Lotek Wireless SRX 400 User manual

LOTEK Wireless Inc. Newmarket, Ontario, Canada
E00033 Rev.A
Rev B, ECO 302, 31 Mar 2001
SRX_400 TELEMETRY RECEIVER
USER'S MANUAL Version 4.xx
Deleted: 3.6x

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TABLE OF CONTENTS
SRX_400 TELEMETRY RECEIVER ........................................................................................................1
USER'S MANUAL VERSION 4.XX ..........................................................................................................1
INTRODUCTION .............................................................................................................3
SRX_400 FUNCTION GUIDE..........................................................................................4
Power Supply and Accessories .....................................................................................................4
Maintenance and storage..............................................................................................................6
Lightning protection.....................................................................................................................6
Memory.........................................................................................................................................6
Start-up and the Command Environment....................................................................................6
PROM initialization.....................................................................................................................7
The Keys and their Functions.......................................................................................................7
SHIFT...................................................................................................................................................................... 7
SET G ................................................................................................................................................................... 7
SET F ..................................................................................................................................................................... 8
SET SCAN.............................................................................................................................................................. 8
SET ∆..................................................................................................................................................................... 9
SEARCH................................................................................................................................................................. 9
SIGNAL.................................................................................................................................................................10
SCAN.....................................................................................................................................................................11
FTABLE .................................................................................................................................................................13
TIME ......................................................................................................................................................................14
COMM...................................................................................................................................................................14
CODE.....................................................................................................................................................................15
F0- F3......................................................................................................................................................................16
Panel Light Switch .....................................................................................................................16
Hardware Reset...........................................................................................................................16
SRX_400 OPERATIONS AND EXERCISES.................................................................17
Preface to the Examples ..............................................................................................................17
Example 1: Tracking...................................................................................................................17
Example 2: Optimization...........................................................................................................22
ADAPTIVE GAIN CONTROL ...........................................................................................................................23
OPTIMIZING NOISE PERFORMANCE IN EVENT_LOG ............................................................................24
Example 3: Automated Data Collection ....................................................................................27
REMOTE OPERATION BY TELEPHONE .......................................................................................................28
APPENDIX A: RS232 PORT CONNECTOR AND NULL MODEM CABLE .........................29
APPENDIX B: ANTENNA SWITCH CONTROL PORT .......................................................30
APPENDIX C: PROM INSTALLATION AND INITIALIZATION.........................................31
APPENDIX D: ADDITIONAL INFORMATION.......................................................................34
Warning......................................................................................................................................34
INDEX...............................................................................................................................35

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INTRODUCTION
The SRX_400 is a data logging, tracking and telecommunicating receiver designed for a wide
range of applications. All of its internal functions are controlled by a dedicated microcomputer
with 64k bytes of program memory (EPROM) and 64K bytes of data memory (non-volatile static
RAM). Besides its regular housekeeping duties, which are automatic and invisible, the
microcomputer provides a number of basic and advanced operations which are accessed through
function keys and menus. Specifically, you may:
Control the receiver sensitivity (gain)
Set the operating frequency
Scan through one or more tables of frequencies
Search for signals in designated frequency bands
Obtain graphic and/or numeric signal strength measurements
Measure and display pulse intervals (rates)
Access the real time clock
Apply audio noise blanking (post-1994 models)
Software modules may be selected from a growing applications library to provide special
services like pulse width measurements, RS232 serial communications, autodial modem control,
temperature monitoring, pulse code discrimination, automatic data logging, etc.. Combined
hardware/software options offer selective switching of up to 8 antennas and provide up to
1Mbyte of additional memory for data storage.
This manual describes the basic operating functions of the SRX_400 common to all software
versions, as well as a number of "support services" available as options. Some of these services
(like serial communications support) cooperate with, or are required by, any of several high level
application programs, details of which will normally be supplementary to this manual. For
information on which options your version does or does not have, refer to the SRX_400
configuration sheet P/N 577, check the appendices, or try the keys.
The manual is organized in two main sections. The first section describes the receiver
hardware and basic key functions. The style is more or less that of a "formal definition"; the
information is complete, with little redundancy. In the second section the approach is more
tutorial, with numerous practical examples. For self-instruction, various paths are possible; for
reference, section 1 is the most concise.
We observe the following typographic conventions:
Example Type of object Typestyle
SCAN Key SMALL CAPS
SHIFT + SIGNAL Keystroke sequence SMALL CAPS
SCAN Function or environment
named by key
BOLD SMALL CAPS
Interval Function (selected from
menu)
Bold
Interval Heading of section defining
menu item
Sans-serif Bold

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SRX_400 FUNCTION GUIDE
Power Supply and Accessories
ANT - RF jack for antenna connection (whip antenna, ASP_8 connection)
CHG - Battery charger connection
EAR - Headphones connection
OFF/VOL - On/Off switch, volume control knob
POWER - External DC power cable connection
ASP_8 - ASP_8 antenna switching unit connection - 15 pin
SERIAL I - serial port used for RS232 communications (dumps, terminal control, DSP) - 9 pin
SERIAL II- serial port used for DSP_500 interface in versions supporting both DSP and terminal
communications - 9 pin
The SRX_400 receiver will operate continuously for about 12 hours (panel light on) or 16 hours
(light off) on a fully charged "C" battery pack. The receiver operates on “C” or “D” type
rechargeable nickel cadmium (NiCad) batteries (Panasonic P-240C, Sanyo KR2800CE, or
Panasonic P-400D, or equivalent). When the batteries need recharging the shift key ^ character is
replaced by a symbol.

