I have upgraded to a 1 watt radio, but even with good dipole antennas I am only getting around 800 meters through trees and buildings (much more when up in the air of course). Better antennas may help, but I am considering using more power and 5 watt amplifiers appear to be possible to connect to the 3DR/Hope transmitter modules. I am concerned about transmitting and receiving with one module though. Has anyone done this before and know if the receiver circuit could be disconnected from the transmitter and bypass the 5 watt amplifier, so that it could transmit and receive half duplex with one antenna?
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Yes, that would be nice. You might have to overpower the other person's transmitter. A 5 watt linear amplifier would probably work for transmitting and you could use a second module for receiving (and two antennas), but it might be worth experimenting to see if you could connect the receiver to the transmitter and have one small module.
Usually antenna placement and checking RF cables for loss will help. In most systems poor quality cable and connectors will have the greatest effect.
You can connect a 5W linear amplifier and it will work. I assuming the 5W Liner amp has a built in 'RF switch' so the transmit power doesn't reflect directly onto the receiving stage. Unless you are building a home-brew solution?
That said using more power may give you distance when line of sight, but trees and buildings are exceptionally good attenuators at these frequencies
FWIW, we're getting 30km comfortably with RFD 900's, with a 900MHz patch antenna on the vehicle and two OEM stick-on dipoles on the plane. I think their max power is 1W.
5W seems overkill unless you want to go 60km+?
21km on a bad day with RSSI's in the 90's:
30km is very good. I don't feel that I need 30km or 60km of range, but I am more concerned about poor reception when flying low near trees or around hills.
yes, it's possible to transmit at 100W too, that would be equally illegal in most countries, and equally bad for all those other devices you would interfere with.
True in most cases, but I have an amateur radio license and I plan on doing it legally like APRS data packets on 440mhz. Amateur handheld transceivers use 440mhz at 5 watts legally and don't interfere with anyone.
then you would know difference between mhz and Mhz ?
-sorry , but you asked for it :)
and between Mhz and MHz...
hahahaha love it :)
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