EMFAD 12/4 UG old model

[wael]

Hello ,

anyone can build radio frequency transmitter transmit selective frequencies between ( 40 to 140 khz ) , the coverage range 200 m , the TX antenna should not be wire , either Omani directional or telescope one, signal should go through air not through ground

this transmitter will be used to generate required radio coverage to operate the EMFAD unit in that areas/ countries, where is no Radio station broadcast signal match with EMFAD receiver band ( 44 khz to 140 khz ) ,


thanks in advance for all ,

wael

[Andi68]

As far as I know, an Emfad works with microwaves

[wael]

it is work with VLF stations

[wael]

Hello,

i see many post in the group but no one confirm that he make the transmitter

[pustareka]

Hello ,

anyone can build radio frequency transmitter transmit selective frequencies between ( 40 to 140 khz ) , the coverage range 200 m , the TX antenna should not be wire , either Omani directional or telescope one, signal should go through air not through ground

this transmitter will be used to generate required radio coverage to operate the EMFAD unit in that areas/ countries, where is no Radio station broadcast signal match with EMFAD receiver band ( 44 khz to 140 khz ) ,


thanks in advance for all ,

wael

Kaneshna
https://www.rimr.ru/eng/

[wael]

thanks for reply ,but i could not find any product in their list matching with my need ,

Kaneshna
https://www.rimr.ru/eng/

[pustareka]

VLF expencive proekt. Not amater proekt.

[wael]

VLF expencive proekt. Not amater proekt.

i am looking for simple and cheap transmitter

[kt315]

simplest transmitter. no electronics. very cheap.

[wael]

simplest transmitter. no electronics. very cheap.

[ivconic]

Hello ,
anyone can build radio frequency transmitter transmit selective frequencies between ( 40 to 140 khz ) , the coverage range 200 m , the TX antenna should not be wire , either Omani directional or telescope one, signal should go through air not through ground this transmitter will be used to generate required radio coverage to operate the EMFAD unit in that areas/ countries, where is no Radio station broadcast signal match with EMFAD receiver band ( 44 khz to 140 khz ) ,
thanks in advance for all ,
wael

Considering the frequency and the wavelength; it would be hard even to imagine such antenna if main condition is not to be coil loop. Forget such condition (especially forget the "telescope" one!)
Besides; for range of 200m is quite irrelevant if antenna is "directional" or not.
Directional TX antennas are used mostly in very long range communications and data transfer.
You don't need directional antenna, any tuned coil will do the job.
But if you insist on "directional" antenna; than it is doable. Again with coil loop.
Just put long ferrite rod in previously wounded coil and there you have quite directional behavior.
Longer the ferrite rod - more "directional" it is.
As for the TX stage; the transmitter: you don't need high power design at all.
Any adjustable oscillator will do. Since you don't need any soil penetration. No need for especial output stage.
Just Copy&Paste any of similar designs of common metal detector TX circuit.
As far as i recall; Emfad UG12/24 is working in 56-156kHz range.
Look the photos:

[Altra]

LRL, LOL

http://www.longrangelocators.com/for...ad.php?t=11431

[ivconic]

LRL, LOL

http://www.longrangelocators.com/for...ad.php?t=11431

Not exactly, far from it.
It is valid science and pretty valid technology. (unfortunately misused from time to time)
This rather belong to industry division topics. Quite valid subject.
...
At the end of this video you can see the directional behavior of ferrite rod antennas.
Rods are just 10cm long.
More "directional"-ity will be achieved with longer rods.

[Altra]

Nice project. But the original poster wants a 200m range. I think Barringer had a patent on aerial survey for mineral deposits using this idea.

[ivconic]

Some years ago i made local TX for similar purposes.
I had demand on 33kHz working frequency, so i used simple clock crystal and it was easy thing to do.
It served as "exciter" to extend and improve Cscope 33XD sensitivity and depth measurements accuracy.
The results were far over my most optimistic expectations! It did the splendid job.
Now.. at this current subject; only output part from schematic can be used to boost 56-156kHz signal from some adjustable oscillator.