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CZ coil connectors
- Thread starter Neil
- Start date
ETEXHunter
New member
Here's a link for the various Switchcraft connectors you would need. The 'special' one will be the in-line female one. They're all on this page,
http://www.switchcraft.com/productsummary.aspx?Parent=598
Good luck...
JR
http://www.switchcraft.com/productsummary.aspx?Parent=598
Good luck...
JR
Blissterd1
New member
Dave J. said:
I have a Sun Ray Invader inline probe on my CZ5 and I don't seem to have issues with this. Since Sun Ray had no way to know what my coil/cable tuning and impedance factors would be, I would think that having it inline would mess up my GB. I have zero issues with GB. As a HAM licence holder I am familiar with feedlines and antennas, which is what we are talking about with detectors, where feedline=cable and antenna=coil. It is a property of transmission lines in general that if a feedline (coil or extension cable) is terminated at both ends by its characteristic impedance, then the current and voltage measured anywhere along it will be the same. As long as this is true, it doesn't matter what the actual length of the line is; its properties won't vary. Some minor attenuation may result but only in the case of long feedlines. I doubt that it will throw the matching (tuning) off that much.
The transmission line analogy is erroneous. The cable is only a meter or two in length, and the wavelength of the signal is about 20 kilometers. It's an electrical circuit, and the antenna is H field.
The only time I've ever seen transmission line issues in a metal detector was dealing with a PI that had ringing at several MHz which investigation seemed to prove was attributable to impedance mismatch.
The CZ is very sensitive to variation in searchcoil inductance, shunt capacitance, and series resistance. It's the most difficult searchcoil we manufacture. If you mess with cable length or anything else, you're probably going to throw off ground balance.
The only time I've ever seen transmission line issues in a metal detector was dealing with a PI that had ringing at several MHz which investigation seemed to prove was attributable to impedance mismatch.
The CZ is very sensitive to variation in searchcoil inductance, shunt capacitance, and series resistance. It's the most difficult searchcoil we manufacture. If you mess with cable length or anything else, you're probably going to throw off ground balance.
Blissterd1
New member
n/t
Blissterd1
New member
Dave J. said:
This seems to support my thoughts that with such a long wavelength, a meter or so worth of extension (feedline) wouldn't have that much of an effect on the tuning of the system. I use them on my White's XLT and DFX without issue. With the FZ-1 and the weight of the CZ already, I need to do something about making a chest mount or hip mount and hope that it won't be too much of a cut in sensitivity. We have quite reasonable soil in Tulsa, no real hot rocks or mineralized soil. (Maybe towards the red-dirt region of Oklahoma) I don't think that GB with be a big issue. It's worth a try at least as I do have access to the Switchcraft connectors.
It's an LCR circuit. Two degrees of phase error could make it impossible to ground balance.. This is precision audio frequency stuff. The cable is not a transmission line and wavelength doesn't have anything to do with it.
If you make changes to the cable you may not notice any difference. Or, you may have just ruined it. Or anything in between. Just depends on the details. I
If you make changes to the cable you may not notice any difference. Or, you may have just ruined it. Or anything in between. Just depends on the details. I
Blissterd1
New member
Dave J. said:
I get it. I'll just have to do the math and try to hit some factors and then use my O-scope to get the phase as close as posible. I know that I will be affecting the R-factor by adding wire, not so much the C (shielding will be a good idea) My kid is a computer engineer with thorough knowledge of circuits (he specializes in OP-amps and stuff with insane gain factors!) and is a hundred times smarter than I and even I understand tank circuits. I have several good O-scopes here and can provide beautiful and clean signals, sine, square, saw-tooth, pulsed, you name it. I have no problem looking at phase points. What you're talking about is exactly what I need to do. I do appreciate your advice here. You were definitely the guy I wanted to talk to! Someone who actually knows, not someone who SOUNDS like they know! Thanks! I'll probably end up putting my head together with my kid. He'll catch something if I get it wrong. However, I have worked with tuning both audio and HF plus VHF tank circuits. My audio tank experience is mostly with Hammond and other vintage organs that use tank circuits to tune the notes assigned to the keys. Once a scale of notes is made they are multiplied to octave up or down. I also used to build RF amps for HAM radio (up to 1000 watts!) and used an LCR with filters to keep them legal. That was back when a "dirty" HAM amp could take out the TV reception for the entire neighborhood! It is all quite clear to me how LCR's function. That is super helpful to know that I have that particular circumstance to contend with. I know there's other things, like velocity factor of the cable and other variables. It's not as if I'm going to fiddle with the circuit board, just the lines to the two coils (inner/outer) in the search loop. Wavelengths are wavelengths, no matter whether it's RF or audio. I'm sure to have a good time coming up with an extension that is relatively transparent to that tank circuit. It gives me an excuse to call my son! If things get interesting I'll see if he wants to see what the other guys at National Instruments think about this and how to get around it. I want to see what my fellow HAMS think. Always looking for a challenge and a chance to expand my knowledge base and involve others in the community. If I can figure it out then I feel others might be interested. I could set up a procedure to build electrically invisible extensions and provide them to those that want some room to stretch out and still use our trust old world (non-Bluetooth!) detectors!
Blissterd1
New member
Dave J.
It just struck me, why couldn't I use a tuning capacitor in that cable extension, that or determine the value and install a non variable cap to compensate the resonance factor. As long as the phase isn't affected and the resonance is "on key" all should be fine, right. Then at most I lose a little depth. Kinda like using a long-wire tuner to compensate for SWR.
It just struck me, why couldn't I use a tuning capacitor in that cable extension, that or determine the value and install a non variable cap to compensate the resonance factor. As long as the phase isn't affected and the resonance is "on key" all should be fine, right. Then at most I lose a little depth. Kinda like using a long-wire tuner to compensate for SWR.
The killers are added resistance in the transmit circuit, and added cable capacitance in the receiver circuit. (There are probably schematics posted over on the G****** forum). Keep additional transmit resistance under 0.1 ohm and additional receiver capacitance under 50 pf and you'll probably be okay.
Blissterd1
New member
Dave J. said:
Awesome! That's a great place to start! Thanks again Dave!