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Old Jan 01, 2012, 05:30 PM
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FPV newbie... questions about signal strength/quality FatShark 5.8 GHz

Hello FPV pilots, I'm an FPV newbie so please be gentle. I picked up a second-hand FPV system from a friend and fellow club member. He bought it new, flew it a couple of times and decided it wasn't for him, so I purchased the entire system from him. The system is a FatShark 5.8 GHz with the 100 mW transmitter, goggles (not the Dominator), and pan/tilt camera. I have it mounted in an RQ-11 FPV vehicle.

I took it to the field today to try it out. I first flew the plane and trimmed it out to make sure all was well. I then flew the plane with someone else wearing the goggles to see how the view was. The signal was, to be honest, pretty terrible. It looked good on the ground during range checks but quickly became to where it was unflyable. These are the things we tried:
  1. Repositioned the antenna several times
  2. Repositioned the TX several times
  3. Powered the TX with the ESC
  4. Powered the TX with its own power source
  5. Removed the metal landing gear

Nothing really helped... when the plane was coming straight towards you, it was fine but it seemed that whenever a turn was made, the signal would drop off drastically.

So we tried to fly the plane via FPV tied to a buddy box. It was really cool when it worked well (I can see why people love FPV) but it was only in 3-5 seconds burts as my friend kept having to take the plane away due to the signal dropping out.

I understand this is a turn-key product and I certainly don't expect to get miles and miles of range with it. What I am looking for, however, is some friendly advise as to what can be done to get the most out of what I have. Different placement of equipment, upgraded antennas, upgraded transmitter, etc. I apologize for coming into this cold as I'm sure I've made some rookie mistakes (again, please be gentle ), but any suggestions and/or affordable upgrades would be most appreciated. I have posted pictures of my setup, listed below. Thank you!
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Old Jan 01, 2012, 06:45 PM
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Try turning the TX upside down so the antenna is pointing straight down. Odds are, when you are on the back leg of the pattern, the Antenna is being blocked, which means it need to pentrate two peices of fiberglass and potentionally a wing, which 5.8ghz isn't the best at.

If that doesn't help, Try to build yourself some Skew Planar Wheel and Cloverleaf antennas. These will help alot.

assuming you've got the predators, your looking at prolly 1500 feet of usable range with stock antennas.

Video of the dropouts would help out alot, helps to diagnose the problems.
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Old Jan 01, 2012, 06:47 PM
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oh yeah, and were you using 2S or 3S to power it?
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Old Jan 01, 2012, 07:01 PM
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Hi gundamnitpete, thanks very much for the replies! I think we tried mounting it with the antenna pointed down but I can certainly do that again. Before I do that, I think I'll put the landing gear back on the airplane so the antenna and/or transmitter doesn't get damaged during landing.

I am using 3s to power the transmitter. At first I was using a y-harness to run it off the battery (3s 4000) that powers the airplane, but then I connected the camera directly to a 3s 450 mAh battery to see if it was the currently draw of the ESC that contributed to my problems (it didn't make a difference).

I think it's the Predators. *runs to workshop to check* The manual doesn't say "Predator" it just says RCV922 "Aviator Edition".

I would be fine with 1500 feet, even 1000 feet. I'm barely getting half that. Our runway is 800 ft. long and assuming I'm standing at a pilot box at the center, I can't get to either end (400 ft.) without the video cutting out.

I saw a link you posted in another thread about SPW CP Antenna... are these the ones I need? I don't mind buying a set if that will help but unfortunately they are out of stock. Does anyone else carry them?
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Old Jan 01, 2012, 07:15 PM
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Originally Posted by Mike_Then View Post
Hi gundamnitpete, thanks very much for the replies! I think we tried mounting it with the antenna pointed down but I can certainly do that again. Before I do that, I think I'll put the landing gear back on the airplane so the antenna and/or transmitter doesn't get damaged during landing.

I am using 3s to power the transmitter. At first I was using a y-harness to run it off the battery (3s 4000) that powers the airplane, but then I connected the camera directly to a 3s 450 mAh battery to see if it was the currently draw of the ESC that contributed to my problems (it didn't make a difference).

I think it's the Predators. *runs to workshop to check* The manual doesn't say "Predator" it just says RCV922 "Aviator Edition".

I would be fine with 1500 feet, even 1000 feet. I'm barely getting half that. Our runway is 800 ft. long and assuming I'm standing at a pilot box at the center, I can't get to either end (400 ft.) without the video cutting out.

I saw a link you posted in another thread about SPW CP Antenna... are these the ones I need? I don't mind buying a set if that will help but unfortunately they are out of stock. Does anyone else carry them?
ah crap, the aviator edition is different than the predators. it will need a slight modification in order to work with CP antennas (SPW and CL).

If you are just gonna be flying around the field, and not behind or through anything, a patch antenna might solve your problems, that way you don't have to modify your goggles. i would shoot for maybe 8dB, and make sure to get either a cable, or a male to male connector to attach them to your goggles.

