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Nov 08, 2017, 11:50 AM
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Discussion

RC Repeater


Project
The research project my group is working on involves us flying a multi rotor at low altitudes around buildings. The pilot is to remain stationary for safety reasons and observers with walky-talky are placed along the UAVs path. Also before any concerns arise we have a range safety officer in contact with Flight Traffic Control during all field operations.

Hardware
We are using a DJI S1000 frame, Pixhawk Autopilot, and Spektrum DX-18 RC.

Question
We are having lost link issues when traveling around buildings. I am looking for an RC repeater that functions as a repeater network. The ones Iíve come across function as boosters which function fine for long range flights but doesnít address our problem with obstructions. Iíd like a system where I could place portable repeaters at intersections so I still have RC link around corners. Does anyone know of anything like what Iíve described?
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Nov 08, 2017, 11:55 AM
AndyKunz's Avatar
The root cause of your problem is that you are using a frequency band which is easily reflected and blocked. You should be using a much lower band (MHz levels) so that the radio waves pass through the buildings instead.

Andy
Nov 08, 2017, 12:07 PM
Registered User
I will look into this but the buildings we are flying around are very dense. Some have anechoic chambers in them for the specific purpose of blocking radio signals.
Nov 11, 2017, 01:23 PM
Forward ever, backward never!
Brainstorm's Avatar
stythys: Lower frequency radio waves can "bounce around" obstructions, so to speak, in addition to penetrating through denser objects. So even if they can't travel straight (aka "line of sight") to your RX, reliability of transmission will be improved. TBS Crossfire is currently the most popular long-range RC radio system. I would look into that.

In terms of repeaters, I haven't heard of any RC specific solutions. My guess would be to inquire with local HAM radio operators. They routinely use repeaters for voice and data transmission. So they will likely be more knowledgeable on the topic.
Nov 11, 2017, 02:55 PM
Registered User
Quote:
Originally Posted by stythys
I will look into this but the buildings we are flying around are very dense. Some have anechoic chambers in them for the specific purpose of blocking radio signals.
Those chambers are designed to block sound waves.
Nov 11, 2017, 10:00 PM
Rust: The poor man's Loctite.
TomM's Avatar
Quote:
Originally Posted by Volt_Ampere
Those chambers are designed to block sound waves.
Not really.. I work here-
http://www3.arl.psu.edu/facil_anechoic.php
Nov 12, 2017, 02:46 AM
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Kambalunga's Avatar
I'd try passive repeaters.
Nov 15, 2017, 10:14 AM
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rgburrill's Avatar
Quote:
Originally Posted by Volt_Ampere
Those chambers are designed to block sound waves.
I love it when people respond with such authority on a subject of which they know nothing. I've used anechoic chambers for 50 years testing EMI/RFI requirements on military electronics systems.
Nov 15, 2017, 11:12 AM
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P.I.Engineer's Avatar
with rfd900's you could pass rc control through telemetry, i believe there will be some latency so be careful.
Nov 15, 2017, 04:20 PM
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rgburrill's Avatar
Quote:
Originally Posted by P.I.Engineer
with rfd900's you could pass rc control through telemetry, i believe there will be some latency so be careful.
900MHz. Won't handle 2.4GHz. Plus the transmit power is way too high and too broadband. Even if one were available at 2.4GHz a broadband repeater would likely distort the very narrowband, frequency hopping signal of the transmitter. And broadband would be necessary for a passthrough device because of the frequency hopping.
Last edited by rgburrill; Nov 15, 2017 at 04:30 PM.
Nov 15, 2017, 04:29 PM
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rgburrill's Avatar
OP will probably have to design his own system. Could possible be done with an OpenTX transmitter with telemetry input. Perhaps it could be programmed so the receiver input would read the original transmitter output and then retransmit it on a different frequency using the transmitters frequency hopping algorithm. The receiver in the drone would tune into that new frequency since the pairing address would still be the same.
Sounds like a good task for our OpenTX fans to look at.
Aug 07, 2018, 12:20 PM
Registered User
Hi People,
I have the same setup as above. I need a full parameters file to upload to my drone. Can someone please share?
Thanks
Aug 07, 2018, 09:25 PM
TAFTS
I have thought about this exact thing in the past.

I have come up with some ideas but haven't tried anything yet.

Hmmm....
Last edited by Scott Todd; Aug 07, 2018 at 11:45 PM.
Aug 08, 2018, 02:45 AM
Registered User
Kambalunga's Avatar
Quote:
Originally Posted by rgburrill
OP will probably have to design his own system. Could possible be done with an OpenTX transmitter with telemetry input. Perhaps it could be programmed so the receiver input would read the original transmitter output and then retransmit it on a different frequency using the transmitters frequency hopping algorithm. The receiver in the drone would tune into that new frequency since the pairing address would still be the same.
Sounds like a good task for our OpenTX fans to look at.
Note that FHSS or FH-DSSS is used. So the frequency changes constantly.
2.4g is quasi optical, no line of sight is always bad!
900 MHz has the better penetration and is therefore also used in the racecopters.
Aug 08, 2018, 08:01 AM
Registered User
I would use a "relay" like another copter placed above the obstacles/buildings (depending on how high they are). Think 3 dimensional
Maybe an autonomus glider which circles your area and retransmits your radio signals. Or a blip. Depending on how long you want to fly. I would use 900MHz as downlink and 2.4G as uplink.

Or let it fly along waypoints.


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