Radio Telescope Mode

The Carryout G2’s firmware includes a built-in radio telescope mode: the azscanwxp command performs an azimuth sweep while cycling through DVB transponders at each position, measuring RSSI (received signal strength) at every grid point. Combined with the Ku-band LNB and motorized AZ/EL positioning, this turns the dish into a rudimentary RF imaging system.

This capability was originally discovered by Chris Davidson in his winegard-sky-scan project.

Hardware requirements

Carryout G2 with firmware 02.02.48 (or compatible)
RS-422 serial connection at 115200 baud (see Cable Wiring)
Motors homed and calibrated (see Calibration & Homing)
TV search disabled (see Disabling TV Search)

Setting up the DVB tuner

Before scanning, enable the LNA and configure the tuner frequency.

Enter the DVB submenu from root.
```
TRK> dvb
DVB>
```
Enable the LNA. The lnbdc odu command enables the LNB low-noise amplifier in outdoor unit mode, setting 13V (V-pol). The boot default is 18V (H-pol).
```
DVB> lnbdc odu
```
Check current channel parameters.
```
DVB> dis
```
This shows the frequency, symbol rate, and LNB polarity currently configured.
Select a transponder (optional). If you want to scan at a specific frequency:
```
DVB> t 1
```
Use freqs to list available transponder frequencies. For ham radio sky mapping, set the DVB tuner to a frequency near your target (e.g., 10 GHz Ku-band downconverted through the LNB to ~1178 MHz IF).
Verify RSSI readings work.
```
DVB> rssi 10
Reads:10  RSSI[avg: 498  cur: 502]
```
The noise floor is approximately 500. If you see readings near this value, the LNA is active but no strong signal is present — this is normal for a clear sky pointing away from any satellites.
Return to the root menu.
```
DVB> q
TRK>
```

The azscanwxp command

Entering the command

The command lives in the MOT submenu:

TRK> mot
MOT> azscanwxp [motor] [span] [resolution] [num_xponders]

Parameters

Parameter	Type	Units	Description
motor	int	—	Motor ID (0=AZ, 1=EL)
span	float	degrees	Total azimuth sweep range
resolution	int	centidegrees (0.01 deg)	Step size per position
num_xponders	int	—	Number of transponders to cycle at each position

Example

Sweep 10 degrees on azimuth at 1.00 degree steps, checking 3 transponders per position:

MOT> azscanwxp 0 10 100 3

Output format

Each measurement point produces a line:

Motor:<id> Angle:<cdeg> RSSI:<adc> Lock:<0/1> SNR:<dB> Scan Delta:<step>

Field	Description
`Motor`	Motor ID being swept
`Angle`	Current position in centidegrees
`RSSI`	Received signal strength (raw ADC count)
`Lock`	DVB carrier lock status (1 = locked, 0 = no lock)
`SNR`	Signal-to-noise ratio in dB
`Scan Delta`	Step count since last position

Sky mapping workflow

Home the motors if not already done.
```
TRK> mot
MOT> h 0
MOT> h 1
```
Position the dish at the starting elevation. Choose an EL angle for the first scan strip.
```
MOT> a 1 30
```

Enable the LNA (if not done already).

MOT> q
TRK> dvb
DVB> lnbdc odu
DVB> q
TRK> mot

Run the azimuth sweep. Log the serial output to a file for post-processing.
```
MOT> azscanwxp 0 360 100 3
```
This sweeps the full 360-degree azimuth range at 1-degree steps with 3 transponders per position.
Increment elevation and repeat. Move up by your desired EL step and run another AZ sweep.
```
MOT> a 1 35
MOT> azscanwxp 0 360 100 3
```
Post-process the data. Parse the serial output into a grid of AZ/EL/RSSI values and render as a 2D heatmap. Each scan line gives you one row of the image.

The azscan command (simpler variant)

The MOT submenu also has a simpler azscan command that doesn’t cycle transponders:

MOT> azscan [az_range] [el_range] [delay]

This performs an AZ sweep with RSSI measurements at each position but without the transponder cycling. It’s faster but provides less frequency diversity.

RSSI and signal interpretation

RSSI Value	Meaning
~233-238	ADC noise floor (no signal, no LNA)
~489-502	LNA active, noise floor (clear sky)
Above 600	Weak signal detected
Above 1000	Strong signal (likely a satellite)

The ADC rssi command (in the ADC submenu) gives raw ADC counts. The DVB rssi <n> command (in the DVB submenu) averages over n samples and provides both average and current readings.

The PEAK submenu’s rssits command alternates between H-pol (18V, even transponders) and V-pol (13V, odd transponders), reporting separate readings for each polarization:

PEAK> rssits
Even_sig = 489, Odd_sig = 235

V-pol (odd) has a quieter noise floor than H-pol (even).

LNB polarity control via DiSEqC

The BCM4515 DVB tuner includes a DiSEqC 2.x controller accessible from the DVB submenu. DiSEqC (Digital Satellite Equipment Control) uses 22 kHz tone bursts on the coax LNB bias line to control LNB polarity and band selection.

For ham radio use, the key commands are:

Command	Function
`lnbdc odu`	Set 13V (V-pol) — enables LNA in outdoor unit mode
`send E0 10 38 F0`	Raw DiSEqC packet: select switch port 1
`send E0 10 38 F1`	Raw DiSEqC packet: select switch port 2

The boot default is 18V (H-pol). Polarity affects which transponders are visible and the RSSI noise floor.

DiSEqC timing parameters

Parameter	Value	Description
`ovraddr`	0x11	Target LNB address (standard first LNB)
`rrto`	210 ms	Receive reply timeout
`pretx`	15 ms	Pre-command TX delay
`tdthresh`	110	Tone detect threshold

Rotctld RSSI extensions

The birdcage serve command adds RSSI support to the rotctld protocol when running with a Carryout G2:

# Read RSSI (10 samples)
echo "R 10" | nc 127.0.0.1 4533

# Enable LNA
echo "L" | nc 127.0.0.1 4533

# Check capabilities
echo "D" | nc 127.0.0.1 4533
# Returns: CAPS:rssi,lna

This allows external software to combine position control with signal measurements over a single TCP connection.

winegard-sky-scan Chris Davidson's original Carryout G2 sky scan and rotator project on GitHub.