Rfd900 coverage/reach

Does somebody use rfd900?
you you tell me something about coverage/reach in praktikal use with standart 3 dbi antennas?


with standard antennas, clear line-of-sight:

with standard antennas, 100m of vegetation obstruction:

many other times I’ve had the grey bars dropping out while working without proper troubleshooting or good information to go on.

hopefully with better antenna placement, new tools and more information, it will get better overall. I know the radios can do the job :wink:

i did buy the modems - they are fine for flying a copter …

but they are useless for agricultural etc…

for sale rfd868 mhz for europe…

you should mention this in your docs!!!


900Mhz and 868Mhz is for line-of-sight operation. And for that the radios are useful. Even a little bit beyond line of sight or a little bit obstructed.

If you want to be away from line of sight, then all you need is a repeater on a high point of ground that can see the base and the rover. RFD radios are multi-point capable, so they can do that job.

If you want a beyond line of sight radio then you need a much lower frequency IMO. See:

(at this link there is a picture of a repeater setup also.)

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@Andreas_Ortner You should also look into more directional antennas and try to locate antenna as high as possible. If I understand correctly you have permanent base location, so radio antenna can be located on top of some building. This can certainly help you increase range.

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i can mount it 15 m above the ground this is perfect…

but i want use it for agricultural, so i need communication 5 km in every direction - directional antennas would not work for this…
there are also buildings and trees between base and rove…

next problem: if did buy 868mhz - they are allowed in europe - but there are many restrictions for this…

i can´t use full transmit power with 100 % duty cycle. i did not find 100 % answers for this in our country.

rfd900 can send with 1000mw but with this only 0,1% dutiy cycle is allowed.
if i want use 100 % i must decrase power to 100mw…

  • An antenna tracker would let you use a directional antenna which means less power required.

  • With the RFD radios, 1% duty cycle might work with the max 250kbps air data rate and 1Hz update frequency. That is pushing the limits though. What power is allowed at 1% duty cycle (and 10% as well)?

  • Apparently people talk to the moon with 1 and 2 watts of power.

  • It seems the best signal booster is more antenna height above ground.

I did have a look.
At 869,4 MHz it’s allowed to send with 500mw and 10 % duty cycle limit…

:smile: Fine I thought I need 100%.

Could you give me suggestion for setting for 1 hz at base and 5/10 hz at Rover …

i still wouldn’t rely on more EIRP (like 500mw) for a distance that long; especially if there are obstructions between the two points;
you could try something expensive like: ARF868 LR 500MW
but with an old APM (with antenna tracker software from ardupilot) and an antenna tracker and a directional antenna you will have a much better signal for probably much less money;

What’s the difference rfd900 has 1000mw up to 40 km…

But nowhere you can read what is the power with standard antennas and so on…

I will try what bide write…

it’s for the 900mhz version (didn’t know there is a 868mhz version - seems i didn’t read your post very thoroughly - sorry):
it tells you how to calculate it under point 3 and some other stuff (like voltage drops)

but yeah stick to bide’s response - it’s actually the right answer;

You can also try an antenna like this one. It has 5dBi gain and optimal directivity for your application.

hi again!

now i have found the document in austrians law.

it is allowed to send

at 869,4-869,65 mhz (rfd868 can do it)
duty cycle limit 10 %
with maw 500 mWatt erp

could somebody help me to calculate it.
rft868 can do from 0-30dbm
i use standart antenna 3dbi



i know this webpage! i am not shure what i should insert.

hallo du kommst ja aus wien!!

meine mail office@gh-ortner.com

hallo, jo, a wiener!

i updated the link - this one’s easier:
according to manual rfd900 has 30db output
cable loss is about 0.3dbi/meter with good ones (edited: “antenna” changed to “cable”)
antenna gain depends on your antenna 2db for standard
30 (output) - 0,9 (antenna loss for 3m) + 2 = 31,1dbm
insert that value
have to go now, good luck!

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do a steirer!!


if i use rfd with 26 db and 3db antennas=29
if i insert this i the calculator erb =484 mW


If you need the max power to be in EIRP (effective isotropic radiated power), then:

21dBmTXpower - 0dBCableLoss + 3dBiAntennaGain * 2 = 27dBm EIRP


10(27dBm/10) = 501mW EIRP

reference: RFD900 Radio Modem Data Sheet, Section 3. Power Levels (page 5)


Thanks you !

In the document it is erb.
If my calculations are right 29 to 30 are ok! 26+2*3

Bide can you give me information for the setup with 10% duty cycle for rfd868
What shall,I,turn on and what off?
I run base with 1hz and rover with 5 or 10 hz…

This is my radio config, with your changes in bold. I’ve left the TXpower for you to decide:

[1] S0: FORMAT=27
[1] S2: AIR_SPEED=64
[1] S3: NETID=8
[1] S4: TXPOWER=?
[1] S5: ECC=0
[1] S6: MAVLINK=0
[1] S8: MIN_FREQ=915000
[1] S9: MAX_FREQ=928000
[1] S10: NUM_CHANNELS=50
[1] S11: DUTY_CYCLE=10
[1] S12: LBT_RSSI=0
[1] S14: RTSCTS=0
[1] S15: NODEID=1
[1] S17: SYNCANY=0
[1] S18: NODECOUNT=2

I picked 64 for air data rate for you to start with based on:

2458bps at 10% = 24580bps at 100% duty cycle
24580bps < 64000bps (leaving some headroom)

These are suggested settings - not tested. Good luck!

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