LF Engineering L-600S User manual

Model L-600S
ELF/VLF H-Field Loop Receiving System
The L-600S Receiving System is designed for listening to VLF/ELF sig-
nals, spurious radiation and phenomenon below 10 kHz. The system con-
sists of the L-600 VLF receiver and L-600 VLF H-Field loop antenna.
The receiving system is highly directional and sensitive enough for effective
utility line noise tracing applications and for ELF research with the serious
Natural Radio experimenter in mind. The L-600S is an effective H-Field
receiving system for use in EMI noisy areas, or within E-field quiet areas.
The directional loop can be used for nulling out noise sources. Frequency
response is 300 Hz to 30 kHz (broadband). The 24 inch square PVC loop
may be broken down into components for storage. The loop antenna and
receiver may be hand held or tripod mounted. Switchable high pass filter
for noise reduction. The extended 30 kHz upper range can be used for
solar flare studies. Tape recorder and earphone outputs included with the
receiver for connection to a recorder, sound card or spectrum analyzer.
The L-600 VLF Receiver is a current mode amplifier and audio amplifier
with with broadband loop equalization. Design features a broadband,
low-cut 1.5 kHz highpass filter for reduction of 60 Hz (hum) harmonics.
The L-600 VLF Loop Antenna is used in a current mode broad band
configuration with the L-600 receiver input circuit. The loop is constructed
of double enameled - UV protected #28 copper wire, and is secured to a
light weight 24 inch diameter pvc collapsible frame.
Operation - The L-600 VLF Loop Antenna
The L-600 loop is a unidirectional unbalanced antenna that can easily null
out 60 Hz power line noise in normal listening situations. If you are sur-
rounded by power lines it will be difficult to null most of the noise effective-
ly. A good location some distance (300 meters minimum) from power lines
is best for VLF/ELF signal and phenomenon monitoring.
Rotate the loop for the best nulling or peaking of signals that you desire to
monitor. As little as 10 degrees of rotation can null or peak a signal. Use
the L-600 antenna with the recommended L-600 VLF receiver for best
results.
For permanent outdoor mounting, we suggest that the loop bundle and
contacts be coated with an anti-fungus varnish. The loop can be hand held
for portable operation or can be mounted onto a standard camera type
tripod. When tripod mounting, it may be easier to first mount the handle
separate from the loop, then reattach the loop to the handle.
Specifications - L-600 VLF Receiver
Receiver Size 4.19”L x 2-74”W x 1-57”H
Frequency Response 300 Hz to 30 kHz
1.5 kHz (-3 dB) to 30 kHz (-3 dB), 60 Hz (-35dB)
highpass/low cut mode.
Audio Output 300 mW maximum, 4-32 ohms (earphones)
10k ohms (recorder)
DC Power 9 volt, 7 to 10 ma typical
Specifications - L-600 VLF Loop Antenna
Loop Size 24 inch square (PVC pipe)
Loop DC Resistance 50 ohms typical (unbalanced)
Loop Inductance 28 mH
Loop Sensitivity .23 µv √Hz @ 5 kHz
WARRANTY
LF Engineering Co. Inc. warrants that at the time of shipment the L-600 VLF
Receiver manufactured by LF Engineering Co. is free from defects in material and
wormanship. LF Engineering Co. obligation under this warranty is limited to the
replacement or repair of the product within 1 year from date of shipment. The L-
600 Loop Antenna under the same conditions, is warranted for 90 days.
L-600 Rev. C
Copyright 2007 by LF Engineering Co.
All rights reserved
Printed in USA

Assembly - L-600 VLF Receiver
Remove the front panel secured by the four screws. Install a standard 9
volt transistor batery (alkaline recommended). Plug in the earphones pro-
vided, turn the receiver on and the LED should illuminate. Note the volume
control, antenna input jack, and the seitch marked “BB” - broadband, “HP” -
highpass.
Assembly - L-600 VLF Loop Antenna
The Loop Antenna is in a partial kit form and must be assembled carefully
to prevent damage to the wire loop - do not twist or kink.
Tools Required: Screwdriver, Contact Cement or PVC Cement.
Parts List: Quantity
2
3
1
1
Description
Elbow Ends
Pipe Legs
Main Loop Assy.
Handle/Mount
Part Number
E5010
L5020
A5030
H5040
1. Assemble the three pipe legs and two elbows to the main frame as
shown in the illustration. The PVC sections will fit friction tight but
should be glued for secure construction.
2. Carefully mount the loop to the corner clips and secure with clip mount-
ing screws. The loop may be tightened on the frame by
offsetting the angle of the clips before securing into place.
3. Assemble the handle to the main frame and tighten mounting screw.
Operation - L-600 VLF Receiver
Connect the L-600 Loop Antenna into the input jack of the receiver. Plug in
the supplied earphones and turn the unit on. A small speaker can also be
used in place of the earphones.
Adjust the volume control to a comfortable level and use the “BB” - broad-
band or “HP” - highpass switch as required. In the broadband switch posi-
tion, the full frequency response is used. Broadband operation is for quiet
areas away from power lines. The highpass position is used to effectively
attenuate 60 Hz harmonic noise.
When using the L-600 receiver with a high volume setting, oscillation may
occur. To reduce this effect, move the loop antenna away from your ear-
phones. Oscillation is normal with some earphones without good shielding.
This condition should not occur with normal listening since full audio gain is
not usually required.
If noticable drop in sensitivity occurs during operation, check your battery.
Battery drain is approximately 7 - 30 ma depending on listening levels.
Note: When listening, be careful not to raise the volume level too high for
ling listening periods to avoid ear injury, Because of receiver sensitivity, do
not use as an audio listening device such as for telephone line monitoring,
since there is no AGC protection to limit audio output.
The belt clip is for the convenience of hand free operation and the thread-
ed through-hole at the base of the antenna is for tripod mounting. See illus-
tration for details.
10 µf
Loop
0.2 µf
47 pf
100k
2
34
6
33k
+
+
1 µf
IC1
33k
470 0.1 µf
12k
100k
Recorder/
Sound Card
0.1 µf
470
IC2
1
8
6
2
+9
470 µf
+
9 Volts
+
4.7k
Audio
IC1 LF356
IC2 LF386
L-600 Rev. C
300 Hz - 30 kHz
220 µf
10
LF Engineering Co.
L-600S Loop Receiving System
Rev. C
2007