What is the difference between BFO/TR/VLF

[keeplooking]

I am new to this and I have been looking at new and used MD's. I love his forum and have learned a lot from may of you. I have also have gone to verious MD Mfr sites and read many of the the manuals for verious detectors. I have not yet purchased a MD but I am leaning toward the ACE250, or Tesore Silver Umax. I live in RI and would probably spend some time on the beach, dry and wet sand but not in the water.

One of the things that I have wondered about is the difference between the BFO, TR, and VLF and if one is better for certian MD'g situations than another. I have not found anything on the Internet that spell out how they are different.

Thank,
Still Looking

 

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[BioProfessor]

BFO ( beat frequency oscillator ) metal detectors use two oscillators, each of which produces a radio frequency. One of these oscillators uses a coil of wire that we call the search loop. The second oscillator uses a much smaller coil of wire, and is usually inside the control box and is called the reference oscillator. By adjusting the oscillators so their frequencies are very nearly the same, the difference between them is made audible as a beat note, this beat note changes slightly when the search loop is moved over or near to a piece of metal.

The terms TR, VLF and VLF/TR can be confusing at first. The fact is they are all transmitter-receiver detectors. The terms TR and VLF are merely used to provide an easy way to distinguish the difference between the two. In electronics, VLF stands for Very Low Frequency (3-30 kHz), but with metal detectors the term is usually used to indicate a "mineral-free all metal" mode of operation. TR stands for Transmitter/Receiver, but usually indicates a "non-motion discriminate mode" of operation. VLF/TR usually indicates "mineral-free all metal" and, "mineral-free discriminate" operation. Although they have their place, the higher frequency TRs are generally not competitive with the latest VLF/TR's with silent search motion discriminators, as they are unable to handle the problems imposed by mineralization in the ground. TR's have long since given way to the superior ground- effect control provided by the very low frequency (VLF) instruments. TR's are normally restricted to use on non-mineralized salt water beaches and for salt water diving as they are capable of ignoring the effects caused by conductive salts, if properly tuned. Since TR's cannot ground compensate for mineralization, they are incapable of obtaining the depth achieved by the newer VLF type instruments thus limiting them to finding only shallow surface targets when used in mineralized areas. Whereas, the newer VLF/TR detectors do ground compensate, thus accomplishing much greater depths of detection when mineralization is present.

Hope this helps.

Daryl

 

[keeplooking]

Thanks for your input. If you look at my initial question, you will see that I would be using this MD for both beach (dry and sandbar applications) as well as non-beach areas. Also, I have been looking at used MD'ers and,based on your response, would I be better off considering a used TR/VLF MD over a new MD (I think most the ones I have looked at are VLF)?

Thanks again, that was very informative.

Still Looking

 

[BioProfessor]

New. The older models don't compete very well with the newer ones.

My VLF machine isn't worth it's weight in pop tops on a mineralized beach. That's why I have a PI. You might at least look in that direction as you find out more about your searching conditions.

Daryl

 

[Tom_in_CA]

Daryl (bio-professor) give a good tech answer. Here's a laymen's answer:

The BFO is a dinasour. Stay away from them. Phased out in the very early '70s. No depth, no disc, blah blah.

TRs (both TR all-metal and TR disc) are also dinasours. Phased out by the late 1970s/early '80s. No way to compensate for the ground minerals, as Daryl says.

VLF all metal goes deep, and is still the current technology (pinpoint mode on machines, for instance), but lacks disc. VLF-disc. is the most common current technology, though it may be called different things by different manufacturers, and have differences in sounds and such. VLF disc. started in the late 1970s, and was very fast motion at first. You had to swing them like golf clubs to get depth :P. By the mid 1980s the technology was getting better, swing speed slowed down, masking decreased, TID added, deeper seeking, etc.... So stick with a motion discriminator that post-dates about 1990-ish, and you're usually ok, for general beach/relic/coin, etc....

Of the two you mentioned, I'll comment on the Garrett 250: That is not a very good wet salt beach machine, in my opinion. It would work, but various other machines would kick its b*tt, like the Sovereign, Excaliber, 6000 Di pro, CZ6, etc....

 

[captain Jack]

I love my new ace 250, but when I tried it on the sand I have mixed feelings. It found the stuff, but it told me a soda can was 100% silver when it was at 8". it was wet sand and was a lot of digging when I probably could have skipped over it if I had gotten an acurate reading. Just one man's experience.

 

[SCOTT (IN ILL.)]

I PERSONALLY HAVE A WHITES XLT AND A CZ20. BOTH GREAT MACHINES, BUT FOR BEACH USE I RECOMEND THE CZ20 SUPER BEACH MACHINE AND GOOD FOR 250FT UNDERWATER. WHATEVER MACHINE YOU PICK THE MOST IMPORTANT THING IS TO GET USE TO IT AND HAVE FUN. GOODLUCK!! DIG UP A SHIP WRECK OR TWO LOL

 

[Tom_in_CA]

Captain Jack: your 250 was not giving you a false signal - to TID a soda can as silver dollar (or half, or whatever). Remember, conductivity is not the same as composition. To illistrate this, take a little wad of tinfoil, about the size of a gum wrapper. It will read "foil", right? Now take that same foil, and get a wad that's as big as your fist. Notice it reads higher, right? But wait! It's the same exact foil, only a larger amount of it! So size of the object plays a part in the TID. So things like penny, nickel, dime, quarter, half, dollar, etc.... are only callibrations of USA coin-sized targets. A tab and a full soda can are made up of the exact same thing (aluminum), yet the tab reads low, and the can reads high. All machines do this, and there is no way around it, except to size it out. Like, the can at 8" will sound too broad to be a coin sized item. You may have to switch to all-metal to size it by sound though.

