SHARI PiHat

The Allstar image from HamVOIP does not currently boot on a Pi4 -8 GB

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 single 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 the 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 100 to 400 milliwatts.

SHARI PiHat is available in two models –

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

Features

  • Uses a Raspberry Pi4
  • Uses the Cmedia CM119B or CM108B USB audio IC
  • Uses a NiceRF SA818 UHF or VHF embedded radio module
  • 100 to 400 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/heatsink
  • 3D printed hole location tool, light shield and USB filler plug
  • Radio settings changed using the SA818-prog program 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, 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. We have had 12 Beta units in use for several months with no reported problems (temperature or otherwise).

Although we do not think that the temperatures that the SHARI PiHat operate at are detrimental to the unit in normal room temperature ambient environments, we are investigating possible cooling techniques that could be implemented by the builder of the kit. One of our Beta testers has two Shari PiHats that ran (70 degree ambient) between 50 to 64C (122 to 147F). He drilled some holes in the cover and mounted a miniature 30mm dual ball bearing fan with a fan guard. He then powered the fan from the Pi. They now run (same ambient) between 31 to 34C (88 to 93F).

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. 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)
SHARI PiHatV (VHF-2 meters)

SHARI PiHat is available as a parts kit for $75 (UHF), $80 (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 can also build the kit for you using a Raspberry Pi4 2 GB and the official Raspberry Pi4 Power Supply 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 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 and Pi4 power supply per the above paragraph is $130 (UHF), $135 (VHF).

If you want us to supply the Pi4 and power supply also, then an assembled PiHatU is $190 and a PiHatV is $195.

Shipping to US destinations is $8 via USPS Priority Mail. 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 send you a customized Paypal invoice to pay.

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