Secondary Link Stations
Secondary Link Stations
There are lots of opportunites to go mountaintopping during our 6 hour 26 July 2009 Golden Packet test from Georgia to Maine as we attempt to relay a text message using hand-held radios the 2000 mile length of the Appalachain trail. See the Golden Packet plan. . Other hikers equipped with APRS ham radios are welcome to participate during the hiker window and these secondary links described on this page can help extent the experience over most of the Eastern states.
SECONDARY LINK STATIONS From the Mountains of this event, we have the potential to extend secondary linear links to some major areas. These links will be operated ONE-WAY-OUTWARD during the first hour of the event so that they do not contribute any added load on the network until after the Golden Packets have been successful. But even during this first hour, these one-way outpbound links will let lots of additional stations monitor the success of the network.
After the first hour, these secondary link stations can come on line and join the fray. But remember, only one packet per station per 10 minutes is the norm to keep loading on the long haul network light.
SPLIT FREQUENCY OPERATION: On the secondary link digipeater that is the one that connects the secondary link to the Appalachian Trail event site shown in green above, that digi must operate SPLIT frequency initially so as to not add any QRM to the main event channel. This is done by setting in two channels for the event. One channel is the 144.34 simplex digital event like all of the main event stations, and the other channel is operated by these secondary stations as 144.34 +600 KHz offset as shown above.
This first digi in this secondary chain will digipeat ALL Event traffic over to 144.94 which is an unused channel in most areas. This prevents any packets from this station and others along the secondary link from injecting any packets onto the main channel. But, during this first hour the next secondary station in this secondary chain may operate REVERSE so that it can communicate with the first digi. And each station further down the chain can also alternate between 144.34 +600 and that same setting REVERSE. Notice that setting REVERSE is the same thing as operating on 144.94 with a MINUS 600 offset.
Using this technique creative neworks can be established radiating outward anywhere on the trail as long as ALL such packets are *NOT* on the main event channel during the golden hour (noon to 1 PM). Using this split frequency approach, those secondary areas are able to participate and to demonstrate their ability to join the long-haul emergency network in time of disaster.
POSSIBLE LINKS: . . . Springer (GA) to Lookout Mountain (Chatanooga TN) to Huntsville
. . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . Westward into WPA and Ohio
. . . . . . . . . . . . . . . . . . . . Down into Connecticut and Rhode Island
. . . . . . . . . . . . . . . . . . . . Northwestward into New York State
SECONDARY LINK CHAINS: In order to allow maximum RF participation throughout the 13 states and more of the AT, there can be Secondary LINK CHAINS that will relay the actual Golden Packet event outward from the trail in favorable directions. For example, the path from Springer Mountain westward over to Lookout Mountain in Chatanooga and from there on to Huntsville Alabama should work fine. The goal of this event is to break the mold of Field Day and VHF contesting and do something different. To test and demonstrate our ability to build an instant ad-hoc linear network using APRS (or packet) for long-haul RF digital communications. The view below shows the path from Lookout Mountain to Huntsville.
The next view shows the path from Lookout Mountain to Springer Mountain. This
path is a one-way path this year so that Chatanooga and Huntsville can monitor
the AT Golden Packet event without adding any channel QRM. But it is a good
test run for the next year, when we will activate all Secondary Links.
As you can see, Lookout Mountain is an easy Drive-up mountain and the RF paths are well known because of the multiple Amateur Radio repeaters already up there. The XXXXX APRS digi is also active from that location.
Bob, WB4APR
See my other GENERAL page on APRS applications and Ideas on the AT
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