⬡ REPAIR & TECHNICAL GUIDES

5G C-BAND INTERFERENCE

Since late 2021, carriers have been deploying 5G services in the 3.7–3.98 GHz C-band spectrum they purchased at FCC auction. This overlaps directly with C-band satellite downlink (3.7–4.2 GHz). The result: if you're within range of a 5G tower, your C-band reception will degrade or disappear entirely. This is now the most common C-band service call on the Gulf Coast.

HOW TO DIAGNOSE 5G INTERFERENCE

• 01Symptom pattern: C-band signals that were fine for years suddenly pixelate, drop lock, or disappear. Ku-band still works fine. Symptoms may be worse during business hours when 5G traffic is higher, or after a new tower goes online nearby.
• 02Check tower locations: Use CellMapper.net or the Antenna Search tool (antennasearch.com) to find 5G towers near your install address. If there's a mid-band 5G tower within 2 miles, it's almost certainly the cause.
• 03Confirm with a spectrum analyzer or SDR: If you have an RTL-SDR or similar, tune to 3.7–3.98 GHz and look for 5G NR signals. You'll see them clearly if present. Not required — if you're in a 5G coverage area and C-band is broken, just install the filter.

THE FIX — 5G BAND PASS FILTER (BPF)

A C-band 5G band pass filter passes the 3.7–4.2 GHz satellite downlink frequencies while rejecting the 3.7–3.98 GHz 5G uplink interference. Install it between the feedhorn/LNB output and the first coax run — outside, at the dish. Installing it at the receiver end does nothing.

• 01Power down everything. Disconnect the coax at the LNB output.
• 02Install the BPF inline between the LNB output port and the coax. Most filters use standard F-connectors. Make sure it's oriented correctly — they have an IN and OUT marked.
• 03Weatherproof the connections with self-amalgamating tape. The filter will live outside in Gulf Coast humidity — protect every connector.
• 04Power up and test. Signal should return. If it improves but isn't fully clean, you may be in a high-interference zone requiring the commercial-grade Xtreme Microwave filter.

RECOMMENDED FILTERS

ALGA 5G Blue for most installs. Xtreme Microwave XMW BPF-4100 for commercial or high-interference environments. Both are stocked by Rick Caylor at rickssatelliteusa.com. See our STORE page for Amazon links.

FEED HORN SETUP & ALIGNMENT

The feed horn collects signal reflected from the dish and guides it into the LNB. For prime-focus C-band dishes, a scalar ring feed horn must be matched to the dish's f/D ratio. For offset Ku-band dishes, the LNBF mounts directly in the feed arm — no scalar ring needed.

UNDERSTANDING f/D RATIO

f/D is the focal length divided by the dish diameter. A dish with a 10ft diameter and 4.2ft focal length has f/D = 0.42. This number determines how wide or narrow the beam from the feed horn needs to be. Wrong f/D = the horn illuminates too much or too little of the dish surface = lost gain.

FEED HORN FOCUS ADJUSTMENT

The feedhorn must sit exactly at the dish's focal point — too close or too far and you lose gain. On most C-band mounts this is adjusted by sliding the feed support arm in or out.

• 01Connect signal meter to the LNB output. Lock onto a strong C-band satellite.
• 02Loosen the feedhorn clamp on the support arm. Slide the feedhorn toward the dish approximately 1 inch.
• 03Note signal level. Slide back to original position. Note signal. Slide away from dish 1 inch. Note signal.
• 04Move toward the highest reading position in smaller increments (0.5 inch, then 0.25 inch) until signal peaks. Lock the clamp.
• 05Adjust scalar rings (if adjustable) for peak signal. Spread rings apart for deeper dishes, closer together for shallower.

POLARITY ADJUSTMENT

C-band LNBs receive either horizontal or vertical polarization by switching the LNB probe orientation. Most modern LNBs do this electronically via 13V/18V switching. Older systems use a servo motor (polarotor) to physically rotate the probe. If you're getting one polarity but not the other, check:

• AElectronic LNB: Check receiver is outputting correct voltage (13V = vertical, 18V = horizontal). Measure at the LNB port with a multimeter if in doubt.
• BServo polarotor: Check the 3-wire control cable from receiver/controller to polarotor. Middle wire is 5V control, outer two are +5V and ground. Polarotor may need skew adjustment — rotate housing until signals on both polarities peak.

DiSEqC WIRING DIAGRAMS

DiSEqC (Digital Satellite Equipment Control) lets your receiver control LNBFs, switches, and motors over the same coax cable that carries the IF signal. Version 1.0 handles switches (A/B/C/D selection). Version 1.2 adds positioner/motor control. USALS (also called DiSEqC 1.3) adds automatic positioning by site coordinates.

SINGLE DISH — SINGLE RECEIVER

  [Ku LNBF]
      |
      | RG-6
      |
  [FTA Receiver]

  Receiver controls polarity (H/V) via 13V/18V on the coax.
  Receiver controls high/low band via 22kHz tone burst.
  No switch needed.
  

