SkyBridge Plus — Vol 1: Introduction & Hardware

1.1 About this volume

The BridgeCom SkyBridge Plus is the turnkey commercial DMR hotspot in this lineup — a Raspberry Pi 3B (later Pi 4B) with an MMDVM modem board, in a black case with a 2.4-inch colour screen and a built-in Ethernet port, as BridgeCom and its dealers describe it. BridgeCom originally shipped it with Pi-Star (“Pi-Star, which is the OS running on the SkyBridge Plus”, in BridgeCom’s backup article); BridgeCom’s current reimaging guide installs the WPSD (W0CHP-PiStar-Dash) image built for the SkyBridge MAX and SkyBridge Plus. It earns the bench slot as the set-and-forget DMR hotspot: pre-configured at the factory, sold as a complete unit by a US distributor with US support and warranty, no soldering, no firmware compile, no Pi-flash, no MMDVM-hat sourcing. Power it up on Ethernet (or with a Wi-Fi file on its card), point a browser at the IP address shown on its screen, fill in the BrandMeister and TGIF and W0CHP credentials, and start talking. That is what the SkyBridge product line solves — the time-to-first-QSO penalty of a DIY MMDVM build, in exchange for the appliance premium and a slight lag on the cutting-edge feature flags that the upstream MMDVM and WPSD communities release first.

The contrast that runs through this volume and the next is the duality between this appliance and the DIY WPSD hotspot in Vol 22 (DIY WPSD HotSpot). Both are based on the same upstream open-source stack — a Linux distribution on a Raspberry Pi (a Pi 3B or 4B in the SkyBridge Plus, anything from Zero W through Pi 5 for the DIY) running the Pi-Star lineage — on current images W0CHP’s WPSD fork — of the MMDVMHost / DMRGateway / YSFGateway / NXDNGateway / P25Gateway / DAPNETGateway family of MMDVM-protocol bridge daemons. Both can serve the AnyTone D878UVII PLUS (Vol 8) sitting on the desk; both bridge that radio’s local low-power UHF DMR signal to BrandMeister, TGIF, W0CHP, FCS reflectors, and XLX rooms over the internet. The DIY hotspot (Vol 22) costs roughly USD 50 to build, takes a few hours of assembly and configuration, and provides a Nextion 3.5” touch display, full SSH and Pi-Star-CLI access, and the ability to track WPSD nightly builds. The SkyBridge Plus retails at BridgeCom for around USD 230-280 mid-2026 (TBD — verify against the current bridgecomsystems.com price), comes in a finished black case with its own 2.4-inch colour screen, and runs the image BridgeCom supplies and supports (BridgeCom states that its reimaging image is meant to be used under the instruction of a BridgeCom technical-support representative). Both are owned and run here — the SkyBridge is the home-base hotspot that sits on the shelf next to the desk and stays up for months between reboots, the DIY WPSD is the experiment platform that gets reflashed and reconfigured when an upstream WPSD feature is worth chasing.

Why someone picks the SkyBridge over the DIY: appliance reliability, factory burn-in, US distributor support, no firmware-flash anxiety, no MMDVM-hat sourcing in a market full of clones with varying-quality TCXOs, no enclosure 3D-print or laser-cut, a label on the back, and a serial number that means something to a vendor when something breaks. Why someone picks the DIY WPSD instead: cost (BOM around USD 50 vs USD 230+ retail), customisation freedom, a choice of display, the learning experience of building the stack from a flashed SD card up, and faster access to upstream-WPSD feature flags. Both produce essentially the same on-air experience — the same MMDVM protocol on the air, the same network bridges to BrandMeister and TGIF, the same talkgroup quality on the audio side. The difference is in the support model and the tinker-friendliness, not in what comes out of the speaker on the other end of the link.

Cross-link discipline: the network on the other end of the bridge — what BrandMeister and TGIF and W0CHP actually are, how talkgroups are addressed, what colour codes and slots mean at the protocol layer — is the load-bearing subject of Vol 2 (DMR Network Architecture), and most of what’s in this volume about TG numbers and slot conventions is shorthand for the deep treatment over there. The radio that talks to this hotspot is the AnyTone AT-D878UVII PLUS in Vol 8. The frequency-coordination question — pick a hotspot frequency that doesn’t stomp on the local repeater plan — is in Vol 4 (Frequency Planning & License Envelope) and gets a cross-tool regulatory framing in Antennas Vol 31 (Regulatory & RF Safety). The hotspot-specific antenna case (you actually want a low-gain antenna here, an unusual conclusion) is in Antennas Vol 29 (Use-case Matrix).

1.2 Hardware tour

Which SkyBridge this is. BridgeCom sells more than one SkyBridge. The SkyBridge Plus documented here is, in BridgeCom’s and its dealers’ descriptions, a Raspberry Pi 3B (later Pi 4B) based hotspot with a 2.4-inch colour screen, a built-in Ethernet port and a black case — BridgeCom’s own reimaging guide identifies it as the “SkyBridge Plus (2.4” Screen, Black Case)”. The unit documented here has the 2.4-inch colour screen, confirming it is the Plus. The SkyBridge MAX is a separate model; the two share one WPSD image (labelled “BridgeCom SkyBridge MAX/Plus” on the WPSD download page), but they are different products. Descriptions of a SkyBridge built on a Raspberry Pi Zero W with a 0.96-inch OLED and Wi-Fi-only networking do not match BridgeCom’s published description of the Plus; they may describe the earlier SkyBridge model or a generic hotspot, which could not be confirmed, and they are not used here.

Host computer. BridgeCom’s reimaging guide distinguishes two builds by their USB ports: units with all-black USB ports are Raspberry Pi 3B based and join 2.4 GHz Wi-Fi only; units with two blue USB ports are Raspberry Pi 4B based and support 2.4 and 5 GHz Wi-Fi. Which build the unit documented here is has not yet been recorded (check the USB-port colours). Either build also has wired Ethernet, the more robust connection for an always-on hotspot.

Screen. The front carries the 2.4-inch colour screen. BridgeCom’s factory configuration (the 2021-10-28 default configuration file) drives it as a Nextion display on the modem port (Display=Nextion, [Nextion] Port=modem, ScreenLayout=3 in the MMDVMHost settings). At start-up it shows “Initializing…”; once running, the hotspot’s IP address appears in the upper-left corner of the screen — the address to type into a browser. No BridgeCom screen-layout file (Nextion .tft) has been found published; the settings suggest a stock MMDVMHost layout rather than a vendor-specific file, but this could not be confirmed.

Modem board and antenna connector — open questions. The MMDVM modem board inside the unit (model, single- or dual-port, TCXO) and the antenna connector flavour (SMA-female or RP-SMA) are not yet confirmed for this unit; the inventory record leaves both as TBD, and no manual is on file. Both are checked on the bench before buying a replacement antenna or changing modem settings: the WPSD/Pi-Star dashboard reports the modem’s firmware and board description, and the connector is identified by whether the socket on the case has a centre pin (RP-SMA) or a centre hole (SMA-female). The antenna supplied must match the connector.

Storage and software. The operating system lives on a microSD card. BridgeCom’s reimaging guide says to remove it by sliding it straight out rather than pulling it upward, and notes that damage from removing and flashing the card is not guaranteed to be covered under warranty. See Vol 3 for the software and reimaging.

Power. BridgeCom attributes most “stuck on Initializing” faults to a failing power supply or a corrupted microSD card. A good supply of the rating BridgeCom ships is the first thing to check; the exact power connector and supply rating for this unit are not yet recorded.