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SRX_400 receivers produced after April 1994 (look for an “A” in the serial number) are
equipped with a new power management system which provides true "fast-charging” of
batteries, independence of charge and external power functions and a bicolor charge status
indicator. The new supply is designed to charge the receiver's battery at or near the
manufacturer's recommended maximum rate until full charge is achieved or until a preset
timeout expires, at which time the charge current is reduced to 1/8 of the fast charge rate
("trickle" charge). For a C pack, a charge current of 500mA will provide a full charge in about 4
hours. In cold weather it is also important to allow the receiver to warm up to at least 10°C
before fast charging. Fast charging will be suppressed if the internal battery voltage falls below
4 volts, so allowing very deep discharge (e.g., leaving the receiver running unattended for long
periods) is not recommended. If this condition does occur, the charge controller will switch to
trickle charge mode (green light goes on) immediately on connecting the charger. When the
battery voltage rises to a safe level, fast charging will commence automatically.
If a charger of lower capacity is used, the fast charge controller will supply current at the
charger's maximum rate for 4.5 hours (preset timeout) but will then either have to be manually
reset for additional charge cycles, or be allowed to trickle charge up to the rest of the battery
capacity. Note also that the chargers supplied with the SRX_400 ‘A’ models will charge older
receivers very efficiently (6 hours for a fully discharged “D” pack), but must be manually
disconnected to avoid overcharging (overheating) when the cells are full. For safety reasons,
therefore, Lotek does not recommend the use of new chargers with older receivers.
Battery service life is specified by the manufacturer to be more than 500 charge-discharge
cycles. NiCad batteries will lose their charge over time even if they are not used, and they
typically exhibit some form of “memory” effect if operated under repeated partial charge or
discharge conditions. If you are going to store the receiver for extended periods (e.g., over
winter) it is recommended that you charge the battery once a month to conserve memory backup
power (see below) and to avoid possible impairment of the battery’s energy capacity and overall
life. To minimize memory effects, the best procedure is to run the receiver until the low battery
symbol appears (when the SHIFT key is pressed), and then charge until the trickle mode engages
(LED switches from red to green). If the receiver is inadvertently stored for an extended period of
time without charging, performing a few (1-3) charge-discharge cycles will often restore the main
battery to a usable condition, but will not recharge the memory backup battery. All batteries are
protected by a resettable fuse. Batteries are replaceable by Lotek Engineering.
The SRX_400 can also operate from an external 11-16V DC power source via a rear panel jack.
An external power cable is supplied. In SRX_400 ‘A’ models, application of external power will
disable the internal battery as long as the external voltage is above ~10 volts. Internal batteries
cannot be charged from the rear panel power jack. If the SRX is powered via the rear panel jack
the applied voltage should not exceed 16V DC.
In order to satisfy electromagnetic compatibility (EMC) and electromagnetic immunity (EMI)
of SRX systems, the wall charger used with the system must comply with corresponding national
regulations. Every wall charger supplied by Lotek Engineering Inc. complies with national
standards of the country of final destination.
The RF signal input jack labeled 'ANT' on the front panel is a standard BNC type which will
accept any appropriate (50 ohm) antenna or mating cable. When using a signal generator be
careful that the signal power does not exceed 0dBm. Other front panel connectors include the
battery charger jack labeled 'CHG' (see above for charger description) and the headphone jack
labeled 'EAR'. Lotek recommends the use of isolating headphones model H10-00 manufactured
by David Clark. The knob labeled 'OFF/VOL' is used to turn the receiver on and off as well as
for volume control. The front panel speaker is a Projects Unlimited AT-38008M.
A 9-pin (DE-9P) connector on the rear panel is used for RS232 serial communications. The
pinout for this connector is given in Appendix A. SRX_400 ‘A’ receivers have a second serial

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port (PORT 2), to accommodate special applications (e.g., GPS or DSP_500 interfaces). A 15-pin
(DE-15P) connector is also provided for antenna switching using Lotek’s ASP_8 controller.
See the figures above for locations of front and rear panel connectors.
Maintenance and storage
The SRX_400 should be protected from dust and moisture. If cleaning is required, the housing
and front panel can be cleaned using a soft cloth. You may need to use cleaning solution. If so,
wipe the housing with a soft, damp cloth using a mild solution of soap and water. Do not allow
any liquid inside the housing. When not in use, the unit should be stored in a dry place.
Lightning protection
Any system with SRX_400 and aerial antennas should be protected from a direct lightning
strike, as well as from voltage induced in antenna cables due to drainage of a surge to ground.
The latter can be achieved through the use of lightning arresters in the antenna lines right at the
SRX antenna input. Working frequency is one of the factors to consider when selecting lightning
arresters. For protection from a direct lightning strike it is recommended to erect a mast with a
lightning rod connected to a grounding pin with a flexible copper cable. The structure will
provide a ‘protective cone shade’ for the antenna. The antenna itself should be connected to the
grounding system.
Memory
Operating firmware is contained in permanent read only memory and cannot be overwritten
or erased. Variables used by the operating system are likewise indestructible, since they are
reinitialized on startup. All other memory, including user-specified parameters like frequency
tables and gain settings, and also the time and date, are saved in battery backed-up RAM. Back-
up power is supplied by the main batteries, as long as they have sufficient charge, and by an on
board lithium battery which will provide memory protection for approximately 6 months if the
main batteries are discharged or removed.
The basic SRX_400 receiver provides 64K bytes of data memory, of which roughly half is used
by the operating system. In models equipped with the ASP-8-512 memory expansion option,
512K bytes of additional (bank switched) memory are supplied for user application data.
SRX_400 ‘A’ models can accommodate 1M byte of extended memory (ASM_8_1M).
Start-up and the Command Environment
The SRX_400 is shipped with the batteries charged and time and date set. To operate the
receiver, attach the antenna to the front panel RF jack and turn the OFF/VOL switch on
(clockwise). The receiver will display the software version information, followed by the date and
time, followed by the current frequency and gain. The receiver is now ready to accept
commands.
From the main command environment (display shows frequency on the left and gain on the
right) all key functions are accessible and the receiver is in its audio mode. By judicious use of
gain and audio volume controls, signal bearings may be obtained using a directional antenna
and isolating headphones. Some keypad commands return you to this environment after
adjusting some receiver parameter (frequency, gain, scan time, etc.). Others transfer control to a

