Question for Tom in Salinas or anyone on TR retuning

[Old California]

Tom or anyone with information regarding TR retuning, My memory kind of went south years ago but with the older TR's having a retuning feature was this putting the TR at a disadvantage for iron laced sites?

Reason why I'm asking, Thinking of getting one of the UK TR Viking series in this case the V6 model with a return feature. Will this effect performance pro or con? I know in regular situations on good clean bumpy ground it may even enhance operation maintaining a smoother threshold, But in older areas with allot of iron will the retune feature take away the higher kHz unmasking abilities?

Appreciate any help,
Paul

 

[Tom_in_CA]

Paul, the only way the auto retune feature would be a detriment to the machine's ability to see through iron is the following phenomenoms:

a) If the re-tune speed is too fast (which would help in "hugging" un-even ground), then the following side-effect begins to occur: When the retune begins to tune out a bigger item, then you a "re-bound" situation at the end of the signal . That is where when your coil is moving OFF of an iron target , and entering ground with no signal, your machine momentarily bumps "upwards" with a signal.

For example of this, try the following experiment. I know this is silly, and no one ever operates like this, but .... just for point of exaggeration, this will show the effect: Bring your coil over a nail, but then stop over the nail. The nail will eventually tune out, and you will return to a normal threshold, right ? (despite being right on top of metal). The speed-at-which this occurs is dependant on the re-tune speed. Ok, now that your threshold has returned to normal, now move OFF of the nail to sterile ground. And you will notice that the threshold spikes upwards, as if there's a signal ! This because it's now interpretting nothing as being the positive tone (if that makes any sense). This effect can occur with multiple nails back to back to back , where you're not necessarily "stopping on them", but in effect, it's like a continuous nail. Such that when you finally get a peak at sterile ground, the machine attempts to beep.

The solution to this is to move faster, to avoid having your machine "track" to the iron, right ? But in doing so, then you're loosing out on the benefit of the retune in the first place. Doh!

b) If you have lots of conductive targets, the effect works the same way in reverse.

The Auto Legend attempted to fix this, by creating a variable auto-tune speed select knob. But even the slowest setting still amply allowed for this to occur. The slowest setting still wasn't as slow as the 77b's in-built "hug" slow auto-tune speed. That was a big mistake on Compass end, to not have it able to slow down that slow AND TURN OFF ENTIRELY. If they had done so, it would have been a great machine.

Not sure which of the Vikings have this addressed. Ie.: a way to variably select speed, based on bumpiness of the terrain and minerals. And hopefully one that allows you to turn it all the way off, if you have flat ground and want to move REAL slow for some reason.

The best see-through ability would be when the machine is in best "hug" mode with the least amount of auto-track. Because don't forget, with any amount of "track-tune", the machine will tend to try to "tune out" very deep whispers. So you loose depth, if you're having whispers tuned out afterall. But this is only a function of depth, not necessarily "see through" ability. I don't think the machine's inherent see-through ability is affected by the re-bound phenonemon. Other than lacking depth to get to the targets you had in mind, in the first place.

Not sure if I've answered your question on not Paul.

 

[vlad]

People shipped detectors to and he changed out a resistor to slow it down to an extreme.
If you were willing to try this I'm sure you could really make a difference on the auto circuits speed.
I sold these and the Judge both back then-but they just did not move.
I can't even remember, was the Judge-2 a 100kHz?

 

[Tom_in_CA]

...he changed out a resistor to slow it down to an extreme. If you were willing to try this I'm sure you could really make a difference on the auto circuits speed.....

I never knew anything about this. But this just goes to show that the ability to variate the speed of re-tune was entirely arbitrary. And I'm sure the ability to find that product (as if someone thought they were going to alter their machine now) is impossible. But I'm wondering if the net-effect ability isn't available in the Viking series of 77b clones.

 

[Old California]

Thanks Tom,

Yes, You did answer my question and also helped me remember some of the differences between several of the Compass Automatics with the retuning feature. I understand what you're saying, With retuning sometimes the machine can tune out iron and when going over a clean patch of ground the ground itself will respond. With the Viking V6 I'd like to purchase, It has a retune button but I'm not sure how advanced it is with having a retune feature. I'll bear in mind it may just be a simple add on just to handle rough terrain and minerals, Nothing spectacular like our Compass Automatics especially the older green can lunch box Automatic.

If memory serves me right, Have six TR Automatics all Compass made. Auto 77 Auto Legend, 77B AutoMatic, 94B AutoMatic, Judge AutoMatic and two Compass Cue Automatics the 500 and 501. Guess will have to wait and see how the Viking 6 operates, Worst case scenario hopefully be a good easy to use machine for beginners out in school yards and such.

Have a soft spot for Automatics, Actually even removed the circuit board from the green can 94B and mounted it inside of the smaller Compass Hustler housing. Pretty neat Automatic setup packaged inside a tiny housing, Even modified the decal on the side housing. Will see if I can dig up a pic.

Thanks Tom for refreshing my memory, Darn TR's still keep us busy guess they'll always he a major part of the hobby

Paul

 

[Old California]

Vlad,

That would have been a cool mod, Changing out the resistor to slow down the retune. Not sure about the Judge-2 kHz but would image it would have been 100kHz, I have one of the Judge Automatics can't remember which one will have to dig it out. That too had a retune button on the handle, May want to compare this model with the Viking 6 if I do get one.

Take care,
Paul

 

[vlad]

GB range was somewhat narrow for my area, so I contacted my dist. Ed Moody in Pasadena, Texas. He told me what resistor to change and the
value on the GB, and it my friend did it--worked fine. But it was a salt marsh and we were hunting shells, and iron is the hardest thing to hit in wet
salt & both neg. and positive ground intermixed. We finally hit them with the PPD1 pulse made by Eric Foster--I think it was a land variant of
the Aquapulse--4 feet down. You could have put a big metal desk in that hole.-4, 32 pounder spherical projectiles.
We get them out and turn on the VLF-TR's, they null on the things because of the cocoons on them, regardless of how we set the detectors up or in what mode.
That place is still full of stuff, but you need a PI or mag [a Fisher FX-3 won't work] and a backhoe.
Digging with shovels is for the birds.

 

[Tom_in_CA]

Paul, thanx for the pix.

1) Re.: the 77b auto: It only had 2 speeds: on and off. I think the "off" would have had an ever-so-slight auto-tune though. Just like the regular 77b had. And the "on" was fairly fast. But no ability to pick anything in-between.

2) The 77b's that had the push-button retune on the end of the handle: There were guys back then who wised up to a creative way to use that button: In the days before VLF ground-cancel (or at least before some guys had bought/discovered VLF yet), the pushbutton on the end of the handle could be taped to continually hold it in the "in" position. So that it would be perpetually auto-tuning super fast. And this was a way you could hunt semi-mineralized wet salt. Granted, it wouldn't go that deep, but it worked. Some guys were working Carmel wet sand in the early to mid '70s doing that. You couldn't slow down to stop on a target, of course

 

[Old California]

Thanks Tom for the additional retune information, think I'm going to squeeze in an entire day with a TR this week. Nothing else just several different types of TR models.

Get reacquainted with the retune type, Automatics and 77B, both serious hunt and surface finds from school yards and such.

Thanks again,
Paul