You SHOULD be able to use this antenna:

http://www.readymaderc.com/store/ind...roducts_id=777

on your receiver/goggles without modification(tho i haven't tested that myself).

and one of these on the plane:

http://www.readymaderc.com/store/ind...roducts_id=459


although that's a set, you normally want to use the cloverleaf on the plane and SPW on the RX, however the CL's alone are out of stock

you can order them direct from alex (Ibcrazy) at videoaerialsystems.com but he's not taking any orders over the holiday season, so you might have to wait a few days.
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Old Jan 01, 2012, 07:18 PM
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BTW those antennas you linked to were the right ones, exactly the same as the ones i linked to but they have a longer whip. you want some distance between the transmitter and antennas most of the time, to keep down on reflections.
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Old Jan 01, 2012, 07:20 PM
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Well first thing that caught my eye in your post was you state that it drops out during turns. That would be explained by the fact that you are on linear polarized antennas so when you turn you cross polarize and this causes a loss in signal of up to and around 20dbi which is huge. You could also be getting Multipathing, How is the Receiver and antenna mounted (exactly which Fatsharks)? Pics of the entire setup and some video from the onboard flight camera would help. Also check out this thread there is a lot of great info here. Also with 5.8 GHz I would personally go with Circular Polarization instead of Linear.

http://fpvlab.com/forums/showthread....iry-FAQ-thread
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Old Jan 01, 2012, 07:25 PM
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The blubeam whips would be the ones to go with. But I know the blubeam standards will be in at RMRC in a few weeks. Alex is behind with 5.8GHz but that should be fixed real soon.
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Old Jan 01, 2012, 11:09 PM
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Guys, thanks again for the replies and suggestions. I do not have video of the flight today. I don't have a camcorder nor a VCR so I'm not sure I can provide video. I guess I could connect the goggles to a monitor and just video the playback on the monitor with my camera. But I will try your suggestion of pointing the antenna straight down and see if that helps. I'll mount the receiver horizontally and bend the antenna down.

I have the FatShark RCV922 "Aviator" edition. You are correct in that I'm not interested in flying around or through anything... I'd just like to fly around our field. So to do that, I'd have to get the patch antenna and the Bluebeam antenna? The square patch antenna connects to the goggles with this cable I assume? My apologies if I come off as whining, but I'm not crazy about spending an additional $132 on this... could I just get away with the Bluebeam antenna set or do I absolutely need the patch antenna for the goggles? Thank you!
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Old Jan 01, 2012, 11:24 PM
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I fly around my local field with just the blubeams I get a few hundred meters on most days (High Humidity here) but I am on 900MHz. I can't speak from personal expirience on 5.8 only from research into it, but I have seen video of guys doing 400 and 500m with a CL and SPW so you should be able to do it. No need for a patch if you are not going for distance. Put the SPW on the FatSharks and the CL on the vTx and fly. $60 and you are flying.
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Old Jan 01, 2012, 11:25 PM
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Originally Posted by Mike_Then View Post
Guys, thanks again for the replies and suggestions. I do not have video of the flight today. I don't have a camcorder nor a VCR so I'm not sure I can provide video. I guess I could connect the goggles to a monitor and just video the playback on the monitor with my camera. But I will try your suggestion of pointing the antenna straight down and see if that helps. I'll mount the receiver horizontally and bend the antenna down.

I have the FatShark RCV922 "Aviator" edition. You are correct in that I'm not interested in flying around or through anything... I'd just like to fly around our field. So to do that, I'd have to get the patch antenna and the Bluebeam antenna? The square patch antenna connects to the goggles with this cable I assume? My apologies if I come off as whining, but I'm not crazy about spending an additional $132 on this... could I just get away with the Bluebeam antenna set or do I absolutely need the patch antenna for the goggles? Thank you!
The problem is the aviator goggles need to have a component removed in order to work with the bluebeams. you could just go with the bluebeams but you need to mod your goggles to do it.

If you want to avoid spending $130, you could just get a regular patch, or build one. Or upgrade to the 600mw transmitter. I personally would mod the goggles and use some bluebeams.
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Old Jan 01, 2012, 11:39 PM
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Here is the mod @gundamnitpete is reffering to. Pull the vrx out of the goggles and remove this little ol' resistor. should take like 5 minutes.

http://www.rcgroups.com/forums/showp...&postcount=786
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Old Jan 02, 2012, 08:30 AM
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Okay great, thanks guys. So I can buy the Bluebeams, pull that resistor out of the Fatsharks and be good to go? I'm pretty adept at soldering so I don't have a problem making that modification. So I want to wait for the Bluebeam whips and not get the Bluebeam standards, is that right?

One final question... the article for the mod states that it's for Airwave receivers. I have a FatShark receiver... am I to assume they are one in the same thing? Sorry for all the questions, but I want to make sure I understand why I'll be spending $65 for antennas and modifying my FatShark googles. Thank you again!
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Old Jan 02, 2012, 10:16 AM
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Yes Fat Shark receivers are the same as Airwave receivers. And as long as you are going to mount the vtx vertical the standards are ok. The whips simply get you up and away from the vtx and is required for a horizontally mounted vtx but no a requirement on the vertical so you don't "have" to wait.
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Old Jan 02, 2012, 10:44 AM
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Originally Posted by MASHTON View Post
Yes Fat Shark receivers are the same as Airwave receivers. And as long as you are going to mount the vtx vertical the standards are ok. The whips simply get you up and away from the vtx and is required for a horizontally mounted vtx but no a requirement on the vertical so you don't "have" to wait.
Yes, the FatSharks have the antenna vertically mounted and I didn't plan on making any modifications so I will just get the set of Bluebeam standards. There appears to be a bit of grass inside the goggles, so I have to take them apart anyway. That will be a good time to remove the resistor.

Thanks so much guys, I'll report back once I've had a chance to test!
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