possible description of
After a parachute drop someone
on the ground needs to find the cargo. This 28 channel
receiver is designed to be worn on the left wrist and the LEDs
help to find the beacon transmitter attached to the
cargo. There is a 10 yellow LED bar graph to indicate
distance to the beacon transmitter. This is a
currently fielded system. The top and bottom lids are
sealed to the main body and so it's not designed to be
repaired. Uses surface mount
. This was one of the first military
electronics units to make use of surface mount
technology. The parts so far all appear to be standard
part numbers, not custom ICs.
This program was shelved when GPS went operational. My
unit has a 1983 contract number and serial No. 110.
I've heard that when the payload is dropped the aircraft that
dropped it has a way to come up with Lat & Lon data that
can be relayed to the ground crew who only need a common GPS
1. Attach Antenna -
Turn to Tighten.
2. Attach Receiver to left wrist with antenna on
outside of arm.
3. Turn knob to assigned channel (1 to 28).
4. Test battery by pushing toggle switch to BAT
position. If yellow light does not illuminate, replace
battery (or connect antenna).
5. Raise left are and turn until green (corner)
light illuminates. Walk in direction arm points.
6. Yellow lights on end of receiver show relative
position to assembly point. TRN on indicates receiption
of active transmitted signal. Other lights move from
left to right as you get closer.
The 9 volt battery goes into a
pouch that's part of the strap system that holds the receiver
on the left wrist.
(see below) clearly shows in Fig 6 that both loops and the
sense antenna are inside the case so the connector has some
other purpose. Patent 4724442 (see below) mentions using
rotating antennas which might be the purpose of the
connector. When an external antenna system is not being
used there is some jumper in the mating cap.
The connector has one 0.070" dia pin (pin #1) and three 0.060"
dia pins (pins # 2, 3 & 4). It has a plastic body
with exterior male threads. I don't see any markings on
it. The outside diameter is about 0.692" If If you
know the model of the mating connector please let
When a fresh 9 volt battery is
connected and the toggle switch held in the "BAT" position the
yellow LED does not light. Normally this would indicate
a bad battery or missing antenna. When the toggle
is held in the "BAT" position and a screwdriver is used to
randomly short pins in the antenna connector the yellow LED
ball of aluminum foil wedged into the connector contacting
pins 1 and 3 causes the BAT test to light the yellow LED next
to the toggle switch. Also the signal strength
yellow LEDs near "FAR" are flickering but the yellow LED
closest to "TRN" is off. I think this is the proper
condition at this stage.
The plot shown in the photo to the left was made with:
the toggle switch =On
Chan 21 (# next to LED)
connector pins 1 & 3 shorted.
spectrum analyzer shows
new signals at:
164.6875 @ -77 dBm, 175.000 MHz @ -74 dBm, 185.3125 MHz @ -76
dBm and 195.625 MHz # -77 dBm.
Note that the adjacent gaps are all equal to 10.3125 MHz
The synthized LO seems to go
from 176.720 MHz for channel 1 to 174.425 MHz for channel 28
so each step is 85 kHz. Typically when the frequency
goes down as the channel number goes up the LO is above the
RF input by the IF. Since the span of the LO is
greater than the common 455 kHz IF the next most likley IF
is 10.7 MHz. So making a slight tweak to the LO
frequencies moves them to:
Chan 1: 176.700 MHz LO - 10.7 IF = 166.000 MHz
Chan 28: 174.405 MHz LO - 10.7 IF = 163.705 MHz RF input
The antenna consists of both a loop and a sense antenna and
these are contained inside the box.
You can see the 9 v battery pouch in the photo at the left and
the cable going into the receiver. The LED in the near
corner is probably the Green To/From LED that's green when you
are pointing To the payload.
Pins 1 (large dia) and 2 are connected toghther. The
yellow BAT test LED lights when pins 1 & 3, 2 & 3, 3
& 4 are shorted toghther. But not 2 &4?