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new environment (e.g., frequency scan or signal measurement) in which keys may be reassigned
and functions redefined. Navigation is guided by interactive menus and the ESCape key.
PROM initialization
Operating system software is contained in one (SRX_400 ‘A’ models) or two (earlier models)
programmable read only memories (PROMs). The SRX_400 can run a variety of different
software versions which are specialized for particular applications. Although some options must
be factory installed (for extended memory, etc.), some version changes and most regular
upgrades may be made in the field. The general procedure for installing and initializing PROMs,
using the New_Prom routine, is given in Appendix C.
Although it should normally not be required, the New_Prom routine can be used as a general
low-level software reset in the event of catastrophic misbehaviour. Note that, unlike the
hardware reset (pressing SHIFT and ESC keys together), New_Prom will typically reset system
status variables (like communication port settings) and purge frequency tables and other data. If
you do need to use it, please report the circumstances to Lotek’s customer support department.
Warning: Changes or modifications not expressly approved by Lotek Engineering could void the
user's authority to operate the equipment.
The Keys and their Functions
All keys except SHIFT have dual markings. The upper markings (above the line) represent
SHIFTed functions or commands. The lower markings include some commands but mostly they
are reserved for the numeric digits 0 to 9 and the decimal point (.). Any key can therefore be
referred to by two names, depending on which key function is being selected. This convention is
used in the discussion below.
Numeric values are normally entered as a specific number of digits, including leading zeros
as necessary.
The SHIFT key selects the functions indicated on the upper half of the keys. When
SHIFT is activated the ^symbol appears in the lower right corner of the display.
When the batteries are low, the ^symbol is replaced by a small picture of a battery.
The SHIFT key is also used as a "continue" or "confirm" operator in some routines (SEARCH mode
and RS232 configuration in COMM) and to return from HELP.
The DOWNARROW key is used to decrement the value of a selected variable
(normally frequency, gain or scan time) by a selected amount. The variable is
selected by whichever of the SET G, SET F, or SET SCAN keys were most recently
activated. The decrement amount is the last value entered using the SET ∆function. In the SCAN
mode (see below), the arrow keys may also be used for manual scanning, frequency table editing
and control of signal window size. The DOWNARROW also provides a line editing function
(backspace) for real number entry (e.g., to calibration tables).
The SET G key activates the set_gain function, which first issues a prompt
SHIFT
SET G

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or, in versions supporting individual antenna or channel gains,
(where XX is the current value) and then waits until it receives two numeric inputs from the
keypad. Shifted or non-numeric keys (except ESC) are ignored. The system gain is then set
according to the received two-digit value. Pressing the ESC (escape) key causes the function to
abort without updating. On exit, the command display (frequency and gain) is restored.
The UPARROW key is used to increment the value of a selected variable (normally
frequency, gain or scan time) by a selected amount. The variable is selected by
whichever of the SET G, SET F, or SET SCAN keys were most recently activated. The
increment amount is the last value entered using the SET ∆function. The UPARROW is also used to
confirm real number entries (e.g., sensor calibration values). See also the discussion of the arrow
keys in the SCAN mode.
The SET F key activates a function which permits programming of the receiver operating
frequency. SET F first issues a prompt:
and then waits until it receives input from the keypad in the form of a 6-digit decimal number (5
digits in 30 - 70 MHz versions) representing the receive frequency in MHz (megahertz). It then
sets the receive frequency by programming the frequency synthesizer. If the requested frequency
is out of range of the hardware it may, depending on the receiver configuration, be automatically
limited to a minimum or maximum value. Pressing the ESC (escape) key causes the function to
abort without updating. On exit, the command display (frequency and gain) is restored.
The SET SCAN key sets the dwell time for the SCAN and SEARCH functions. It issues a
prompt:
and then waits until it receives five numeric inputs (0 to 9) which it automatically formats as
X:XX.XX (minutes:seconds.hundredths). Shifted or non-numeric keys (except ESC) are ignored.
The scan time is then set according to the received five-digit value. Pressing the ESC (escape) key
causes the function to abort without updating. On exit, the command display (frequency and
gain) is restored, with the scan time now appearing in the lower left quadrant.
ENTER GAIN (00-99)
>
MASTER GAIN (XX)
>
SET F
ENTER FREQUENCY
>
SET SCAN
9
ENTER SCAN TIME
>

