#Upcoming Meetings * **September 19, 2013 [NOTE: Third Thursday] Dolley Madison Library, McLean, VA.** - Mark Braunstein, WA4KFZ, will provide an overview of printed circuit board fabrication for the electronics experimenter. Mark has personal experience using CNC routers in a commercial enterprise. Other options for do-it-yourselfers include conventional photo-etching and contact etching with laser printed masks. A number of domestic and foreign fabricators offer fast turn around at low cost but with confusing choices for software and file formats. [[!img PCB_CNC.JPG alt=""]] * **October 10, 2013 - To Be Determined [NOTE LOCATION: Oakton Library, 10304 Lynnhaven Place, Oakton, VA 22124**] * **November 21, 2013 [NOTE: Third Thursday] - Ron Payne, WA6YOU - Applying Coax Connectors ** Dolley Madison Library, McLean, VA. #Recent Meetings * August 8, 2013 - Maitland Bottoms, AA4HS, introduced us to digital voice communications on HF using FreeDV software. FreeDV is an application for Windows, Linux and MacOS (BSD and Android are in development) that allows any SSB radio to be used for low bit rate digital voice. The software compresses speech to 1400 bit/s then modulates a 1.1 kHz wide quadrature phase-shift keying (16-QPSK) signal which is sent to the Mic input of a SSB radio. On receive, the signal is received by the SSB radio, then demodulated and decoded by FreeDV. Communications is readable down to 2 dB S/N, and long-distance contacts are reported using 1-2 watts power.
* July 18, 2013 Dr. Frank Eliot, W3WAG, discussed Weak Signal Detection. Thanks to the rapid increase in digital processing availability, hams have implemented sophisticated and user-friendly techniques that enable us to communicate with much weaker signals than we had dreamed of exploiting just a few years ago. In this session, Frank discussed weak signal detection, exploring under what circumstances we might detect even weaker signals, thus communicating over even more difficult paths. Also, on a related topic, he described how earth antennas behave, and experiments one might perform to sort out their modes of operation. * June 13, 2013 AMRAD hosted a doubleheader for slow modes: DFCW and JT65.
FreeDV is unique as it uses 100% Open Source Software, including the audio codec. FreeDV represents a path for 21st century Amateur Radio where Hams are free to experiment and innovate without being locked into a single manufacturer’s proprietary technology. The same cables and hardware that you use for other digital modes that are based on PC programs will work with FreeDV, but you will need a second sound interface for the microphone and speaker connections to the FreeDV program. A USB headset of the sort used by gamers is all you need for the second sound interface.
**Click here for [[Past Meetings|pastmeetings]]** #Upcoming Events * **September 27, Mid-Atlantic VHF Conference and Mini-Fest**, Bensalem, PA, Mt. Airy VHF Radio Club (Pack Rats),
The first presentation was by André N4ICK titled An Arduino-based DFCW Beacon for the 479 KHz Band. André discussed Dual Frequency CW (DFCW) and updated us on the ARRL petition to the FCC Office of Engineering and Technology regarding the new band. He demonstrated his design of an Arduino-based 479kHz beacon, and expanded on the eventual possibility of "crossing the Pond" to communicate with British Hams who have been experimenting for a while with this new allocation. Dual Frequency CW, or DFCW, is a technique where a CW signal is transmitted at a very slow symbol rate, typically at 3 seconds per dot. This allows reception in very narrow bandwidths. Terry McCarty, WA5NTI, made a presentation on The JT65 Weak Signal Digital Soundcard Mode. JT65 can decode signals many decibels below the noise floor making an exception to the old rule “if you can’t hear them, you can’t work them.” Terry has racked up an impressive list of contacts on nearly every band. The mode was developed by Joe Taylor, K1JT as an offshoot to his WSJT weak signal mode widely used in moonbounce contacts. Although JT65 was originally intended for troposcatter and Earth-Moon-Earth paths, Terry is one of the pioneers in using it for low power HF contacts. Terry told us where to get the free software, how to configure it, and what you can expect in a contact.