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44
IBM 8265: Planning and Site Preparation Guide
Common Mode Attenuation
Common mode attenuation measurements are made with the twisted pair driven and
monitored common mode with respect to the shield using a 50 ohm network analyzer.
No additional impedance matching devices are required.
Common mode attenuation in dB/km, measured on 100 m reels, must be bounded by
the following function:
f
( )
≤
A f
k 0
------ -
50
for all frequencies (f) in MHz between 50 MHz and 600 MHz. k
1A and 135 dB/km for Type 9A.
Near-End Crosstalk (NEXT)
Frequency
Type 1A
9.6 kHz–5 MHz
-58 dB
8 MHz
-54.9 dB
10 MHz
-53.5 dB
16 MHz
-50.4 dB
20 MHz
-49.0 dB
5–20 MHz
see note 3
25 MHz
-47.5 dB
31.25 MHz
-46.1 dB
62.5 MHz
-41.5 dB
100 MHz
-38.5 dB
20–300 MHz
see note 3
Notes:
1. Crosstalk measurements from 9.6 kHz to 20 MHz were performed on 305 m
(or greater) reels.
2. Crosstalk measurements from 20 MHz to 300 MHz were performed on 100 m
reels using a North Hills 13410 balun or equivalent.
3.
≤
( )
NEXT(f) NEXT 5
(f) in MHz.
Type 9A
-52 dB
-48.9 dB
-47.5 dB
-44.4 dB
-43.0 dB
see note 3
-41.5 dB
-40.1 dB
-35.5 dB
-32.5 dB
see note 3
f
15
+
log
---
5
is 95 dB/km for Type
o
Type 6A
Notes
-52 dB
1
-48.9 dB
1
-47.5 dB
1
-44.4 dB
1
-43.0 dB
1
see note 3
1, 3
-41.5 dB
2
-40.1 dB
2
-35.5 dB
2
-32.5 dB
2
see note 3
2, 3
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