1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice
Dismiss Notice
This forum does not allow a single user to have more than one username. If anyone wants to change their username contact an admin and it will be done. Multiple accounts belonging to the same member will be deleted without warning.

Base New Imax wont tune 11m....this sucks

Discussion in 'CB Antennas' started by 357, Apr 25, 2018.

  1. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

    Joined:
    Oct 23, 2005
    Messages:
    6,553
    Likes Received:
    1,596
    Here is a link to an article done by W9Ji using an Imax model that produces a similar pattern to the Imax I just posted in post #240 above...if you want to see the rest of the information, click the link below and scan down to the topic "I-Max 2000 Solarcon A-99 Antenna"..

    https://www.w8ji.com/end-fed_vertical.htm#IMAX


     
    #241 Marconi, Jan 16, 2020
    Last edited: Jan 16, 2020
    357 and AudioShockwav like this.

  2. HomerBB

    HomerBB Sr. Member

    Joined:
    Jan 4, 2009
    Messages:
    3,445
    Likes Received:
    1,554
    end-fe17.gif

    Looks like a butterfly that did a nose dive into the concrete...
     
    wavrider likes this.
  3. 357

    357 Walkin' the dog

    Joined:
    Sep 12, 2009
    Messages:
    1,137
    Likes Received:
    498
    I bet thats when they put the capacitor in the middle section!
    2007

    Dscf0003.jpg
     
  4. Recon

    Recon NY 881

    Joined:
    Jul 28, 2019
    Messages:
    385
    Likes Received:
    548
    For what purpose?
     
    357 likes this.
  5. 357

    357 Walkin' the dog

    Joined:
    Sep 12, 2009
    Messages:
    1,137
    Likes Received:
    498
    not sure, I think to stop electrocution if it hits a line
     
  6. The DB

    The DB Sr. Member

    Joined:
    Aug 14, 2011
    Messages:
    1,828
    Likes Received:
    1,113
    When modeled, this capacitor has the opposite effect of a loading coil on a mobile antenna. It has the effect of lengthening the antenna beyond a half wavelength, yet still providing the feed point impedance of a half wavelength antenna. This has several effects. 1, it lets them use a similar (if not the same) matching section as the a99 antenna, and 2, itt has the effect of, unlike other end fed antennas of this length, keeping the entire length of the antenna in phase with itself.

    I have not seen any models from anywhere but this forum that includes the capacitor in the model, and that includes the W8JI models linked to above.


    The DB
     
    M0GVZ, wavrider, bob85 and 3 others like this.
  7. HomerBB

    HomerBB Sr. Member

    Joined:
    Jan 4, 2009
    Messages:
    3,445
    Likes Received:
    1,554
    @The DB
    Cool
     
  8. 357

    357 Walkin' the dog

    Joined:
    Sep 12, 2009
    Messages:
    1,137
    Likes Received:
    498
    https://www.worldwidedx.com/threads/imax-2000-continuity-query.170384/#post-561527

    I think Marconi did somewhere in this thread
     
  9. Riverman

    Riverman Intermittent Member

    Joined:
    Nov 12, 2013
    Messages:
    2,342
    Likes Received:
    2,085
    Could use one of these. Just screw it in between the two sections. And paint white if desired. The 11” version is $15. https://www.buddipole.com/exanar.html
    Antenna Arm.gif
     
    #249 Riverman, Jan 17, 2020
    Last edited: Jan 18, 2020
    Slowmover and HomerBB like this.
  10. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

    Joined:
    Oct 23, 2005
    Messages:
    6,553
    Likes Received:
    1,596
    Very good description DB.

    In the PDF file below I've added images for a rough idea of what DB is describing as highlighted above in bold.
     

    Attached Files:

  11. The DB

    The DB Sr. Member

    Joined:
    Aug 14, 2011
    Messages:
    1,828
    Likes Received:
    1,113
  12. The DB

    The DB Sr. Member

    Joined:
    Aug 14, 2011
    Messages:
    1,828
    Likes Received:
    1,113
    Redid my lost models for this. All of these images can be clicked to show larger versions.

    The current distribution for the Imax with no capacitor (left) and the Imax with the capacitor (right).

    nocap cap
    As we can see, the imax with a capacitor is completely in phase. Marconi's model above also shows this as well. In the model without the capacitor we have a typical 5/8 wavelength current distribution, and in the model with the capacitor we do not.

    Here we see a comparison between the Imax with and without the capacitor in free space.

    fs
    As we can see, the Imax with the capacitor has a superior horizontal gain in free space. This tells us that the model with the capacitor will be superior for making local contacts in most (but not all) cases.

    Now a look at comparisons for just the Imax (first), the Imax with a mast but no choke (second), and the imax with a mast and a choke mounted 9 feet below the feed point (third). In these models, the Imax is mounted 20 feet above the earth.

    cnc20
    cnc20mast
    cnc30mast

    Now we do the same for the antenna mounted at 30 feet. Again, just the antenna (first), antenna with mast but no choke (second), and antenna with mast and choke mounted 9 feet below the feed point (third).

    cnc30
    cnc30mast
    cnc30mastchoke

    I will let you make your own judgements on these last six models, and the change caused by the addition of the capacitor.


    The DB
     
    Marconi likes this.
  13. 357

    357 Walkin' the dog

    Joined:
    Sep 12, 2009
    Messages:
    1,137
    Likes Received:
    498
    The capacitor was an after thought. I think the SWR problem happened awhile after the capacitor was added but thats a mystery too.
    The Imax when it was done right got out like stink and I'd buy 10.
    Whatever happened is a shame because it was a kickass antenna.

    Now other companies are coming back because it sucks, thats whats really going on.
    Other companies will get my cash unless I can find an original Imax, which will probably get $300 on Ebay now
     
    S&W357 likes this.
  14. Recon

    Recon NY 881

    Joined:
    Jul 28, 2019
    Messages:
    385
    Likes Received:
    548
    Have you tried calling the sellers and ask if they would measure the antenna prior to shipping?
     
  15. Riverman

    Riverman Intermittent Member

    Joined:
    Nov 12, 2013
    Messages:
    2,342
    Likes Received:
    2,085
    I discovered I have a spare one of these left over from my Buddistick days.
    If anyone wants it for their Imax, let me know.
     
    #255 Riverman, Jan 21, 2020
    Last edited: Jan 21, 2020
    RT431 likes this.

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!