I’ve been using the 3Dr radios in my MR’s but just started a Pixhawk install on a longer range fixed wing mapper. I got a few RDF900 modems, but given their power would it be wise to install a 5v BEC at the modem? I presume you’d just pull the jumper off the USB5v and the 5v pins and hook the 5v and G to the BEC.
Hi there,
personally I wouldn’t power it off any control board. I’m pretty sure the RFD900 webste has instructions on how to provide standalone power to the modem. That’s what I did many moons ago in my build that uses one. Never had any trouble that way.
If you run anymore than 20dBm, don’t do it. Do as you stated above. Look on RFD900 site for directions and the 5V UBEC. Don’t forget the Tx is only about 33% efficient, so at 1W you will be pulling 3W of power from that poor little 3DR Power Module.
Do you think the RFD900 at 20dbm would be ok powered off the telemetry port then? I’m just running into problem with my 3DR radios when pushing over a 1 km mapping with my hex. So tonight I wired up the RFD900 to the Pixhawk. Unfortunately the cts goes low and put the radio into bootloader if it’s powered off a separate bec. The only fix is to unplug the radio while the Pixhawk is powered up and plug it back in. Then the modem will power up normally. Of course if you put the jumper back in and power from the telemetry port it boots up fine. Arggg. The RFD900 worked flawless with the APM 2.5, but it didn’t have the cts wire.
If you run anymore than 20dBm, don’t do it. Do as you stated above. Look on RFD900 site for directions and the 5V UBEC. Don’t forget the Tx is only about 33% efficient, so at 1W you will be pulling 3W of power from that poor little 3DR Power Module.[/quote]
BTW, I’m not using the 3DR power module as this hex is using 6s packs. I’ve got Attopilot 180 sensor with a 5A bec (Hobbyking Turnigy which seems to be rated at 3a continuous and 5a max lol). Not sure if that makes any difference.
[quote=“X1Aero”]Do you think the RFD900 at 20dbm would be ok powered off the telemetry port then? I’m just running into problem with my 3DR radios when pushing over a 1 km mapping with my hex. So tonight I wired up the RFD900 to the Pixhawk. Unfortunately the cts goes low and put the radio into bootloader if it’s powered off a separate bec. The only fix is to unplug the radio while the Pixhawk is powered up and plug it back in. Then the modem will power up normally. Of course if you put the jumper back in and power from the telemetry port it boots up fine. Arggg. The RFD900 worked flawless with the APM 2.5, but it didn’t have the cts wire.
If you run anymore than 20dBm, don’t do it. Do as you stated above. Look on RFD900 site for directions and the 5V UBEC. Don’t forget the Tx is only about 33% efficient, so at 1W you will be pulling 3W of power from that poor little 3DR Power Module.[/quote][/quote]
Yes, it should work fine. At 20 dBm, it is same as 3DR radio. Btw, what is your ground radio? I get over 5 miles using 3DR air and RFD900 on the ground. I use good dipole in the air like this one, store.rfdesign.com.au/rfdflex1-9 … 0mm-rpsma/ . Of course you have to change the connector to SMA.
I’ll use an RFD900 for the ground radio and keep the 3DR radio in the air. Didn’t realize you could get that kind of range being the air side only has 100mw. I thought you’d be limited to the weakest transmitter… Shows how much I know about radio.
The RFD900 has very sensitive Rx. Use the big dipoles that come with it. On the air side u need a good antenna like I pointed out. The little monopole won’t cut it.
Thanks for the help! Can’t really wait for a new antenna as I need to map today, but being I’ve got 4 or these radio’s I could use one of the larger dipoles they came with on the air end of the 3DR radio and two on the RFD900 ground radio. Actually I’ve got some really nice DJI 900mhz antenna’s kicking around that are for a LK900 modem. Same length but a lot lighter than the one’s that came with the RFD’s. Maybe the only thing I like from DJI lol!
The RFD900 has very sensitive Rx. Use the big dipoles that come with it. On the air side u need a good antenna like I pointed out. The little monopole won’t cut it.[/quote]
Time to go try it out!
I find a very shallow vee on ground dipoles with some equal front to back offset works a treat.
The big dipole will work fine on a plane, but the weight is the killer!!
The ones I linked to are feather light and work great. I stick them on the tail with no CG issues at all.
Good luck!
I’ll try the v today. The 25g antenna won’t make a big deal. This hex only weights 6kg with payload and has a max thrust of 21kg lol!