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Oct 24, 2013, 06:29 PM
When a hobby gets a passion
Quote:
Originally Posted by farmertom
What are the units for the rssi and remrssi parameters? Percent, or raw units. These parameters started out about 150 and drop to about 40 during the flight.
I also have no clue what they stand for, but I know if it drops below 40, you will loose connection. I have now good results with the 915MHz home made antenna's. At 8.5 Km still have good connection with RSSI and REMRSSI slightly above 50. So I think I can go up to 10Km.
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Oct 24, 2013, 06:38 PM
My planes plow into the field
farmertom's Avatar
Quote:
Originally Posted by Pattaya01
I also have no clue what they stand for, but I know if it drops below 40, you will loose connection. I have now good results with the 915MHz home made antenna's. At 8.5 Km still have good connection with RSSI and REMRSSI slightly above 50. So I think I can go up to 10Km.
Thanks for the info. I am assuming that the RSSI/REMSSI is the 3DR radio and not my rc receiver? Correct? Why would my 3DR radio signal be so weak? I was never more that 0.4 Km out. The antenna is on the end of the left wing.
Last edited by farmertom; Oct 24, 2013 at 06:48 PM.
Oct 24, 2013, 09:34 PM
When a hobby gets a passion
Quote:
Originally Posted by farmertom
Thanks for the info. I am assuming that the RSSI/REMSSI is the 3DR radio and not my rc receiver? Correct? Why would my 3DR radio signal be so weak? I was never more that 0.4 Km out. The antenna is on the end of the left wing.
Yes, it is the RSSI from the 3DR radio and not the receiver. You are probably using the stock antenna's. They suck. Those are 2.4 MHz antenna's and bundled with the radio. They are OK if you are flying in close proximity. If you want more range, you need to modify them or build (or buy) other antenna's. A few pages back I made a post regarding this, page 7 and page 12.
Oct 24, 2013, 09:37 PM
When a hobby gets a passion
And another (this time in 720p HD):

FPV flight to Golf course and Chinese Cemetery (4 min 31 sec)
Oct 24, 2013, 10:09 PM
My planes plow into the field
farmertom's Avatar
Quote:
Originally Posted by Pattaya01
Yes, it is the RSSI from the 3DR radio and not the receiver. You are probably using the stock antenna's. They suck. Those are 2.4 MHz antenna's and bundled with the radio. They are OK if you are flying in close proximity. If you want more range, you need to modify them or build (or buy) other antenna's. A few pages back I made a post regarding this, page 7 and page 12.
Again thanks for the info. YOU much be a radio or antenna type person! I know little to nothing about antennas, but I think I need to learn more. Can you help me? From what i have read the 3DR radio is a 915 MHz radio, but the antennas they sell you are 2.4 GHz. Correct, close? So I need to purchase or build a 915 MHz antenna to get better range, correct? I read the post you have about extending the length of the OEM 3DR antenna. I think I can do that. What about the antenna on the ground station? Do I need to the same with it also?
Thanks
farmertom
Oct 24, 2013, 10:16 PM
FPV in Hawaii
iskess's Avatar
Quote:
Originally Posted by farmertom
Thanks for the info. I am assuming that the RSSI/REMSSI is the 3DR radio and not my rc receiver? Correct? Why would my 3DR radio signal be so weak? I was never more that 0.4 Km out. The antenna is on the end of the left wing.
remrrsi means remote RSSI, that's the airborne module. rssi is the ground station module.
rxrssi is your RCRx
Oct 24, 2013, 10:21 PM
My planes plow into the field
farmertom's Avatar
Quote:
Originally Posted by iskess
remrrsi means remote RSSI, that's the airborne module. rssi is the ground station module.
rxrssi is your RCRx
Thanks, learning more all the time!
farmertom
Oct 24, 2013, 11:51 PM
The only R/C pilot in the city
Scorpio9999's Avatar
Quote:
Originally Posted by farmertom
I am not brave enough to turn off the radio to see if RTL really works.
farmertom
Farmertom,
At home (if you haven't OSD setup yet) you can plug USB cable to APM and computer. Check in Mission Planner if you can get info from APM. Switch on your transmitter select Manual mode, throttle idle. Then connect flight battery in plane. In Mission Planner you should see current flight mode - Manual. Then just switch off the transmitter. Motor will not run as APM knows that you didn't fly. In Mission Planner check the mode. It should be RTH now. Switch on transmitter again. In second or less you should see Manual mode again.

In flight before check of RTH you should check two modes: stabilize and FBW-A. If they are Ok then you can proceed with RTH. Be sure that in Mission Planner you set safe altitude as 50-100 meters AGL not MSL.
Oct 25, 2013, 02:09 AM
When a hobby gets a passion
Quote:
Originally Posted by farmertom
Again thanks for the info. YOU much be a radio or antenna type person! I know little to nothing about antennas, but I think I need to learn more. Can you help me? From what i have read the 3DR radio is a 915 MHz radio, but the antennas they sell you are 2.4 GHz. Correct, close? So I need to purchase or build a 915 MHz antenna to get better range, correct? I read the post you have about extending the length of the OEM 3DR antenna. I think I can do that. What about the antenna on the ground station? Do I need to the same with it also?
Thanks
farmertom
Yes, the antennas they sell are 2.4 GHz. I guess they don't even know that themselves, or just don't care. Yes, you need to purchase or build 915 MHz antenna's, but it is not as hard as you may think. Both your plane as well as your ground station need to be changed. Only changing 1 doesn't make much of a difference. If you make both antenna's longer as I mentioned in page 7, you get a range of a few Km. If you manage to make an antenna for your groundstation as I mention on page 12, you get around 10Km. That is what I have now.

