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Feb 20, 2015, 12:41 PM
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Control frequency for flying drone through forest?


I'm in the early planning stages of a Woods Witch build, in other words an FPV 250 quad copter capable of flying through the woods with a range of about 500M.

Based on my research this will require OpenLRS 433MHz for control. Is this correct? I'd rather go with 2.4GHz and 1.3GHz vTx + bandpass filter. Some guys claim a FrSky 2.4GHz system can penetrate obstacles but I can't find anything about woods flying. Hard to imagine 2.4GHz could work for my needs but I thought I'd ask before committing to OpenLRS.
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Feb 20, 2015, 01:03 PM
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coriolan's Avatar
You could take a look here:
https://www.rcgroups.com/forums/show....php?t=2014759
Feb 20, 2015, 01:32 PM
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Originally Posted by coriolan
Thanks but I believe they are talking about the FPV vTx system frequency. I've already selected a 1.2/1.3GHZ vTx so I'm trying to figure out if I can get away with a 2.4GHz controller frequency or if I need to go with OpenLRS at 433MHz.
Feb 20, 2015, 02:44 PM
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coriolan's Avatar
The best way to find out for sure is to try itNothing wrong with being a "trail blazer"!
Feb 20, 2015, 04:24 PM
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I think I just might have to.

In that case, my question becomes, which 2.4GHz transmitter/receiver combo is best for penetrating objects? I see a lot of praise for the FrSky system - does anyone have other suggestions?
Feb 20, 2015, 04:47 PM
AndyKunz's Avatar
I don't know of any which bypass the laws of physics. Multipath and absorption are going to be monstrous in a forest, especially in summer.

Andy
Feb 20, 2015, 04:58 PM
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Due to the high moisture content (foliage), the higher the frequency, the lower the penetration (shorter range). Also a problem with reflections; circular polarization will help with that problem as the reflections will be 180 degrees out of phase so no cancellation from them.
Feb 20, 2015, 06:21 PM
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Wintr's Avatar
Quote:
Originally Posted by Rodney
Due to the high moisture content (foliage), the higher the frequency, the lower the penetration (shorter range). Also a problem with reflections; circular polarization will help with that problem as the reflections will be 180 degrees out of phase so no cancellation from them.
This may be an argument for a 72MHz system.
Feb 20, 2015, 06:47 PM
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richard hanson's Avatar
Weather conditions also play a large role. Increased moisture in the air increases path loss. The higher the frequency, the higher the path loss.

Beware leafy greens. While a few saplings mid-path are tolerable, it’s very difficult for RF to penetrate significant woodlands. If you’re crossing a wooded area you must elevate your antennas over the treetops.
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Feb 20, 2015, 07:04 PM
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Quote:
Originally Posted by AndyKunz
I don't know of any which bypass the laws of physics. Multipath and absorption are going to be monstrous in a forest, especially in summer.

Andy
These guys seem to have demonstrated the viability of the physics.

Edit: Another link to the Airgonay race course.

Looks like they're using 5.8GHz FPV with circular polarized antennas, but I can't tell what controller frequencies they're using.
Last edited by Caraxes; Feb 20, 2015 at 07:20 PM.
Feb 20, 2015, 07:06 PM
AndyKunz's Avatar
150m course. They haven't done anything yet. OP wants 500m of woods between him and his model.

Andy
Feb 20, 2015, 07:30 PM
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Edited my previous post before I saw yours, Andy.

Looks like they're using 5.8GHz vTx with circular polarized antennas on both Tx and Rx. So 1.2GHz FPV video should get decent range in the woods. Maybe not 500M but surely more than 150M, you think?

That leaves the controller frequency. Since so many are flying at once my guess is 2.4GHz, and I did see a few FrSky transmitters. I wonder how much more range they get beyond the 150M course?
Feb 20, 2015, 07:48 PM
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ivanc's Avatar
150m course and they are in the center - that is no more than 75-80m away which is nothing for 2.4GHz even in a forest like the Airgonay course.

500m away from the transmitter in that forest is a totally different story though.

Ivan
Feb 20, 2015, 10:04 PM
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What range do you suppose is possible for a good 2.4GHz Tx/Rx combo in such a forest?
Feb 21, 2015, 10:44 AM
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One last question before I try this: you guys who say this is physically impossible, have you actually tried flying in obstructed areas using 2.4GHz or 433GHz?

If I could get even 250M I'd be happy, though 500M would be nice for some headroom.


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