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10/6/2/440 mobile antenna for FT-8900

Discussion in 'Mobile Radio Systems' started by K3TD, Jan 15, 2017.

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  1. K3TD

    K3TD Ham Member QRZ Page

    Would appreciate any feedback from users of the Diamond CR8900A and/or Comet UHV-4. I will be using it with a K400 mount on my Subaru Outback.

    Thanks and 73,
  2. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    Here is something to consider. In order to cover the four band, compromises must be made. As a result, the overall performance is not as good as say a dual bander is.
  3. K3TD

    K3TD Ham Member QRZ Page

    I agree Alan. I've considered 2 different antennas, but would still be limited in what will fit though my garage door so unfortunately roof top NMO mounts (which I would prefer) are not an option. I'm going to start with one antenna and see how that does for the local 10 simplex and 6 simplex/repeaters.

    By the way, your web site is the finest reference I have ever seen for amateur mobile operations - thank you!

  4. KG5RZ

    KG5RZ Ham Member QRZ Page

    The CR-8900 works, not as well as a dedicated antenna for each band, but it works. Diamond's literature says it is designed/optimized to work on a trunk lip mount on the side of the trunk.

    Many people make the mistake of trying to save money by ordering from an Asian vendor. When you do the one you get may not be cut for the US band segments. Many of the bad reviews are from people who have done this only to find they have a serious mismatch especially on UHF.
  5. K3TD

    K3TD Ham Member QRZ Page

    Thanks for the tip about making sure I get one for the US band segments!
  6. KG5RZ

    KG5RZ Ham Member QRZ Page

    You're welcome!
  7. WR4L

    WR4L Ham Member QRZ Page

    I installed a CR-8900 on the bed side-wall of my Nissan pick-up truck on a UHF L-bracket mounted underneath the passenger side rear cargo tie-down lug. It is well grounded to the truck body and frame with the use of silver grease on the bolts. Also grounded the tailgate to the truck body. The antenna would not resonate close to any of the four U.S. bands of intended use. Went to Lowes and bought a 36" section of 8-24 threaded rod for a buck and began experimenting with different lengths for the antenna's lower section - the section just above the base coil.

    After several pruning attempts, I discovered that the lower rod supplied with my CR-8900 is too short by several inches. The correct length of the lower section for optimum performance on the 6 meter and 10 meter U.S. FM band segments is 11 15/16" (exposed). Exactly 1/16" under one foot is visible between the base coil and middle phasing coil. Before cutting, be sure to add back the length of the wells inside the lower base coil and middle phasing coil to your 11 15/16" exposed rod length. I also found it necessary to cut the tip stinger to about 4" total in length and bury over one inch of it in the top coil section. I ordered a 7/32" stainless rod to replace the supplied too-short lower section.

    The SWR is below 1.15 : 1 in the FM segments of both the 6 meter and 10 meter bands. Because I had no success tuning the antenna for 2 meters and because the SWR was too high for my comfort on 440, the antenna has become my go-to dual band antenna for 6 meter and 10 meter FM.

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