TWO DISHES — ONE RECEIVER (DiSEqC 1.0 SWITCH)

  [C-Band LNB]          [Ku LNBF]
        \                    /
    Port A \              / Port B
            \            /
         [DiSEqC 1.0 Switch]
                  |
                  | RG-6
                  |
           [FTA Receiver]

  Receiver sends DiSEqC 1.0 command to switch between Port A (C-band)
  and Port B (Ku). Power passes through selected port to power the LNB.
  Important: only ONE LNB is powered at a time through the switch.
  

FOUR LNBFS — ONE RECEIVER (4-PORT DiSEqC SWITCH)

  [LNBF 1] [LNBF 2] [LNBF 3] [LNBF 4]
     |        |        |        |
    A|       B|       C|       D|
     +--------+--------+--------+
              |
        [4-Port DiSEqC 1.0 Switch]
              |
              | RG-6 to receiver
              |
        [FTA Receiver]

  Receiver selects port A/B/C/D via DiSEqC 1.0 tone burst commands.
  Get a switch with 25dB+ isolation — cheap switches let ports bleed
  into each other causing polarity confusion and signal loss.
  

MOTORIZED SYSTEM — DiSEqC 1.2 / USALS

  [Ku LNBF]
      |
      | RG-6
      |
  [H-to-H Motor (DM2800)]  ←── DiSEqC 1.2 commands from receiver
      |
      | RG-6
      |
  [FTA Receiver]  ←── Enter site lat/lon for USALS auto-positioning

  Motor passes IF signal through + receives DiSEqC control commands
  on the same coax. No separate controller cable needed.
  USALS: receiver calculates motor position automatically from
  entered site coordinates and selected satellite longitude.
  

LARGE DISH — LINEAR ACTUATOR SYSTEM

  [C-Band LNB + Feed Horn]
              |
              | RG-6 (IF signal only)
              |
        [FTA Receiver]

  Separate control wiring:

  [Receiver DiSEqC output]  →  [PR1200 Controller]  →  [Linear Actuator]
                                      ↑
                              36V DC motor power
                              Reed switch position sensing
                              East/West limit switches

  The actuator control runs on SEPARATE cable (3-5 wire, 18AWG min)
  from the IF coax. Do NOT run control wire bundled with coax —
  interference causes phantom position counts and erratic movement.
  

COMMON DiSEqC WIRING MISTAKES

FTA RECEIVER SETUP

Setting up a new FTA receiver for the first time. This guide covers the Enigma2-based receivers (Octagon SF8008, Amiko, etc.) which are the current community standard for serious FTA use on the Gulf Coast.

FIRST BOOT — CRITICAL SETTINGS

• 01Load North American satellite list first. Enigma2 boxes ship with European channel lists. Connect to your network, go to Settings → System → Software Management and find a North American satellite/transponder list update, OR manually delete all European transponders and enter NA satellites. The Amiko boxes ship pre-configured for NA — use one as a reference.
• 02Set LNB type correctly. For C-band: LNB type = Universal, LO freq = 5150 MHz (for Norsat 5150F). For Ku universal LNBF: LNB type = Universal, Low LO = 9750 MHz, High LO = 10600 MHz, threshold = 11700 MHz.
• 03Set DiSEqC port. If using a switch, set the correct DiSEqC port for each satellite (A, B, C, or D). If using a motor, set DiSEqC to 1.2 or USALS and enter your site coordinates.
• 04Set voltage: 13V for vertical polarity, 18V for horizontal. If your LNB has a single output (not dual), leave this on Auto.

BLIND SCAN PROCEDURE

Blind scan is how you find all currently active transponders on a satellite without a pre-programmed list. Essential for catching wildfeeds and backhauls that aren't in any database.

• 01Point dish at target satellite and confirm signal lock on at least one known transponder.
• 02In the receiver menu, select Scan → Blind Scan (or Manual Scan → Blind). Set frequency range: 3700–4200 MHz for C-band, 10700–12750 MHz for Ku.
• 03Select both polarities (H and V) and all symbol rates. Start scan. This takes 5–15 minutes per satellite.
• 04Review results. Channels marked with a lock icon are encrypted. Unmarked channels are FTA. Look for unexpected feeds and backhauls — anything with an unusual transponder ID or generic name.

COMMON RECEIVER PROBLEMS

SATELLITE POINTING — AZ/EL BY LOCATION

To point a fixed dish at a specific geostationary satellite, you need the correct azimuth (compass bearing) and elevation (vertical angle above horizon) for your specific location. The table below covers common FTA satellites visible from the Gulf Coast. Use the calculator for a custom location.

AZ/EL CALCULATOR

GULF COAST REFERENCE TABLE — PENSACOLA (30.4°N, 86.9°W)

REFERENCES

Lyngsat — North American satellite charts
SatBeams — Satellite footprints and coverage maps
SatelliteGuys.US — FTA community forum
Rick's Satellite USA — Equipment and technical resources