[Moderator Edit] This is a clone of an old thread on reddit HERE. This user account is for a known spammer who included spam links in the post, so those have been removed and the user account has been banned. The thread will remain [undeleted] because other members have already added contributions that might still be useful to others.


Just seen a video about TBS crossfire. Is something like this what you need above 200mw ? Does it enhances the video signal to your goggles?
I am going to build a mini quad for starters So for short range like a few 100 meters. I just need a Vtx and goggles right? When does something like a Tbs crossfire come into play? And why does 2.4ghz video setups don’t need allot of equipment for long range. Like with the mavic pro I know that the latency is huge on 2.4ghz I am not into that I want a race drone
Really like to know this
I come from the rc Heli scene so I don’t know much about fpv.

TBS Crossfire has nothing to do with your video signal. This is basically an RC link.

Perhaps you should start with the basics of what the various systems are on an FPV quad and what components comprise these systems and how they in some way of the other interact with each other: https://rotorriot.com/pages/beginners-guide

First your questions.
1. No you dont need 200mw for Crossfire. Even 25mw is plenty.
2. 0 impact to video/goggles.
3. Regardless if only 300m, you ALWAYS need RC link. Its seperate. How would you control quad with goggles? Move head?
4. Frequency does not affect latency. DJI video drones have HIGH latency because its tradeoff for video quality.

Some basics
1. Lower frequency go farther. With less power.
2. Why not 100Mhz? There are only a few small open spaces for amateur use. 99% of frequencies are used up. Navigation. Ships. Planes. Military. GPS. Cell phones. TV broadcast. 
3. 99.9% of fpv analog video is 5.8Ghz - because the equipment is very cheap, and you can easily have 8-16 people.
4. Why not 2.4Ghz.. because your RC is also 2.4Ghz.. interference.
5. OK, so use 900Mhz for RC like Crossfire, R9M or ExpressLRS.
now can I use 2.4Ghz for video? Yes. But antenna are bigger.
6. Why not 900Mhz video? Tiny free space. 1 person flying would block out anybody else using 900Mhz.
7. Why is DJI video high latency? High quality image takes longer to send.
8. old FrSky / Spektrum / FlySky can fly 1mile+ in ideal conditions. You can't just keep cranking power up. For long range, and better penetration, people use Crossfire, R9M and ExpressLRS.

2.4 video isn't really an antenna issue or latency issue. Truerc singularity is probably smaller than the old fatshark antennas and about the same as a pagoda 5.8. Linear antennas are very unobtrusive and the lower frequency does make up for some of the downsides of the multipathing.
It's the available frequency allotment for public use that's the main issue and the data rate. Higher frequencies allow more data, lower allows less.

5.8 shares wifi frequencies but the range is very broad so it's easier to find a clean channel. 2.4 is quite narrow in the legal ranges so 2.4 wifi and security systems regularity stomp on your signal. The one highest channel is usually the only clean-ish signal with 2.4 equipment.

1.3ghz video is also common for long range flights but at a reduced video quality. 900mhz video is possible but the quality would be further reduced and it's likely not off the shelf equipment so specific proprietary components would likely need to be developed for the purpose for less than stellar results.

But exactly as romangpro is getting at, there's only so many open use frequencies we can use that dictate the frequency along with the limitations of using the different ones and the purpose of the use. Video needs to transmit higher amounts of data than the radio control link. That's why we use 5.8/2.4 video and 433/900/2.4 for control link.

TBS crossfire is great for longer range flights. I don’t trust most other receivers past 500m.

As others mentioned Crossfire is specific to your controller.

For FPV video there are two major routes, Analog or Digital.
For analog video feed you’ll need, VTX (TBS Unify, Rushtank, or even Matek are all great), camera (Caddx Ratel one of my favorites) and a pair of goggles.

For digital video feed you have to decide between DJI and SharkByte. DJI is the most popular but SharkByte is beginning to show promise as a good alternative. I just picked up a system and will be testing it this month.

Coming from RC helicopters you should be able to learn the controls pretty quickly, but start with something small, cheap and slow. Feel free to ask questions, cheers!