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Multi-Dongle & Wideband SDR Setup for GopherTrunk
GopherTrunk can drive a whole pool of SDRs at once — locally over USB or remotely over rtl_tcp and SoapySDR — and it can channelize several control channels from a single wideband Airspy capture. That means one instance can cover multiple sites, split control and voice across dongles, or feed many decoders from one wideband front end.
Key takeaways Pool of dongles: assign each RTL-SDR a unique serial and a role (control / voice / wideband). Wideband path: one Airspy channelizes several control channels from one ~10 MHz capture. Remotes: mount SDRs over rtl_tcp or SoapySDR from another host. Power: use a powered USB hub. Watch overload on shared captures. SDRplay/Lime/USRP are network-only via SoapyRemote.
Two ways to cover more than one channel
There are two distinct strategies, and many builds combine them:
- A pool of narrow dongles. Each RTL-SDR tunes its own frequency. Perfect when a system’s sites or control channels are spread far across a band — assign a dongle per site, or one dongle to the control channel and another to follow voice.
- One wideband receiver, channelized. A single Airspy grabs up to ~10 MHz in one capture and GopherTrunk channelizes it — extracting several control channels from that one stream in software. Ideal when the channels you want fall inside one wideband window.
| Approach | Best when | Hardware |
|---|---|---|
| Dongle pool | Sites/channels spread across a band | Several RTL-SDRs + powered hub |
| Wideband channelize | Channels within ~10 MHz | One Airspy R2 |
| Hybrid | Big multi-site systems | Airspy wideband + dongles for the outliers |
Serials and roles
The first practical step with multiple dongles is making them addressable.
Set unique serials first. Fresh RTL-SDRs often share the same default serial, so the OS enumerates them in an unpredictable order. Use
rtl_eepromto give each a unique serial (e.g.00000001,00000002), then refer to each dongle by serial in GopherTrunk. Now “the control dongle” is always the same physical stick.
With serials set, you assign roles: which dongle tracks a control channel, which follows voice grants, which does wideband capture. GopherTrunk coordinates the pool so grants read on the control dongle are followed on a voice dongle without missing calls.
Remote SDRs over the network
Dongles do not have to hang off the same machine. Run rtl_tcp or a SoapySDR server on another host — commonly a Raspberry Pi at the antenna — and point GopherTrunk at it over your LAN. You can freely mix local USB dongles and remote network sources in one pool, keeping the noisy USB and the long coax runs out at the antenna while the decoder runs wherever is convenient.
SDRplay, LimeSDR, USRP, bladeRF, and PlutoSDR are network-only. GopherTrunk speaks pure-Go USB directly to the RTL-SDR family, HackRF, and Airspy. Everything else is mounted through SoapySDR/SoapyRemote or rtl_tcp as a network device — plan on running a Soapy server for those.
Power, hubs, and heat
Several dongles are a real electrical and thermal load:
- Use a powered (active) USB hub. Multiple RTL-SDRs draw more current than an unpowered hub — or a bare Raspberry Pi — can safely source. A good powered hub gives each dongle clean, stable power.
- Space them out. Dongles run warm and can couple noise into each other when stacked. A hub with spacing, or short USB extensions, keeps them cool and quiet.
- Mind total current. Add a bias-tee-powered LNA and the draw grows again — size the supply accordingly.
Overload on shared captures
The catch with wideband and shared-antenna setups is front-end overload, and it bites harder here than with a single dongle:
A strong local signal poisons every channel in a shared capture. When you split one antenna across dongles, or channelize many signals out of one wideband Airspy stream, an overloading broadcast FM, pager, or AM transmitter degrades all of them at once. Put a broadcast notch or bandpass filter ahead of the split, keep gain conservative on wideband captures, and check the noise floor before blaming the decoder.
Bottom line
GopherTrunk scales from one dongle to a coordinated pool — by serial and role, over USB or rtl_tcp/SoapySDR — and can channelize a wideband Airspy to cover several control channels from one capture. Set unique serials, feed the dongles from a powered hub, keep SDRplay/Lime/USRP in mind as network-only devices, and filter strong locals before any split. Plan the whole system in best SDR for P25 trunking and wire it up from the hardware guide.
Frequently asked questions
Can GopherTrunk use more than one SDR at once?
Yes. GopherTrunk can drive a pool of SDRs simultaneously — locally over USB or remotely over rtl_tcp and SoapySDR — and assign each a role such as control-channel tracking, voice following, or wideband capture. That lets one instance cover multiple sites or split control and voice across dongles.
How do I tell multiple identical dongles apart?
Give each RTL-SDR a unique serial number with rtl_eeprom, then reference dongles by serial in GopherTrunk’s configuration. Without unique serials the operating system can enumerate identical dongles in an unpredictable order, so setting serials is the first step in any multi-dongle build.
Can one wideband Airspy replace several dongles?
Often, yes. A wideband Airspy captures up to ~10 MHz at once, and GopherTrunk can channelize several control channels from that single capture in software. If a system’s control channels fall within one Airspy’s bandwidth, one wideband receiver can do the work of several narrow dongles.
Do I need a powered USB hub for multiple SDRs?
Yes. Several RTL-SDRs draw more current than an unpowered hub or a Raspberry Pi can supply, and they run warm. A quality powered (active) USB hub gives each dongle stable power and keeps them physically spaced so they run cooler and interfere less.
Can GopherTrunk use SDRplay, LimeSDR, or a USRP in a pool?
Only over the network. SDRplay RSP, LimeSDR, USRP, bladeRF, and PlutoSDR are supported through SoapySDR/SoapyRemote or rtl_tcp, not as direct pure-Go USB devices. RTL-SDR, HackRF, and Airspy are the direct-USB devices; everything else is mounted as a network source.
Does sharing one antenna across dongles cause problems?
It can. Splitting one antenna into several dongles adds loss and, more importantly, a strong signal in a shared wideband capture can overload the front end for every channel you extract from it. Filter strong local signals ahead of the split and watch gain on shared captures.
Can I run SDRs on another machine?
Yes. Run rtl_tcp or a SoapySDR server on a remote host — say a Raspberry Pi at the antenna — and point GopherTrunk at it over the network. You can mix local USB dongles and remote network sources in the same pool.