Results 1 to 8 of 8

Thread: SWR, or lack there of...

  1. #1
    New 4x4 Ham Member
    Join Date
    Jul 2017
    Location
    San Antonio, TX
    Posts
    4

    SWR, or lack there of...

    I just finished my install of my first ham radio. I have quite a bit of experience with CB antennas and SWR so I figured it would be a good idea to check my ham rig. I have an icon I'd-5100 with a comet SBB5 antenna connected with a Comet 5 meter pl-259 cable assembly. Comet claims the antenna is "ground independent" so there is no ground whatsoever. The antenna is basically hanging in free space. It's on a Jeep. I tested using an MFJ -842 SWR meter. I tested both 2m and 70cm using several frequencies on each band. My issue is that the SWR needle never moved at all. Does that sound right? I didn't adjust the "tuned from the factory" antenna at all. There really isn't much of a ground plane to speak of either. I'm worried that my brand new meter might be messed up. Anyone ever experienced this? If all is good then this is the best radio install I've ever done... I'm just not sure I'm buying that...
    IMG_3790.jpgIMG_3789.jpgIMG_3792.jpg

  2. #2
    Administrator Supporting Member K7VZ's Avatar
    Join Date
    Jun 2008
    Location
    Arizona
    Posts
    3,110
    The left needle is showing 50 watts? I'd think the right needle would move a little bit, but not much. Does the Icom have SWR reading on it's display?
    Virgil - K7VZ
    Offroad and on the air.

  3. #3
    New 4x4 Ham Member
    Join Date
    Jul 2017
    Location
    San Antonio, TX
    Posts
    4
    I read the directions for the meter and you have to divide by 10 on low power. It's actually 5 watts... I was testing on low power. I didn't try it on high power but I'm gonna try that after work today. The Icom doesn't have a meter built-in. From what I'm seeing online, it's not uncommon to have ham antennas be pretty close to swr-free. I'm not sure why that is though... Probably something to do with the fact that this antenna is a real 1/2 wave on 2m and two stacked 5/8 wave on 70cm whereas most cb antennas are closer to 1/8 wave at best. You'd need an 36 foot whip to make a full wave cb antenna so I suppose that makes the ground plane more of a concern and antenna tuning more difficult on cb. I THINK I saw the SWR needle move ever so slightly at some point, but I could have been seeing things. Like I said, this is my first ham rig (just got my ticket 2 weeks ago) so I don't have much experience with setting these things up and what is "normal" for these frequencies. I have never messed with an antenna system that was this "true" out of the box so it kinda threw me...

  4. #4
    New 4x4 Ham Member
    Join Date
    Jul 2017
    Location
    San Antonio, TX
    Posts
    4
    Well... I tried it on 50 watts and the SWR needle move very slightly so I guess that means I'm good. Still seems weird to not see high SWR without tuning but I'm not complaining. ������

  5. #5
    Administrator Supporting Member K7VZ's Avatar
    Join Date
    Jun 2008
    Location
    Arizona
    Posts
    3,110
    That's good news. Are you planning on running a CB from the spring? I'd try to move those further apart.
    Virgil - K7VZ
    Offroad and on the air.

  6. #6
    New 4x4 Ham Member
    Join Date
    Jul 2017
    Location
    San Antonio, TX
    Posts
    4
    Yes, I do run a CB on that spring. The two are resonant pretty far apart so I'm not getting any issues with bleed-over, but I need to check SWR with both antennas installed to see if there is an issue with that. I ran around for a few hours with both radios turned on and was talking on ham and CB never noticed. The antennas don't touch so I'm thinking I'm ok. I'm going to get one of those Comet rubberized dual band antennas for off road anyway so that should keep things separated a little better. Around town, I don't run a CB anyway, just the ham. The CB is mainly for trail use so...

  7. #7
    4x4 Ham Member prerunner1982's Avatar
    Join Date
    Jun 2013
    Location
    Oklahoma
    Posts
    143
    Tex, glad you got it figured out.

    If you are on Facebook feel free to join the Texas Off Road Amateur Radio Club group.

  8. #8
    4x4 Ham Member
    Join Date
    Oct 2014
    Location
    Western Oregon
    Posts
    30
    That's a good antenna I have one. It has a matching network in the base of it. That's why they typically show low swr. Even when you mount them in bad spots. I once saw one mounted a few inches away from a truck cab on the bed rail. It showed good swr but the install undoubtedly caused RF pattern problems. They really do come pre tuned as well. They need very little metal to work. You have more than enough. HOWEVER do not mount antennas that close together. They will electrically couple and cause problems. You need at least 19inches of separation for 2m vhf. Your setup puts the antennas so close together I would worry about damming both radios. Stick that Cb antenna on your bumper, cowl or windshield frame.

    PS: That antenna is also great for APRS!

    R

Posting Permissions

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