Radios

SkyBridge Plus · Volume 4

SkyBridge Plus — Vol 4: Reference

BridgeCom commercial DMR hotspot — turnkey appliance

4.1 Tips and tricks

The non-obvious things worth knowing about running a SkyBridge for any length of time:

4.1.1 BridgeCom firmware updates — the support-portal cadence

BridgeCom pushes SkyBridge firmware through their support portal rather than via the upstream WPSD auto-update flow. The dashboard’s Configuration > Update panel checks the BridgeCom update server, not the upstream WPSD update server. The practical implication: you can be a few weeks behind upstream WPSD on the SkyBridge, which is the appliance-vendor tradeoff at work. Check monthly; if a security advisory hits the upstream WPSD community, BridgeCom usually pushes a matching update within a week, but the latency exists and the user has no control over it. If immediacy on a specific feature matters, that is the DIY WPSD’s job — see Vol 22.

4.1.2 Last-heard transmissions across the network

The WPSD dashboard’s “Live Caller” and “Last Heard” panels show every transmission the hotspot has decoded, with caller’s callsign, DMR ID, talkgroup, duration, and RSSI. The view is intoxicating once you realise it — the “is anyone talking on the talkgroups I’m subscribed to” question goes from “press PTT and hope” to “scroll the dashboard panel.” Use it to find active talkgroups before committing them to the static-subscription set; use it to verify that a transmission you keyed was actually heard by the network.

4.1.3 OLED customisation

The 0.96” OLED on the front cycles through a small set of pre-defined screens (TX/RX state, talkgroup, network status, IP, callsign). The cycle interval and the screens shown are customisable via the dashboard’s Display panel — typically you can pick which screens to include, adjust the dwell time per screen, and pick a font flavour. Useful customisation: turn off the IP-address screen if you have the IP memorised, and increase the dwell on the “current talkgroup” screen, which is the one you actually look at when the radio’s mid-QSO.

4.1.4 Ghost activity

When the WPSD dashboard or the OLED displays TX/RX on a talkgroup you’re not listening to, it’s not a malfunction. The hotspot is receiving DMR network traffic from the talkgroup over the internet (because the talkgroup is in the dynamic-subscribe window or there’s a cross-mode bridge active), decoding it, queuing it for RF transmission, and turning on the TX LED. From the user’s perspective the hotspot looks like it’s “doing something” without being asked. This is normal — the dashboard’s “Live Caller” panel will show the inbound transmission. The only operational concern is that ghost activity on a busy talkgroup that’s been bridged onto your slot 2 will block your own transmissions until the inbound finishes; if this happens often, the talkgroup is too busy for static subscription and should be moved to dynamic.

4.1.5 Power supply quality matters more than it should

Pi Zero W is famously sensitive to USB-supply undervoltage. The factory BridgeCom 5 V 2 A supply is fine; a generic phone charger or a USB-C cable shared with a hub is sometimes not. The symptom is the WPSD dashboard’s “Under-voltage detected” warning at the top of the page; the on-air symptom is intermittent dropped transmissions and dashboard alerts. Use a known-good 5 V 2 A USB-C power supply or the BridgeCom-bundled one; don’t share the supply with another device through a hub. If you’re powering off a USB-C hub on a laptop, the laptop sleeping will drop the SkyBridge.

4.1.6 Frequency coordination is on you

Pick a hotspot frequency that is not used by local repeaters within roughly a 5-mile radius — the hotspot’s TX is low-power but its RX is wide-open, and a local repeater on the same frequency will desense the hotspot’s receiver into uselessness. Check your local repeater coordinator’s database (e.g. for Michigan, the Michigan Amateur Radio Council; for other regions, the corresponding state or regional coordinator) before assigning the hotspot’s frequency. Most regions publish a “low-power simplex / hotspot” allocation specifically for this case — use that range. The deep regulatory and band-plan treatment is in Vol 4 (Frequency Planning) and Antennas Vol 31 (Regulatory & RF Safety).

4.1.7 Wi-Fi is the most common failure mode

The SkyBridge is Wi-Fi-only — no Ethernet. The Pi Zero W’s onboard 802.11n single-band 2.4 GHz Wi-Fi is functional but not robust under congestion; if the home Wi-Fi’s 2.4 GHz band is noisy (lots of neighbours’ APs, microwave ovens, baby monitors, USB 3 emissions) or if the router is on the other side of the house, the SkyBridge will intermittently drop its connection. The dashboard’s network status will show “disconnected” and the OLED will stop updating talkgroup activity. Most failures clear themselves on the next supplicant reconnect (which takes 30-90 seconds). Persistent failures usually mean the SkyBridge is too far from the access point — move the hotspot closer, add a 2.4 GHz mesh node near it, or accept that the appliance has a Wi-Fi reliability ceiling that the Ethernet-equipped DIY WPSD in Vol 22 doesn’t have. Keep wpa_supplicant.conf / the .nmconnection file backed up (already in ../../programs/skybridge-plus/ and ../../programs/wpsd-hotspot/) — if the SD card has to be reimaged, the Wi-Fi credentials are otherwise lost.

4.1.8 Don’t change colour code from 1 unless you have a reason

The DMR colour code is a per-channel layer-1 squelch — a radio with a different colour code on its channel won’t decode the hotspot’s transmissions even if everything else matches. CC 1 is the convention; the AnyTone D878 defaults to CC 1 on a new channel; every codeplug template uses CC 1; every shared-codeplug file uses CC 1. Don’t change it on the hotspot unless you have a specific reason (e.g. you’re operating two hotspots in close proximity on the same frequency and want to keep them from cross-talking, which is itself an unusual configuration). The hours-of-debugging trap is “I changed the hotspot to CC 5, forgot, then changed the radio codeplug and couldn’t figure out why nothing decoded.”

4.2 Resources

Local manuals and configuration backups (../../programs/skybridge-plus/):

  • SkyBridge Plus.xlsx — per-device configuration spreadsheet (serial, DMR ID, frequency, talkgroup map)
  • WPSD_Config_skybridge_2025-Dec-29.zip — most recent dashboard export (entire /etc/pi-star/ config tree)
  • FBI_Surveillance_Van__3.nmconnection — NetworkManager profile for the SkyBridge’s Wi-Fi (SSID + PSK + supplicant config)

Vendor pages:

Upstream open-source projects (the SkyBridge is built on these — useful for the SSH-and-tinker case):

DMR network registration and infrastructure:

Cross-references within this series:

Cross-references into the sibling Antennas project:

Wider amateur DMR references: