Thread Tools
Sep 22, 2010, 05:02 AM
Suspended Account
Okay, this one is for mattay, as he seems dead set on proving his point. I had to do some digging into some of my old stuff, but here's two Google earth screenshots showing ground based testing of the following configuration:

- Futaba 10C with 2.4GHz FASST
- 1W eBay WiFi booster, verified to output +30dBm
- Stock whip antenna on the 10C
- R6014FS RC diversity receiver, antennas up in a V
- Lawmate 1.2GHz 500mW Tx with stock whip antenna at 50cm from the RC receiver
- Channel selection from 1080 to 1180MHz, best result shown
- One Hitec HS65HB servo used

The Tx was put on a tripod out in the field, the Rx was on the roof of my car and the 10C was in servo test mode, hence the servo was moving all the time. I kept on driving to a point where servo movement stopped completely. Below is the best result attained with 1080MHz selected on the 1.2GHz Lawmate Tx, other channels fared worse.



Fig 1. Maximum range without a audio/video transmitter nearby.



Fig 2. Maximum range with a 1080MHz audio/video transmitter nearby.

It has to be noted that my flying location is very clean RF wise, as I'm out in the boonies. And the road I'm travelling on has very little obstructions, just trees at regular intervals and the occasional farm.

I've done similar testing without the 1W WiFi booster but I can't find my test results, probably because they were abyssmal. However it should be noted that in the air things obviously look a lot better, as there's clear LOS and no obstructions. What I wanted to show however is that a 2.4GHz RC receiver is (severely) desensitized by a strong source of RF nearby, such as the audio/video transmitter used.

Cheers,

Sander.
Sign up now
to remove ads between posts
Sep 22, 2010, 08:50 AM
Registered User
Sander,

I think your results are actually quite similar to what mattay is saying. Using 30dBm Tx power he calculated 6900m distance while you measured about 2km. Consider that you where on the ground (Tx and Rx height ~2m or so) while he assumed that the Rx height is 60m, he also did not consider interference from the video Tx. From the top of my head, assuming free space propagation, the difference 2km->8km should be 12dB. I think a ~12dB difference can be explained by not being in the Fresnel zone and by the increased noise floor caused by the video Tx.

Regarding video Tx, what is your opinion on 5.8GHz video? It should theoretically not degrade the performance of the 2.4GHz RC equipment.

Best,

Shredder
Sep 22, 2010, 09:10 AM
Suspended Account
Quote:
Originally Posted by HeliShredder
... he also did not consider interference from the video Tx. ...
One of the problems is he's approaching this from paper specs or calculations on a paper napkin. I've done that too when I first started with this hobby. Only to find out that on many occasions there's a significant difference between what your calculations tell you and what happens out on the field.

Several factors come into play, some of which are beyond your control or understanding, such as the design of the RC receivers front end, its hopping sequence, the FHSS algorythms, the BER it is able to recover from etc. etc. all that is IP from the respective manufacturers. Just making this a simple matter of calculating losses in dB is a little too simplistic really.

Quote:
Originally Posted by HeliShredder
Regarding video Tx, what is your opinion on 5.8GHz video? It should theoretically not degrade the performance of the 2.4GHz RC equipment.
My experience with 5.8GHz has been positive thusfar, although obviously losses are larger then at lower frequencies so connector and cable losses play a significant role here. However when you do install a 600mW 5.8GHz Tx on a plane you are still desensitizing the 2.4GHz RC receiver to some extent, although some are affected more than others.

One thing I'd like to mention again in that regard is that not all 2.4GHz RC control systems are created equal, some really have a much better design and are far better able to handle out of band RF on their frontend. Spektrum, although popular for non-FPV flying, is not faring well unfortunately.

