Antenna for T3 transmitter?

Discussion in 'Rocketry Electronics and Software' started by Nathan, Sep 12, 2019.

Help Support The Rocketry Forum by donating:

  1. Sep 12, 2019 #1

    Nathan

    Nathan

    Nathan

    TRF Supporter

    Joined:
    Apr 20, 2012
    Messages:
    2,014
    Likes Received:
    245
    The Missileworks T3 has an option to get the transmitter with either a wire whip antenna or an RP-SMA connector to attach an antenna. They show a picture of it with a stubby antenna attached but they don't sell the antenna. Where can I get an antenna like this that will work with the T3 transmitter? I need a short one like this for it to fit in my smallest rocket.
    [​IMG]
     
  2. Sep 12, 2019 #2

    mikec

    mikec

    mikec

    Well-Known Member

    Joined:
    May 9, 2009
    Messages:
    2,045
    Likes Received:
    100
  3. Sep 12, 2019 #3

    cerving

    cerving

    cerving

    Owner, Eggtimer Rocketry TRF Sponsor TRF Supporter

    Joined:
    Feb 3, 2012
    Messages:
    3,154
    Likes Received:
    313
    I would recommend against purchasing any antenna that doesn't have full technical specs, they rarely live up to what they say on the web site. Since the T3 uses the same band as Eggfinders, I recommend the Linx ANT-916-CW-QW, it's designed specifically for the 902-928 MHz band. They'e about $7 plus shipping from Mouser or DigiKey. The antenna in that picture looks similar to a Pulse-Larsen W1911, which "will" work in that band but it's really designed for cell phones on 850/1900 MHz... the gain in the 915 MHz band is barely above zero, and the SWR isn't good.
     
    Last edited: Sep 12, 2019
    Chris_H and BradMilkomeda like this.
  4. Sep 12, 2019 #4

    swatkat

    swatkat

    swatkat

    Well-Known Member

    Joined:
    Jun 25, 2014
    Messages:
    1,309
    Likes Received:
    112
    THIS^... I only have the 1/4 wave on mine. I've not seen one shorter... 20180730_151308_resized.jpg
     
  5. Sep 12, 2019 #5

    Nathan

    Nathan

    Nathan

    TRF Supporter

    Joined:
    Apr 20, 2012
    Messages:
    2,014
    Likes Received:
    245
    Okay thanks, that's what I will get.
     
  6. Sep 12, 2019 #6

    Cameron Anderson

    Cameron Anderson

    Cameron Anderson

    Well-Known Member

    Joined:
    Sep 14, 2018
    Messages:
    383
    Likes Received:
    97
    Gender:
    Male
    Location:
    Reno, NV
    Is there better range with the stubby antenna on the T3? More power consumption?
     
  7. Sep 12, 2019 #7

    mikec

    mikec

    mikec

    Well-Known Member

    Joined:
    May 9, 2009
    Messages:
    2,045
    Likes Received:
    100
    Thanks to Cris for his response. BTW, I always just use the wire antenna on my 900 MHz transmitters. There's not much additional benefit from the other antennas and they're harder to fit and can load the connector in a crash and break it.
     
  8. Sep 12, 2019 #8

    RocketDestroyer

    RocketDestroyer

    RocketDestroyer

    Well-Known Member

    Joined:
    Jul 31, 2014
    Messages:
    241
    Likes Received:
    9
    Probably less range with the stubby antenna as compared to the wire antenna. The power consumption should be the same with either antenna. I agree with mikec the antenna with the connectors will be harder to fit in and more likely to break.

    Here is a youtube video comparison of various antennas for the 2M Ham bands. The stubby antennas didn't do so well.

     
    Last edited: Sep 13, 2019
  9. Sep 13, 2019 #9

    cerving

    cerving

    cerving

    Owner, Eggtimer Rocketry TRF Sponsor TRF Supporter

    Joined:
    Feb 3, 2012
    Messages:
    3,154
    Likes Received:
    313
    The stubby antenna that we ship with the Eggfinder Mini is a Linx ANT-916-PW-LP, it's a helically-wound 1/4 wave antenna rated at 2.4 dB and a maximum SWR of 1.9 within its range (902-928 MHz). That's a pretty good upgrade from a wire antenna (which you assume is near 0 dB)... unfortunately they only offer it in a screw mount, so it basically has to be built into the tracker. If Linx starts shipping it in a RP-SMA version, we'll start selling it in a heartbeat.
     
    jrkennedy2 likes this.
  10. Oct 7, 2019 #10

    John Kemker

    John Kemker

    John Kemker

    Forum Supporter TRF Supporter

    Joined:
    Aug 25, 2019
    Messages:
    31
    Likes Received:
    8
    Gender:
    Male
    For the most part, a stubby antenna will give worse gain than a properly cut wire antenna that's stretched out fully and is not run near anything that will affect the antenna pattern. While a stubby is *electrically* the same length as the full-size wire, physically it is not. (Obviously) That does affect the range, usually in a negative way.

    Gain, in any antenna, is a modification of how the energy is radiated, not a change in the overall energy in the system. So, it shouldn't increase power consumption, but instead increases power seen in certain directions. For example, a 5/8 wave vertical antenna over a decent ground plane will not radiate more overall energy than a 1/4 wave over the same ground plane, but it will radiate more energy to the sides of the antenna and less towards the sky. A good explanation of this can be found @ https://ham.stackexchange.com/questions/1142/what-makes-a-5-8-wavelength-vertical-desirable, complete with a good graphic comparing a 1/4 wave vs. a 5/8 wave.
     
    gfunk likes this.
  11. Oct 7, 2019 #11

    cerving

    cerving

    cerving

    Owner, Eggtimer Rocketry TRF Sponsor TRF Supporter

    Joined:
    Feb 3, 2012
    Messages:
    3,154
    Likes Received:
    313
    I like to think of antenna gain as a round balloon, with the gain at any given point being the distance from the center. An isotropic antenna is the round balloon, equal in all directions. A dipole is the balloon squished at the poles, it bulges out in the middle but is low at the poles. A directional antenna would be if you squished it so that it sticks out a lot on one direction but is narrow in all the others. The total amount of radiated/received signal (the air in the baloon) is the same, it's just how it's distributed.
     
  12. Oct 7, 2019 #12

    Nathan

    Nathan

    Nathan

    TRF Supporter

    Joined:
    Apr 20, 2012
    Messages:
    2,014
    Likes Received:
    245
    Very interesting. But but my original post was about the antenna on the transmitter in the rocket. When the rocket in on the ground and you are trying to locate it, the orientation of the rocket and the antenna are going to be pointing in some random direction. So it seems to me that any type of antenna with a non-isotropic gain distribution could cause the signal to not be received, depending on the orientation of the transmitter lying on the ground.
     
  13. Oct 8, 2019 #13

    John Kemker

    John Kemker

    John Kemker

    Forum Supporter TRF Supporter

    Joined:
    Aug 25, 2019
    Messages:
    31
    Likes Received:
    8
    Gender:
    Male
    Chris: Wow! I never thought of it that way, but it's an excellent way to think of gain!

    Nathan: I agree. For a transmitter that is trying to be found, the closer you can get to isotropic, the better your chances of finding it.
     

Share This Page