31st ARRL and TAPR Digital Communications Conference

September 21-23, 2012, Atlanta, Georgia

Experimenting with High-Speed Wireless Networking in the 420 MHz Band 
By David Bern, W2LNX

Abstract: This paper reports on our testing the Doodle Labs DL435-30 and Xagyl Communications XC420M wireless networking miniPCI cards. They behave like IEEE 802.11 wireless networking cards but operate in the 420 MHz band. We have successfully tested these cards over 10 miles at about three Mbit/s data rate at a 5 MHz bandwidth in the 420 to 426 MHz ATV sub-band. Our test applications were a Webcam video streaming program and a file download server program that ran on inexpensive netbook computers.

Proceedings Paper   –   Presentation Slides

DATVexpress – Project Testing Update

By Charles Brain, G4GUO and Ken Konechy, W6HHC

Abstract: The DATV-Express project was formed to create low-cost solution for Digital-ATV transmission. The open-source project was first announced and described at the TAPR Digital Communications Conference (DCC) in 2011.

This DCC 2012 presentation in the proceedings provides an update on the project progress. The project’s hardware board design appears to have the capability to go well beyond just DVB-S transmission, it should be able to transmit any waveform of up to 8 MHz bandwidth using SDR techniques…including DVB-T, DVB-S2 and ATSC .

Proceedings Slides

On-line Alternation of Modulation Techniques using a Dynamic Switch

By Shashank Gaur, Sankalp Agarwal, Ammar Almasri and Anas Bennani 

Abstract: In the ongoing era, the need of wireless communication is increasing at an exponential rate, alongside the development requirement is also rising in order to provide efficient, uninterruptable and effective services all around the globe. We propose an intelligent system, which would be able to switch inbetween, the modulation techniques during online transmission in order to communicate with the surrounding environment and to provide efficient SNR and throughput.

Proceedings Paper

aprsc, an open-source high-performance APRS-IS core server

By Heikki Hannikainen, OH7LZB 

Abstract: aprsc is a high-performance, open-source APRS-IS server software for Unix-like systems such as Linux, FreeBSD, Solaris and Mac OS X. This paper documents its main features, design, some implementation details and results of performance measurements.

Proceedings Paper 

Technical aspects of Lentus (4.21.1) and use

By Patrick Lindecker, F6CTE

Abstract: This new mode benefits from the fact that it is nowadays quite easy to synchronize a computer with reference clocks, through an automatic WEB communication. A precision of 50 ms is easy to get with WEB time servers. So if the symbol length is sufficiently large (>2 seconds), the relative precision is quite good. Consequently, the symbol synchronization is done directly through programmed times, without need to extract synchronization from the signal itself, as it is done in the majority of modes (PSK31 for example). This permits a gain in term of minimum S/N ratio and to increase the robustness of the transmission. The goal of this mode is to perform VLF to HF communications at a very low S/N ratio (-34 dB with anoise bandwidth of 3 KHz).

Proceedings Paper

YAAC: The Development of “Yet Another APRS Client”, an Open-Source Cross-Platform Application

By Andrew Pavlin, KA2DDO

Abstract: Of the many APRS clients currently available, all of them have some limitations or constraints. YAAC (Yet Another APRS Client) was designed and implemented to meet the author’s needs and hopefully some unfulfilled desires of the Amateur Radio community, while also being a personal research projectin the grand old Amateur Radio tradition of home-brewing.

Proceedings Paper 

Digital Amateur Radio in Support of Situational Awareness, Common Operating Picture and Community Resilience for 21st Century Emergency Communications

Aleksandra M. Rohde, W3JAG 

Abstract: The Department of Homeland Security has identified core capabilities necessary for rapid and effective response to man-made or natural emergencies. These include: (1) collecting real-time situational awareness of the emergency; (2) developing a common operating picture; and (3) building resilient communities capable of effectively adapting to changing circumstances. Amateur Radio operators — particularly those who are digital radio enthusiasts in wireless networking — are ideally suited to help develop these core capabilities through current and future technologies.

