Background
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 technology.
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 receiver.
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 receiver.
Receiver Operation
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.
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.
DC Power
The 9 volt battery goes into a pouch that's part of the strap system that holds the receiver on the left wrist.
Connector
Patent
5003316 (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 me know.
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 does light.
A
small 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.
The 4395A 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 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 me know.
A
small 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.
The 4395A 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
Local Oscillator
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 RF input
Chan 28: 174.405 MHz LO - 10.7 IF = 163.705 MHz RF input
Chan 1: 176.700 MHz LO - 10.7 IF = 166.000 MHz RF input
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 me know.
Top Inside
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.
Patents
The Class 342/4xx seems to be common to both of the E-systems patents for the DZAAS and as of 7Jan7 there are 7810 patents in the linked search.5003316 (.pdf) Single null miniature direction finder March 26, 1991, , E-Systems, Inc., 342/429 ; 342/419
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 transmitter.
4724442 (.pdf)
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
5706010 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.
5502450 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.
5461387 Position and direction finding instrument Oct 24, 1995, Georgia Tech Research Corporation, 342/357.08
5394161 Path finder/tracker system Feb 28, 1995, John & Richard Ubaldo, 343/702 ; 33/290; 343/894; 701/224
4876549 Discrete fourier transform direction finding apparatus Oct 24, 1989, E-Systems, Inc., 342/417 ; 342/194; 342/195
4489327 Direction finding Dec 18, 1984, Racal, 342/432 ; 342/433
4410890 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
4003060
Direction 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
4263597 Nondisruptive ADF system April 21, 1981, United States of America as represented by the FCC, 342/434 ; 342/435; 342/436; 342/438 - does not disturb the modulation like doppler type DF sets
4121216
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.4263597 Nondisruptive ADF system April 21, 1981, United States of America as represented by the FCC, 342/434 ; 342/435; 342/436; 342/438 - does not disturb the modulation like doppler type DF sets
Related?
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.00879 hits since July 31 2007 page created 5 Jan 2007.