30th ARRL and TAPR Digital Communications Conference

September 23-25, 2011, Baltimore, Maryland

DATVexpress – a Lower Cost Approach to Digital-ATV Transmitter
By Charles Brain, G4GUO and Ken Konechy, W6HHC

Abstract: Modern Digital Amateur Television (DATV) techniques have brought the goal of producing broadcast quality television within the reach of every amateur. No longer are we faced with the demons of the old analogue system like ghosting, poor contrast, improper sync pulse levels and poor colour. The considerable improvements in spectral efficiency that DATV brings means also we can do more with our crowded bands. The use of Forward Error Correction (FEC) techniques also goes a long way to mitigate the adverse effects of the RF channel. 

Until now the entry bar to DATV costs has been set very high. For those hams not able to obtain surplus broadcast MPEG encoders and DVB-S transmitters it has meant paying over US$1000 for equipment aimed at the ham radio market. This is all changing, read about the exciting developments in low cost entry level DATV. In this paper we describe our DATVexpress project to develop an inexpensive flexible Digital Television transmitter for the Amateur Service using software defined radio techniques and the power of the personal computer. 

Presentation Slides

A Shadow Ad-Hoc TEMPn-N Network
By Bob Bruninga, WB4APR

Abstract: Of course stations and rovers have nearly perfect connectivity using the existing national APRS network on the established national channel of 144.39. But the problem is, it is hard to see who is involved in the event among the other thousands of permanent users there. Or at other times, a temporary digipeater may be needed because certain key digipeaters might be down during an emergency and a station needs to use other surrounding stations to get out. For these reasons, it is nice to have a backup, shadow ad-hoc networking capability built into every packet station that is always on and ready to be used.

Proceedings Paper

CW Mode for the NUE-PSK Digital Modem
By Dave Collins, AD7JT and George Heron, N2APB

Abstract: Operating PSK-31 without a PC has been a big capability of the NUE-PSK Digital Modem for several years. RTTY support was added along the way and even more advanced digital modes continue to be in development. But modem owners are also clamoring for support of the oldest digital mode of them all … CW!

This paper describes our open source implementation of this venerable digital mode as an implementation of the Goertzel DSP filtering technique used on the modem’s dsPIC33F processor. Innovative approaches are used to solve the classic problems of speed tracking (up to 50 wpm!), adaptive weighting adjustment, and tuning.

Proceedings Paper

APRS and the Android Smartphone
By Sagar Gupta, KC2VSG

Abstract: This paper discusses a means of using the android smartphone as a Global Positioning System (GPS) receiver unit to provide serial location data to an APRS beacon transmitter. Using an application I developed, an android smartphone with a GPS receiver sends its location to a laptop computer via Bluetooth. Through a program written for the laptop the position data is sent to a serial port in NEMA-0183 format. This serial data can then be sent to a TNC/radio to transmit an APRS beacon with location information. After appropriate digipeating, the beacon information reaches an I-gate station and appears on the APRS Internet System. Although an APRS App is available for android smartphones, which puts the location information directly on the Internet, that application is not useful when there is no cellphone coverage, Wi-Fi access, or one does not want to pay for the android data plan.

Proceedings Paper 

Practical Implementations of Bluetooth in Microcontroller Circuits
By John A. Hansen, Ph.D., W2FS

Abstract: Bluetooth has become the standard technology for external interfacing to laptop PCs and mobile devices. This paper describes a number of ways to implement serial data communication using the Roving Networks Bluetooth devices.

Proceedings Paper 

Public Service Event APRS Web Mapping for Wireless Devices
By Ted Jacobson, W8KVK and  Rob Jacobson, KB9AFT

Abstract: A case study describing real-time APRS web mapping support for Lead and Last runner tracking during the 2011 Athens Ohio Marathon. Objectives were: (a) to provide real-time web-based runner location maps for race officials, emergency services, and spectators without the use of JAVA or Flash; (b) to support a wide range ofweb-capable wireless devices; and (c) to optimize display speeds while reducing bandwidth demands.

Proceedings Paper 

WRC-12 Agenda Item 1.19: Regulatory Considerations for Software Defined and Cognitive Radio Systems
By Brennan Price, N4QX

Abstract: As I reported at the 2009 Digital Communications Conference in Elk Grove, Illinois, the agenda for what was then the 2011 World Radiocommunication Conference includes an item of potential concern to Amateur Radio experimenters: 1.19 to consider regulatory measures and their relevance, in order to enable the introduction of software-defined radio and cognitive radio systems, based on the results of ITU-R studies, in accordance with Resolution 956 (WRC-07).

Proceedings Paper 

More experiments with Delay and Disruption Tolerant Networking over AX.25 Networks
By John Ronan, EI7IG, Darren Long, G0HHW and Kristian Walsh, Waterford Institute of Technology

Abstract: Previously the authors gave an overview of a Delay Tolerant Network Convergence Layer implementation that operates over Connected Mode AX.25, and detailed the results of some performance tests using it to transfer data over Amateur Radio channels. These results were compared to both a native AX.25 and a TCP/IPover-AX.25 implementation. The investigation of TCP/IP was undertaken because, while it is generally accepted that TCP is unsuited to wireless links, it has become the dominant protocol in real-world applications, with over 50% of internet traffic now accounted for by TCP over port 80 [1].

As some issues were highlighted in experiments leading to the authors prior publication, these have been worked on and have been largely resolved. It was also found that our model for an ideal AX.25 communications channel had deficiencies, so a correction is offered. Additionally, we also tested our Convergence Layer alongside a TCP/IP over AX.25 implementation on both a 1200 and 9600 baud point-to-point link and give comparative results between our Convergence Layer implementation and TCP/IP. Real-world behaviour of the data link still diverges from the model, but the authors provide some possible reasons for this.

