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During the special event of PA6VSM, where a group of radioamateurs was operating an ameturradio station from a steam train, it was the plan to broadcast the position of the train in APRS.
But the track of the steam train was not fully covered by APRS digipeaters. Also the track was in forest areas where energy to power a temporary APRS digipeater is not always available.
PA6VSM crew
The task was to position a temporary digipeater at such a location that the pices of track that ware not covered bij existing digipeaters could be reached by the temporary digipeater. Because of the a power issue the temporary APRS digipeater had to be positioned at one of the locations at the track where powersockets ware available.
Used features
In this analysis example the following features of Radio Mobile are used:
Analysis
To perform this task the Radio Mobile function 'find best site' is used. Initional on the track a number of units ware placed that represent the train. In adition to that the involved digpeaters ware added as units. Finally the possible locations where the temporary digipeater cold be installed ware added. Based on the units, a network per scenario was created and the results calculated.
The minimum required scenarios ware:
- Current coverage without aditional digipeater,
- prediction of best position for the temporary digipeater.
- Composite coverage of the temporary extend APRS digipeater network.
All object is the overview
The predicted postions of the temporary digi wher all units can be seen.
The event
Prior to the event the temporary APRS digi was installed in a abandoned relais-box on the track.
The digi, a DIGI_NED digi on a laptop with a baycom modem and a Motrola MC-Micro VHF radio, had a 9 meter Clack pneumatic mast and a 2 dBd vertical antenna.
Relais cabinet in which the digi was installed.
The train passes the digi (the mast is the digi antenna)
In the train a Laptop and a general APRS setup was installed with a GPS to send the positon beacon. Als from the client messages could be send back in to the APRS network.
The antenna was installed on the roof of the cabin.
 
Left: the laptop with THD7, Right: Tinytrack and GPS on the window.
The Result was a nice track of the route of the train.
 
Results of PA6VSM APRS mobile on PocketAPRS
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