ad: expert-3

Ground the Boom?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N7AY, Feb 28, 2021.

ad: L-HROutlet
ad: l-rl
ad: abrind-2
ad: Left-3
ad: L-MFJ
ad: Left-2
ad: MessiPaoloni-1
ad: HRDLLC-2
ad: L-Geochron
  1. N7AY

    N7AY Premium Subscriber QRZ Page

    Two questions about my current home brew yagis in progress.... one VHF, one UHF.
    Both are 50 ohm, isolated element, dipole-fed.

    1. What do I do with the aluminum boom? Float it, tie it to the coax shield, earth ground?

    Also, I have a good handle on the choke design for both using the appropriate ferrite toroids and beads. However given they will be mounted next to each other (ie satellite work)

    2. Do I need to worry about affects on each other or just filter on each yagi for it's resonant frequency range?
  2. N7AY

    N7AY Premium Subscriber QRZ Page

    No takers on these questions?
  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    If mounted on a conductive mast then the mast must be grounded, which would presumably also ground the boom.
    KC1NY and K0UO like this.
  4. KH6AQ

    KH6AQ XML Subscriber QRZ Page

    The metal booms should be grounded to stop charge from building up. The dipole element coax shield can be tied to the boom after the balun, or left unconnected.

    I hear that some ops use the Comet Duplexer, CF-416C to isolate the TX and RX.
    N0TZU and K0UO like this.
  5. N7AY

    N7AY Premium Subscriber QRZ Page

    My mast will be nonconductive (i.e. Sch40 PVC).... unless someone talks me out of that. Can I float the boom or should I run a separate earth ground to it?
    Am I understanding correctly that the shield side of the driven element can optionally be connected to the boom but if connected to the boom it should be done so on the antenna side of the common mode choke?
    It's sounding like the optimal connection would be to tie the coax shield to the drive element and the boom, all after the choke. ??

    At this point I plan to use two VHF/UHF radios I already own rather than buying a full-duplex transceiver, and my coax run is short. However, thanks for the pointer to the duplexer, I may need one one day.
  6. N7AY

    N7AY Premium Subscriber QRZ Page

    I'd like to bring this topic up again - time having passed and a little learning acquired.

    The original question was, on a 2m or 70m yagi with isolate elements (not electrically connected to the aluminum boom - they are about 1/2" away from the boom) should the boom be grounded or floating?

    I got my satellite antenna built and have been using it (picture on QRZ page). I never did get a good answer on whether the boom should be grounded or floating. So I did the easiest - I floated it. The 2m and 70cm yagis seemed to be working well. I don't have anything to compare them to and no equipment to measure their performance so I'm not sure how well they really work. Last week I made some modifications to my support system (rotor, poles, booms) for the two yagis and unconsciously connect the boom to feed-line shield and ground. Over the past week the antennas seem to not be working so well. Now I'm wondering if the grounding of the boom is having a negative affect on the yagis.

    Should the boom float or be grounded?
  7. AI5DH

    AI5DH Ham Member QRZ Page

    You were given the answer already. It is required by electrical and equipment codes to be grounded. It is a metal electrical apparatus containing electrical wiring exposed to lightning. So you can follow code or ignore it.
    Last edited: Sep 16, 2021
    AG6QR likes this.
  8. N4UFO

    N4UFO Ham Member QRZ Page

    SPPFFFT! NO body looked at the picture... the antennas are mounted on a very short pole in the yard. As long as you properly ground the feedlines and rotor cables as they come into the house, you are up to code. NO, I would NOT connect the booms to the feedline shield, not designed to perform that way. Just let them float and not cause any interaction. Same reason it is suggested to use a non-conductive crossboom. - I really wouldn't ask satellite questions anywhere but the satellite forum.
    Last edited: Sep 17, 2021
    AK5B likes this.
  9. AK5B

    AK5B Ham Member QRZ Page

    Good point---I wholeheartedly agree---unfortunately, it was not made clear by the OP that he was referring to a SAT specific set-up, initially.


  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Good advice when experimenting with such things is "lower the boom.":p

Share This Page