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The ESC key is the general "return" operator. Most commonly it returns you to the
main program, restoring the command display on line one. Sometimes it provides a
return from a subprogram to the menu from which it was called. Sometimes it is
used to terminate data entry (of lists or table values) from the keyboard.
The SET ∆("set delta") key is used to set incremental values of frequency, gain or time for use by
the increment and decrement functions (arrow keys). Which variable is set depends on which of
the three other "set" keys (SET F, SET G, or SET SCAN) were activated last. The three prompts are:
The HELP key puts the receiver into its help mode. Once HELP has been activated you
may then press any key to get information about its function or about appropriate
entry formats for data. Note that HELP automatically performs a shift operation (help
data is naturally provided only for functions). Since help is provided for the SET ∆function
(shifted ESC), the SHIFT key, rather than ESC, is used to exit the help mode.
Note that HELP services are limited to basic information about key functions only and is not a
substitute for the operating manual. In order to conserve program memory, HELP is not provided
in advanced software versions.
The SEARCH key provides access to several functions. Its menu is:
The search functions scan through a range of frequencies looking for a signal, using the
frequency increment set by the SET ∆operation. If an active signal is found at any frequency the
routine continues scanning until it finds a local maximum, at which point it stops and displays
the maximum signal intensity and the frequency at which it was found. Pressing the SHIFT key
will continue the search. Because of the pass band characteristics of the receiver's ultra-stable IF
filters there may be more than one local maximum for a given signal, and if the signal is subject
to dynamic fading (due to relative motion of transmitter, receiver or interfering objects) the
maximum signal point(s) may move slightly or change in relative intensity. The search
algorithm is designed to discriminate multiple peaks of equal or increasing magnitude, and locks
on to each one individually until you press SHIFT. Search functions cycle through their ranges
repeatedly until terminated by ESC.
SET ∆
ESC
ENTER -> GAIN (01-99)
>
ENTER -> FREQUENCY
(001-999kHz) >
ENTER - >TIME (01-99 SEC)
>
SEARCH
HELP
SEARCH: 1)RANGE 2)CONT
3)NEIGHBOURHOOD 4)EXIT

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The Range function requests a beginning and ending frequency for the search and then scans
this range. This function may be used to find the frequency of an unknown transmitter or to
check for the presence of any of a known group of signals.
The Neighbourhood function searches a range of frequencies from 8KHz below to 8KHz
above the current selected frequency. This function may be used, with the frequency increment
(∆F) set to 1 kHz, to find the frequency of best reception for signal data (though not necessarily
the best audio response).
The Continue function continues a search which has been stopped by ESC.
SEARCH is provided in SRX_400 tracking configurations but may be absent from (or have a
different function in) some advanced data collection versions.
The SIGNAL key is used to select signal measurement and display options. Its menu is
Power Graph uses the bottom line of the LCD display to provide a graphical display of signal
strength, with the top line showing the selected frequency and numerical signal strength value
between 0 and 255.
While in this mode, the arrow keys can be used to increment and decrement gain and frequency.
Interval displays pulse intervals in milliseconds or pulse rate in beats per minute and relative
signal strength. In most software versions, received pulses are filtered using a pulse interval
window (see Boundaries, below). A pulse is considered valid if the time elapsed since the last
received pulse is within the window. Valid pulses will trigger a dynamic "strobe" character in
the lower right quadrant of the display.
Note that Interval does not exercise any automatic control of receiver gain. In a noisy
environment (e.g., in an aircraft or in the vicinity of computer equipment) it is possible to set the
gain high enough so that the receiver is saturated with noise and cannot detect even a reasonably
strong signal. Simply reducing the gain will normally correct this situation. (See also the
Optimization example in section II of this manual).
Interval and Power Graph routines pass control to a new environment, in which the
following limited set of key functions is available.
SHIFT +SIGNAL assigns the arrow keys to open and close the pulse interval window (Interval
only). This assignment is indicated by a "W" in the delta status position (see Figure 1, below) in
the lower right quadrant of the display, and changes in window size are indicated in the upper
right display quadrant. Note that if the pulse rate display format has been selected (see below)
the window boundaries will be displayed in beats per minute, rather than milliseconds.
SHIFT + TIME toggles the interval display format between time in milliseconds and rate in beats
per minute (Interval routine only). Both pulse measurements and displayed window values are
affected.
SHIFT + CODE selects digital code discrimination in software versions which support coded
transmitters (see the Code_Log user’s manual that accompanies W17 firmware). When this
function is selected a #symbol appears in the signal status position of the display. When a
transmitted code burst is recognized the code, channel number (user assigned index into the
frequency table) and signal strength are displayed.
SIGNAL
7
1)POWER GRAPH 2)INTERVAL
3)BOUNDARIES 4)CALIBRATE
149.450MHz +102
min ²²²²²²|
Deleted: , and also to enable/disable
audio noise blanking, as discussed
below under Interval and Scan
functions.

