Favorite Magnetic Locator
I’ve used a GA-52 Schonstedt.
I’ve used a GA-72 Schonstedt.
I’ve used a GA-92 Schonstedt. Pistol
The pistol has been in for repair 2x. The ribbon that connects the sliding extension seems to be the weak part.
The GA 52 is my favorite. I’ve got a malfunctioning one now.
The GA 72 works, but is not as versatile, because it uses clicks, for preset sensitivity positions.
I also have the Javad. It’s not very versatile. It has to be used through the LS. This ties up the LS, and I don’t like that.
Dunham and Morrow (supposedly leftovers employees of schonstedt) make one that is lighter than a schonstedt.
of course there are several other brands. CST
anyway, what have you used, and what is your favorite?
I'm probably just going to get my old 52, and 92 fixed. But, I’d like to see what options others are using. Metal detectors are critical, useful, and essentially indispensable to an honest surveyor. I also wish they could do more than ferrous metal. Aluminum and brass are also common monument material.
I think all of those you mentioned are MAGNETIC locators, so won't find aluminum and brass caps. They respond to either changes in the earth's field induced by long iron objects, or to permanently magnetized objects.
For non-magnetic metals you need a conductivity detector, commonly known as a treasure hunter, which usually has a search coil several inches in diameter.
A rule of thumb for those is that they respond according to the product of the metal's electrical conductivity and the surface area presented to the coil, reduced by distance as compared to the diameter of the coil. Vertical extent of the object has very little effect on detection.There are some processing tricks that can often distinguish different metals, but I've not found mine to give reliable discrimination.
Aluminum has very good conductivity (after gold, silver, and copper in the commonly used metals). Bronze and brass are good. iron is somewhat less but not bad. But the top of a rebar, the most common monument, has small surface area, so gives a treasure hunter a lot less response than a big bronze cap. That's why surveyors carry magnetic locators as their main search machine.
As a bench mark hunter, I carry both kinds of detector, and use the treasure hunter much more of the time, because iron rods are not commonly used for NGS BMs. Bronze caps and stainless steel rods do not register on a magnetic locator. I've found many of the 1960's-70's USGS marks in this area used iron rods.
I used nothing but Schonstedt for 30+ years. I tried out a Magna-Trak 202 for a couple of days. I ended up buying it. I’m not saying it’s better. But it works just as well for me, it feels good in my hand, and it only cost me $450 used. 6-months and no issues.
I have a GA-52 I use on my County job.
I personally own and use a GA-32... yes, very old (I think I bought it around 1976) and needs headphones but I find that its so much more accurate in pinpointing a spot than the 52. And with the 32 I can wave it over 2 or more feet of snow and it will 'respond' to an iron much better than the 52. Seems like the 52 needs to be held pretty much vertical to get any results... the 32 can be held almost horizontal and it will still work good. Granted, the 52 is an older version (circa 1994)... maybe the new ones are better..don't know. I do have a like new 32 as a backup.
For locating objects that have no magnetic field I have an original Fisher Gold Bug. Finding an old GLO concrete monument with brass cap (no embedded iron) is like finding gold! The Gold Bug has come through several times looking for those! It picks up on the brass - I 'tune' it buy throwing an unused brass cap on the ground and adjusting the settings on the Gold Bug to react to it.
The 32 is my favorite for sure.