A leading Taiwanese MSO (cable operator) fitted 3 dB inverse EQ (IEQ) plug-ins to UGRID YLA series high-value taps 8T23, 4T23 and 8T17 (not 4T11, which was already down-tilted), and reduced excessive up-tilt in short-span, heavily branched networks.
The problem: excessive up-tilt in short, heavily branched plant
Coaxial cable loses more signal at high frequencies than at low frequencies, so nodes and amplifiers are set with up-tilt (higher output at the top of the band) to compensate over long cable runs. In DOCSIS 3.1 networks extended to 1.2 GHz (5–1218 MHz), the band is wider, so tilt matters more at the top of the spectrum.
Where nodes sit close to the taps and the signal is split many times, there is too little cable to absorb that up-tilt. Taps near the start of a run, typically the high-value taps, then deliver an excessively up-tilted signal to subscriber drops.
How an inverse EQ plug-in helps
A forward inverse equalizer adds more loss at high frequencies than at low frequencies on the tap ports, with only a minimal effect on reverse tap loss. The YLA spec sheet recommends it for tap locations with high forward RF levels and significant up-tilt, typically the taps closest to nodes and amplifiers. Fitting IEQ plug-ins at those taps brings the port tilt down without adding separate equalizer components to the run.
Where the operator applies them
According to UGRID, the operator mainly fitted 3 dB IEQ plug-ins to the high-value taps 8T23, 4T23 and 8T17 (not 4T11, which was already down-tilted), in networks with short node-to-tap distances and many splits.
YLA series specifications (from the UGRID spec sheet)
- Models: YLA-2T (2 outputs), YLA-4T (4 outputs) and YLA-8T (8 outputs) taps for DOCSIS 3.1 / OFDM, 5–1218 MHz, IP68, up to 6 kV surge protection, AC/RF bypass switch, 10 A power passing.
- Nominal tap loss: 8T23 23 dB, 4T23 23 dB, 8T17 17.5 dB, 4T11 11.5 dB (tolerance ±1.0 dB at 5–862 MHz, ±1.2 dB at 863–1218 MHz).
- Maximum insertion loss (5–65 / 471–600 / 863–1002 / 1003–1218 MHz): 8T23 1.1 / 1.4 / 1.8 / 2.2 dB; 4T23 0.8 / 1.2 / 1.6 / 2.0 dB; 8T17 2.0 / 2.2 / 3.2 / 3.5 dB; 4T11 3.6 / 4.8 / 4.9 / 5.3 dB.
- Inverse EQ plug-ins (1.2 GHz, TCS series): 3, 6 and 9 dB. The 3 dB IEQ adds 0.1 dB at 85 MHz, 1.2 dB at 550 MHz, 2.3 dB at 1000 MHz and 3.2 dB at 1218 MHz (slope −3.1 dB, 5–1218 MHz). Forward EQ plug-ins (TEQ series) are also available for taps near the end of the line.
Before & after: illustrative example
Illustrative calculation based on spec-sheet values, not field measurements from the operator.
Assumptions: node output 40 dBmV at 85 MHz rising linearly to 52 dBmV at 1218 MHz (12 dB up-tilt); CommScope P3 500 JCA hardline (spec 5302002) with 0.68 / 1.82 / 2.52 / 2.84 dB per 100 ft at 85 / 550 / 1000 / 1218 MHz; spans of 150, 100, 100 and 100 ft before each tap; nominal tap loss and maximum insertion loss from the YLA sheet. “Standard” = no EQ. “With IEQ” = 3 dB IEQ on 8T23, 4T23 and 8T17. Connector, temperature and other passive losses are ignored.
| Tap | Cable before (ft) | Standard 85 MHz (dBmV) | Standard 1218 MHz (dBmV) | Standard tilt (dB) | With IEQ 85 MHz (dBmV) | With IEQ 1218 MHz (dBmV) | With IEQ tilt (dB) |
|---|---|---|---|---|---|---|---|
| 8T23 | 150 | 16.0 | 24.7 | 8.8 | 15.9 | 21.5 | 5.7 |
| 4T23 | 100 | 14.1 | 19.7 | 5.6 | 14.0 | 16.5 | 2.5 |
| 8T17 | 100 | 18.0 | 20.4 | 2.3 | 17.9 | 17.2 | −0.8 |
| 4T11 | 100 | 21.5 | 20.0 | −1.5 | 21.5 | 20.0 | −1.5 |
In this example, the 3 dB IEQ cuts port tilt from +8.8 to +5.7 dB at 8T23, from +5.6 to +2.5 dB at 4T23 and from +2.3 to −0.8 dB at 8T17. At the last tap (4T11), the cable has already absorbed the up-tilt and the port is slightly down-tilted (−1.5 dB); a 3 dB IEQ there would increase the tilt to −4.6 dB, so 4T11 is shown without EQ. In a real network, whether a given tap needs IEQ depends on the tilt measured at that location.
Illustrative calculation based on spec-sheet values, not field measurements from the operator.
YLA series availability
YLA series taps and IEQ plug-ins are different from the standard BCV series taps listed in our online store and are not currently available online. To ask about YLA availability, tap values, plug-ins or a project, email info@ugridnet.com or request a quote.