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Passives, Actives & High-Split

Directional Taps

Module 15 of 26

Directional coupler theory applied to taps: through vs tap loss, value selection, cascade math intro, terminators, power passing, GigaXtend 5–1225 MHz bandwidth, and high-split upstream relevance.

Time ·
18 min
Pages ·
2
Quiz ·
12 Q · pass 80%

Company SOP governs the job. This module is training content. Follow FBR / host procedures and the OEM craft card for the connector, tool, or amplifier you are using.

Learning objectives

  • Explain directional tap operation as coupled trunk energy to drop ports
  • Differentiate through loss and tap (coupling) loss and read tap value labels
  • Select tap values conceptually for cascade level planning
  • Apply basic cascade math — cumulative through loss along a tap string
  • Install terminators on unused drop ports and verify 75 Ω seals
  • Recognize GigaXtend 5–1225 MHz capability and power-passing requirements on trunk

Page 1 of 2

Tap Theory & Cascade Math

Tap Theory & Cascade Math

Role of the Directional Tap

A directional tap is a passive directional coupler on the hardline trunk. Most RF energy passes IN→OUT (through path) toward the next amplifier. A fixed fraction couples to drop port(s) facing customer pedestals.

Taps are directional — coupler geometry favors coupling toward drops and isolation in reverse on the through path. Installing backward reverses tilt and power-passing orientation.

Designers chain tap values so each pedestal receives target level while enough trunk energy remains for downstream taps and the next active device.

Through Loss vs Tap Loss

Tap value in dB (4, 7, 11, 15, 23, 26) describes coupling loss trunk→drop. Higher number = less energy to drop, more on trunk (lower through loss). Example: 11 dB tap ≈11 dB to drop and ~1 dB through; 23 dB tap ≈23 dB to drop and ~0.5 dB through (verify datasheet).

High tap values (23/26) early in a string where drop counts are low; lower values (4/7) near cascade end. Replacing 23 dB with 11 dB without engineering overdrives local drops and steals trunk level downstream — 'one street hot, rest cold.'

Cascade math: trunk level drops by cumulative through loss plus cable attenuation between taps. Drop level = trunk at tap minus tap coupling loss minus pedestal jumper loss.

GigaXtend directional tap
ATX GigaXtend directional tap with IN, OUT, and drop ports labeled
Modern taps support 5–1225 MHz class for high-split downstream and return. Verify IN/OUT arrow before torquing.

Reading the tap in the field

IN arrow
Trunk from node/upstream amp — match cascade direction
OUT
Through line continuing to the next tap/amp
Drop ports
To customers; terminate unused with 75 Ω
Tap value
dB coupling to drops — must match strand map

Tap terminology

Through loss
Trunk attenuation IN→OUT — lower on high-value taps
Tap (coupling) loss
Trunk-to-drop coupling — higher tap value = more loss to drop
IN / OUT
Trunk flow direction; must match cascade arrow on map
Drop ports
Feed pedestals; unused ports require 75 Ω terminators
Power passing
15 A class typical on trunk taps feeding powered cascades
5–1225 MHz
GigaXtend-class wideband for high-split field upgrades
Open drop ports

Unterminated drop port = ingress entry on shared return. On high-split, one open 75 Ω port can degrade upstream SNR for the segment. Terminate before leaving pedestal.