RF Specifications

RF Input Parameters

Parameter	Value
IF frequency range	950 — 2150 MHz
Symbol rate	256 Ksps — 30 Msps
Input connector	IEC F-type female

The IF frequency is the intermediate frequency after LNB downconversion. The host computes it as (RF_freq - LO_freq) * multiplier and sends it in the TUNE_8PSK command payload.

LNB Power Supply

Parameter	Value
LNB voltage (standard)	13V / 18V
LNB voltage (boosted)	14V / 19V (with USE_EXTRA_VOLT)
Maximum continuous current	450 mA
Maximum burst current	750 mA

LNB voltage is controlled via GPIO P0.4 on all firmware versions. The voltage selection determines the polarization:

wValue	Voltage	GPIO P0.4	Polarization
0	13V	LOW	Vertical / Circular-Right
1	18V	HIGH	Horizontal / Circular-Left

The USE_EXTRA_VOLT command (0x94) enables a +1V boost for long cable runs by toggling bit 3 of the LNB control register at XRAM 0xE0B6 (0x62 = normal, 0x6A = boosted). See Vendor Commands for the command interface.

Switch Control

The SkyWalker-1 supports multiple satellite switching protocols:

Protocol	Implementation	Command
22 kHz tone	GPIO P0.3 gates external oscillator	SET_22KHZ_TONE (0x8C)
Tone Burst (mini DiSEqC)	Timer2-based carrier gating	SEND_DISEQC_COMMAND (0x8D)
DiSEqC 1.0	Timer2 Manchester encoding	SEND_DISEQC_COMMAND (0x8D)
DiSEqC 1.2	Timer2 Manchester encoding	SEND_DISEQC_COMMAND (0x8D)
Legacy Dish Network	7-bit serial bit-bang on P0.4	SET_DN_SWITCH (0x8F)

22 kHz Tone

The 22 kHz tone signal is generated by an external oscillator on the PCB, gated by GPIO P0.3. The firmware does not generate the 22 kHz carrier directly — it only enables or disables the oscillator output.

wValue	State	GPIO P0.3	Band Selection
0	OFF	LOW	Low band (9.75 GHz LO on universal LNB)
1	ON	HIGH	High band (10.6 GHz LO on universal LNB)

Signal Path

Satellite
   |
   v
[ LNB on Dish ]  <-- 13V/18V + 22kHz from SkyWalker-1
   |
   | Coax (950-2150 MHz IF)
   v
[ SkyWalker-1 F-connector ]
   |
   v
[ BCM4500 Demodulator ] -- demod + FEC decode
   |
   | 8-bit parallel MPEG-2 TS
   v
[ FX2 GPIF Engine ] -- zero-copy DMA to EP2
   |
   | USB 2.0 High-Speed Bulk
   v
[ Host PC ]

The USB/GPIF data path has substantial headroom over the satellite link throughput:

Metric	Value
USB 2.0 HS bulk (practical)	~280 Mbps (~35 MB/s)
GPIF engine (theoretical)	48 MHz x 8 bits = 384 Mbps
Typical DVB-S TS rate	1—5 MB/s
Maximum symbol rate (30 Msps)	~58 Mbps

The bottleneck for all supported modulation modes is the satellite link, not the USB data path.