VHF/UHF Multi-SDR Setup - One Antenna for Many Frequencies

After the Flightradar ADS-B setup one thing was clear: RTL-SDR is a blast and I want to receive more. Air band, ACARS, NOAA weather satellites, marine VHF, ISM band - all in the VHF/UHF range between 100 MHz and 500 MHz. A discone antenna can do all of it, but with a single dongle I can only ever listen to one frequency at a time. So I'm planning to grab an LNA, a 4-way splitter and four RTL-SDR sticks.

What I want to receive

• Air band (118-137 MHz) - pilots talking to the tower
• ACARS (131.550 MHz) - aircraft automatically sending weather and status messages
• NOAA (137 MHz) - receive weather satellite images live
• Marine VHF (156-162 MHz) - ship communication
• ISM band (433 MHz) - IoT, weather stations, garage doors

All in the VHF/UHF range, perfect for a discone antenna. ADS-B (1090 MHz) stays separate on the dedicated setup described in the Flightradar post.

Why not just one dongle

A single RTL-SDR can only receive ~3 MHz of bandwidth at a time. I can listen to either air band OR NOAA OR marine VHF, but not all in parallel. Software multiplexing (one dongle, several programs) doesn't work either when the frequencies are too far apart.

The plan: Multi-SDR with a splitter

A discone antenna receives 25-1300 MHz, so all of my frequencies. The signal runs through an LNA (Low Noise Amplifier) for +20 dB of gain, then into a 4-way splitter (-8 dB loss), and from there to four RTL-SDR dongles. Each dongle can then independently receive a different frequency.

Signal flow:

Discone (25-1300 MHz)
  |
LaNA (+20 dB)
  |
4-fach Splitter (-8 dB)
  |-> RTL-SDR #1 (Flugfunk)
  |-> RTL-SDR #2 (ACARS)
  |-> RTL-SDR #3 (NOAA)
  |-> RTL-SDR #4 (Marine VHF / ISM)

Net: +12 dB gain. The LNA compensates for the splitter loss and still gives some extra power for weak satellite signals.

Hardware list

Antenna:

• Albrecht SE 900 Discone - €88
  • 25-1300 MHz reception
  • 66 cm tall, 80 cm diameter
  • Transmit-capable 200W (in case of amateur radio later)

LNA (amplifier):

• Nooelec LaNA - €38
  • 20 MHz - 4 GHz broadband
  • ~20 dB gain
  • USB-powered

Splitter:

• Axing BVS 4-01 - €17
  • 5-1800 MHz
  • 4-way splitter
  • Optimized for FM/DAB+/DVB-T

SDR receivers:

• 4× RTL-SDR Blog V3 - ~€140
  • 100 kHz - 1.75 GHz
  • TCXO (stable frequency)
  • Bias-Tee built in

Cables & adapters: ~€20-30

Total: ~€303

Why LaNA + splitter instead of four antennas

Four separate antennas (one per frequency) would be cheaper on antenna price alone, but:

• Space: four antennas on the roof is impractical
• Mounting: pulling four cables through the roof is a pain
• Flexibility: with a splitter I can repurpose the dongles (NOAA today, DAB+ tomorrow)

The LNA makes the setup more expensive (+€38), but without it weak satellite signals (NOAA) would drown in the noise. The 8 dB of splitter loss is too much for signals that are already weak.

What I want to do with it

Automatic receivers:

• NOAA: noaa-apt will automatically decode satellite images when the satellite passes overhead
• ACARS: acarsdec logs aircraft messages into InfluxDB
• AIS (marine): maybe, if marine VHF comes in well enough

Manual:

• Air band: listen in live with SDR++ or GQRX
• ISM band: reverse-engineer IoT devices with rtl_433

All four dongles will run in parallel on the server, each writing into InfluxDB, and everything ends up in Grafana.

Realism

This is a broadband setup. A discone is good for many frequencies, but not optimal for any single one. For the best NOAA reception a dedicated V-dipole would be better. For marine VHF a 1/4-wave vertical antenna. But I want to stay flexible and not bolt five antennas onto the roof.

The hardware will be ordered and mounted over the next few weeks. Then there'll be an update on how well it actually works.

Tech stack: RTL-SDR, Nooelec LaNA, Axing BVS, Python, InfluxDB, Grafana, Ansible