Cheers,

Sander.
Sep 22, 2010, 11:08 AM
Registered User
Quote:
Originally Posted by ssassen
Okay, here's where you need to put your money where your big mouth is. Quote me, where did I write that exactly, in those exact words? If you cannot, please shut the f*ck up as you're trolling.
https://www.rcgroups.com/forums/show...&postcount=167

In the post you note
Quote:
"Not really, but we do kind of grow tired of the typical Spektrum user getting into FPV and strapping his parkflyer Spektrum Rx to his EasyStar and not making it out further than the nearest tree and subsequently complain about it here"
https://www.rcgroups.com/forums/show...&postcount=155

And
Quote:
"...and then someone in your neighbourhood complains because they get noise and static on their 2.4GHz equipment and calls the FCC. The FCC drops by and gives you a big fine for using an illegal device."
As we've covered, these are not illegal.

and https://www.rcgroups.com/forums/show...&postcount=160

And
Quote:
"So if you want to start out with FPV and just want to buzz around the local field you can certainly do that. If you however want to grow into the hobby and start exploring further 2.4GHz RC control quickly becomes a bottleneck. The majority 'OMG I lost my plane' posts on these forums are from 2.4GHz RC control users, that should tell you something.

But hey, don't take my word for it, I just am an electrical engineer with a masters in communication technology that designs and sells FPV equipment. I'm just a n00b, many of you just starting out with this hobby know better than me ... for sure"
And as we've covered, the majority of RC gear sold is 2.4 GHz, so of course the majority of losses would be on 2.4 GHz.

Should I expand outside this thread? Yes, I've screen captured the best gems.
Sep 22, 2010, 11:13 AM
Suspended Account
trappy's Avatar
matttay: can you find one post here on the FPV section of the RCGroups forums where someone lost signal on 35 / 72 and crashed subsequently? One will do ... until then, just let it go. Please. You're making a complete out of yourself
Sep 22, 2010, 11:23 AM
Suspended Account
Quote:
Originally Posted by matttay
No, I don't, you might want to read again, I wrote:

Quote:
... and not making it out further than the nearest tree and subsequently complain about it here ...
Now please quote me exactly, where have I written that with 2.4GHz RC control you can't fly behind a tree. You keep using that as an argument against me, yet I have never claimed anything like that. So please, give me an exact quote or STFU!

Quote:
Originally Posted by matttay
As we've covered, these are not illegal.
Well, you seem to be operating under the assumption that there's only US readers here. Or, which would be more disturbing, seem to think only US laws matter. In most of Europe data packet based wireless communication in the 2.4GHz band (WiFi for example) has a 100mW EIRP with a 10% duty cycle limitation. I already outlined that, but you seem to conveniently brush that aside.

Quote:
Originally Posted by matttay
[And as we've covered, the majority of RC gear sold is 2.4 GHz, so of course the majority of losses would be on 2.4 GHz.
So? I have another eye opener for you; car accidents happen because many people own and drive a car. You are stating the obvious. There's a direct correlation between 2.4GHz RC control and FPV flying, for reasons I'm not going to outline for the umpteenth time.

Quote:
Originally Posted by matttay
Should I expand outside this thread? Yes, I've screen captured the best gems.
Yes please, I'm in the mood for ripping someone a new one. Oh, but before you do that, make sure you have ample ammunition, calculations on a paper napkin are not going to cut it here I'm afraid. You need to actually try it all in practice, or you'll be coming up wanting. If you don't want to go to that length you might as well want to stop right now ...

Cheers,

Sander.
Sep 22, 2010, 11:34 AM
Registered User
Daemon's Avatar
Quote:
Originally Posted by ssassen
Ps. @ian, regarding camera noise, you did notice my posts in the 'Camera noise' topic didn't you?

https://www.rcgroups.com/forums/show...&postcount=226
https://www.rcgroups.com/forums/show...&postcount=237

Cheers,

Sander.
Yes I did, but can you guarantee that the same is true for the various other
devices I listed? For instance, my UHF range testing also showed that the VSN500 is
much noisier than the VSN505 (SN777) and it's actually the more popular of the two.

