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Satellite LNB Calculator

Calculate satellite LNB Intermediate Frequency (IF), Local Oscillator (LO) offset, 22 kHz tone state, and DVB-S2 tuner ranges locally in your browser.

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Coaxial RG-6 cable cannot carry raw 4 GHz C-Band or 12 GHz Ku-Band microwave signals from a satellite dish down to an indoor receiver without massive signal attenuation. An LNB (Low-Noise Block downconverter) mixes the satellite downlink frequency with a Local Oscillator (LO) to shift the signal into the L-Band Intermediate Frequency (950–2150 MHz). This local satellite LNB calculator computes exact IF tuner frequencies, high/low band 22 kHz tone switching, C-Band spectral inversion (LO - RF vs RF - LO), and reverse IF-to-Downlink lookups in real time.

When broadcast engineers, VSAT technicians, and DXers need exact L-Band math

Whether you are aligning a dish with a spectrum analyzer, configuring a headend IRD (Integrated Receiver Decoder), troubleshooting a multi-switch distribution rack, or setting up a custom SDR (RTL-SDR / HackRF) receiver, you constantly translate between satellite RF Downlink Frequency (MHz / GHz) and coax L-Band Intermediate Frequency (IF):

  • Checking whether a transponder falls inside standard DVB-S/S2 tuner limits (950–2150 MHz): Verifying if a newly launched Ku-Band or Ka-Band transponder can be received with an existing 9750 / 10600 MHz Universal LNB or requires a dedicated PLL LNB with a custom Local Oscillator (10000, 10750, 11300 MHz).
  • Diagnosing 22 kHz continuous tone switching issues on Universal Ku-Band LNBs: Seeing whether a transponder lies below or above the 11700 MHz crossover threshold and what happens to the IF frequency if a 22 kHz tone generator is stuck ON or OFF.
  • Identifying C-Band high-side injection (5150 MHz - Downlink) vs Ku-Band low-side injection (Downlink - LO): Avoiding off-by-one transponder tuning mistakes on C-Band (3400–4200 MHz) where lower RF downlink frequencies map to higher L-Band IF numbers!
  • Reverse calculation (IF → Satellite Downlink): Looking at a peak at 1420 MHz on an L-Band spectrum analyzer and calculating which exact satellite transponder (MHz) produced that spike.

How to calculate satellite LNB frequencies step by step

Method 1: Forward Downconversion (Satellite RF Downlink → L-Band IF)

  1. Select an LNB hardware preset or Custom LO: Choose Universal Ku-Band (9750 / 10600 MHz), Standard C-Band (5150 MHz), Dual/Extended C-Band (5150 / 5750 MHz), North America DBS Circular (11250 / 10750 MHz), Ka-Band, or type a custom Local Oscillator (LO) frequency in MHz.
  2. Enter the satellite transponder Downlink Frequency: With Forward (RF → IF) mode active, type the published satellite transponder frequency in MHz (for example, 12522 MHz for Ku-Band or 3840 MHz for C-Band).
  3. Set Polarization (13V / 18V) and Symbol Rate: Pick Vertical/RHCP (13V DC) or Horizontal/LHCP (18V DC) and optionally enter the transponder Symbol Rate (MS/s) to calculate occupied passband edges.
  4. Verify tuner compatibility and tone state: Read the exact L-Band IF Frequency (MHz), Active LO, 22 kHz Tone State (ON above 11700 MHz / OFF below), Spectral Inversion flag (High-Side LO - RF vs Low-Side RF - LO), and whether the signal falls inside the standard 950–2150 MHz DVB-S2 tuner window.

Method 2: Reverse Spectrum Analyzer Lookup (Coax L-Band IF → Satellite RF Downlink)

  1. Switch to Reverse (IF → RF) calculation mode: Toggle the direction switch to IF → Downlink when you are looking at an unknown carrier spike on an L-Band spectrum analyzer or SDR waterfall.
  2. Select the active LNB and 22 kHz tone state: Pick the LNB mounted on the dish and specify whether the headend multi-switch or receiver currently has the 22 kHz tone ON (10600 MHz High-Band LO) or OFF (9750 MHz Low-Band LO).
  3. Enter the measured L-Band IF peak: Type the coax frequency read off your meter (e.g., 1420 MHz) to immediately resolve the exact satellite RF Downlink Frequency (MHz) in orbit.

The core formulas behind C-Band, Ku-Band, and Ka-Band downconversion

1. Low-Side Injection (Downlink > LO, used in Ku-Band & Ka-Band)

When the Local Oscillator frequency (f_LO) is lower than the satellite RF downlink frequency (f_RF), the mixer subtracts the LO from the RF signal: $f_{\text{IF}} = f_{\text{RF}} - f_{\text{LO}}$

  • Universal Ku-Band Low Band (10700–11700 MHz):
  • 22 kHz Tone = OFF (0 kHz)
  • f_LO = 9750 MHz
  • Resulting IF range: 10700 - 9750 = 950 MHz up to 11700 - 9750 = 1950 MHz.
  • Universal Ku-Band High Band (11700–12750 MHz):
  • 22 kHz Tone = ON (22 kHz continuous wave superimposed on 13V/18V DC)
  • f_LO = 10600 MHz
  • Resulting IF range: 11700 - 10600 = 1100 MHz up to 12750 - 10600 = 2150 MHz.