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SHIFT + SET F, SHIFT + SET G assigns the arrow keys to increment/decrement frequency and
gain. The delta status position (see Figure 1) shows an "F" or a "G".
F0 (without SHIFT) toggles audio noise blanking (a new function available in SRX_400 ‘A’
receivers) which uses the automatic signal detection features of the SRX_400 to enhance audio
performance, especially in aircraft or other high-noise environments. The audio noise blanker
suppresses the receiver’s audio response except when a signal is passed by the internal phase
locked loop detector’s noise blanking mechanism, which rejects pulses that are too short to be
valid signals. (This mechanism is described in more detail in Example 2 of the Operations and
Exercises section of this manual).
In a typical tracking application, very weak signals (detected with the noise blanker off to take
advantage of the powerful frequency-domain processor in the human auditory cortex) will
quickly pass the automatic detection threshold as the aircraft (or other vehicle) is turned to
approach the target. Switching the noise blanker on at this point will make further bearing
determinations easier (using the numeric or graphic display) and will also greatly reduce
auditory saturation and fatigue.
UPARROW/DOWNARROW increments/decrements frequency or gain and opens/closes the
pulse interval window in 5 millisecond increments.
ESC exits.
Boundaries allows you to specify a time window in milliseconds for valid pulses. Enter
boundary values as 5-digit numbers, including leading zeros, if necessary. If you don't want any
time interval filtering, open the window by setting the boundary values far apart (e.g., upper
bound = 10000 and lower bound = 00001). Whatever values you set for the window will be
remembered by the receiver until you change them. Note that window values are always
entered in milliseconds, even though they may be displayed (using the SHIFT + TIME key sequence
in Interval) in beats per minute. To specify a window value in beats per minute use the
conversion: interval(msec) = 60,000 / rate(bpm).
Calibrate refers to a specialized software feature which is not supported in any current
versions. Selecting this option should have no effect.
Figure 1: Display Status Characters (lower right display quadrant, positions 45-48)
Signal Status Delta Status Scan Status Shift Status
The SCAN key calls a function which scans through the frequencies entered in the
current active FTABLE partition, stops at each frequency for the time set by SET SCAN
and cycles continuously through the table. SCAN also maintains its own
environment, which provides a number of options and control features described below:
Pulse interval and signal strength information may be displayed for any signals detected. This
feature may be toggled on and off using the SHIFT + SIGNAL key sequence. Interval
measurements, window operations and the dynamic strobe character function exactly as in the
SCAN
.

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SIGNAL/Interval routine (see above). When the signal measurement option is turned off, the
signal strobe character (signal status position) is replaced by a small square. The SHIFT + SIGNAL
key sequence also assigns the arrow keys to the job of closing (DOWNARROW) and opening
(UPARROW) the pulse interval window, and SHIFT + TIME switches back and forth between pulse
interval (in milliseconds) and pulse rate (in beats per minute) display formats.
UPARROW and DOWNARROW keys may also be assigned to their usual (command environment)
increment and decrement functions while scanning, using the key sequences SHIFT + SET F, SHIFT +
SET G and SHIFT + SET SCAN.
The decimal point (.) key stops (or starts) the scan at the current frequency and writes a colon
(":") or a direction arrow symbol in the scan status position in the lower right display quadrant.
The SHIFT + SCAN key sequence assigns the arrow keys to control of scan direction (UPARROW =
forward, DOWNARROW = backward) and manual scanning. This allows you to step quickly
through the scan table in either direction to find a particular frequency. Arrow key assignment is
indicated by a <=> symbol or a direction arrow in the delta status position.
Frequencies may be removed from and restored to the active partition while scanning is in
progress using the SHIFT + F TABLE key sequence to assign the arrow keys to delete (DOWNARROW)
and restore (UPARROW) functions. The assignment is indicated by a "+" character in the delta
status position, which changes on activation of either arrow key to a "+" or a "-" to indicate the
last operation performed. Restoration is applied on a "last out first in" basis only to frequencies
which have been previously deleted. Frequencies which have been deleted but not restored at
the end of a scanning session may be restored en masse using the FTABLE/Copy function (see
below).
The
SHIFT + F2 key sequence calls a "scratch pad" routine for manual entry of mercator
coordinates, environmental measurements, or any other numeric data. The routine expects two
numbers, each up to 9 digits long, with each entry terminated using the UPARROW key and/or
edited using the DOWNARROW (= backspace) key. The two numbers are recorded, along with the
time and date and the frequency of the transmitter currently being scanned. In version W16, the
applications library program Code_Log uses the scratch pad memory area for "active code"
tables, which are allocated and de-allocated dynamically as the program runs. Memory is shared
rather freely, but Code_Log has priority in the sense that its initialization sequence also
initializes the scratch pad (destroys all scratch pad data) while memory initialization in SCAN
does not affect the status of Code_Log's tables. For instructions on retrieval of scratchpad data,
refer to the Operations and Exercises section, or to the documentation supporting Event_Log or
Code_Log, where applicable.
SCAN key functions are summarized in the table below:
Key Sequence Direct Effect Arrow Keys Delta Status Scan Status
.Stop/Start : - > or <-
SHIFT + SCAN Scan up/
Scan down
<=> - > or <
-
SHIFT + SET F Inc/Dec Frequency F
SHIFT + SET G Inc/Dec Gain G
SHIFT + SET SCAN Inc/Dec
Scan Time
T
SHIFT + SIGNAL Signal
Measurements
Open/Close
Window
W
SHIFT + F TABLE Remove/Restore
Frequency
+ + or -
SHIFT + TIME Pulse Interval/
Rate

