[OZAPRS] Hang Glider APRS

Terry Neumann tfn at rbe.net.au
Wed Apr 19 17:48:17 EST 2006


Andrew Rich wrote:

>Gudday
>
>In contact with the local hang glider club. One guy is going to fly 100
Km's
>cross country.
>
>Now I have to make the decision wether the pocket tracker will make the
>distance.
>
>I measured it with a comms test set - 168 mW.
>
>Anyone had expereince with RF vs Distance from airborne objects ?
>  
>

My experience with conventional gliders suggests that this would be 
pretty marginal at the power levels offered and the distance expected.

I need to stress that this "experience" is with voice communications 
using the dedicated air band radios.    These use frequencies in the VHF 
air band - most often 122.7 Mhz on AM - and with outputs of around 2 - 5 
watts (depending on how these things are measured) we expect distances 
of 100 km from airborne aircraft at (say) 2,000 feet back to ground 
stations.  It's all a function of having sufficient altitude to maintain 
a line of sight path.   If you get very low, this can be compromised 
severely.   It seems reasonable to assume that these observations will 
also be valid for the 2 metre band which is what I imagine you will be 
using.

The efficiency of the antenna needs to be considered as well as it's 
proximity to the metal bits of the airframe and how these might enhance 
or shield the signal.    Hang gliders, like us, circle a lot in thermals 
to gain height (hopefully).

It's possible but it really looks like this will be a true experiment at 
the power levels proposed.    That is to say that it may or may not work 
all the time or all the way.

My 10c worth,
Terry




>-----------------------------------------
>Andrew Rich
>Amateur radio callsign VK4TEC
>email: vk4tec at tech-software.net
>web: http://www.tech-software.net
>Brisbane AUSTRALIA
>
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>  
>

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