This may mean that there are two different antennas that can
be used. If you know please let
In order to open the
lid the four screws were removed and a dead blow rubber hammer
used to crack the glue used to seal the lid to the box.
The bottom lid has not yet succumbed to the hammer so more blows
are needed to get it off.
This photo shows the top lid removed and the digital PCB hinged
out. In the bulges beside the channel switch and the
battery wire are two 5 turn coils oriented at right angles to
each other and each has a variable trim cap. These are the
two orthogonal loop antennas.
The Class 342/4
to be common to both of the E-systems patents for the DZAAS and
as of 7 Jan 2007 there are 7810 patents in the linked search.
Single null miniature direction finder March 26, 1991, ,
E-Systems, Inc., 342/429
A single null miniature
direction finder which may be worn on the arm of the user and
is fully automatic in operation. Signals from a single loop
antenna and a sense antenna are summed; however, the amplitude
of the sense signal is adjusted at first and second phase
angles and the phase of the sense antenna is automatically
switched from the first phase angle to the second phase angle
prior to summing to produce either a single null or a no null
pattern. These patterns are compared to each other as the user
extends his arm horizontally and rotates his body. When the
null occurs an indicator gives the relative direction to the
Method and apparatus for loop direction finding with no
ambiguity Feb 9, 1988, E-Systems, Inc. 342/434 - uses two loops
and a sense whip antenna. Replaced by 5003316 that uses
only one loop and a whip sense antenna. Includes 28
channel switch and LED indicator.
This patent mentions Contract DAAK20-83-C-0639 which is the
contract number on the DZAAS label. This patents olso
shows a 28 position channel switch.
The below patents relate to direction finding
Method and apparatus for determining location of
an unknown signal transmitter Jan 6, 1998, E-Systems, Inc.342/47
; 342/13; 342/147; 342/193; 342/417 - The locator device
transmits a pulsed signal that's close to the unknown
transmitters frequency. This causes intermodulation
distortion to occur in the unknown transmitter. By
measuring the time from sending the pulse to the time when the
3rd order IM return signal arrives an estimate of the distance
to the unknown transmitter is calculated. The power level
of the interrogating signal is not mentioned.
Single antenna direction-finding system March 26,
1996, E-Systems, Inc. 342/451 ; 701/300 - not DZAAS but instead
intended for use on an aircraft.
Position and direction finding instrument Oct 24,
1995, Georgia Tech Research Corporation, 342/357.08
Path finder/tracker system Feb 28, 1995, John
& Richard Ubaldo, 343/702 ; 33/290; 343/894; 701/224
Discrete fourier transform direction finding apparatus Oct 24,
1989, E-Systems, Inc., 342/417 ; 342/194; 342/195
Direction finding Dec 18, 1984, Racal, 342/432 ; 342/433
VHF Directional receiver October 18, 1983, United States
of America as represented by the FCC, 342/419 ; 343/767;
455/269; 455/351; D10/65 - VHF slot antenna and non conductive
tube to earpiece for covert operation
finding receiver Jan 11, 1977, United States of America as
represented by the FCC, 342/419 ; 455/333; 455/351; D10/65 -
CB radio by channel number
Nondisruptive ADF system April 21, 1981, United States of
America as represented by the FCC, 342/434
342/436; 342/438 - does not disturb the modulation like
doppler type DF sets
Direction finder antenna and system Oct 17, 1978, E-Systems,
Inc., 342/424 ; 343/728 - uses crossed vert loops & sense
antenna PLUT a horizontal loop to detect sky waves.
DIRECTION FINDER RECEIVER DZ-2 CRV-46152 28 VOLTS DC this is an
RCA tube type aircraft receiver. Not sure if it's also a
Drop Zone type radio or general D.F. radio.
- transmits around 164 MHz
pulses maybe 600 uS wide.
