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FPV static blackout, HELP!

#1
Hello, I am very excited to be getting into the FPV side of the hobby. I did some research and choose the blunt nose versa for
my airframe, I have a Spektrum dx6i for a transmitter, and Hobbyking's Quanum Complete FPV Bundle Set w/ Goggles, 5.8GHz 32ch Video TX & RX.

http://www.hobbyking.com/hobbyking/..._Video_TX_RX_CP_Antennas_and_Camera_PNF_.html

Got the system, super excited for my first flight. Once in the air, however, I started to have these "signal blackouts".
Not to be confused with a blue screen, it was like my video feed would turn solid static for a second or two, then come back.
I'm sure you can see why this is a problem when it comes to flying exclusively under the hood. This problem caused me
to total my first blunt nose. Then (after building the second blunt nose) I decided to upgrade my antenna, another circular polarized 5.8Ghz (Anbee® FPV 5.8Ghz Circular Polarized Clover Leaf Antenna from Amazon).

https://www.amazon.com/Anbee®-5-8Gh...F8&qid=1470272231&sr=8-3&keywords=fpv+antenna

This helped me to have fewer blackouts, but they still occured (just less frequently). Why am I not having slow static start to overcome my screen instead of a complete loss of signal?

Thanks for the help.
 

PsyBorg

Wake up! Time to fly!
#2
Several things come to mind that could cause this. First the simple things.. antenna placement. Is it at the highest point on the air frame? is it set up so when you make any turns the signal could be blocked or effected by the airframe? FPV signals will always fade or show static in turns simply because the way they transmit and receive. There is no 100% coverage from all directions. Sometimes if you are at the edge of your range you may have to zig zag the craft to keep a strong enough signal to get back in range. Done that a few times in my quad because I got too far away. Are they both either right hand or left hand polarized? That has to be the same. also make sure the connectors match. Several "kits" have been known to come with SMA connectors on one piece and RP sma on the other and that wont work well after the tx and rx get seprated.

Next would be what conditions do these black outs occur? is it near the end of you flight time for your battery? are you pushing the range limits to far? Is there something like over head high voltage electric wires or some kind of radio tower nearby that may be over powering the signal?

Finally (and I have done this a few times when I first started FPV) is your tx and rx on the same frequency AND band? There are plenty of frequencies that will bleed over and give signal at close range but drop very quickly in a short range since they are not perfectly matched.

Oh and I have learned that having matched antennas helps extend range the most. Mixing and matching different brands can have weird effects
 
#3
Alrighty, first thing I did was separate the plane's receiver and video transmitter as far apart as possible. they are all the way on the wing tips. My video feed does not show a little bit of static. It is either all or none. Why does this happen? In all the FPV video that I have seen, they acquire a gradual static as signal gets weaker, or they make turns. Both antennas are left hand polarized, and the connectors are both
RP-SMA. The blackouts occur all throughout the flight. It does not change from battery life, and I fly from the top of a hill in the middle of nowhere( as I live in Texas it is not hard to find that sort of environment). Now for frequency and band, the FPV set came with a manual that showed which dip switches to flip for what frequency and channel.

Honestly my question is, why do I get total blackouts on weak signal instead of gradual static overtaking the screen? It is impossible to fly when you can not see what the model is doing. All I want is to get gradual static across the screen instead of the entire screen going out when weak signal occurs. Thank you for the quick reply none-the-less.
 

makattack

Winter is coming
Moderator
Mentor
#4
My guess is that there might be a loose connection between the camera/vtx or the battery supply to both? Heck, that might even be the case for the ground station/VRX.

If you're seeing sharp cut outs that come and go, I'd recommend a test where you power up everything (no props for safety) and start shaking the airframe in a bunch of different ways. Make big oscillations, then lots of tiny ones to see if you can recreate the cut outs.

If that does, then start isolating the cables / securing them. I actually use hotglue to secure the wires to the connectors on a lot of my RC gear -- it also acts as a good strain relief for connectors that need to be constantly connected/disconnected. Some of those molex type pico connectors with FPV equipment might not have pins that are securely inserted into the plug housings, etc.

If that doesn't resolve the problem, I would go back and double check everything else... heck, I would probably do that first... make sure all the antenna to VTX and VRX connections are good and tight... you really need a little bit more than finger tight. I wouldn't use a wrench, but I know IBcrazy/Alex Greve loves using a 3D printed torque wrench to secure them. When secured this way, you really need a lot more than finger force to loosen them.

Double check the frequency and static range. If you have an electronics store nearby, or search online, you can find attenuators that you can connect to the transmitter/antenna to do some range testing without having to walk too far. I personally use a 10 and 20 db attenuator that I can link together for up to 30db in loss. You can use a RF link budget calculator to help:
https://www.pasternack.com/t-calculator-link-budget.aspx

The 30db would cut my range by about 1/30th; here's one from readymaderc, with SMA connectors, so you'd need converters with this one:
http://www.readymaderc.com/store/index.php?main_page=product_info&cPath=11_45_58&products_id=902

Oh yikes... just saw how expensive that one is... sheesh. I went to my local electronics store (You Do It Electronics) and bought the 10 and 20 db attenuators for a total of $10-15...

They're even cheaper on ebay: http://www.ebay.com/itm/SMA-attenua...542272?hash=item19f4c21440:g:vtIAAOSwU9xUM1j3

Ok, sorry, I went down a rabbit hole there... so, bringing it all back... it seems to me like you need to do some troubleshooting before flying FPV with this gear... I hope the above helps. If you have any more questions, definitely ask!
 
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