6BTV 80M broadband idea

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AA7QQ, Nov 13, 2019.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: MessiPaoloni-1
ad: L-MFJ
ad: Subscribe
ad: Left-2
  1. AA7QQ

    AA7QQ Ham Member QRZ Page

    On the 80M resonator:
    I was thinking (Sometimes, I do) that I might put 4 horizontal whips & 1 vertical whip all cut to different lengths to see if I may be able to cover the whole phone spectrum.
    Or, should I orient them like the bottom half of a discone?
    I thought of this, due to the way you can put 3, 4, or 5 Hustler elements on a single mast.
    Possible?
    I have double walled masts to the bottom of the 30M trap. I could sleeve the upper, too.

    What say?

    Ed
     
    NH7RO likes this.
  2. AA7QQ

    AA7QQ Ham Member QRZ Page

    @W7UUU
    Could please move this to the antenna section.
    Being blonde makes me do dumb things.....

    Thanks, man. Still burnt out from the move & unpacking.

    Ed
     
  3. W1VT

    W1VT Ham Member QRZ Page

    Sounds like the idea is to force all the current into just one radial that is close to ground. Typically a bad idea, but if your idea is to broadband the antenna regardless of efficiency it may be workable.
     
  4. AA7QQ

    AA7QQ Ham Member QRZ Page

    I was thinking of putting several whips atop the RM-80 resonator. The discone idea was for possibly using it upside down & attached to the top of the resonator with different length whips. Kind of like a crown.

    Ed
     
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Interesting idea, but my gut feel is that it won't work as you're thinking. I suspect the multiple whips up above the RM-80 resonator will just act as a bulk cap hat and not really work as discrete different length resonating whips. IOW, I suspect it would lower the resonant frequency of the antenna on 80m but wouldn't necessarily widen the SWR bandwidth by much.

    It would be interesting to model it, but try this thought experiment:

    - Build the antenna with an RM-80 resonator up top and a very short top mast maybe just a few inches long.
    - Add a spoked hub up there and install say 4 different length whips as you suggest perhaps angled out a bit from one another. Looking at it that way it does sound a bit like a true fan vertical with multiple resonant lengths.

    - But then change the angle of those whips till they all stick out at right angles from the hub. Now you've got a bit of an asymmetrical cap hat where the four horizontal spokes of the hat happen to be different lengths. Viewed this way it would just add capacitive top loading proportional to the bulk end capacitance provided by the hat and wouldn't really give you four independent resonant whip lengths. Sure a cap hat design does tend to broaden the SWR bandwidth but likely by a very small amount in this scenario.

    - The two scenarios above, angled whips vs horizontal whips, may look a bit different but electrically they're very similar so even though one sounds plausible for creating an 80m fan vertical with broad SWR bandwidth I suspect they'd behave the same and just lower the 80m resonant frequency without noticeably broadening the SWR bandwidth.
     
    KW6LA likes this.
  6. KH6AQ

    KH6AQ Ham Member QRZ Page

    Multiple RM-80 resonators might work to broadband the antenna. The multiple resonators might detune 40 meters.

    The antenna can be broadbanded on 80 meters using a DX Engineering HotRodz assembly on an RM-40 resonator. Another way to do this is an RM-40 with ~20' of wire routed horizontally. This renders 40 meters inoperative.

    https://static.dxengineering.com/global/images/instructions/dxe-hr-1p_vn.pdf
     
    K7TRF likes this.
  7. NH7RO

    NH7RO Ham Member QRZ Page

    If Hustler takes up your idea and starts offering the AA7QQ Mod Kit that could well be your crowning achievement, Ed! Good for you!
     
  8. AA7QQ

    AA7QQ Ham Member QRZ Page

    Well, I took the calipers to everything & the base of the discone should have about .060 clearance on the hustler top. I'll gather some junk together & give it a whirl.
    It'll be a couple weeks before I can get to setting the mast & radials, but trying to get it all done before the TDN.
    Also, got offered an A3s, 6M, 2m & 440 yagis, along with the heavy duty Yaseu rotator from a friend here. He moved into a condo & stuffed it all in the attic, because he knew I'd be back some day & he will use my shack remotely.

    Ed
     
    NH7RO likes this.
  9. AA7QQ

    AA7QQ Ham Member QRZ Page

    I think I have it figured out. I will try a slug of 2" solid aluminum drilled for 4 whips going vertical at different heights. Each will have a set screw to fasten it. I will drill the center to tightly slide onto the top of the 80M resonator & drill/tap for set screws.
    Good thing I did keep a bunch of mobile antennas & scrap aluminum from the last QTH.
    The XYL let me do the final loading of the truck, "Because I don't want to keep you from your junk".
    I did give away a boatload of stuff before the move to another ham. He did 2 carloads of stuff. I hope his XYL never finds me...

    Ed
     
    NH7RO likes this.
  10. HAMHOCK75

    HAMHOCK75 QRZ Member

Share This Page