Larsen KG2/70CXPL on tinted glass

Discussion in 'Mobile Radio' started by N0ZUP, Jan 9, 2015.

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  1. N0ZUP

    N0ZUP Ham Member QRZ Page

    Have read many threads and see mixed answers. I would like to mount the Larsen KG2/70CXPL antenna on the fixed glass above main window in my 05 Itasca Suncruiser motorhome. This is a tinted glass and I am trying to determine if this location will work. I would appreciate opinions from people that have actually mounted this or similar antenna on a tinted window.

    Thanks
     
    KX4O likes this.
  2. N8MSA

    N8MSA Ham Member QRZ Page

    I've used this antenna, and several other Larson through-glass antennas, and works reasonably well. Coupling losses render it about -1.8 dB down from a base and/or center-loaded antenna of the same length, but I have found that they provide about 80% of the real-world range of those antennas.

    Coupling compromises aside, I think that the reason for conflicting opinions on through-glass antennae is the subject of "passivation" (metal particles mixed into the glass substrate as a form of tinting), the extent of which is grossly exaggerated. The best way to test this is to simply measure the capacitance through the glass, or have someone do it for you. Note that finding someone with a capacitance meter and the probes needed for doing this is becoming difficult because:

    Passivation has been largely abandoned in the automotive industry. Reasons include cost, increased effectiveness of chemical treatments and interference with cellphone signals. I know this because I designed, and now sell, vehicle data-loggers and have tested them in honest-to-goodness automotive OEM EMC chambers. The same holds true for most over-the-road vehicles...

    Bottom line: try one, and send it back of you don't like it. You can temporarily install these for a stationary test with non-metallic "gaffer tape", which is easy to remove and leaves less residue than "duct tape"; this way you don't have to use the adhesive pads shipped with the antenna and can just send it back if you don't like it.

    Further reading:

    http://www.pulseelectronics.com/products/antennas/larsen_antenna_products/technical_reference/faqs
     
    KX4O likes this.
  3. N0ZUP

    N0ZUP Ham Member QRZ Page

    Excellent reply. Thank you for your suggestions.
     
  4. K0RGR

    K0RGR Premium Subscriber QRZ Page

    I've never tried it on a tinted windshield, but I did try one on a side window and it plain didn't work. It wasn't the tint, because there wasn't any, it was just a different thickness of glass than the windshield, I think. Could never get it to tune on 2 meters. It could also be the close proximity of the side of the vehicle as about 2/3 of the whip was below the top of the MH.
     
  5. N8MSA

    N8MSA Ham Member QRZ Page

    Bill -

    Just as an FYI for you, or anyone else trying to install one of these, the best way to orient the coupler units is to determine a rough location, affix one coupler, test-place the other coupler (with tape) and then test the SWR. The best results are typically obtained when the two couplers are "square" (visibly aligned), but it's best to check.
     
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