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Which frequency to choose?

Discussion in 'FPV (First Person View)' started by gfo315, Feb 28, 2015.

  1. gfo315

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    I have a Vision Plus which has WiFi "FPV" and all that stuff via the Vision app, but as I've already said a few posts ago, I want something more immersive and which has less image lag (real FPV goggles, not these Moverios or others which base on Vision App).

    As you may know, it uses 5G8 for RC and 2G4 for WiFi. I already know I can't use the 5G8 because, even though it has 32 channels, it will cause some interference (something I don't really get), and should happen the same with 2G4.
    I've seen some alternative frequencies like 900MHz or 1.2GHz that will work with 2.4GHz video RX in Goggles. Would I have interference in this case, as the RX is still 2.4? Also, is 1.2GHz a good frequency? I've read some articles about it seems to be good for short/mid range and it goes through trees/walls because of low frequency. But what about video quality?

    Let me know, thanks a lot.
    Guido
     
  2. PhantomFanatic

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    Maybe it is my migraine, but I'm having trouble following. The 2G4 and 4G8 confused me. They are commonly referred to as 2.4Ghz and 4.8Ghz although you stated it correctly later. Can you state your question a bit more clearly? :)

    Edit: I read again and I get that 5.8Ghz is your control frequency is 2.4Ghz. You don't understand why, with so many channels, that you can't use 5.8Ghz for vision too. Theoretically, it should be possible with a receiver that has high selectivity.

    There are two problems: The selectivity isn't good enough as a stand-alone ham or other high quality receiver. The other problem is you would have two antennas, inches apart. One antenna is receiving control signals on one channel, while the other would be transmitting video signals on another channel.

    Without excellent selectivity, the transmitting antenna would override the receiving antenna. So, it isn't possible with the equipment that you have. Space limitations, along with weight limits, keep the designers from being able to use one frequency range for both transmitting and receiving.

    I assume that this is a theoretical question, right? Is your system working fine? Is there a reason that you want both on 5.8Ghz? Anyway, I hope my answer helps. :)

    Edit2: I think I have it now! Because of the video lag, you think 900Mhz or 1.2Ghz might work. You say your video goggles, meant for 2.4Ghz, will also receive these other frequencies. Do they receive channels within these two bands?

    It is feasible if you could find a suitable video transmitter for those frequencies. Whether they have selectable channels is another matter. You wonder if there will be a problem with 2.4Ghz. No, as you will be replacing that transmitter. Your goggles could no longer plug into your controller. You would have to find a receiver with a plug in for goggles. If you want your IPhone or iPad to work, that will,be impossible.

    I suggest that you first verify if you do have a lag. If so, how long is it? How much does it really affect whatever you are using your Phantom for. Another possible problem with 1.2Ghz is that it's second harmonic will be 2.4Ghz, so forget using that receiver. If the problem is with framing for video or photos, couldn't you just hover for the period of the lag, then couldn't you just take your photos or start your video?

    I think that is a much better solution, which is to work with the problem if you can't reduce or limit your lag. I don't have a vision model, so perhaps someone, who does have one, could solve your lag problem. If no luck here, post your question in your Phantom's model. Good luck! :)
     
  3. SteveMann

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    2G4 and 5G8 is how most countries except the USA refer to 2.4GHz and 5.8GHz equipment.
    The reason, as PF indicated, that you don't want to use the same frequency band, even on different channels, is because of a problem with inexpensive receivers called desense. If your control is on 5G8 and your video transmitter is also on 5G8, then when you get some distance from the R/C transmitter, the Phantom can't "hear" it because the video transmitter is so strong.
    I haven't seen any FPV gear in the 900 MHz range (but I am not really into FPV), but this would give you a superior video range over either microwave band.