20m mobile?

Discussion in 'Mobile Radio Systems' started by AK4PX, Jul 29, 2014.

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  1. AK4PX

    AK4PX Ham Member QRZ Page

    Was considering a trunk mount antenna.

    I've been particularly eyeing the Diamond HF20FX (3.9ft), but the much longer HF20CL (7.2ft) is more prevalent.

    Anyone use either one?
  2. K0BG

    K0BG Ham Member QRZ Page

    They are both, minimal antennas, and very inefficient. You'd be better off with hamsticks!

    It pays to remember, that length matters, and so does Q, at least to a point. Tiny coils work passably for some people I suspect, or there wouldn't be a market for them.
  3. AD4U

    AD4U Ham Member QRZ Page

    I run an old Yaesu FT100D in my little Nissan truck. While far from being the best mobile antenna, I have had very good success with the standard 54 inch Hustler mast and Hustler resonators modified as follows. To operate on 20M I use the Hustler 15M resonator with a much longer whip. The standard Hustler 20M resonator only uses a whip some 12 inches long or so. I don't remember how long the whip has to be to resonate the 15M resonator on 20M, but it is around 42-48 inches. The total antenna length (mast + resonator + whip) is around 8-9 feet. Add to that the height that you mount the base of the mast on your vehicle and you don't want to go under any low bridges or parking garages. The difference in performance between the standard 20M Hustler resonator and the 15M Hustler resonator with a much longer whip is quite noticeable.

    Dick AD4U
  4. AK4PX

    AK4PX Ham Member QRZ Page

  5. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Yes, the Ham Stick folks went out of business a year or more ago. MFJ knock offs are the nearest thing.
  6. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Don't forget the idea of making your own capacitive hat's!
  7. K7RTF

    K7RTF Ham Member QRZ Page

    If your just using 20M mobil, remember, " Longer " !!! is always better . Larger diameter coils are better, larger size wire for coil is better, also I have found that 200Watts, is a great improvement over 100 watts for HF mobil work . ( ie: TS-480 HX ??? = 200 watts )

    My best 40 Meter mobil antenna so far, is a 80M Hustler coil, stripped of OEM wire, and re-wound with #10 stranded ( Insulated ) wire.
    ( About 50 turns), and add 102 inch whip, and trim that to the Center freq. on 40M.

    I also use a 40M Hustler coil, stripped of OEM wire, and rewound with #10 stranded ( Insulated ) , a 24 to 36 inch base, and a LONG, whip, tuned to about 14.225 center freq.

    It works ( you will be very pleased with useable bandwidth, on the 20M setup !!! )
  8. K5VV

    K5VV Ham Member QRZ Page

    I am not sure about larger diameter coils always being better. I have seen a 1.5:1 length:diameter ratio thrown around which is practical. Not sure what is most efficient.
  9. K0BG

    K0BG Ham Member QRZ Page

    The truth is, coils over about 3 inches in diameter have excess amounts of distributed capacitance, hence lower Qs. And, mount coil Qs over about 250 are almost impossible to obtain, no matter what hype you read to the contrary.

    As noted, the L/D ratio is also important, as high reactance could tens to be around 4:1, when lower reactance coils are closer to 1:1.

    Lastly, antennas with large metal end caps are the worse of all. This includes the large Hustler coils, and more than one remotely-tuned multibander.
  10. N5STU

    N5STU Ham Member QRZ Page

    Hmmmm... "get both?" ;)
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