Satellite block upconverters (BUCs) · L-band IF in, Ku- or Ka-band RF out, local oscillator and 10 MHz reference, saturated and linear output power, gain and flatness, spurious and phase noise, power supply, monitoring and control, and outdoor ratings
A block upconverter (BUC) is an outdoor unit in a satellite earth station's transmit chain. It takes the L-band intermediate frequency (IF) signal arriving over the IF cable, shifts the whole band up to the uplink frequency by mixing it with a local oscillator locked to a 10 MHz reference, and amplifies it into a waveguide output. Ask three things first: which band and sub-band you transmit in, how much linear output power the link needs, and how the unit will be powered, referenced and monitored.
Outdoor block upconverters, including integrated BUCs with built-in power amplifiers, for C-, X-, Ku- and Ka-band satellite uplinks. Low-noise block downconverters, indoor frequency converters and high-power amplifier systems sold alone are outside this page except where compared.
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01
Norsat lists its ATOM 40W Ku-band BUC with an input IF band of 950–1450 MHz, a 13.05 GHz local oscillator and an output band of 14.00–14.50 GHz, with an extended 13.75–14.5 GHz version. It needs a 10 MHz sine-wave external reference at −5 to +5 dBm, with an internal reference available as an option. [1]
Editorial calculation: 950–1450 MHz plus the 13.05 GHz local oscillator gives 14.00–14.50 GHz, the stated output band, so each IF frequency lands 13.05 GHz higher without inverting the band.
Terrasat's Ka-band IBUC 2G has two software-selectable sub-bands, 29.0–30.0 GHz and 30.0–31.0 GHz, with local oscillators at 28.0 and 29.0 GHz and a non-inverting sense. Its 10 MHz external reference, at −12 to +5 dBm, is multiplexed on the transmit IF cable (IFL), and an internal reference is optional. [2]
Give the supplier the band and sub-band, the IF range of your indoor equipment, the reference arrangement (external 10 MHz on the IFL or internal), the required linear output power, the antenna feed interface, the power supply available at the antenna, the monitoring and control interface, and the site temperature, humidity and altitude.
02
BUC ratings quote more than one power figure. Norsat lists at least 47 dBm saturated output (Psat) and at least 46 dBm P1dB for its 40 W Ku-band unit. Terrasat lists typical Psat and minimum linear power (PLin) for each model, from +37 dBm Psat and +34 dBm PLin at 5 W to +47 dBm Psat and +44 dBm PLin at 50 W. It defines PLin as the maximum linear power under MIL-STD-188-164C. [1] [2]
Editorial calculation: 47 dBm is about 50 W, 46 dBm about 40 W, 44 dBm about 25 W and 37 dBm about 5 W. Size the BUC on the linear power your link budget needs, not on the nameplate saturated power.
Terrasat's FAQ says it uses both GaAs and GaN amplifier devices. It credits GaAs amplifiers with better linearity and advantages in multiple-carrier operation, while GaN allows a smaller package and lower power consumption. [3]
03
Norsat lists ≥ 60 dB linear gain, gain flatness of ≤ 2.0 dB p-p over 40 MHz and ≤ 6.0 dB p-p over the full band, in-band and out-of-band spurious of ≤ −55 dBc, and phase noise of −72 dBc/Hz at 1 kHz down to −102 dBc/Hz at 1 MHz. The unit draws up to 305 W at Psat from an 18–56 V DC supply and is rated IP65 for −40 to +60 °C with 100% condensing humidity. [1]
Terrasat lists minimum small-signal gain from 68 dB (5 W) to 78 dB (50 W) on its standard version, with lower-gain WGS-compatible versions. It specifies spurious of −60 dBc at PLin and compliance with ETSI EN 301 428/430 and MIL-STD-188-164C. Power is 48 ± 11 V DC or 100–240 V AC, drawing up to 330/440 W (PLin/Psat) for the DC 50 W model. Monitoring is over Ethernet (HTTP, Telnet, SNMPv2c) or RS-232/485. [2]
04
In the United States, FCC rule 47 CFR 25.218 sets off-axis EIRP density envelopes that fixed FSS earth station applications in the C-, Ku- and Ka-bands must meet to qualify under its paragraph (b), "Routine processing", where θ is the angle from the line to the target satellite. For digital operation in the conventional Ku-band, co-polarized in the plane tangent to the GSO arc, the limit is 15 − 25 log θ dBW/4 kHz for 1.5° ≤ θ ≤ 7°, −6 dBW/4 kHz for 7° < θ ≤ 9.2°, 18 − 25 log θ dBW/4 kHz for 9.2° < θ ≤ 19.1° and −14 dBW/4 kHz beyond. For digital Ka-band operation the tangent-plane envelope is 32.5 − 25 log θ dBW/MHz for 2.0° ≤ θ ≤ 7°. Levels above 7° may be exceeded by up to 3 dB in up to 10% of the angles and by up to 6 dB in the main-reflector spillover region. [4]
The BUC's output power, the antenna gain and pattern, and the carrier bandwidth together set the EIRP density, so the BUC power you buy is bounded by this envelope as well as by the link budget. [4]
Editorial calculation: at θ = 2° the digital Ku-band limit is 15 − 25 × log 2 ≈ 7.5 dBW/4 kHz, and at θ = 3° about 3.1 dBW/4 kHz; at θ = 2° the digital Ka-band limit is 32.5 − 7.5 = 25.0 dBW/MHz. A 40 W (46 dBm, 16 dBW) Ku-band BUC on a high-gain antenna can exceed such a density on a narrow carrier, so check the off-axis pattern with the carrier plan before choosing output power. [4] [1]
Editorial note: ask the supplier for the BUC's output power back-off at your carrier size and confirm with the antenna maker that the combined system meets 25.218 or the rule of your market.
