User's Manual

Rev B
25
(A Sample Session)
This is a transcript of a real experiment. Four transmitters were used, having the
following characteristics:
Frequency Period (rate) Repetition Code Interval
151.450 936ms (64bpm) N.A.
151.138 622ms (96bpm) N.A.
151.149 973ms 2 pulses at 348ms
151.158 1106ms 3 pulses at 339 ms
These frequencies were installed in FTABLE partition 0, along with a "dummy"
frequency, 151.666. The transmitters were located about 30 metres from the receiver
and the receiver was placed on top of the video monitor of a 12MHz 80286
computer (about .5 meters from the computer case) and connected to its serial port
by an unfiltered cable. The receiving antenna was a short loaded whip connected
directly to the receiver's antenna jack. Under these (just about worst possible)
conditions, the SIGNAL/Interval routine exhibited self-triggering on noise at a gain
of 57. Besides this, there was an interfering 60 bpm signal at 151.158, comparable in
power to the test transmitter but slightly off frequency, so that its received pulse
was somewhat attenuated in both time and amplitude.
The reporting period was set at one minute with rate group size = 4 and PRC
group size = 16, so that all four transmitters could be captured in a single report
period almost every time under ideal conditions (high signal to noise ratio), but in
the presence of noise the action of the local gain reduction algorithm would slow
down acquisition so that this would not generally be possible.
In the first series of runs, the gain was set at 60 (substantial received noise), the
global noise threshold was disabled (set to 50) and the noise blank level was
adjusted to see whether the interfering signal on 151.158, as well as any impulsive
components of the computer noise, could be rejected by the noise blanking
algorithm.
The first value tried was the default (=48).
Gain = 60, Noise Blank Level = 48:
10/11/89 14:30:07 151.450*64*126 151.138*96*97
10/11/89 14:31:05 151.158*3R*114 151.450*64*99
10/11/89 14:32:15 151.138*96*117 151.149*2R*196 151.158*3R*130
10/11/89 14:33:17 151.450*64*99 151.138*96*119 151.158*3R*152
10/11/89 14:34:20 151.450*64*89 151.138*96*135 151.149*2R*187
10/11/89 14:35:53 151.450*65*98 151.138*96*125 151.149*2R*190
151.158*3R*128
Note that while the 3-pulse transmitter was recognized during four of six 1-minute
report periods, all four transmitters were reported only once. This is actually quite
a good result for the test conditions, as will be seen below.
In the next run, the noise blank level was set at 72.
10/11/89 14:37:08 151.450*64*95
10/11/89 14:38:07 151.450*64*106 151.138*97*122 151.149*2R*186
10/11/89 14:39:21 151.450*64*106 151.138*97*127
10/11/89 14:40:07 151.149*2R*196
10/11/89 14:41:09 151.450*64*121 151.138*65*100