obec Holstejnnase i jine lokalityfotogalerie

Thru-the-Earth RadioLocation Device - ver.2


Published 31.10.2020

Complete device

Cave radiolocation device based on B. Pease immortal design (radiolocation.tripod.com). The scheme remained the same, new PC boards for SMD components were designed.

The article describes the construction inc. production documentation. How to use the device is decribed here or here. Aletrnatively in Speleonics #26, page 2-3



Class-E Beacon scheme

Beacon Beacon Beacon Beacon Beacon Beacon

Transformer T1

is wound on MPP (Molypermalloy Powder) toroid core (27x14x11mm 125u). Primary winding is wound in two layers and has 90 turns 0,8mm Cu wire. Inductance is about 1242 uH.

The secondary winding has about 15-25 turns 1mm Cu wire. The number of turns depends on transmit loop antena parameters.

Transmitter loop

Usually I use antenna from 40 turns  and 55cm in diameter. This allows measurements even at a transmitter depth exceeding 100 meters

Capacitors C1,C2,C3,C4,C13 - are connected in parallel and their final value (like the secondary winding T1) depends on the transmitting antenna. The total value is typically from 1uF to 2,5uF

Info about tunning are described here (page 4 - Beacon notes)


LED D3 lights up only if a signal is actually being transmitted.

PCB has dimensions 100x74mm for placement in a Hammond box 1455K1201 (120x78x43mm)


RF amp

RF Amp scheme for DQ Receiver



PCB for RF amp. has size 25.4x40.6mm for placement into shielding minibox - e.g. AH100 (45x30x22mm)

The input from the antenna is connected with a small coax cable.  BNC conenctor is insulated - is not connected with the box.

Switch S3 and potentiometer R22 are connected with a shielded 3-wires cable.

DQ Receiver

DQ Receiver scheme

Beacon Beacon DQ Recv - PCB DQ Recv - PCB

PCB has size 71.1x65.7mm for placement into shielding  box AH102 (92x67x22mm).

Complete receiver (ie RF amp and DQ receiver) is built into a Hammond box 1455K1201 (dimensions 120x78x43mm). Example of placing controls on the top panel:

DQ Receiver panel

Receiver settings - see DQ RECEIVER NOTES, page 2,3

DQ Receiver - Complete device DQ Receiver - Complete device

Receiver loop

Receiver antenna is wound from 0.3mm cu wire, 55 cm in dia. The number of turns from 1kg package is about 550. The inductance is about 430mH. Loop is tune to resonance by connecting a 6.8nF capacitor. The capacitor(s) should be at least 600V.


Part list


Qty Parts Value Package
1 C1 2u2/250V XC27B13
1 C11 27p/50V 0805
1 C12 33p/50V 0805
1 C13 10n/50V XC15B5
1 C2 1u/250V XC27B11
1 C3 560n/250V XC15B10
1 C4 470n/250V XC22B10
1 C5 2200u/25V E5-13
2 C6, CX6 680n/250V XC27B11
1 C7 4.7n/250V C102-043X133
4 C8, C9, C10, C50 100n C0805
1 D1 5A 30V Schottky SMC
2 D2, D4 1N4148 SOD80C
1 D3 3mm LED 6410-02
1 R1 1M 0805
1 R2 100k 0805
1 T1 viz. text TOROID
1 U1 74HC4060 SO16
1 U2 78L05 SOT89
1 X1 3MHz HC49U-V


RF Amp

Qty Parts Value Package
1 C13 1n/50V 0805
3 C14, C17, C202 100n/50V 0805
2 C15, C16 10u/16V 1210
3 C18, C201, C203 150p/50V 0805
2 D3, D4 1n4148 SOD80C
2 R17, R18 10k 0805
2 R20, R20-2 1M 0805
1 R204 1k 0805
1 R21 20k 0805
1 R22 100k pot. RF Gain Potentiometer
3 R23, R26, R202 2k2 0805
2 R24, R201 100k 0805
1 R55 200 0805
1 S3 RF Gain x1 x100 Toggle Switch
1 U0 LF356 (TL071) SO08
1 U1 LF412 (AD712) SO08


DQ Receiver

Qty Parts Value Package
1 BZ Buzzer 3-18V
2 C1, C2 33n/50V 0805
1 C19 10-60p Trimm capacitor
1 C20 56p/50V 0805
1 C21 2u/16V 0805
1 C23 2.2u tant./16V SMC_A
1 C24 47n/50V 0805
7 C25, C30, C31, C32, C37, C38, C42 100n/50V 0805
1 C27 3.3u tant./16V SMC_A
1 C29 100u elect./16V E2,5-6
4 C3, C4, C22, C40 1u/25V 0805
1 C41 4u7/100V 0805
2 C5, C26 1u tant./16V SMC_A
4 C6, C7, C8, C39 10n/50V 0805
2 C9, C28 10u tant./16V SMC_A
1 D1 Power ON 3mm green LED
1 D2 1N4001 DO214AC
1 D5 1n4148 SOD80C
1 D6 RF_Overload 3mm red LED
1 D7 Phase Lock 3mm green LED
1 IC1 78M12 DPACK_3
1 IC2 78M09 DPACK_3
1 J1 DVM 200mV DVM (WPB5035-DV)
1 P1 Headphones 3.5 mono jack
2 R1, R2 221k 0805
11 R10, R11, R14, R28, R43, R44, R47, R48, R49, R50, R54 100k 0805
2 R15, R45 2.4k 0805
2 R150, R450 180 0805
2 R16, R46 750k 0805
1 R19 5k6 0805
2 R29, R40 220k 0805
4 R3, R4, R25, R27 1M 0805
2 R30, R37 1k 0805
1 R32 9.1M 0805
1 R33 2k 0805
1 R34 Volume 10k Potentiometer + on/off switch
1 R36 10 0805
1 R39 27k 0805
1 R41 2k2 0805
1 R42 1k RTRIMT93YA multiturn
1 R5 5k RTRIMT93XA multiturn
1 R51 4.7M 0805
1 R52 2M 0805
2 R6, R7 47.5k 0805
6 R8, R12, R13, R31, R35, R53 10k 0805
1 R9 Front panel audio null Multiturn Potentiometer
1 S1 Bandwidth Toggle Switch
1 S4 Alarm On Toggle Switch
1 S5 Slow meter Toggle Switch (not used)
1 S6 PLL/RCV Toggle Switch
1 U2 LF412 (AD712) SO08
4 U3, U4, U8, U11 LF442 (LF412/AD712/TL072) SO08
1 U5 4016 SO14
1 U6 4060 SO16
1 U7 4070 SO14
1 U9 LM386 SO08
1 V1 MV2109 SOT54H
1 X1 3Mhz HC49U-V