2. High-Side Injection (LO > Downlink, used in Standard 5150 MHz C-Band)

In C-Band (3400–4200 MHz), if an LNB used a low-side oscillator (say 2450 MHz), the second harmonic (2 × 2450 = 4900 MHz) and image frequencies would cause severe interference inside the passband. Instead, standard C-Band LNBs place the Local Oscillator above the downlink band at 5150 MHz: $f_{\text{IF}} = f_{\text{LO}} - f_{\text{RF}} = 5150 - f_{\text{RF}}$

  • Notice the spectral inversion: a lower C-Band transponder (3700 MHz) outputs a higher IF (5150 - 3700 = 1450 MHz), while a higher C-Band transponder (4180 MHz) outputs a lower IF (5150 - 4180 = 970 MHz).

Two worked examples with verified frequency arithmetic

Example A: Ku-Band High-Band transponder at 12,522 MHz (SR 27500)

Suppose you are tuning a DTH / broadcast transponder at 12522 MHz Vertical (SR 27.5 MS/s) using a standard Universal Ku-Band LNB (9750 / 10600 MHz):

  1. Band Check: Because 12522 MHz ≥ 11700 MHz, the transponder sits in Ku High Band.
  2. Control Signals: Receiver sends 13V DC (Vertical polarization) + 22 kHz Tone ON (High Band select), activating the 10600 MHz Local Oscillator.
  3. Center IF Calculation: f_IF = 12522 MHz - 10600 MHz = 1922 MHz.
  4. Tuner Range Check: 1922 MHz sits comfortably inside the standard 950–2150 MHz DVB-S2 L-Band tuner window (with 228 MHz of headroom to the 2150 MHz upper edge).

Example B: C-Band transponder at 3,840 MHz Horizontal on a 5150 MHz LNB

  1. Control Signals: Receiver sends 18V DC (Horizontal polarization), 22 kHz Tone OFF, using f_LO = 5150 MHz.
  2. Center IF Calculation (High-Side Injection): f_IF = 5150 MHz - 3840 MHz = 1310 MHz (Spectrum Inverted).
  3. Tuner Range Check: 1310 MHz is right in the middle of the 950–2150 MHz coax passband.

Practical field tips and common pitfalls

  • The 11550–11700 MHz Universal Ku-Band overlap zone: Because Low Band (LO 9750) covers up to 11700 + 200 = 11900 MHz (IF 2150 MHz) and High Band (LO 10600) starts at 10600 + 950 = 11550 MHz (IF 950 MHz), transponders between 11550 MHz and 11900 MHz can actually produce a valid 950–2150 MHz IF on both oscillators! Always verify whether your headend receiver has the 22 kHz tone enabled or disabled when reading an IF spectrum chart in that overlap window.
  • 5G C-Band interference filters (3700–4200 MHz): In regions where terrestrial 5G base stations transmit between 3400–3800 MHz, a standard 5150 MHz C-Band LNB without a bandpass waveguide filter will saturate even if you are tuning a 4000 MHz transponder.

Privacy and 100% offline-ready local execution

Field technicians often work on rooftops, remote earth stations, or OB vans with spotty cell coverage. This calculator runs 100% locally in your browser's JavaScript engine with zero external API or network calls - once loaded, it calculates everything offline on your phone or laptop.

Related tools

Working on audio baseband signals or acoustic frequencies? Check out the Real-Time Audio Frequency & Spectrum Analyzer. You can also organize transponder frequency tables with CSV Cleaner or format headend configuration files in JSON Formatter. Read our complete engineering guide on how to calculate satellite LNB frequencies.

Frequently Asked Questions

What is the formula to calculate satellite LNB Intermediate Frequency (IF)?

For Ku-Band and Ka-Band (where the downlink frequency is higher than the LNB's Local Oscillator), the formula is IF = Downlink Frequency - LO Frequency. For standard C-Band (5150 MHz LO) (where the Local Oscillator is higher than the 3400–4200 MHz downlink), the formula is IF = LO Frequency (5150) - Downlink Frequency.

Why does a Universal Ku-Band LNB have two Local Oscillator frequencies (9750 and 10600 MHz)?

The full Ku-Band satellite spectrum (10.7 GHz to 12.75 GHz) spans 2,050 MHz of bandwidth, which is too wide to fit into a standard satellite receiver's 1,200 MHz L-Band tuner window (950–2150 MHz) using a single fixed oscillator. Splitting the band at 11,700 MHz between a 9750 MHz Low-Band LO and a 10600 MHz High-Band LO keeps both halves inside 950–2150 MHz.

How does the receiver tell the LNB to switch between Low Band (9750) and High Band (10600)?

The satellite receiver superimposes a continuous 22 kHz tone (~0.6V peak-to-peak) onto the coaxial DC power line. When the 22 kHz tone is OFF, the LNB uses the 9750 MHz oscillator; when the 22 kHz tone is ON (for frequencies ≥ 11700 MHz), the LNB switches to the 10600 MHz oscillator.

How does the LNB switch between Vertical (V) and Horizontal (H) polarization?

Polarization is controlled by the DC voltage level sent up the coaxial cable from the receiver: 13V DC selects Vertical (V) or Right-Hand Circular (RHCP) polarization, while 18V DC selects Horizontal (H) or Left-Hand Circular (LHCP) polarization.

Why are C-Band IF frequencies "upside down" compared to Ku-Band?

Because a standard C-Band LNB uses high-side injection (LO = 5150 MHz, which is above the 3700–4200 MHz signal band), subtracting a larger RF frequency from 5150 yields a smaller IF number (5150 - 4180 = 970 MHz). This causes spectral inversion, which DVB-S/S2 demodulators handle automatically.

What is the standard L-Band IF input range of a DVB-S2 satellite receiver or spectrum analyzer?

Almost all commercial and consumer DVB-S/S2/S2X satellite tuners accept an L-Band input range of 950 MHz to 2150 MHz (with some wideband tuners extending from 250 MHz to 2350 MHz). If a calculated IF falls below 950 MHz or above 2150 MHz, the calculator flags an out-of-band warning.