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SHIFT + CODE Digital code
recognition
F0 Toggle audio
noise blanking
SHIFT + F2 Scratchpad
The FTABLE key accesses five functions. The menu is:
Partition allows you to select one of sixteen separate tables (numbered 00 to 15) as the "active
partition".
Size displays a count of all frequencies currently in memory in all tables, including those
which have been deleted but not restored during SCAN. ESC exits, or, by entering a new value (a
positive number or 0) you can remove (and restore) blocks of frequencies on a last in first out
basis, or purge all tables at once. In some software versions this “coarse” control is not provided,
but the size of the current active partition, as well as the master table, is reported.
Add accepts frequencies (in MHz) from the keyboard and adds them to the "top" of the active
partition. Note that some application programs, which assign "channel" numbers to frequencies
in the active partition, number the frequencies sequentially, in the order in which they are
entered, while others (e.g., W16) request a unique channel number for each frequency entered.
Delete steps through the active partition one frequency at a time and offers the option to
delete or continue. In some software versions this item is called Del/View and allows scrolling
through the frequency table using the arrow keys.
Copy causes all frequencies which have been deleted, but not restored, while scanning to be
written back into the active partition. Frequencies deleted by the FTABLE/Delete command
cannot be recalled in this way, but must be re-entered using Add.
Some SRX_400 software versions provide a facility for uploading frequency tables from disk
files via the serial port. If your software supports this feature a continuation arrow (“->“) will
appear on the lower right in the FTABLE menu, and the selection Upload table from Host will be
presented on a second menu page.
In order to use this facility you must first create a text file (ASCII format), containing a list of
frequencies and corresponding partitions, using any ASCII editor. Most word processors, and
many database and spreadsheet programs, provide ASCII text files as an output option. Program
editors, and simple editors like Windows Notepad or DOS Edit, will produce ASCII files by
default. The file should have the attribute .TXT with the data arranged in lines, as shown below
(comments in italics are not part of the file):
148070 (Frequency 148.070 MHz; partition defaults to 0. )
148090 0, 1, 2, 3 (Frequency 148.090 Mhz in partitions 0,1,2,3. )
148110 1 (Frequency 148.110 Mhz in partition 1 only)
Note that both the space character and the comma are valid separators (as is the TAB).
FTABLE
8
1)ADD 2)DELETE 3)COPY
4)PARTITION 5)SIZE

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14
Because one or more partitions are specified for each frequency, the file is essentially a master
list (all frequencies, all partitions). Once it has been sent to the receiver it may be modified by
adding or deleting frequencies as described above, but when a new table is uploaded it will
completely replace the existing one. If a partition is not specified for a particular frequency,
partition 0 will be assigned by default.
The complete procedure is summarized in the following table:
SRX or HOST Action
Host-SRX Establish/check serial connection between SRX_400 and Host computer.
Text editor Create a file with frequencies and corresponding partitions.
Text editor Save it as a text (ASCII) file (extension .TXT) in your Host data directory.
SRX Start SRX_400.
Host Start Host software.
Host Use Host software’s Display file command to view the text file, if desired.
Host Press 7for the utility Upload F Table to SRX;you will see a list of files in the
data directory.
Host Highlight your file and press <ENTER>.
SRX Select Upload table from Host routine (SHIFT, FTABLE, ->).
SRX Press 1
On completion of the upload operation, the SRX_400 will notify you by displaying the number of
frequencies loaded and/or a diagnostic message.
The TIME key gives a display of date and time and allows you to make changes. The
time on the display is actively updated approximately once per second. In the SCAN
and SIGNAL environments the TIME key is used to select pulse interval or pulse rate display
formats.
The COMM key accesses various RS232 communications options. The main menu is:
Configure calls the configuration submenu:
or, in some firmware versions,
Each of these functions allows you to select values for
the named serial communications parameters. These are:
TIME
6
COMM
5
1)CONFIGURE 2)DEFAULT
3)TERMINAL 4)AUTO-ANSWER
1)BAUD 2)PARITY/FORMAT
3)FLOW 4)INTERCHAR
1)BAUD 2)PARITY/FORMAT
3)FLOW 4)DELAY 5)MODEM
Deleted: ¶

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15
Baud = baud rate from 110 to 19,200
Parity = odd, even, or no parity
Format = number of data bits (7 or 8) and stop bits (1 or 2)
Flow = XON/XOFF or other flow control protocol (version dependent)
Interchar (Delay) = intercharacter delay, to allow interfacing with slow peripheral devices.
Modem = provides some special modem options for cellular telephone links (version specific).
The Default selection sets the default values of the configuration parameters. These are:
Baud = 4800
Parity = none
Data bits = 8
Stop bits = 1
Xon/Xoff = enabled
Intercharacter delay = 0
In versions which support remote control of the receiver by a host computer, Terminal puts
the receiver in its remote mode. Once terminal mode is activated the receiver keypad is locked
out; commands will be accepted from the serial port only. Local control can be restored from the
host or by a "hard" reset (simultaneous activation of SHIFT and ESC). See the WILDLIFE HOST
User's Manual that accompanies HOST software for further information on terminal control.
Auto-answer is a modem control function which allows a remote host to establish terminal
control by telephone. This feature is available for system service from Lotek, as well as for user
applications involving telephone, local radio or satellite links between the receiver and a central
processing station.
If the receiver is connected to a “Hayes compatible” modem (that is, a modem which supports
the basic “AT” command set), selecting auto-answer mode initializes the modem to its power-up
defaults and sends the current SRX_400 communication settings. The modem will enable its
auto-answer feature (on some modems an LED “AA” indicator will light up) which means it will
answer all incoming calls and negotiate a data link with the calling modem. The SRX_400 also
asserts its own auto-answer state, which will cause it to enter terminal mode when a call is
received, echoing all display information to the serial port and responding to commands from a
remote terminal. Auto-answer defaults to OFF on power up, so if the receiver is turned off
between sessions auto-answer must be invoked again, even if the modem’s auto-answer feature
is still enabled. Also, because the auto-answer command sends SRX_400 communication settings
to the modem, it must be re-enabled if these settings are changed.
Use of the Auto-answer feature in remote terminal communications is further described in the
WILDLIFE HOST User's Manual for Lotek’s HOST software, and in Example 3, at the end of
this document.
The
CODE key is used in some software versions to enter a five-digit "pass code"
which authorizes access to functions which can reformat, reallocate or overwrite
memory. There are currently three such functions: New Prom initialization (SHIFT +
F1), Memory Test in the Event_Log or Code_Log menu, and the memory initialization sequence
provided on entry to a number of data logging programs. Once it is entered, a new pass code
may be "locked", which means that it will also be required to authorize further changes. Use this
CODE
4
Deleted: point-to-point