- snaps on 9V
strobe distress beacon- can be
equipped with IR filter
1951 - need for IR beacon visible from
aircraft to guide paratroopers.
on a Preliminary Investigation of Factors Influencing the
Design of a Lightweight Paratroop Beacon
, 1951 - design
constraints for an X-band beacon
with Signal Corps about Field Marking Equipment, Drop
Zone and Night Landing
1951 - Fluorescent and
phosphorescent materials, aircraft mounted IR viewer so pilot
doe need to wear special goggles, SE-11
flashlight with IR filter, UV activated fluorescent material,
Marking Equipment (Drop Zone and Night Landing)(RDP-60)
1951 - DZ: use fluorescent ultraviolet-autocollimator
illuminated by BH-6 or AH-8 UV light on plane. Night Landing:
use Welshback mantle gasoline lamp (Wiki
Marking Equipment (RDP-60), Beacon, Field Marking, Infrared
(RDP-60A), Night Landing System, Ultraviolet (RDP-60B) -
Progress Report and Request for Requirements
IR: Coleman w/IR mods (used with Metascope (similar to PAS-6
to work at night) the aircraft could use: M-2 Snooperscope,
Electronic Viewer US/C3, IR Binoculars, Image Metascope.
Ground viewers: US/F Metascope, Image Metascope, US/AM
UV: UV light source in plane and fluorescent auto-collimator on
ground. Originally designed to guide ships into harbors in
Marking Equipment (RDP-60)- Tests of Beacon, Infrared
- C-47 Plane: M2 Sniperscope, Radio Firing Device Transmitter, Handie Talkie
Ground: [redacted], 6 beacon lamps, Firing device, Radio
Detonator (VHF), Radiophone pack, Image Metascope, 2 IR
flashlights. hard to separate real beacons from other
lights, a flashing light would help.
Drop Zone (DZ) Location Equipment
1954 - 235 Mc +/-
0.1 Mc 7uS wide pulse with 100 to 300 uS pulse spacing (coding)
Report Project 2039 Drop Zone Beacon Program
started in 1952.
British Gee and Consul, American LORAN and SHORAN.
S & X band radar
Infrared Beacon, Viewrs and Metascopes.
AN/ARA-8 vs. AN/URC-4
AN/ARA-25 vs. AN/URC-4 (UHF)
) and other small transmitters.
The URC-4 with a modification to mount on a tripod with a 5/8
wave ground plane antenna was the best.
The ARA-8 is a VHF system using a pair of antennas and indicates
by a "U" or "D" Morse code tone in the pilot's headset. It
works with the ARC-3 transceiver. Needs a visual pointer
type indicator for the needed accuracy.
Ground based (Fig 6 pg 18) pulse transmitter at about 220 Mc
paired pulses with a 5 mS interval. A number of different
beacons can operate at the same time and be distinguished from
Aircraft (fig 5 pg17): Dual yagi antennas, CRT indicator, C-47
Voice communications are very poor.
Report in the Ferrite Antennas for Very Low Frequencies
1957, 61 pgs - aimed at submarine reception of 25 kHz
Report, Drop Zone Beacon Program R&D
Lab Support of Drop Zone Beacon Program
1957 - SARAH
beacon Project Initiation From R&D Lab
Flight Tests 1957
- stock URC-11 (240 Mc) and two
each Mk 220 SARAH beacons (213.5 Mc) also a modified
URC-11 (240 Mc) and two each TSS transponder beacons.
1958 - CIA beacon
program, Ground set Tx on 1200 kHz compatible with aircraft
ADF,. Uses "unique" transmission method. maybe the Light Weight Beacon
. Not all
aircraft have S-band or X-band radar equipment so a beacon in
those bands is not suitable. An option might be a sonobuoy
- RADAR cross band system which would require an on/off switch
for the aircraft RADAR.
1/2 mile range, 30 minutes
duration, sterile in external appearance, camouflage finish, Drop
Zone Beacon Tests
1959 - helicopter: 300# 25 cu
ft. ground: ?
