SHARI PiHat

Overview

SHARI (SA818 Ham Allstar Radio Interface) PiHat is a ham construction project designed by N8AR that implements a Raspberry Pi hosted Allstar node in an Argon40 Neo enclosure using a NiceRF SA818 embedded UHF (420 – 450 MHz) or VHF (144-148 MHz) radio module. SHARI PiHat is designed as a kit for construction and use in the amateur radio service by licensed amateur radio operators who can assure that their assembled SHARI PiHat kit meets FCC mandated operating requirements including RF frequency, deviation and required power levels at the fundamental and harmonic frequencies.

SHARI PiHat plugs into the GPIO connector of a Raspberry Pi4. Two wires from the PiHat are soldered to pads on the Pi4 for a connection to a USB connector. Programming of the SA818 module uses the GPIO RX and TX signals from the Pi4 UART.

Three LEDs indicate the CONNECTION STATUS (blinking green), COS (yellow) and PTT (red)] . SHARI PiHat RF output power is around 300 to 500 milliwatts.

SHARI PiHat is available in two models with a fan option –

  • SHARI PiHatU (70 cm)
  • SHARI PiHatV (2 meters)
SHARI PiHat
SHARI PiHat with Fan Option
SHARI PiHat Node With Top Cover Removed

Features

  • Uses a Raspberry Pi4 (see our PiHat Unistorm model for a Pi3)
  • Uses the Cmedia CM119B or CM108B USB audio IC
  • Uses a NiceRF SA818 UHF or VHF embedded radio module
  • 300 to 500 milliwatts RF output power
  • Small, portable with self contained radio and antenna
  • Kit includes PCB with all surface mount parts installed
  • You modify the case, assemble the PC board, make 2 soldered connections to the Pi4 and complete final mechanical assembly
  • Rugged RFI-resistant metal enclosure that also is a heatsink for the Pi4 CPU/ram
  • 3D printed hole location tool simplify drilling holes in the case.
  • 3D printed light shield and USB filler plug
  • SA818 radio module settings changed using the SA818-prog program (included with the HamVOIP Allstar image) running on the Raspberry Pi4

Temperature Considerations

A thermally conductive pad is used to heatsink the Pi4 CPU and RAM to the Neo case. The case itself does not have vent holes so the exterior of the case becomes noticeably warm. We have measured the a Pi4-2 GB CPU temperature (using cpu_stats in HamVOIP) of 48 to 52 degrees C with the SA818 module in RX. With the SA818 module transmitting continuously (like listening to a net for a long time), the CPU temperature rises to 58 to 64 degrees C. This is still at least 16 degrees C below the point where the Pi4 CPU frequency is throttled to reduce power dissipation. There is also a fan option for use in hot environments (like mobile in a vehicle).

Construction

SHARI PiHat(U or V) is a kit construction project. It consists of the parts shown in the photo below (ferrite core and USB connector filler plug not shown)

SHARI PiHat Kit (ferrite core and USB connector filler plug not shown)

The kit builder supplies the Raspberry Pi4, the Pi4 power supply and a microSD card to complete the self-contained Allstar node.

SHARI PiHat uses a single circuit board. The circuit board contains installed surface mount (SMD) parts as well as 2 through-hole parts, a surface mount SMA connector and the SA818 (UHF) radio module.

Fully Assembled SHARI PiHatU PC Board

Construction Manual

A comprehensive step-by-step construction/assembly manual to construct an Allstar node using the SHARI PiHat is available.

Allstar Node Setup and Configuration

An Allstar Node setup and configuration guide for a SHARI PiHat Allstar node is available.

SA818 Radio Module Programming

A Python program SA818-prog which is used to program the NiceRF SA818 radio module used in all SHARI devices is also provided. It is included with the HamVOIP Allstar Image and can be downloaded from our SHARI group on groups.io. The SHARI PiHat Setup and Configuration guide explains how to download and use it.

Ordering Information

SHARI PiHat is designed as a kit for construction and use in the amateur radio service by licensed amateur radio operators who can assure that the SHARI PiHat kit they are using meets required operating requirements including frequency, bandwidth and required power levels at the fundamental and harmonic frequencies. There are two SHARI PiHat kits:

SHARI PihatU (UHF-70cm, 420-450 MHz)
SHARI PiHatV (VHF-2 meters, 144-148 MHz)

SHARI PiHat is available as a parts kit for, $80 (UHF and VHF). You supply the Raspberry Pi4, Pi4 power supply and microSD card . Please be sure to download and study the SHARI PiHat Construction manual to be sure you own the required tools and possess the required mechanical and soldering skills to build the kit. We will solder the SA818 radio module onto the PCB for an additional $5.

We can also build the kit for you using a Raspberry Pi4 2 GB that you procure and send (or have drop shipped) to us. We will completely assemble and test the kit but you must still procure a Raspberry Pi4 Power Supply and microSD card, download the image and perform the setup of your node. A fully assembled and tested SHARI PiHat kit with you supplying the Pi4 per the above paragraph is $135 (UHF and VHF). .

If you want us to assemble a complete SHARI PiHat, supplying the Pi4 and power supply also, then an assembled PiHatU or PiHatV starts at $205 (price depends on Pi4 cost and is currently very limited availability).

Shipping to US destinations is $9 via USPS Priority Mail provided your order fits in our standard shipping box. Payment via Paypal is preferred.

Send an email including your amateur radio call indicating the SHARI PiHat model and type (kit or assembled) you would like to buy to kitsforhams@gmail.com for ordering and delivery information. We will work with you to solidify the details of your order and send you a customized Paypal invoice to pay.

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