Tesoro Tejon coil

[Wiltran]

I am making a DD coil for a tesoro tejon. The TX section is measuring 17.4 Khz on a frequency counter. The RX coil is apparently non resonant on this detector. On a dual trace scope, the RX sine wave is leading the TX sine wave. Should'nt the TX sine wave lead the RX signal on this detector? How do I make the RX signal lag the TX signal? add more turns to RX coil? I am trying to get ground balance and discrimination to work properly.

[Carl-NC]

If the RX leads by just a few degrees then it is likely due to the the TX coil resistance and is normal. The GB & Disc phase comparators should account for this if you've gotten the TX coil specs right.

[Wiltran]

Thanks for the reply Carl, no the Rx is leading by about 40-60 degrees.To get the Rx to lag, do I add turns to the Rx coil?

[waltr]

Do you have the original coil?? If so measure the phases to use as a reference.

Does the Tejon have a similar circuit to the Golden Sabre?

[Wiltran]

No I dont have the original coil to compare. As far as I know the tejon and golden saber are completely different.

[kac]

I'm pretty new to this but do have 3 dd coils for the Tejon. 10x12 wide scan, 8x11 dd and a Cors Shrew as well as the stock 8x9 concentric.
The 10x12 widescan is a much better coil than the 8x11.

I do have a dual channel scope so if I can make a measurement for ya I will, just let me know where you are reading from on the machine.

[Wiltran]

Thanks KAC, connect channel 1 (TX) on scope to TX coil pin. Connect channel 2 (RX) on scope to pin 7 of 33178 chip (its the ic chip on the top right corner of the board.) and please show a picture of the scope screen.

[ivconic]

I am trying to find something usefull on my disk, relating to this.
Not sure if any of this will help:

RX 16.56m 67.4 ohm
TX 1.03m 045ohm
....

Tejon-SEF 10/12
25,4cm x 30,48cm
Rx - 160 turns , 0,20mm.
Tx - 40 turns , 0,38mm.

[Wiltran]

Thanks Ivconic, your always helpfull! I am building a 10 inch DD coil and I am trying to get the best phase on the scope for best discrimination.

[Wiltran]

A question to coil builders: The tejon TX coil is resonant at 17.5 khz, but the RX coil appears to be non-resonant, its capacitor is series connected. Ive seen widely different inductances on RX coils made for the tejon from different sources. What determines the non- resonant RX coil inductance (number of turns) to maintain proper phase relationship with the TX coil for good discrimination and ground balance?

[Carl-NC]

If the RX coil has a series cap then it is resonated, but series resonance instead of the typical parallel resonance. You need to get the RX inductance reasonably close to maintain a proper RX phase so I'm not sure how widely different inductances will work.

[kac]

What about the grounds? Clip them together and ground to the board?
Also do this with a coil on I assume.

[Carl-NC]

Depends on the design, I don't know how the coils are connected on the Tejon.

[Op04]

Hope this help,
Nel Tornado spec
TX 910uh 3.2 ohm
RX 17.9mH 74.9 ohm

[Carl-NC]

Per that schematic, the TX shield connects to filtered -5V and the RX shield connects to ground.