HamShield Documentation

If you are looking to purchase HamShield, you can find it here.

Warnings

⚠️ Operate only on frequencies you are licensed to use

⚠️ Always connect an antenna before powering HamShield

⚠️ Make sure the antenna is correct for the band you are operating on. Avoid bad SWR and poorly matched antennas

Ignoring warnings may violate local laws and damage your HamShield. Damages caused by transmitting without an antenna are not covered by warranty.

Connecting and Powering HamShield

Installing the Arduino Environment and HamShield Library

To install Arduino, visit https://www.arduino.cc/en/Main/Software 

At the time of this writing, 1.8.5 is the latest Arduino software available. You will want to install this software. Arduino is available for Windows, Mac, and Linux.

You will want to run Arduino after you install it.

Next, you will want to make use of the Arduino library manager to install the HamShield libraries. This is important if you wish to take advantage of any future updates once they are released. 

Go to the menu, and select "Sketch" ➡ "Include Library" ➡ "Manage Libraries.."

You will want to install all three libraries. To do this, click on each one once and click "install".

Your library is now installed. You will also see several examples appear under "HamShield". A test sketch is also available under "DDS".

HamShield Libraries and Purpose

HamShield covers the core functions of HamShield, including transmitting and receiving.

HamShield KISS covers the packet radio library interface.

HamShield DDS contains the specific code for Direct Digital Synthesis and is essential for our packet radio functionality. It is used when generating phase correct tones through our PWM filter. 

Hardware Overview and Technical Description

The center of the HamShield is the Auctus AT1846, which is an advanced radio System on Chip (SoC). The AT1846 contains a software FM "modem", which makes the HamShield capable of the most popular voice and data modes (FM and AFSK/AX.25).

Since the Arduino is not capable of directly generating analog waveforms, the HamShield contains a specially tuned PWM smoothing filter. This filter turns the mostly crude digital PWM signal into a phase correct analog signal. While this allows Arduino to generate a wide away of pleasant tones and digitized voice, its primary purpose is to make data communication possible. While HamShield 0.9 contains a well designed filter, HamShield 1.0 has some additional improvements, which further improves data performance. Enhanced Radio Devices spent a substantial amount of R&D to tune this filter.

An additional filter is placed on the analog receive line. While the Arduino does have a native ADC, we perform some light filtering to make data decoding as reliable as possible.

The AT1846 is able to transmit and receive on three distinct bands. We simply call them the 144/220/440 bands, Since we are USA-based, we tuned our filtering and amplifiers to these ham bands. But it has capabilities far beyond ITU Region 1 amateur radio.

Since the AT1846 was intended for FCC Part 90 devices (general commercial two-way radio), with FCC Part 94 (Amateur Radio) simply being a byproduct, it has a very wide range of band coverage. 

These include:

  • 134MHz to 174MHz
  • 200 to 260MHz
  • 400 to 520MHz

It is also interesting to note that the PLL will operate well outside these 3 ranges, but we have found it to be unstable at the extreme tuning range.

While we do not encourage or condone transmission illegally, users are free to receive outside of the amateur radio bands, turning HamShield into a powerful Arduino controlled radio scanner. This makes HamShield interest to even non-amateur radio operators and scanner enthusiasts. It also allows for some unique prototyping applications for those with FCC experimental licenses.

Making your first transmission