A-6
D.
The following procedure checks for second harmonic interference to the glide slope receiver
from the TFM-138. All transceivers produce harmonics (multiples of the wanted frequency) and
while the TFM-138 far exceeds FCC requirements, interference can still be experienced
depending upon antenna position and separation. Furthermore, harmonics can be generated by
other equipment in the aircraft and the structure of the aircraft where dissimilar metals make
contact or where grounds are isolated, etc. This is also true of aircraft hangers, therefore testing
should be done outside away from any structures where possible.
With a portable glide slope generator, provide enough signal to firmly activate the indicator
needle and hide all flags. Increase the signal level by 3 dB. Modulate the TFM-138 transmitter
on the following frequencies for at least 20 seconds. Observe the Glide Slope displays. Look
for any movement of flags or needles on the navigation display. If an interference condition is
detected, then the installation will have to be flight tested according to the following procedure.
Using the table below, determine the glide slope frequency based on the localizer frequency of
the ILS to be used. Divide the glide slope frequency by 2 and program into the TFM-138. Fly the
aircraft to intercept the localizer and glide slope (both needles centered) at 26 nm from the
runway. Transmit on the TFM-138 for 10 seconds and watch for any deflections or flags.
Repeat the test every 2 nm until the indicators are not affected. If the distance is greater than
18 nm then a pass shall be recorded. Otherwise the TFM-138 shall be placarded “Do not
transmit while on ILS approach”.
Localizer
Glide slope
Localizer
Glide slope
108.10
334.70
110.10
334.40
108.15
334.55
110.15
334.25
108.30
334.10
110.30
335.00
108.35
333.95
110.35
334.85
108.50
329.90
110.50
329.60
108.55
329.75
110.55
329.45
108.70
330.50
110.70
330.20
108.75
330.35
110.75
330.05
108.90
329.30
110.90
330.80
108.95
329.15
110.95
330.65
109.10
331.40
111.10
331.70
109.15
331.25
111.15
331.55
109.30
332.00
111.30
332.30
109.35
331.85
111.35
332.15
109.50
332.60
111.50
332.90
109.55
332.35
111.55
332.75
109.70
333.20
111.70
333.50
109.75
333.05
111.75
333.35
109.90
333.80
111.90
331.10
109.95
333.65
111.95
330.95
Summary of Contents for TFM-138
Page 13: ...2 2 FIGURE 2 1 Operator s Switches and Controls TFM 138 F10 B software...
Page 24: ...3 2 FIGURE 3 1 Outline Drawing for Model TFM 138 Transceiver...
Page 26: ...3 4 Figure 3 2 Wiring Connections for TFM 138 Transceiver...
Page 30: ...3 8 FIGURE 3 4 Microphone and Sidetone Level Main and Guard Squelch Adjustment Access Holes...
Page 42: ...STEP SYSTEM PASS FAIL NOTES A 11...