05
This is a functional reference built from the sources cited; it is not one maker's specification.
| Function | Role | Fix in the order |
|---|---|---|
| IF input | Takes the L-band IF over the IF cable. [1] [2] | IF range; connector (N or F). |
| Local oscillator and reference | Fixes the frequency shift; 10 MHz lock. [1] [2] | LO frequency; internal or external reference. |
| Power amplifier | Sets Psat and linear power; GaAs or GaN. [2] [3] | Power class; linearity. |
| RF output | Waveguide to the feed (WR-75 Ku; WR-28 Ka). [1] [2] | Flange type. |
| Monitor and control | RS-232/485; Ethernet with SNMP. [1] [2] | Interface; mute control. |
| Power supply | 18–56 V DC; 48 V DC or 100–240 V AC. [1] [2] | Supply at the antenna. |
06
A BUC quotation needs values for your uplink. The table explains each field, gives published values where a reviewed source states them, and says what to ask the supplier for.
| Field | What it means and published values | Ask the supplier for |
|---|---|---|
| Band | Examples: Ku 14.0–14.5 GHz; Ka 29.0–31.0 GHz. [1] [2] | Sub-band and LO. |
| IF | Examples: 950–1450 MHz; 950–1950 MHz. [1] [2] | Match to the indoor equipment. |
| Output power | Examples: Psat 47 dBm; PLin +44 dBm (50 W). [1] [2] | Linear power at your carriers. |
| Gain | Examples: ≥ 60 dB; 68–78 dB min. [1] [2] | Gain and attenuator range. |
| Spurious | Examples: ≤ −55 dBc; −60 dBc at PLin. [1] [2] | Regulatory compliance. |
| Environment | Examples: −40 to +60 °C; IP65; 100% condensing. [1] [2] | Site conditions. |
07
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Band: [C; X; Ku; Ka; sub-band] IF: [range; connector] Reference: [external 10 MHz on IFL; internal] Power: [linear output needed; carriers] Interface: [waveguide flange] Supply: [DC voltage; AC] M&C: [Ethernet/SNMP; RS-232/485] Site: [temperature; humidity; altitude]
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Product scope checked 2026-10-12
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It shifts the L-band IF up to the uplink band with a local oscillator and amplifies it; Norsat's Ku-band unit turns 950–1450 MHz into 14.0–14.5 GHz with a 13.05 GHz LO. [1]
Psat is saturated output; Terrasat also lists PLin, the maximum linear power under MIL-STD-188-164C, which is about 3 dB lower on its Ka-band models. [2]
Terrasat credits GaAs amplifiers with better linearity and advantages for multi-carrier use, while GaN allows a smaller package and lower power consumption. [3]
Not without limit: in the US, 47 CFR 25.218 caps off-axis EIRP density, for digital Ku-band at 15 − 25 log θ dBW/4 kHz between 1.5° and 7°, so BUC power, antenna pattern and carrier size must be checked together. [4]
Sources checked 2026-10-12. Norsat and Terrasat describe their own BUCs; their figures are examples, not limits. The FCC rule 47 CFR 25.218 sets off-axis EIRP density envelopes for US earth stations.
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