102 inch fiberglass whip as top section on a Solarcon A99 antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KJ7ACR, Apr 21, 2021.

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  1. KJ7ACR

    KJ7ACR Ham Member QRZ Page

    Does any one have any idea what kind of resonance / band width you could get close to if you put a fiberglass 102" whip as the top section of a Solarcon A99 10/11 meter antenna with a ground plane radial kit on it, or extra counter poise ?
    Just wondering if it would work on any particular band if using a MFJ 989d tuner.

    Bruce, KJ7ACR
     
  2. KI8DJ

    KI8DJ Ham Member QRZ Page

    Don't change the top section. It will alter the operating frequency. The antenna will work best as is. It is quite good on 10 through 17 meters with your tuner. You may get more bands to tune but performance will be very poor.
     
  3. K7JOE

    K7JOE Subscriber QRZ Page

    If you replace the existing 6 foot whip with a top whip of 102 inches, the resonant frequency shifts from 10 meters to 17 meters. I used this successfully on a dxpedition in SE Asia about 20 years ago and made about 8000 qso's on 17 meters with it. It was light, easily transported, self supporting, and got minimal "interest" from customs officials. The tuning rings could be adjusted for 20M too but it didn't see to work well there... but it really performed on 17M... I was surprised and that's why I chose it as one of the antennas for that trip.

    For use, it was mounted on a 10 foot pole buried about 2 feet in the ground, no other guy wires as it was temporary. It worked well. No ground radial kit or other stuff. I put 100W through it no issue.
     
    AK5B and WS9K like this.
  4. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Let's do the math:

    102" /12 = 8.5 Ft.

    Quarter Wave estimation formula (including End Effect) = 234/ Ft = Mhz resonance.

    234/8.5Ft = 27.53 Mhz resonance.

    What we cannot know without taking measurements is the inductance/ capacitance of the A99 lower section.

    Suggestion: If provide the length of the A99 standard whip, we could algebraically estimate the effect of adding the 102 whip.
     
  5. K7JOE

    K7JOE Subscriber QRZ Page

    The A99 is an "extreme" OCF aka End fed antenna that is 18 feet long, approx 1/2 wavelength on 11 meter band.

    The "add 3 feet and do the algebra" math doesn't work because there is, as you note, some base inductance in the lower section (and some capacitance too, they call it tuning rings). That's why it resonates at 18 mhz rather than 22 mhz (*which is where it should resonate after adding 3 feet of upper length if not for the base L and C components)...
     
    AK5B likes this.
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    When I hear "Solarcon" I always think of somebody trying to sell solar installations.:)
     
    KB9JCW, N1VAU and WA4SIX like this.
  7. N1VAU

    N1VAU XML Subscriber QRZ Page

    @KJ7ACR The solarcon ground radial kit is more of the "con" in the name. It's snake oil for the uninformed. Those kit elements are too short to be effective as a ground plane (needs to 1/4 wave long of operating frequency)
     
  8. KI8DJ

    KI8DJ Ham Member QRZ Page

    I believe they are helically wound to 1/4 wave. Although they don't seem to help much if any. Feed line end up being counterpoise.
     
  9. K7JOE

    K7JOE Subscriber QRZ Page

    Ya snake oil. They basically add to the counterpoise role that the feedline plays on this (any ) end-fed antenna.
     
  10. KI8DJ

    KI8DJ Ham Member QRZ Page

    You gotta wonder how many CB finals were blown with the 102 inch whip add on.
     

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