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feature with caution! In software versions which support coded transmitters, the CODE key
also allows code set selection from the command environment and controls the code
discrimination option in SCAN and SIGNAL routines.
Finally, the
CODE key is used to set I.D. codes for identification of records from individual
receivers in automatic data logging situations
The top row of keys is reserved for application software and user-specified macros.
The F3 key is currently reserved (in all versions) for turning the display luminescence
on or off (see below).
The F2 key is used in several versions to set the active antenna outside of the Event_Log or
Code_Log program. This feature requires hardware option ASM_8_512 (antenna switch
controller) which provides drive signals for the ASP_8 antenna switch peripheral or, optionally,
logic level (5 Volt) outputs for other user equipment. One of eight antennas may be selected, as
well as (in W16) a combination of antennas 1-3 (select antenna "0"). Note that in software version
W16 the ASP_8 peripheral, antenna 0 will correspond to antenna 8 in the software. F2 is also
used for scratchpad data entry in the SCAN routine.
The F1 key accesses the system initialization functions. These include the New Prom routine,
which resets the value of all system variables to their factory default values and, optionally,
purges scan tables and data storage. Access to this routine is restricted by the pass code.
The
F0 key calls Event_Log, Code_Log, Temp_Monitor or other application programs,
described in the supplementary user's manual that accompanies each program.
F0-F3, like all other “upper” key functions, are normally prefaced by a SHIFT operation.
However, since the unshifted keys are used for numeric input only in certain specific situations,
the F0-F3 keys, without SHIFT, can also be used for access to “single-keystroke” services. Currently
the F0 key (without SHIFT) is used in all environments to toggle the audio noise blanking feature
(see the discussion of key functions in the SIGNAL routine, above).
Panel Light Switch
SHIFT + F3 toggles the display luminescent panel on and off. Turning the panel off will conserve
battery power and extend the operating life on a charge by about 30%.
Hardware Reset
If you should experience a lockout (receiver won't respond to keys) or find yourself in a place
from which you can't escape, pressing ESC and SHIFT simultaneously will cause a hardware reset.
F0- F3
0-3

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SRX_400 OPERATIONS AND EXERCISES
Preface to the Examples
The following exercises are designed to enhance familiarity with SRX_400 functions and
operating modes . They are modeled as faithfully as possible on real applications and include a
basic radio tracking session, an optimization procedure and an automatic monitoring system
installation.
Example 1: Tracking
You are studying caribou populations on a group of islands off the Labrador coast. There is
some physiognomic evidence that these populations have experienced some degree of isolation,
but a quantitative measure of their independence, and in particular the impact on their genetic
viability of a proposed mainland development, cannot be assessed without some behavioural
data. You have 200 animals instrumented with radio collars, 50 on each of four islands. The
transmitters are at individual frequencies spaced 10KHz apart. Your method is to overfly the
islands twice a week (weather permitting) and try to locate as many of these animals as possible.
One strategy that occurs to you is to install your frequency list in four separate partitions of
the scan table, one for each island. This will keep your initial search list small, your "round trip"
scan time short, and your probability of missing an animal while your receiver is scanning
through a largely inactive list as low as possible. You recognize, however, that in order not to
bias your experiment, you will need an efficient procedure for finding animals which have
"jumped" islands, so you have reserved a partition also for the complete list, one for a
combination of the lists from islands 1 and 2 (which are close together), and one for a
combination of the lists from islands 3 and 4 (which are closest to the mainland, though distant
from each other). This gives a total of 7 tables.
PROCEDURE: SELECT TABLES AND ENTER FREQUENCIES
From the command environment, press
SHIFT FTABLE
The display will prompt you to make a selection using one of the numbered keys.
To select the table you want to be active, press 4. The display will prompt you to
make a selection of a table where you wish to store the frequencies, and will make
this the active table.
Press the desired number between 00 and 15. Note: 2 digits must be entered. After
you have entered a two digit number the FTABLE menu will once again be displayed.
Press 1 to "add" frequencies.
Enter the frequencies you wish as six digit numbers, or five digit numbers if you
have a 30 or 50MHz receiver. The decimal point is supplied by the program but
nothing bad happens if you enter your own. You may keep entering frequencies
one after another; when you have entered all the frequencies you want, press ESC.
This takes you back to the FTABLE menu. You can now select another table to enter
Deleted: ¶
¶

