I see there is a lead for the hero 3 which plugs into the USB port of the gopro to obtain audio/video to feed into a TX…
If this is used does the Gopro record onto the SD card in full HD at the same time - so you get to see what is being recorded onto the card in real time?
does anyone know?
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Yes,I believe you get SD from the video out and HD onto the card. I’m no expert but I think very few fpv goggles support HD.
Yes you can use this gopro FPV cable to get video out to a transmitter. We also sell another one for the hero 3 that supports power input if you want, and also another cable for the older gopro cameras.
But as @Jim said, it will only transmit SD quality video we only use analogue transmitters right now. There are not realy any cheap options of wirelessly transmitting HD video, although there are some options that are small enough if you have some money to spend!
Attached is an image of the cable connected to a transmitter from another topic posted a while back. Although the cable line up properly with the transmitter, the little clip on the cable will need to be cut off so as it does not line up properly with the one on the transmitter. Its fairly easy to do.
Owch, $600 for HD streaming to 300 feet, Owch
No I don’t want HD through the FPV link, I guess it would be handy in that you could just record at the base station but that was not what I meant.
I was just unsure if the Gopro would record in hd onto the sd card at the same time as the lower quality video being sent over the radio link.
I have the hero3 black, does that mean I could dispense with the hero battery and have a single small lipo or bec to power the tx and gopro?
Yes you can record HD and output live video at the same time, great for when you want to seehat you are recording. If you are not flying much further that 100m you could try the built in WiFi to stream video to your phone too (although I have never tested this while flying) 
Yes you could power it directly and get rid of the battery but I refer to use the yellow cable with battery as it as a smaller 90deg connector and less chance to damage your gopro if your bec fails or you connect a giver voltage battery 
I was going to use the GP wifi but I read on a couple of places that the Gopro wifi has interfered with the 2.4ght RC causing crashes. I figured it was probably not worth the risk as they are both on the 2.4ghz band.
This was one source…
I know this is a very old topic but I’m trying to use my hero 4 to do this with the tx5803 my F7 picks up transmitter but no video it only shows a blue screen. Any help would be awesome. Thank you.
First thing I would check is that your transmitter and Devo F7 radio are compatible, and are both set to exactly the same frequency.
Assuming that is done then you might have an issue with either your camera, cable, or transmitter. Its kind of hard to tell right away what the problem is but if you can provide a photo showing your transmitter setup I might be able to help. But I would suggest you try to double check the connections, and also if you can try another receiver, or camera, or transmitter if you can too try find what part of the system is causing the issue.
I tried everything and i read more than 100 articles about live streaming from GoPro and i finally found this right one - One moment, please... Check It, I hope it will helps you