BTW, adding the dpcav filter solves the 2.4Ghz range issue just as surely as
adding the ferrite ring to the VSN505 appears to solve its noise issue, so why
keep battling that straw man?

ian
Sep 22, 2010, 11:45 AM
Suspended Account
trappy's Avatar
Ian, you like to bring that one up as well - fair is fair and that's just a part of the problem.

but who am I talking to ... guys, use 2.4GHz for R/C, especially Spektrum, preferrably with a video frequency that is as low as only physically possible to get the most out of your range. it's obviously the solution to all your long-range requirements, and should you ever run out of range, just boost it with a high quality wifi booster. you will soon experience the most thrilling FPV flights possible, make the best FPV videos known to man and chicks will all fall down on their knees right in front of you.

In the meantime, I'll be right over here flying away with my old analog R/C and UHF system at a fraction of the range, a fraction of the reliability and will spend an arm and both legs for the pleasure.

YOU ROCK!








.... NOT
Sep 22, 2010, 11:53 AM
Registered User
Daemon's Avatar
Quote:
Originally Posted by trappy
matttay: can you find one post here on the FPV section of the RCGroups forums where someone lost signal on 35 / 72 and crashed subsequently? One will do ... until then, just let it go. Please. You're making a complete out of yourself
Then here's one (actually have reported this before back in 2008).
I've lost signal on 72Mhz and crashed an FPV plane while flying at two
different large slope soaring events with about 15-20 other people in the air who were *not*
on my channel. Was using Futaba PCM with a double length antenna. In fact, severe
glitches for a number of people are pretty common on 72Mhz at such events
and I've seen it happen with as little as 4 or 5 Tx's active.
They're worse when the plane is flying closer to someone else's Tx or a small
cluster of other R/C pilots, than your own Tx. Generally the way people work around
the problem is to walk toward the direction that the glitches occur to increase
their own Tx's signal strength relative to the source of the noise. Of course this is
not really viable with a fixed FPV ground station so it's just a major hassle. This
problem is actually what originally drove me from 72Mhz to 2.4Ghz (switched right
before my next largest soaring event at the time, Soar Utah 2008).

Beyond that, on my home slope, 72Mhz (same setup.. Futaba PCM, double length
Rx antenna) would only reach out a mile before onset of failsafe. Pretty much
exactly the same range as a stock 2.4Ghz system at the same location despite
having 5x the power.

ian
Sep 22, 2010, 11:59 AM
Suspended Account
trappy's Avatar
I said I was out ... and I'm out ... this is just ridiculous and at this point I have nothing left but to wish you best of luck in your long range efforts. as a small advice, do follow mine ... and let's not compare our results. adios!
Sep 22, 2010, 12:00 PM
Registered User
Quote:
Originally Posted by ssassen
One of the problems is he's approaching this from paper specs or calculations on a paper napkin. I've done that too when I first started with this hobby. Only to find out that on many occasions there's a significant difference between what your calculations tell you and what happens out on the field.

Several factors come into play, some of which are beyond your control or understanding, such as the design of the RC receivers front end, its hopping sequence, the FHSS algorythms, the BER it is able to recover from etc. etc. all that is IP from the respective manufacturers. Just making this a simple matter of calculating losses in dB is a little too simplistic really.



My experience with 5.8GHz has been positive thusfar, although obviously losses are larger then at lower frequencies so connector and cable losses play a significant role here. However when you do install a 600mW 5.8GHz Tx on a plane you are still desensitizing the 2.4GHz RC receiver to some extent, although some are affected more than others.

One thing I'd like to mention again in that regard is that not all 2.4GHz RC control systems are created equal, some really have a much better design and are far better able to handle out of band RF on their frontend. Spektrum, although popular for non-FPV flying, is not faring well unfortunately.

Cheers,

Sander.
If it makes you feel any better, my first FPV flight was 2006, on a easy star with a 600 mW system from the now-defunct Microwireless. The "ground station" was an Aiptek DZ0V38 that had a tendency to shut down without warning with larger SD cards. That required me to dial in a few clicks of rudder trim to hold the airplane in a big loop until I could restart the aiptek and see where I was. All that flying was done from my TX6H.