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other frequencies, review the frequencies you have just entered (using the delete
option), or press
ESC
to leave the menu of FTABLE. If you run into trouble, press the ESC key repeatedly
until you are back to the main menu (frequency and gain display), and then start
over.
When you have created your frequency tables you will set the scan (or dwell) time. This is the
amount of time the receiver will stay at each frequency in the scan table before proceeding to the
next frequency. You can choose this time in hundredth of a second intervals over a range of 1
second to 10 minutes.
PROCEDURE: SETTING SCAN TIME
From the command environment, press
SHIFT SET SCAN
The screen will prompt you to enter a 5 digit number (minutes:seconds.
hundredths); the colon and decimal point are automatically supplied. Normally
you will select a scan time that is (at least 100 msec.) longer than the longest pulse
interval of your transmitters to ensure that no signals are missed. For example,
Enter 0:10.50 for 10.5 seconds
Enter 1:23.00 for 1 minute, 23 seconds, etc.
NOTE: All digits must be entered. After the last digit is entered, the receiver will automatically
return to the command environment display (frequency and gain) with the addition of scan time
in the lower left quadrant. The arrow keys will now adjust the scan time using the time
increment selected by the SET ∆function.
Since you will be flying, you will be concerned about the levels of noise generated by the
aircraft engine and how this will affect your receiver sensitivity. Your first flight is in fact
dedicated to setting up your antennas and establishing a "noise floor", using one or more
reference transmitters in a known location on the ground. While flying, you will use the
SIGNAL/Interval routine to assess the level of noise.
PROCEDURE: NOISE AND SIGNAL MEASUREMENTS
The SIGNAL key controls the SRX_400's pulse interval and signal strength
measurement functions. All of these functions except Power Graph are also
available in the SCAN environment. This example illustrates the use of SIGNAL
functions for a single frequency.
First, from the command environment, set a frequency using the SHIFT + SET F key
sequence, with appropriate five or six digit data entry. Then press
SHIFT SIGNAL
and, at the menu, press 2 to select the Interval routine.

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If a signal is present, the bottom line of the display will show the pulse interval
(repetition period) in milliseconds, relative signal strength and two status
characters. These are an expanding "strobe" which follows the signal pulses and a
letter (Gor F) which gives the status of the arrow keys (control of gain or
frequency). You may use the arrow keys to increment/decrement gain or frequency
while the Interval routine is running.
To determine the noise floor for your environment, start with a low gain (try 50) and watch
the strobe while slowly increasing the gain using the UPARROW key. For this measurement it is
easier if their are no transmitters running, and it is usually advantageous to have your gain
increment set to 1. If you haven't done this, observe the following.
PROCEDURE: SETTING THE GAIN INCREMENT
If you are not in the command environment you must first return there. From
the SIGNAL/Interval routine, for example, press
ESC ESC
to leave Interval and SIGNAL respectively.
If you were adjusting gain in the SIGNAL environment you are ready to set the
gain increment. If not, you must perform a SET G operation. You may do this
without specifying any new value of gain. Press
SHIFT SET G ESC
Arrow keys and SET ∆now control gain. Now press
SHIFT SET ∆
and enter the two-digit gain increment value (e.g., 01).
Returning to the
SIGNAL/Interval routine, you continue to increase the gain until you begin to
see random triggering of the signal strobe character (lower right display quadrant). For
automatic signal recognition by the receiver you should set the gain just below this value. In
many applications this will also be the optimum gain for audio tracking as well. For a further
discussion of these issues, see the Optimization section, below.
On tracking flights, you will be using the SCAN routine to search for animals and record their
locations. You want to minimize the probability of missing animals, either because they are not
where you expect them to be or because they are in a radio shadow (e.g., in a steep ravine) and
their detection window is very short. In the interest of economy you also want to minimize the
flight time. As the study evolves, you develop a plan for which tables to check in which
locations, and in all cases you use the remove and copy utility to facilitate the aims listed above.
PROCEDURE: USING THE SCAN TABLE
To start the SCAN routine, press
SHIFT SCAN
You will see a prompt:

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20
The available memory belongs to the scratchpad, and the reported size will vary
depending on the software version and on the current status of memory use by
other programs. Initializing the scratchpad will erase current scratchpad data only.
If you choose to continue, new scratchpad data will be appended to the existing
record.
The program will begin scanning the current active partition (active table). On
entry, the signal measurement strobe will be inactive. To activate it, press
SHIFT SIGNAL
The upper right quadrant of the display will show the lower and upper boundaries
of the time interval window and the arrow keys will control the window size. For
tracking, you will normally want to have access to gain or frequency control, so you
may use
SHIFT SET G or SHIFT SET F
to restore arrow key control of gain or frequency respectively, while leaving the
signal strobe active.
If you are using a set of isolating headphones, you will be able to hear very weak
transmitters before the receiver does (see Example 2: Optimization, below). You may
wish to turn the aircraft in the direction of the strongest signal to obtain a more
accurate position estimate, in which case you can stop the scan by pressing the
decimal point key
.
If the program has already scanned to the next frequency before you are able to
stop the scan, press
SHIFT SCAN
to assign the arrow keys to manual scan functions. Then press
DOWNARROW
to backup one frequency.
As you get closer to the signal, the receiver will start showing pulse interval and
relative signal strength on the bottom line of the display. You may use the signal
strength indication to guide the airplane, and to provide an indication of the point
where you have passed over the animal. When you have fixed the animal's location
to your satisfaction you may record its position in the scratchpad. Press
SHIFT F2
You will see a prompt:
AVAILABLE MEMORY 49746
1)INITIALIZE 2)CONTINUE