[quote saginawian]Hello, this is a stupid question, I know - but what does all of this mean? I use a Tejon - but I never really understood this terminology. What exactly does it mean to detune / retune the machine and what is fast and slow retune?[/quote]
[size=medium]Ian, this is not going to be in the order you asked, but I think it will explain the terminologies for you. All of these functions are related to operating with either a Threshold-based TR (old technology) or in a threshold-based All Metal ground balanced operating mode as use don almost every popular detector today
In the earlier days of TR models, you had to Tune the detector for a slight audio threshold of sound. Initially, you adjusted the Tuner control for an audio Threshold of sound. Today, many manufactures refer to this control as a Threshold control rather than the Tuner control. It's the same thing. As you searched, due to changes in the coil-to-ground relationship, or due to drift in the electronics or drift caused by moving from sun to shade or shade to sun, etc., the threshold setting would change, either getting louder or nulling out and going silent. When this happened, the operator had to srop and manually adjust the Tuner/Threshold control to restore a 'proper' threshold setting for peak operation.
Auto-Tune: This is an electronic function that was developed whereby the electronic circuitry would maintain, or automatically retain or retune, the threshold setting you set to start out hunting. You would adjust the Tuner/Threshold control for a 'proper' slight audio hum (threshold of sound) and go about your detecting and the auto-tune circuitry would maintain the proper threshold where there were changes due to temperature or ground changes, etc.
Fast and Slow Auto-Tune: the Compass 77-Auto had the first selectable auto-tune that I remember using back in the '70s. You could select a slow-speed Auto-tune, or automatic-re-tune to restore the threshold sound, or a fast-speed Auto-Tune. The faster auto-tune was sometimes preferred in higher mineralized sites or those with rapidly changing ground mineral make-up.
Manual Re-Tune: This is a usually accomplished with a pushbutton or a spring-loaded toggle switch. This was a switch control added to a model that electronically re-tuned or restored the threshold setting you manually set when you started out hunting. If the threshold audio shifted or drifted higher (louder) or lower (even nulling out and going silent) , the operator simply restored the threshold without having to alter the Tuner/Threshold control knob, just press the button or toggle the switch and it was electronically restored.
De-Tuning: This refers to a method of manually de-tuning or desensitizing the detector to a specific located target in order to be able to pinpoint it better. We used this technique with success through the years with the TR's and then especially with the very popular VLF Ground Balanced models in their All Metal modes (when used for pinpointing). The idea is this: You search and locate a target. The next step is to pinpoint the target to be able to make a quicker and cleaner recovery.
You switch to the All Metal mode (a true, threshold-based All Metal mode) and move the coil over the target and the loudest response is generally going to be when the target is located in the center axis of the coil. However, if the target is too large and /or too close to the surface, you might get a more broad-sized response and have difficulty pinpointing the exact location.
To more effectively pinpoint the target, you would move the coil part way toward the target until the audio response gets a little loud, then STOP. Holding the coil stationary, you would use the Pushbutton or Toggle switch to Re-tune the detector. This is actually DE_TIUNING it as it now reduces that louder signal to the threshold level. Once accomplished, you continue to move the coil over the target and, since the detector has been "de-tuned" or "desensitized' to that specific target, the result is a smaller or narrower audio response that makes pinpointing much easier.
Personal thoughts regarding Auto-Tune: It can be a good thing, for sure, but I prefer to have manual re-tune ability, and if there is any auto-tune designed in a model, I like it to be a slow, comfortable auto-tune. For example, the original Bandido and Silver Sabre II had what I considered a very good, functional Auto-Tune. It maintained the detectors performance, and it also allowed the operator to use the manual re-tune to de-tune for target pinpointing.
With the Bandido II, Tesoro gave as a toggle to select what they called "normal" or "Auto". The Normal function had no auto-tune and the operator could manually re-tune as desired. But the Auto-Tune was, in my opinion, too fast for many people and many hunting applications. I preferred the original Bandido's slower auto-tune speed by far. many models made since then have, so far as I am concerned, a too-fast Auto-Tune speed in All Metal. Sometimes, and it depends upon the make and model, you can have no auto-tuning in the pinpoint function, or a you might have auto-tune, but it might be at a different retune speed than in the All Metal search mode.
I feel, the best model approach is to give the operator both a manual re-tune capability, and also a variable control to set the auto-tune speed preference.
Happy Hunting, and if I left you confused, drop me an E-mail at: MonteVB@comcast.net
Monte[/size]
