Section II. TESTING PROCEDURES

TM 11-5820-695-35

d. Coating Cure, Circuit Side.

(5) Check the thickness of the coating using a

(1) Place board into an air circulating oven

wet gage. A total buildup of .006 t.0025 inches is

with the coating side up.

adequate.

(2) Follow the baking and curing time periods

(6) Place board (coated side up) on a clean

for the various materials as indicated in the chart below.

air bench for a period of 2 hours thereby insuring that all

thinning solvents have been vaporized and carried off.

Mfr.

Baking time

Curing time

Hysol Corp.

4 hrs. at 148F

Same, plus 2 days at room

temp.

PC-26M

PC-29M

3 hrs. At 150F

Same, plus 2 days at room

temp.

CONAP Inc.

3 hrs. At 138F

Same, plus 2 days at room

temp.

Essex Chemical

3 hrs. At 150F

Same, plus 2 days at room

temp.

e. Conformal Coating Application, Component Side.

component side. Follow the curing time periods for

materials used in accordance with the chart ind above.

Follow steps described under c above, to coat

Section II. TESTING PROCEDURES

generator (via the elbow adapters). When a load

4-14. General

impedance terminating a, coaxial cable matches the

cable characteristic impedance, no wave will be

Testing is limited to verifying the quality of rigid coaxial

reflected and the oscilloscope will display only the

cables used in Transmitter, Radio T1054/GRC-144 and

indicent voltage propagated down the cable. If a

Receiver, Radio R-1467/ GRC-144.

mismatch exists, part of the incident wave is reflected.

The reflected voltage wave will appear on the

4-15. Equipment Required

oscilloscope display algebraically added to the incident

wave. These waveforms are illustrated in views A and

Equipment required for testing is listed below.

B, figure 4-5.

a. Time Domain Reflectometer Plug-in HP1415A.

b. Oscilloscope HP-140A.

The quality criteria for the rigid coaxial cable

c. Calibrated Mismatch 1.10 VSWR Mecca Model

used in the T-1054/GRC-144 and R1467/GRC-

400-1.10.

144 is a VSWR of 1.1 maximum. This can be

d. Adapter GR874-TO-Type N General Radio 874

measured using the reflectometer as follows:

GNP.

e. 60 ohm Termination, HP908A.

f. Elbow Adapter General Radio GR874 (two

required).

g. Adapter, GR874B-to-SMJ OMNI

Spectra

21210.

h. Adapter, UG-29B/U N female-o-N female.

4-16. Coaxial Cable Test

a. Coaxial cable assemblies are tested using

Oscilloscope HP-140A with Time Domain Reflectometer

Plug-in HP-441&A. The reflectometer incorporates a

step generator which produces a positive-going incident

wave which is fed into the coaxial cable undergoing test.

The incident and reflected waveforms are then analyzed

to determine if 'there is a mismatch or if there are any

Figure 4-5. Reflectometer test waveforms.

discontinuities along the cable.

b. The oscilloscope high impedance input bridges

the cable at its junction with the reflectometer step

4-9