Proceedings Paper

Web Servers on the HSMM-Mesh

By Joesph P. Scanlan, N7XSD 

Abstract: Here we demonstrate the practicality of ptoviding web servers on the HSMM-Mesh. The first example shows a standalone server connected to its own Mesh node. In the second example, the Mesh node is added to an existing network that has servers on its private and perimeter sub-networks,

Proceedings Paper 

MDSR TX Compliance and RX Performance Testing

By Alex Schwarz, VE7DXW and Adam Farson, VA7OJ/AB4OJ 

Abstract: The RX section of the Modulator-Demodulator-Software- Radio (MDSR) has been published in the last 2 years of the TAPR show and most recently in the July 2012 issue of the QST magazine. This document describes the hardware and the software of the TX section of the MDSR development. The TX section has been tested with the help of Adam Farson (VA7OJ/AB4OJ) in his RF test lab. The RX section has also been tested and compared with amateur radio transceivers that Adam had previously tested.

Proceedings Paper

MDSR Additional Feature released with V2.4 Software

By Alex Schwarz, VE7DXW and Guy Roels. ON6MU 

Abstract: The Arduino Frequency Counter Windows software program has been designed primarily for use with the Arduino chip and the Arduino C controller software. In addition to being used with the Arduino chip and the Arduino C controller software, the Arduino Frequency Counter can also be used in conjunction with the MDSR software to display the measured frequency in the MDSR

Proceedings Paper

Is the unlicensed band “good enough” to deploy a muni-Wi-Fi network without mesh infrastructure?

By Devabhaktuni SriKrishna  and Rajeev Krishnamoorthy 

Abstract: We explore a municipal mesh networking architecture called SocialMesh that can be built entire.ly from end-user devices (analogous to amateur radio, HAM, and CB-radio). without requiring dedicated infrastructure mesh nodes, cell base stations, or spectrum licenses. Compared to using Wi-Fi for mesh backhaul, our estimates show it may be possible to achieve up to 10x more coverage area and reliability, and operate 10x faster using SocialMesh to backhaul Wi-Fi client connections. This implies a minimum end-user device density of a few per square mile or less and it can scale up to support much higher densities of several thousand per square mite. This is ideat for increasing the connection probability in challenging RF environments, and extending battery life for handheld devices by an estimated factor of 1Ox. Open design specifications for Social Mesh will be updated at http://www.sogatmesb.org. Question to members of the amateur radio community: “Is there any experience and lessons learned from the operation of global and wide-area amateur radio networks that may be applied to the unlicensed band infrastructureless network?” Please contact the authors with your advice and suggestions.

Proceedings Paper

Design of a Practical Handheld Software Radio

By Chris Testa, KD2BMH 

Abstract: We’ve stood on the precipice of the software radio revolution for many years. However, these devices still only sit in expensive commercial and military applications. State of the art radios use power-hungry SRAM based FPGAs that demand fast interconnects to host processors operating under heavy loads. These devices lack the capability of low-power operation which barrs wide scale deployment. A new architecture is presented for the software radio, using a Flash based FPGA to enable true low power operation. Duty cycling is possible since the FPGA, processor, and radio front ends can all be shut off. An integrated hard ARM Cortex-M3 on the same die as the FPGA allows for rapid and efficient communication over an on chip AHB-Lite interface. Linux runs on top of the ARM, enabling robust networking tasks from a battery operated software radio.

Proceedings Paper

A High-Performance Sound-Card AX.25 Modem

By Sivan Toledo, 4X6IZ 

Abstract: This article describes the problems with current AX.25 software modems, the design methodology I followed in implementing the new modem, and of course, the resulting software. The methodology is particularly important; it has allowed me to design and implement a high-performance modem with little background in digital processing and absolutely no background or experience in designing digital decoders.

Proceedings Paper

Programmable PLL (Si570) Local Oscillator for HF Receivers, Transmitters and Tranceivers

By Craig Johnson, AA0ZZ 

Abstract: A new product has recently been developed by Silicon Labs, the Si570 DSPLL programmable frequency synthesizer, and it has great potential for use in many Amateur Radio applications. The PLL synthesizer is one good example. In this paper we will explore some possible uses.

Proceedings Paper

A Simple Internet VoIP Board

By Bob Simmons, WB6EYV 

Abstract: This article describes a full duplex Internet audio board (a VoIP board) using a PIC microcomputer and a Lantronix XPORT Ethernet module. A pair of these boards will provide a full duplex Internet audio link. This board sends and receives (approximately) 16 user datagram protocol (UDP) packets per second, with 512 payload bytes per packet. Each payload byte expresses an 8 bit audio sample, taken 8000 times per second.

Proceedings Paper