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Antenna Proximity concerns

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KI7HSB, Nov 15, 2020.

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  1. KI7HSB

    KI7HSB Ham Member QRZ Page

    I finally got my antenna tower upright and am getting ready to populate it with a variety of doo-dads and wires... The list of planned items are:

    Center of an 40m/80m dipole
    Cushcraft R-6000 multi-band vertical.
    Digital Television receiver antenna ( I cut the cable!!!)
    Weather station (haven't bought yet and don't know what model) and...

    One or more Discone antennas to feed the SDRPlay RSPdx that I bought with my invention bonus at work :)

    My question is concerning the the discone antenna in such close proximity to the dipole and multi-band vertical transmitters.

    Would there be any problem with over driving the SDR or some other unintended ungood from putting them so close together, or should I put the discone as far away from the main tower as I can on my property?
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd keep it as far away as practical, unless you run QRP on HF.
    KI7HSB likes this.
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    Since the discone likely only works 50MHz or 100MHz on up to 1GHz, then a VHF SDR receiver is likely to survive if you transmit on less than 30MHz, especially if you are using only 100W. If QRO, then you might need to do something a bit more complex...

    I am running an SDRplay on HF when I transmit a kW into a HF antenna separated only 10s of feet from the one connected to the SDR (sometimes on the same band I'm transmitting on).

    To do that, I cobbled an antenna shorting relay for the SDRplay actuated by the PTT line out of my HF transceiver (the same output that keys the HF amplifier and mutes my PC speakers). I had to do that while I was messing with a phasing noise canceller, too.
    KI7HSB likes this.
  4. KI7HSB

    KI7HSB Ham Member QRZ Page

    I'm making arrangements to park the discone at least 65' away from the mast. Should I also avoid the ends of the dipole?
  5. KI7HSB

    KI7HSB Ham Member QRZ Page

    I am making the executive decision to self limit my power output at this location to 100w (the standard output of my IC-718). I'll save the KW+ amp fun for after I get relocated to the lazy R ranch in Idaho next year or so...

    Even though the discone isn't potentially resonant at 40 and 80M, should I still avoid placing it near the ends of the dipole as well?
  6. KI7HSB

    KI7HSB Ham Member QRZ Page

    And, yes, I will only be running 100W at this QTH.
  7. N5TJD

    N5TJD XML Subscriber QRZ Page

    You could use a Transmit /Receive switch if you are so inclined. You can trigger it with your radio's amp keying line so that when you transmit, it disconnects the SDR from its antenna.
    KI7HSB likes this.
  8. KI7HSB

    KI7HSB Ham Member QRZ Page

    Looking into one of those for the low bands... I'll be using one or more discone antennas for the upper and mid bands, but down around 40m or lower, having multiple long pole antenna is a bit of a hassle, so was investigating using the primary dipole and an automatic switch.
  9. WA7ARK

    WA7ARK Ham Member QRZ Page

    I just home-brewed one using a 12Vdc automotive sugar-cube relay that looks like this:

    I buy those relays at an auto-wrecking yard for $0.25...
  10. W3TKB

    W3TKB XML Subscriber QRZ Page

    I have and quite like the AcuRite "Iris" 5-in-1 weather station with color display, which is currently on sale at the AcuRite website for $150. (
    Check it out along with all it's features. I highly recommend using Lithium batteries in the external sensor, especially in the wintertime...regular batteries just don't seem to last very long and nobody likes climbing a ladder in the freezing cold to change 'em. Not sure how far your tower is from where you would put the display, I think there is a range limitation based on line-of-sight, obstructions, etc, so double check on that beforehand. My sensor and receiver are about 20 feet apart with a metal roof and external insulated wall to transmit through, and I have no issues with connection.


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