 

[BioProfessor]

Tell me about it. I'm hunting in the Netherlands and the icon calibrations are all screwy.

Daryl

 

[TreasureTales]

OK, I'm going to add my 2 cents' worth here.

A metal detector is like a golf club in some ways, each one has a special function. Some golf clubs are good for making long drives down the fairway while other clubs are good for chipping out of sand traps -- each has its function. Sure, you can use a driver in a sandpit, but you won't have much luck getting the ball to roll to the cup. And you can use a chipping wedge to drive down the fairway, but the ball won't go very far. Better to have a full set of clubs and use each one as it was intended. The same is true of metal detectors.

Some detectors are great for beach work, some are lousy. Some are good for finding coins, some are better for finding relics. And some are only good for finding gold nuggets. So you really need to determine what type of detecting you want to do...and why. If you are sure you want to use it at the beach, then you will want to get one that is specifically built to work well under those conditions. If, however, you want to find relics at the old lumbercamps, you need to concentrate your research on finding a machine that is built for relic hunting. Generally speaking, you can use the same machine in either application, but the results will vary widely depending on the machine and its intended treasure specialty.

I happen to use a Tesoro Lobo Super Traq because in my experience it's the most versatile and reliable machine on the market today. It also has a lifetime warranty. I can't afford to buy a different detector to cover each specific type of treasure, so I spent a little more initially and bought a good, all-around machine (although it is known as a great nuggetshooting detector.)

Continue to research, ask questions, and take a few machines for a "test drive" at your local detector retailer. Sometimes the hands-on experience is the best way to make a determination. Good luck.

 

[keeplooking]

I really appreciate your advice and input. I have read your responses and looked at many of the MD'ers you have suggested. Basically current understanding of MD'ing seems to be a marriage of technology and skill, and price is not necessarily equal to a better detector unless you can buy top of the line name brands. So, with the technology available and available funds, I am considering Garrett, one of the low end Fishers or Tesoro, or the Whites Prizm 2(maybe 3). I have also been looking at used MD on EBay, but what I see is that they are older technology or, if it is a current model, they are not really a bargain at the prices they are selling for - for a few $'s more I can buy a new one and get the whole package plus the warranty.

SO, what it comes down to is this; I can not afford a $6-1000 MD at this time or 2-3 different types of MD’ers. I am looking at the $2-300 range that will get my wife and I started. I am hoping to get something that will give us the best of both world - relic and beach, if it doesn't work that well on wet sand, I guess I will have to live with that right now. We would be probably be MD’ing 1-2 times a month except in the cold winter months and I think we would be using it 30-40% on a saltwater beach, the rest of time would be general use just to see what we can find (parks, forest, and old building).

I understand that a general MD’s (non-PI type) do not work well on wet saltwater sand; however, a PI MD does not work well for relics-coin-gold, so I guess that I will have to consider a PI MD something in the future. So I guess it comes down to a question of which model MD would be best for us out there and get us started - what do you think?

Once again, I want to thank you all for your input. You have been real helpful in clearing up several concerns, miss-understandings, and clarified the differences between current technology and old technology for me.

Thanks,
Still Looking

 

[TreasureTales]

Hang out in the beach detecting forum for awhile and see what those guys are using. Ask them which machines they prefer at the beach. Then go into the relic forum and ask what those guys consider the best machine for relic hunting. You might get lucky and find that one make and model overlaps in both forums.

The real thing to keep in mind is this: any machine in working condition will find treasure IF the detectorist knows how to use it properly. Learn the machine. You are talking about maybe getting two low end machines. Usually people get frustrated with them and then lose interest in the hobby. You might be better off looking at a mid-price detector ($400.00) and then you and your wife work as a team when detecting.

Be sure your wife will actually enjoy treasure hunting before spending the money on a machine for her. Being a woman myself, I don't want a machine that consists of lots of bells, whistles, and knobs. LOL, I like my machine to be easy to operate and reliable. It's hard to tell somebody which machine to buy .. it's like which car to buy, very much a personal choice.

 

[BioProfessor]

The Ace 250 is a machine that a lot of people here on the forum tell newbies to buy to get started. It is a good starter machine or it wouldn't get so much press. For around the $4-500 mark, Tony in CT will sell you two of them with all the stuff you need to be good to go. That way, both you and your wife would have a decent detector. Then the one with the most clad can spend it on an upgrade if they want.

Just a thought. I think it would be more fun this way. Same detector. A little friendly competition?

Daryl

 

[U.K. Brian]

There were deep BFO's and it was BFO's with large coils that found most of the gold in the old days.
Don't believe they didn't discriminate either. Garrett produced a BFO discriminator as did Arado with the VFA 90 variable acoustic detector.
Older machines Induction balance (IB), off resonance etc all still have their place and on certain sites will outperform the lastest all singing/dancing machines. For the best discrimination, iron see through etc you have to look at the older pre motion machines.