Proceedings Paper  

A Further Comparison of Different TCP/IP and DTN Protocols over the D-STAR Digital Data Mode
By John Ronan, EI7IG and Cathal O’Connor, Waterford Institute of Technology

Abstract: This work examines the performance of the Digital Smart Technologies for Amateur Radio – Digital Data mode with various IP and non-IP based protocols. A throughput comparison was performed between TCP/IP and two DTN convergence Layers. The experimental results show that the DTN NORM Convergence Layer exhibits better performance than TCP/IP and TCP based convergence layers, and, furthermore appears to be more suited for use on difficult radio links. 

Proceedings Paper 

Codec 2 – Open Source Speech Coding at 2400 bit/s and Below
By David Rowe, VK5DGR

Abstract: Codec 2 is an open source, low bit rate codec for speech over HF/VHF digital radio. Most low bit rate codecs are.proprietary, closed source, and require licensing fees. Codec 2 is unique in that it is open source, allowing experimentation and modification. It fills a gap in open source, free-as-in-speech voice codecs beneath 5000 bit/s and is released under the GNU Lesser General Public License (LGPL).

This paper describes the motivation for Codec 2, status, and future plans. The Codec algorithm is described using figures, avoiding high level maths and Digital Signal Processing (DSP) theory.

Proceedings Paper   –   Presentation Slides

PhoneSat: Balloon Testing Results
By  Mike Safyan, KJ6MVL

Abstract: Why use a phone for a high-capability spacecraft? A phone can increase on-orbit processor capability by a factor of 10-100. A phone can also decrease cost by a factor of 10-1000. Learn the results of their testing.

Proceedings Paper

Modulation – Demodulation Software Radio (MDSR) Software for the BiLiF computer interface
By Alex Schwarz, VE7DXW

Abstract: What a year it has been. Last September, we successfully demonstrated the BiLiF hardware at the 29th.TAPR show in Portland, Oregon. More recently, the MDSR team has worked on the software transceiver; MDSR (Modulation � Demodulation Software Radio). Since the BiLiF hardware can be adapted to any 455kHz IF transceivers (adaptations were also made for the 9MHz IF of the IC-706 series transceivers), the software is also designed to be flexible and user friendly. This software can be downloaded from the MDSR website or Yahoo user group and is free as long as it is used for amateur radio purposes.

Proceedings Paper    

TAPR Banquet Presentation – Village Telco 
By David Rowe, VK5DGR

Abstract: In many countries mobile phone calls are very expensive; costing $0.25/min when the Average Income is $1.52/day. Mesh WiFi provides simple advantages over Regular WiFi. Mesh Potato can provide a solution for poor countries. The first real world deployment of Village Telco was in Timor, near Indonesia. Learn how this project is really helping people every day!

Proceedings Paper   –   Presentation Slides

Introduction to DIGITAL DATA MODES
By George Heron, N2ABP

Abstract: So just what is “Digital Mode Communication?” Results of a survey of some popular digital modes … What the heck are all those weird-sounding stations I hear as I tune around the bands? From Packet, RTTY, and PSK31…through MFSK16, Olivia, and JT65. This is a good introduction to ham radio digital modes and programs to run them on your rig.

Presentation Slides

Introduction to D-STAR Basics

By Mark Braunstein, WA4KFZ

Abstract: A good introduction to D-STAR (Digital Smart Technologies for Amateur Radio); providing simultaneous digital voice and data on the same signal. Includes an overview of the D-RATS communication tool.

Presentation Slides    

High Performance Software Defined Radio – OpenHPSDR Project Update
By Scotty Cowling, WA2DFI

Abstract: The OpenHPSDR Project is a modular, open source hardware and software platform for development of all components of a Software Defined Radio. The presentation provides an overview of the OpenHPSDR architecture and modules and the openHPSDR project status as of September, 2011…including the availability of the modules.

Presentation Slides

High Performance Software Defined Radio – Alex LP/HP Filter Board Testing
By Scotty Cowling, WA2DFI

Abstract: The presentation provides a description of how the Alex RX and Alex TX production boards are tested. 

The following MPEG movies show an Alex RX board test running in real time. One shows a successful PASS result, and the other shows what happens when a board FAILS the manufacturing test.

Presentation Slides

FlexRadio – Recent Developments in Software Defined Radio
By Bob McGwier, N4HY

Abstract: FlexRadio has doubled the shipments of Software Defined Radio (SDR) units and doubled their office space. The presentation includes discussion of WBIR software written by N4HY to allow rejection of near-in images with direct-conversion.

Presentation Slides

Practical Software Radio – Why Things Don’t Always Match the Textbooks
By Matt Ettus, N2JMI

Abstract: An introduction provides an overview of Radio Architectures and Real-world impairments. The next section covers interpreting Spectrum Analyzer measurements and SNR-CNR. The following section digs deeper into Radio Architectures. The last section digs deeper into Hardware Inherent impairments and Architecture Specifc impairments.

Presentation Slides

D-Star Ideas
By Mark Braunstein, WA4KFZ

Abstract: Mark Braunstein WA4KFZ proposes changes that could make D-Star even better. These proposals including adding Forward Error Correction (FEC) to data-only modes, providing a 4800 bps data-only mode, and building new models of radios equipped with a D-STAR-only display mode. There are many other suggestions provided as “food fo thought”.

Presentation Slides