Product: AURSINC MMDVM Hotspot Board + Antenna Support UHF VHF Support P25 DMR YSF DSTAR NXDN POCSAG for Raspberry Pi-Zero W, Pi 3 (OLED Board)
Brand: AURSINC
Compatible with P4 settings:
 Method 1: Remove the R1 resistance of the hotspot board(single/dual) ; 
 Method 2: Cut off the 2 Raspberry Pi pin headers on the corners of the board ( pick one to operate on your MMDVM board, refer to the product image for the R1 and 2 pin headers locations)
 Features
 High efficiency, less power comsumption, High quality TCXO, stable, low BER
 Support Raspberry Pi 3B, 3B +, Pi ZERO, compatible with NanoPi NEO, Orange Pi, compatible with BlueDV (requires USBtoTTL or Bluetooth model) 
 Support MMDVM mode DMR / YSF / P25 / NXDN / DSTAR / POCSAG 
 Support online upgrade, User-friendly OLED and Nextion special design location, reserved for additional installation of Bluetooth modules 
 Package List
 1x MMDVM motherboard(UHF/VHF)

MMDVM hotspot supports UHF VHF, frequency range: 144MHz-148MHz, 420MHz-475MHz, 842MHz-950MHz (depending on ADF7021 and TCXO, HAT firmware amateur radio brand license restrictions)
AURSINC hotspot board supports Raspberry Pi 3B, 3B +, Pi ZERO, compatible with NanoPi NEO, Orange Pi, compatible with BlueDV (requires USBtoTTL or Bluetooth model)
Hotspot board saves electricity, High quality TCXO, stable, low BER. Support MMDVM mode DMR / YSF / P25 / NXDN / DSTAR / POCSAG
Support online upgrade, User-friendly OLED and Nextion special design location, reserved for additional installation of Bluetooth modules
Compatible with P4 settings:since our mmdvm board is defautly setup for Pi-Zero W, Pi 3. and if you do want to connect it with your Pi 4, you could try below methods. PICK ONE. Method 1: Remove the R1 resistance of the hotspot board(single/dual) ; Method 2: Cut off the 2 Raspberry Pi pin headers on the corners of the board ( pick one to operate on your MMDVM board, refer to the product image for the R1 and 2 pin headers locations)

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