Changing Q and Impedance

[Cody]

I will do one more of this type because I believe it is important to see the implications of a smart coil.

If a coil is matched to the transmitter, the idea of impedance match is for maximum transfer of power from circuits X to Y as you know, we have what we want. The Q of the coil is of interest in that this is a number that represents the efficiency of the coil.(Some comments are for folks that are not familiar with the electronic.) So, we want a high Q coil on our detectors. Here is a problem that I believe Minelab is addressing with the smart coils. When we lower the coil to the soil the Q changes and as we sweep the coil over the soil it varies. Also, the Q of a coil changes as the coil ages for a host of reasons. Unfortunately the Q is not constant and always a perfect match. There are ways to adjust for the changing Q. (Patents indicate it is the Q of the coil that is the major problem due to soil minerals. We get tied up in soil minerals but it is that the coil Q changes due to soil minerals that is the major problem.)

Designing a coil with a chip that communicates with the transmitter seems to me to imply more than handshake logic in saying I am a 7.5khz coil so send down a 7.5 khz signal. I cannot imagine an engineer not designing the smart coil to send Q data to the receiver and track the coil by adjusting the frequency.

I don

 

[Ralph Bryant]

Just as a follow-up to your comments, I think it is interesting that one of the admitted best performing detectors out there is one that also has the capability of manual coil tuning, that being the Nautilus DMC IIb. Alot of time is spent on discussions about TX power, RX discrimination, multi-frequency, and this or that, while we mistakenly "assume" that our coils are always designed and operating at an optimum level.....which as you show, is rarely the case.

Ralph

 

[Cody]

Why are you so good at expressing yourself? I think it is from all those traffic tickets you hand out. I had the Nautilus in the back of my mind as I looked at the X-terra and started to it several times. I am always interested in something that deals with the transmitter and receiver and not just one or the other. You know how adjusting the power on the Nautilus requires a re-balance of the coil.

I got go feed this diabetes so catch you later.