator circuits in LT spice using the values in this “found” list. I think it should fit.
Thanks again.

[pito]

The resonant frequency = can be corrected by changing the value of capacitor (s)
to adopt your coil, show the schematic

[Walter Aster]

hello, thank you for your inspirational help.
I think I have solved the problem in the meantime. The values from the list seem to fit the 1266. They even seem to be pretty accurate. I have a 77.5 Khz and a 153.6 Khz crystal available. Divided by 1:16 and 1:32 respectively, I should be able to match the resonant frequency of the coil pretty well in both cases. I can then compensate for the remaining small inaccuracy with a capacitor.

[kt315]

you need to measure the inductances AT FIRST. sorry, but you ignored Carl's question, for unknown cause. the Ohms are telling nothing.

[Walter Aster]

Hello...
that was a misunderstanding
The only values I have are the millimeter dimensions of the coil and the values of 4.9 and 39 ohms measured on the cable.
The total diameter of the housing is 201.5mm.
The diameter of the outer coil shell, measured on the underside, is 113mm. The outer diameter of the inner coil shell is 102.5mm.
The total height of the coil shells is 117mm.
The radius (small coil shell) inside is 47.5mm.
The average winding diameter of the outer coil (TX) is 187mm.
The average winding diameter of the inner coil is 107mm.

Now my logical thinking tells me that these coils are manufactured by machine and therefore vary only slightly in their electrical values.
Example: 4.8 ohms can sometimes become 4.9 ohms. It must also be possible to divide the ohm values between the two partial coils (TX and bucking) and the cable.

The coil windings are encased in epoxy resin. The diameter of the windings can therefore hardly be more than +/-5-6 mm at the most.


Online calculator: https://www.electronicdeveloper.de/I...LuftMehrl.aspx
Fisher 1266 Coil
Rx 10-10.4mH / 38.2-39.3 Ohm
Tx 2.14-2.2mH / 4.7-4.9 Ohm

Values also work in the LT spice simulation.

[kt315]

i have especial folder in Archive with all coil calculators, all of them i checked. https://drive.google.com/file/d/1JB4...usp=drive_link

[Walter Aster]

Thank you.
I have now found the very best coil calculator. It's on my table.
A present from my son. Well, half of it. We share the machines.
And yes, that particular list above, the one with the coil parameters, is OK.
My coil has TX 2.2 mh / 4.87 ohms.
RX 38.44 ohms. 10.3 mH.