1959 - similar to Development of DZ
of Drop Zone Beacon
Characteristics of the System:
1. Guide helicopter at 200 - 300 feet and 15 miles out.
2. Transmit a minimum amount of signal consistent with the
success of the mission, with the major ephhasis placed on
3. Operate without visual reference to the ground.
4. Reasonable free of local interference or enemy jamming.
1. Weight no over 50 pounds.
2. Minimal signal emission from aircraft consistent with
obtaining an accuracy of 10% in residual range and 50 feet
in azimuth over the DZ marker.
3. Visual signal to crew members to include range and
4. High reliability.
1. Readily carried by one person.
2. [redacted] Guess a stealth signal so the enemy
can not hear it.
3. Weight under 10 pounds.
4. If a power source is required, it should have a shelf
life of at least six months or be rechargeable by a hand
generator, solar or therom-couple chargers. It
should operate the equipment continuously for at least 10
5. Limited emission consistent with range requirements.
6. adaptable to hot, cold, humid climate.
7. Simple to erect and operate.
8. High degree of reliability and accuracy.
9. Should meet CIA standards of sterility.
10. Voice transmission is an optional requirement, but a
simple system of coding would be desirable in order to
maintain a limited secure contact between the ground and
1960 - Motorola data sheet
- 30 - 39.95 Mc, 200 channels, 5 Watts, FM, Transpond, CW
Compatibility: ARC-44, ARC-54, ARA-31, PRC-10
Zone Location Aids
1960 - Modified Coleman lantern
IR beacons & IR red plastic filter material.
Proposal X III HRT-2 Beacon Transmitter Production
1961 - 1500 - 1800 kc, Crystal controlled, 15 Volt battery
or ext supply, >10 Watts out, 1 or 2 kc audio tone,
10 HRT-2 & 20 battery packs: Jan 1, 1961
50 HRT-2 & 100 battery packs: Jan 15, 1961
100 HRT-2 & 200 battery packs: Jan 30, 1961
Frequency Drop Zone Beacon, HRT-2 Requirement
for Hand Crank Generator F/U/W HRT-2
HRT-4 (aka: BN-2) Homing Radio Beacon works with
GN-58 hand crank generator. But the HRT-1 and
HRT-4 are no longer being purchased.The HRT-2
requires 15 to 20 VDC at up to 2 Amps which no
current hand crank generator supplies. A
thermo-electric power supply running on kerosene is
1961 - 1600
- 1800 kc, 10 Watts out, A-42 balloon 150' antenna, 16'
whip, Mercury battery pack or hand crank generator T9D,
Thermo-electric power source HFP-1. Wesponder
Beacon: 1670 kc
Beacon Test Program
1961 - HRT-1 (Wesponder) and
HRT-2 (MF ADF beacon) were tested in 1961. The HRT-2
worked well with the Lear ADF receiver outperforming the
ARN-6 in range. HRT-1 only marginally useful.
with HRT-t Beacons
1961 - Meting minutes: color code
ant terminals: red hot and black ground, longer battery
cable, "hot" transmitter housing with using 16' antenna,
use captivated screws,
Plan for Radio Set RS-8 Project No. 2054
Cargo Chute Beacon Transmitter (Not RS-8 radio) -
of Cargo Chute Locator System
1980 - CIA-RDP78-03535A001800010020-8.pdf
Accomplish the following:
a. Aid in locating a cargo parachute dropped on a
re-supply mission where the recipent is already on the
ground in the drop area.
b. Aid in locating a cargo chute when it and the recipient
are dropped at approximately the same time.
c. Aid in tghe rendezvous of a number of chutists who have
dropped into the same general area at about the same time.
Wireless for the Warrior - Vol 4
Supplement, Chap. 66-1 AN/URC-4 Country of origin: USA
Apr 2016 - photos of modified URC-4 radio, horizontal "X"
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