Re: APRS trackers IDs for all balloons.

James Ewen VE6SRV


Not sure where you got the misunderstanding

I'm not sure what conclusion you think I came to which would cause a misunderstanding. I asked if the chase crews had RF based APRS reception capabilities, and then explained why having RF based APRS is a good thing, and why trying to install infrastructure as described below would probably not be worth the effort involved. 

I am not familiar with the local topography of the recovery area as far as elevation goes but how about the possibility of using a temporary mobile digipeater  on the non standard APRS frequencies to repeat the APRS packets to an I-Gate. This would require a public accessible high elevation spot for max range. 

As I stated in my previous message, the chances of having a recovery vehicle in the right location for reception of payload packets is much higher than attempting to place a temporary digipeater in a location that might happen to be located where it picks up a final landing location of a payload. 

The only people that need to have the exact landing coordinates are the people that are physically picking up the payload, and even then, close is usually close enough to get you in visual range. With RF based APRS reception capabilities in the chase and recovery vehicle, those final landing coordinates can be received directly from the payload over RF. If that chase and recovery vehicle has I-gate capabilities, then the bonus delivery of packets to the APRS-IS happens as well. 

The work required to deploy a temporary digipeater in an effort to get better reception and delivery of payload packets to an I-gate that is most likely closer to the payload than the temporary digipeater seems to be a fools errand. 

The primary concern is local RF reception of packets from the payload. A distant second is the bonus delivery of those payload packets to the APRS-IS. 

It makes far more sense to invest the effort to drive the mobile I-gates closer to the payload than to install a temporary digipeater in an attempt to get the landing coordinate packets delivered to an I-gate. 

Remember, packets from a flying payload will most likely have a better line of sight to an I-gate than a land based digipeater will have to that same I-gate. 

Digipeaters help ground based trackers get heard by giving the packets better LOS to other stations by digipeating from advantageous physical locations. Airborne trackers have much more advantageous locations than ground based digipeaters by virtue of the airborne nature of the tracker. Until the height above average terrain (HAAT) of the airborne tracker is less than the HAAT of the digipeater, the airborne tracker will have a larger RF footprint than the digipeater, and thus greater range. (Barring specific terrain obstructions.  A ground based digipeater will probably have a higher gain antenna, and higher RF power, but HAAT trumps gain and power in a hurry at VHF)

These two messages are just my attempt to get people to stop thinking that in order for a packet to exist, that it needs to be handled by a digipeater and /or an I-gate. RF packets can exist in the world without digipeaters and/or I-gates. 

While the world may ponder the age old question, "If a tree falls in a forest and no one is around to hear it, does it make a sound?", there is a definitive answer to the question, "If a packet isn't heard by an I-gate or digipeated by a digipeater, did it ever exist?". The answer to the second is a resounding "Yes!".  


On Jun 15, 2016, at 12:48, Michael <mw@...> wrote:

Hi James!

Not sure where you got the misunderstanding, but almost all the vehicles have APRS radios on board and most of us are very seasoned ARHABr's.

You are likely questioning the focus on i-gates. We are using standard and some non-standard frequencies, so we are setting up I-gates to service those non-standard frequencies. We have a lot of balloons flying and the DFW area is extremely saturated with APRS '390 traffic, so those i-Gates for those odd frequencies allow guys like you to see those flights on findu or too. Some are using mobile i-Gates - we have a fair bit of coverage with cell towers here - but not 100% by any means, so there will be drop outs. However, yes we have radios in our cars and with some setups like mine, remove the GPS unit and GeoCache right to the balloon.


On 6/15/2016 1:37 PM, James Ewen ve6srv@... [GPSL] wrote:

Are any of the chase crews going to have radios onboard?

With an APRS capable radio in the chase vehicle, you can hear the payload right down to ground level if you are located close enough to the landing area.

It's pretty hard to have a fixed I-gate installed right next to where a payload will land, but a chase vehicle with an APRS capable radio onboard can usually drive fairly close to the landing area, even when the winds aloft and burst altitude change the landing area from the predicted landing area.

Trying to get a final landed position report to the APRS-IS via fixed assets is a difficult proposition. Mobile I-gates can help get packets to the APRS-IS where cellular coverage allows, but the best bet is to receive the packets directly off air with a radio in the chase vehicle.

Using the APRS-IS stream as your intercept source leaves much to be desired as both the payload can disappear from view of the APRS-IS, but your chase vehicle can lose access to the cellular network as well.

Rarely do remote observers ever recover payloads. People watching the flights from hundreds or thousands of miles away are probably content to see the general landing area within a couple hundred feet based on a last heard position from a thousand feet above terrain as last heard via an I-gate located a hundred or so miles away.


--Michael Willett
Advanced Sourcing, Inc.

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