FPVLAB

image
Page 1 of 26 12311 ... LastLast
Results 1 to 10 of 257

Thread: LRS UHF: Letís talk about antennas

  1. #1
    Pilot sircana's Avatar
    Join Date
    Mar 2011
    Posts
    1,163

    LRS UHF: Letís talk about antennas

    Except for Roberto Montiel, Trappy and some other crazy guys, the reality is that all the LRS UHF RC systems offer a reliable RC signal over distances way bigger than what we use to fly.

    However, when we start looking at the antennas, Thomas Scherrer recommends dipoles, ImmersionRC promotes the world wide known ďSander StyleĒ monopole, and there are also some nice smaller antennas from different FPV shops.

    Even Sander confirms that ďnothing beats a dipoleĒ, butÖ what about real field data?

    Under this scenario, I decided to conduct my own tests, and even if the conclusions confirmed the initial thoughts, some interesting data were found.

    So, I built some lab tuned dipoles, monopoles (Sander StyleÖ;-)) and even a normal mode helical (these are the small whips you can find everywhere for 433MHz), and I compared these three handmade, perfectly tuned antennas with the cheapest and smallest 433MHz antenna I was able to find in the Internet.



    http://www.goodluckbuy.com/45mm-433m...05-3pcs-1.html

    Only $1.56Ö





    The fact that Sander is a good engineer , and that in the same way that the EzUHF software includes a spectrum analyzer, he designed the EzUHF and the EzOSD in a way that you can get the RSSI in ĖdBm from the two diversity antennas, makes the EzUHF the ideal platform test to compare two antennas.

    The following video is quite self-explanatory. The RSSI readings correspond to the antennas in the same order (left antenna, first RSSI data), and you should remember that the EzUHF-EzOSD combination gives you the actual ĖdBm reading. Zero is maximum received power, and -80dBm is close to the absolute minimum to be able to decode the RC signal. So, the bigger the number, the worst the RC signal. We should also remind that 6dB difference means doubling the range (i.e. if you have got -20dBm at X distance, at 2X distance you should have -26dBm).




    Conclusions:

    1. Sander was right: nothing beats the dipole.

    2. Sander style monopole is way enough (you just need to watch Trappyís long range flights using this antenna).

    3. If you are not going for extreme long range, small commercial antennas (normal mode helicals) are a good option.

    4. Donít lose your time trying to build your own perfectly tuned normal mode helical. There are very cheap options around as good as yoursÖ

  2. #2
    Pilot Pixturethis's Avatar
    Join Date
    May 2012
    Location
    Kansas
    Posts
    260
    Great video. What about turnstile antennas.

  3. #3
    Take off... Eh Technoweenie's Avatar
    Join Date
    Apr 2011
    Location
    Niagara Region, Ontario, Canada
    Posts
    380
    I use a turnstile horizontal on the plane with a Moxon Rectangle on my ground station. Nice advantage is that there is little to no fade on the bank to turn back home on longer flights. Moxon Rectangle has a nice wide 100 degree forward beamwidth, but a large null to the rear so it's no good for "all around yourself" flying, but for going out in one direction it doesn't need constant aiming like a yagi or similar. Currently using Flytron's OpenLRS, so range is a bit limited at the moment.

    Though of trying a V dipole on the plane and a UHF Co-linear antenna on the base.

    Something along the lines of this: http://www.rason.org/Projects/collant/collant.htm
    Regards,
    Bryan VE3OYN
    "Technoweenie"
    If it ain't broke, don't fix it.
    If it is broke, deny everything.

  4. #4
    Pilot Pixturethis's Avatar
    Join Date
    May 2012
    Location
    Kansas
    Posts
    260
    I'm getting ready to try mine out this week, With my Thomas LRS.

  5. #5
    FPV Addict Scotttu's Avatar
    Join Date
    Dec 2011
    Location
    Silverdale, WA, USA
    Posts
    9,997
    Quote Originally Posted by Technoweenie View Post
    Though of trying a V dipole on the plane
    IMHO - that would be a very bad idea - please correct me if I'm wrong.

    My experience is when you turn a Dipole into a V it gets very directional very quickly!!!
    "Truly superior pilots are those who use their superior judgment to avoid those situations where they might have to use their superior skills"- Author unknown

    KF7TRX

  6. #6
    Pilot Pixturethis's Avatar
    Join Date
    May 2012
    Location
    Kansas
    Posts
    260
    I think your right. I've tried a v on my video and didn't like it as much as the dipole.
    Last edited by Pixturethis; 30th May 2012 at 10:57 AM.

  7. #7
    His Royal Sassiness ssassen's Avatar
    Join Date
    Feb 2011
    Location
    Netherlands
    Posts
    9,693
    Thanks Juan, that lines up with my testing exactly. We need some meta materials to build small, yet efficient, SPW antennas on 433MHz
    Velvety smooth drone pilot for hire

  8. #8
    Michael Mictronics's Avatar
    Join Date
    Jul 2011
    Location
    Bavaria, Germany
    Posts
    1,010
    Excellent work and video.

  9. #9
    No Artificial Sweeteners. kev.au's Avatar
    Join Date
    Feb 2011
    Location
    Down Under ⇩⇩⇩⇩⇩⇩
    Posts
    1,823
    Appreciated sir, thanks!.
    HŚvard StÝre : Sir I humbly bow down to your balsa bashing abilities!!.
    chicken sashimi : my T-Shirts are all 100% guaranteed to get you laid.
    Roberto : you're a legend Kev.
    ssassen : I bow humbly before kev.au's greatness.
    Danub : Sir I humbly bow down to your tree bashing abilities!!.
    MonZon : Damn, Kev you are gooooood!.
    R. Montiel : For sure the limiting factor is the earth curvature

  10. #10
    I Like Waffles... SENTRY's Avatar
    Join Date
    Feb 2011
    Location
    Atlanta, GA
    Posts
    10,849
    What does having the rc Tx against a reflector (the wall/fence) do to the test results?

    Those shoes look comfortable.
    "I Like Waffles" : FPVLab on Facebook and FPVLab on Twitter

Page 1 of 26 12311 ... LastLast

Similar Threads

  1. LETS TALK CHARGERS
    By SENTRY in forum RC TECH
    Replies: 194
    Last Post: 13th July 2017, 11:19 PM
  2. Replies: 0
    Last Post: 1st April 2012, 10:22 PM
  3. OK, lets talk about batteries
    By roberto in forum RC TECH
    Replies: 26
    Last Post: 15th July 2011, 05:49 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •