APRN.TXT AUTOMATIC PICTURE RELAY NETWORK ========================================================================== Document version: 8.1.2 Document dated: 24 Nov 98 Author(s): Bob Bruninga, WB4APR ABSTRACT APRN.TXT APRN is a network concept to improve the distribution of WEB-CAM type in the field images to users at special events, emergencies or general ham radio applications ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ APRN is a concept that will revolutionize the use of amateur radio in support of emergencies, special events and public service. It allows mobile, portable and handheld operators to send back live images from the field for real-time review anywhere! Prior to APRN, images could be sent from one SSTV station to another, but since fewer than a fraction of 1% of ham operators had SSTV capability, there was no way to get the image from the receiver to the person, VIP, or agency that needed it. All of that has changed with the advent of five powerful technologies that have coalesed in the last few years: * ANY Multi-media PC can receive SSTV images directly from any radio * Kenwood last year introduced the hand-held Ken-Cam (VC-H1) * Kenwood this year introduced the hand-held APRS Radio (TH-D7) * The Internet can distribute images anywhere worldwide * APRN is only the network concept that provides users with a consistent and reliable interface SSTV (Slow Scan TV) has been around for 30 years or more but has always been a relatively boring exchange of pre-captured images between hamshacks. Recently Camera interfaces have existed, but it still required a PC or other large appliance to convert the image to SSTV. The arrival of the Kenwood KEN-CAM last year, completely changes the playing field, since the entire system fits in a shirt pocket or the palm of your hand and can be used anywhere. This combined with the public's general acceptance of still-frame video over the internet totally embraces a complete paradigm shift to a totally new real-time in-the-field imaging capability. The final key to the automation of the WEB PAGE inerface was the imminent introduction by Kenwood of the TH-D7 APRS packet walkie-talkie. Thus, without a computer, or any external components, a user cannot only Capture the picture with this handheld Ken-Cam, but he can also then transmit a machine readable single packet identifier that includes the CALLSIGN, LOCATION, TIME and TITLE of the image! The keypad on the TH-D7 can be used for entering the necessary alphanumerics and the built-in TNC then transmits it. If a GPS is plugged into the radio as well, then the LAT/LONG of the station is also automatically included! Thus you can transmit the WHO, WHAT WHEN, and WHERE needed for full automation of the WEB page for cataloging and indexing real-time images from multiple remote users. APRN NETWORK The APRN network is not really a network at all. It is only the establishment of designated frequencies in cities everywhere for Ken-Cam operators to uplink their images to the nearest APRN WEB page. These local networks can be as simple or complex as needed to provide the mobile converage needed. A few examples follow: Local Simplex Uplink - This is simply a 2 meter radio at the WEB server that listens for SSTV uplinks. Range is limited by the height of the antenna at the web site. Crossband relay - This is probably the most practical arrangement since it allows placing a 2m receiver at a high remote receive site and then linking the audio down to the valley Web server. Besides vastly increased range due to the high site receiver, this system also permits other SSTV operators to monitor the SSTV linked images live. Metropolitan Crossband Relay - This just adds additional remote 2 meter receive sites that all link back to the WEB site still on the same UHF channel, or multiple UHF channels depending on popularity of the system. The web page can operate a scanner to capture images on all crosslink channels. Voice Repeater Relay - This simply takes advantage of existing 2 meter voice repeater inputs by adding only the crosslink UHF transmitter at existing repeater sites. A mute circuit mutes the output of the repeater while an SSTV link is in progress. It is doubtful that there is any technical advantage to this arrangement since it will in most cases be politically unacceptible. FREQUENCIES: Frequencies are a local issue only. Typically, only one frequency is needed and it can be shared with other applications. ALso, since only mobiles or remotes uplink on the channel in simplex to the APRN receiver, any simplex frequency can be used. There is no need for the APRN site to transmit anything on the channel back to the user other than a brief 1 second acknowledgment. Thus it is consistent with simplex shared use. APRN is a concept presented by Bob Bruninga, WB4APR at the Digital Communication Conference in Chicago, 25 September 1998.