So on the plane I have a modified 2.4 GHz, on the groundstation a Yagi. You can see from the graph, RSSI and REMRSSI do not drop below 50, at almost 8 Km distance.

Yes, I am an antenna guy
Last edited by Pattaya01; Oct 25, 2013 at 02:38 AM.
Oct 25, 2013, 07:38 AM
My planes plow into the field
farmertom's Avatar
Quote:
Originally Posted by Scorpio9999
Farmertom,
At home (if you haven't OSD setup yet) you can plug USB cable to APM and computer. Check in Mission Planner if you can get info from APM. Switch on your transmitter select Manual mode, throttle idle. Then connect flight battery in plane. In Mission Planner you should see current flight mode - Manual. Then just switch off the transmitter. Motor will not run as APM knows that you didn't fly. In Mission Planner check the mode. It should be RTH now. Switch on transmitter again. In second or less you should see Manual mode again.

In flight before check of RTH you should check two modes: stabilize and FBW-A. If they are Ok then you can proceed with RTH. Be sure that in Mission Planner you set safe altitude as 50-100 meters AGL not MSL.
Thanks again. I have done the "turn off the transmitter" checking the RTL on the ground, in the shop, and it works as advertised. I just am chicken to do it for real. Currently my RTL altitude is set to 250 ft. I am going to chance that to 350 ft. AGL.
thanks
farmertom
Oct 25, 2013, 07:50 AM
My planes plow into the field
farmertom's Avatar
Quote:
Originally Posted by Pattaya01
Yes, the antennas they sell are 2.4 GHz. I guess they don't even know that themselves, or just don't care. Yes, you need to purchase or build 915 MHz antenna's, but it is not as hard as you may think. Both your plane as well as your ground station need to be changed. Only changing 1 doesn't make much of a difference. If you make both antenna's longer as I mentioned in page 7, you get a range of a few Km. If you manage to make an antenna for your groundstation as I mention on page 12, you get around 10Km. That is what I have now.
So on the plane I have a modified 2.4 GHz, on the groundstation a Yagi. You can see from the graph, RSSI and REMRSSI do not drop below 50, at almost 8 Km distance.
Yes, I am an antenna guy
OK, Well I guess I am off to build or buy some 915 MHz antennas. Thanks for the info. I will be looking back at your older posts.

I looked at my flight log again looking for the rssi of my tx radio. My current set-up is a FrSKY DJT tx and rx. The value for the rxrssi parameter was about 20, but remained constant though out the flight. Again anyone know what the units are for that parameter? Is that good or bad? any comments?
Thanks again
farmertom
Oct 25, 2013, 09:07 AM
My planes plow into the field
farmertom's Avatar
Quote:
Originally Posted by Pattaya01
I also promised to publish how to change the antenna to work on 915MHz. After I opened the antenna, it was clear they were for 2.4MHz, as 1/4 wavelength of 915MHz is 82mm. These were clearly not 82mm. So:
1. Remove the rubber stub
2. Cut the wire and leave a few mm
3. Solder a wire of about 85mm to the remainder
4. Cut it at 82 to 83mm from the shield (as on the pictures)
5. Drill a hole with a slightly bigger diameter than the wire you just solder on
6. Put the stub back
Done. I have tested it up to about 300mtr, still had around 70% signal. Not too bad and I will try to get the maximum distance.
Found it! Looks easy enough. How did you remove the rubber stub? What gauge wire is needed?

Have you discussed this with the 3DRobotics people. Seems like a mistake they would want to fix.
Oct 25, 2013, 12:47 PM
My planes plow into the field
farmertom's Avatar
Me again,
I am posting the graph of the first flight, showing the rssi and noise of both the tx and the rx radio, distance from home and the rc radio rssi (I think the parameter has been renamed). Looks like I almost lost the connection between 12:37 and 12:38.
I found how to convert the raw data from the graphs to signal dBm.
signal_dBm = (RSSI / 1.9) - 127

Comments?
thanks
farmertom
Last edited by farmertom; Oct 26, 2013 at 08:35 AM.
Oct 25, 2013, 04:48 PM
Registered User
does latest code is reliable
are you happy with it
Oct 25, 2013, 07:34 PM
When a hobby gets a passion
Quote:
Originally Posted by farmertom
Me again,
I am posting the graph of the first flight, showing the rssi and noise of both the tx and the rx radio, distance from home and the rc radio rssi (I think the parameter has been renamed). Looks like I almost lost the connection between 12:37 and 12:38.
I found how to convert the raw data for the graphs to signal dBm.
signal_dBm = (RSSI / 1.9) - 127

Comments?
thanks
farmertom
Thanks for the calculation, that clarifies a lot. A very well build radio, with a good quality receiver, usually can work with signals up to - 100 dBm. When the RSSI shows 40, that is - 105 dBm, which is very low. Most radios give up below - 110 dBm. In your graph, your lowest RSSI is around 60, - 95 dBm. Still OK. But it clearly shows how bad these antenna's are. You'll never be able to get more range out of them. Take your soldering iron and start modifying.

You can remove the cover but you have to use a bit of force. They are pretty tight fitted. The wire diameter you use is not important, the length is important. I am using the core wire from a coax cable, which is about 1mm diameter. It's quite stiff because it is not 100% pure copper wire, but bronze.

By the way, I found a way to make the graph more clear. If you first left click on RSSI and REMRSSI, you can then right click on DIST_HOME. Try it and you will be surprised.
Last edited by Pattaya01; Oct 25, 2013 at 07:42 PM.


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