On the Avalon and the subject of the reach you can comment as follows: transmitter and receiver are both a gps and the issuer uses radio waves to send your gps position to the receiver. I believe that the extent to which comment (20 km) is in conditions optimal and it is because the radio signal has to get strong enough to load the gps which is very "heavy" information sent by radio. If it comes loose beep does not have capacity to load the gps information. Not is if in fact at some point it have been sold, maybe someone from here can give us more information, nor is prices. The drawback that I see, apart from the scope rather limited removing part of the interest of having a gps, is also their weight and how great that is.
Another system David Silva sells it,(creo que David Falco aqui en el foro), the same you may talk about your system I much better. It combines a gps and a phone and call the issuer to locate it. If I am not mistaken it has no built-in normal radio transmitter. Also manufactures altimeters that among others used in the days of Leon. Placed before the bird flight and after flight can connect to a pc to view the height, graphics etc...
We will draw for this season (or at least I hope, because I've been waiting for more than two years) three systems manufactured in Spain, took months with tests that are going quite well:
-A transmitter that incorporates an altimeter and you give the height of the bird in real time on the receiver, weight +-6.5 gr
-A transmitter that incorporates the above mentioned but a gps that you will receive the exact position of the bird in your receiver, with indication of direction and distance or map according to the model. It weighed +- 9.5 g and will be fully digital, or that with enough beyond the Avalon
-A transmitter that incorporates the above mentioned more, i.e. radio-altimeter-gps-gsm phone. Tea will locate your bird's normal form and advance to the gps-gsm if things get ugly and is out of reach. For Europe is perhaps the perfect because it combines everything and there is good coverage of phone. You will have a weight of about 15 grams. You can program in any frequency range 430 for those who want to keep your old receiver for the part only buy the issuer or the issuer (if you already have a gps or a pda) and radio + PDA. Clear this with receivers from other brands do not you will have access to the data of height.
"Born to fly"