I currently have a 800 mw 1.2 GHz system in a skywalker, Gopro, FY stab + OSD. Yes, with Spektrum. The RTH functionality gives me piece of mind.

Wrt desense, the easiest thing folks can do is ensure the vidTX and cont RX are somewhat removed, and then confirm the range check with the video TX on and off. If the number of paces in the range check are not identical, or within 1 step, then adjust your setup.

Excellent data, thanks for sharing. It helps one to understand the foundation upon which you have built your beliefs.

Note others have done ground tests without VTX and shown distances for both Futaba and Spektrum (stock) well over >3 km without video (http://www.rcuniverse.com/forum/m_98..._1/key_/tm.htm).

You are showing 4.73 km boosted without video, which seems a bit low (but probably withing reason) compared to stock units above and Crist and Daemon reports below. But it is what it is.

Crist has shown 6.2 km in a boosted Spektrum with video.

Daemon has shown boosted FASST at 8 km (ground test) with significant degradation (3-4 dB) from 1.2 GHz video. With filter added, back to >8 km range.

It seems the state of the art, with existence proofs, have motored past your somewhat dated tests. Perhaps it's time to re-evaluate?
Sep 22, 2010, 12:08 PM
Suspended Account
trappy's Avatar
ohh ... and before I leave ...

Quote:
Originally Posted by matttay
It seems the state of the art, with existence proofs, have motored past your somewhat dated tests. Perhaps it's time to re-evaluate?
matttay: >8km on 1W you say? wow now that's impressive. seriously. you might break the long range record of 2002 with that, although they probably did it on 100mW

this is an open invitation that you may take up anytime. please do come by my place, we'll fly a bit. as I've said before, and I will say again, the one who walks up the mountain will have the final verdict on what's state of the art, ok? until then, enjoy your RTH "for peace of mind". when I finally require a RTH at least I'll know my R/C no longer is state of the art
Last edited by trappy; Sep 22, 2010 at 12:14 PM.
Sep 22, 2010, 12:14 PM
Suspended Account
Quote:
Originally Posted by matttay
The RTH functionality gives me piece of mind.
And on that bombshell I think we can end this show, you've just cut the legs from under your own chair ... I'm sorry, ROFL ...

Cheers,

Sander.
Sep 22, 2010, 12:18 PM
Suspended Account
Quote:
Originally Posted by Daemon
Yes I did, but can you guarantee that the same is true for the various other
devices I listed? For instance, my UHF range testing also showed that the VSN500 is
much noisier than the VSN505 (SN777) and it's actually the more popular of the two.
No, unfortunately not. I tried this on three KPC-VSN505 cameras I have here and they showed similar improvement. I'd be lying if I'd say a similar approach works on all cameras that are considered 'noisy'. I'd be happy to try the VSN500 though, but I don't have one handy unfortunately.

Cheers,

Sander.
Sep 22, 2010, 12:21 PM
Registered User
Quote:
Originally Posted by ssassen
Now please quote me exactly, where have I written that with 2.4GHz RC control you can't fly behind a tree. You keep using that as an argument against me, yet I have never claimed anything like that. So please, give me an exact quote or STFU!
The quote is reproduced here again, where you said:

Quote:
"Not really, but we do kind of grow tired of the typical Spektrum user getting into FPV and strapping his parkflyer Spektrum Rx to his EasyStar and not making it out further than the nearest tree and subsequently complain about it here"
Are you joking? Even Spektrum park flyers RX's can spec-out a plane. And you claim they can't even make it to the nearest tree? Could you be any more unfair?

Do you honestly feel this is a fair characterization of their technology? Seriously?


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question How far can you go with 1000mw 2.4ghz Carlyle Harper FPV Talk 19 Jan 20, 2013 04:30 PM
Discussion Atkins diet, How far did you get and are you still on it? Bilbobaker Life, The Universe, and Politics 28 Sep 29, 2010 03:37 PM
Poll Did you or are you going to take advantage of Spektrum's 2.4Ghz Giveaway? thomer Radios 56 Apr 23, 2008 05:04 PM