Ask Bob: What are your favorite machines?

GMT™
Gold Master Metal Detector

This is the workhorse
of the White’s Prospecting Detectors
The newest version of the Legendary
Whites Goldmasters, this unit
has Three ways to Groundbalance: Manual, Automatic
and Grab
For price and raw performance on small gold the GMT is without competition

gmt

TDI™
SL 7.5/12 Metal Detector

Watch my Videos
for the Low Down on this Killer Detector

tdi_sl

MXT™
E-Series Metal Detector

This cousin of the GMT offers Coin
and Jewelry and Relic Hunting
along with serious prospecting. The trade off
on Gold is versatility
At 15Khz you will not hear the sub grain nuggets that
the GMT will hear
But you will be able to hunt dry beach, parks and Ghost
Towns with full
target ID and discrimination. This unit cannot be beat as
the all around best
unit for the West.

mxtv2

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Ask Bob: How do I weigh my gold?

When weighing gold, we always weigh in troy ounces (ozt). The troy ounce is derived from the Roman monetary system and has been used to weigh precious metals to this day. It is not the same as an avoirdupois ounce, the unit we use to weigh just about everything else.

The troy ounce is heavier than the regular ounce by about 9%. Thus, it takes 1.09 regular ounces to make a troy ounce. So, because the price of gold is always quoted in troy ounces, you’d be getting less gold for your money if you were to buy gold weighed on a regular scale!

Another oddity that comes to us from Rome is the symbol for pennyweight: dwt. The d stands for denarius, which equates to about a penny.

The table below shows comparisons between various measurements used to weigh gold. You can use this table to convert from one measurement to another.

PENNYWEIGHTS GRAMS GRAINS
Troy Ounces 20 31.1 480

For instance, say you have 10 grams of gold. You can use simple math to convert that to any other measurement:

10g ÷ 31.1 = 0.32 ozt
0.32 ozt × 20 = 6.4 dwt
0.32 ozt × 480 = 153.6 gr

Ask Bob: Which coil should I use?

We all want to use the biggest coil we can for the condition. The ground ant type of terrain will determine what you can use. In big open areas with medium ground you can swing a good size coil and cover more ground, however, big coils tend to give up sensitivity to smaller gold targets. If hunting relics and coins, this will not hurt much. This can also be a bonus, allowing you to not detect the very tiny shards of metal.

Areas that are very rocky and have lots of brush will present a challenger for big coils. Ground mineralization can also be a huge factor with big coils. Noisy ground from high mineral content will need a smaller coil to get a smooth threshold. Choose the largest coil for the conditions. If the big coil is not smooth, you have ground balanced well, and have lowered the gain by several numbers, this would be the time to drop coil sizes… Small coils have their place, and if one only has a choice of one or two coils due to the backpacking in or funds, then go for small to medium coils. They will work everywhere no matter what. You just will not get the coverage. It’s easier to pinpoint a target with smaller coils, and they’re more

sensitive to smaller items and gold. They ground balance much easier and are also much lighter.

DD or Mono?

.Coil-Mapping-mono

Mono coils, under most conditions, are deeper coils than DDs. They give a bowl shaped field and “see” a lot of ground under the coil. Your first choice should be a Mono if you can. However, if the mineral content of the ground is very high, or there is a huge amount of trash, then a DD is going to serve you better.
DD coils have a narrow blade field running the center of the coil. These coils have both a transmit (TX) and receive (RX) coil inside, which overlap in the middle. These coils also do well in areas where you have lots of electromagnetic interference (EMI). The blade shape of the DD also has a greater target separation. This means that, if a quarter were next to a pull tab, the detector could “see” both targets as separate items, where a mono field would cover both targets at once and you’re going to have a harder time determining that there are two separate items.

Coil-Mapping-DD

If a larger piece of iron is next to gold, the detector will “see” the iron and pass gold with a mono, but you have a chance of separating the gold from the iron with a DD coil, DD coils do not hit as deep as monos, but under severe hot ground, they are deeper as they “see” less ground under the coil than a mono of equal size. If you are finding that you just cannot seem to get a smooth threshold in a spot, or the trash is very high, then you should switch to a DD for better results.