some old school metal detector

[giuhalftrack]

to make a long story short... I was reading the "treasure hunting manual 7" by karl von mueller, and he talks about a circuit he found in a raytheon booklet of '50 and he built, he dub that "the little monster"
I found the circuit and i build them (I made a video long ago on YT).

I know that a treasure hunters club named "exanimo establishment" build those "Little Monsters" but they are improved version of the detector of the raytheon booklet. The detector is a simple BFO but if someone remeber or have the schematics for this detector please share them with me.

Another detector I'm interested too is the "spartan 125" that was a detector designed by Garrett.

thank you.

[Carl-NC]

Somewhere I have a White's Little Monster. Seems like Garrett also made a Little Monster model.
Do you have the Raytheon booklet?
Do you have a picture of what the Spartan looked like? I have an strange old Garrett BFO that has no model name.

[giuhalftrack]

Somewhere I have a White's Little Monster. Seems like Garrett also made a Little Monster model.
Do you have the Raytheon booklet?
Do you have a picture of what the Spartan looked like? I have an strange old Garrett BFO that has no model name.

I attach here a picture of schematics... for the Little Monster (as describet in Raytheon booklet. it was published in Italy too in a magazine).

the spartan 125 was a detachable hip mount with a little green box and a piggyback meter. Unfortunately I don't have a picture from the net, later i will take a picture in the book (treasure hunter manual).

[giuhalftrack]

sorry for all this reply,
this is a picture of the "garrett spartan 175" (sorry before i write 125) from the book.
I found today another clue for the "little monster": maybe the schematics was published in the National Prospector's Gazette Vol.6 (i saw a picture on the net)... (not sure).

[Carl-NC]

My Garrett has the same small control box but not the meter, and the control box is mounted on the shaft. I'll look around for it.

[giuhalftrack]

My Garrett has the same small control box but not the meter, and the control box is mounted on the shaft. I'll look around for it.

thank you !!

p.s.
the meter was an "add on" I read this somewhere

[Carl-NC]

Found them. Here is the Little Monster:



Here is the Spartan (I assume):



Both detectors look like they were never used, not a single scratch on the coil bottoms. Other than the coils, the Spartan has no identifying marks. I always wondered if it was made by someone who simply used Garrett coils. As I look more closely, I do see some sticker residue on the back of the case so maybe a label fell off. And I see that the box can be hip-mounted, never noticed that before.

[giuhalftrack]

Thanks Carl they are amazing !!!!

May be I managed to find the schematic of the little monster:
As I said before the project was taken from a raytheon booklet (see schematics on previous post), but I want to know if they (exanimo) modify the original circuit because in "selection from the national prospector's gazette" they talk about a knob to match "homemade coils" that don't show in the original design (raytheon).
The design of the "little monster" (exanimo version) is on the Treasure hunters manual 6 by karl von mueller but.... only in the first edition (1961 - Gold bug publisher) that is very rare.
After the treasure hunter manual as edited by RAM publisher (Garrett) and the schematics disappear .

Spartan:
according to Karl Von Mueller, C.Garrett accept to make this "spartan", that is not a little monster (there is a quartz).
seams that changing book publisher (from gold bug to RAM) the suggested detector changes, that's make sense in amarketing prospective

I write all this as a resume of my researches.

p.s.
I'm trying to aquire a scan from the NY public library.

[ivconic]

[Carl-NC]

Interestingly, I was poking around on eBay and a Spartan recently sold for $167.50. It has the meter. Also has the label mine is missing.

[ivconic]

Found them. Here is the Little Monster:



Here is the Spartan (I assume):



Both detectors look like they were never used, not a single scratch on the coil bottoms. Other than the coils, the Spartan has no identifying marks. I always wondered if it was made by someone who simply used Garrett coils. As I look more closely, I do see some sticker residue on the back of the case so maybe a label fell off. And I see that the box can be hip-mounted, never noticed that before.

Look at the size of that crystal! lol
I have few of such size, 200kHz, from IIWW radios.
For the last couple of days, I've been downloading almost all the issues of various electronic magazines,
I skimmed through most of them, I came across a dozen old designs, I didn't take notes in which issue they were in.
There are a lot of BFO type, some simpler PI and VLF I/B.
Who has patience; can find everything at this link: https://worldradiohistory.com/UK/

[kt315]

I'm trying to aquire a scan from the NY public library.

can you scan articles 'reports' on GMT KING COBRA from the magazines, for me? tia.

[kt315]

[giuhalftrack]

I'm trying to aquire a scan from the NY public library.

can you scan articles 'reports' on GMT KING COBRA from the magazines, for me? tia.

sorry but I'm not on the site, I'm in Italy and scan cost $20.00 dollars 20 pages....

did you already try here ? https://archive.org/ there are lots of books free...

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Plus I have to say that i found the Treasure Hunter Manual 6 (Gold bug edition -1961) in google books.
The preview is disabled, google shows only a snipped centered on the word you search.
Sardinian people (me) are notoriusly stubborn !!! so am I... I make a lot of search word and I manage to recover the schematics piece by piece
It just miss a little part..

Conclusions:
It appear to be the same exactly schematic present on rytheon booklet ... So I really don't know what the "improvement" of the original design are...

here the booklet cover (you can find it easy on the net) and the schematic (recoverd)

case closed ?

[giuhalftrack]

Look at the size of that crystal! lol
I have few of such size, 200kHz, from IIWW radios.

charles garrett say in the Master hunter manual that frequency is 288Khz so I think it make sense to be 200Khz on the reference oscillator

There are a lot of BFO type, some simpler PI and VLF I/B.
Who has patience; can find everything at this link: https://worldradiohistory.com/UK/

I'm preparing a list of all BFO and alternative (off resonance etc.) metal detector I found, and i found a lot
I return with a new post when that list will be completed.