Antenna Choices

WA2ZKDWA2ZKD
in KiwiSDR Discussion

In addition to my KiwiSDR use, I have been doing similar stuff with Perseus for a few years. I have evaluated many antennas. The Clifton whip is a great antenna but I found it to be susceptible to VHF/UHF overload from the many TV/FM stations 1/2 mile from me. I have tried Wellbrook (older), Pixel (now DX Eng.), W6LVP and now MFJ loops.  The Pixel is my first choice while the W6LVP and MFJ follow closely behind.  More details in the future. 

Comments

  • G8JNJG8JNJ
    Hi James,

    You should be able to fix the FM BC interference problem that you have with the Clifton whip.

    Three or four turns on a small single hole ferrite bead in series with the connection from the whip to the amplifier should do it. If not add an additional 1 to 2 K Ohm resistor also in series with the bead. This will roll off the VHF gain quite substantially without too much impact on the HF bands.

    I used a similar active whip antenna for the MF band on our SUWS WEB SDR, where we had a 25w VHF DMR base station antenna about 3m away from the whip and it fixed the problem.


    Regards,

    Martin - G8JNJ
  • WA2ZKDWA2ZKD
    The interference is the OV of the whip's own active device, not downstream.
  • jksjks
    WebSDR's creator P.T. de Boer, PA3FWM, has an excellent article about how to add an LPF to the tricky super-high-impedance E-field probe of an active antenna: http://www.pa3fwm.nl/technotes/tn05.html#lpf

  • WA2ZKDWA2ZKD
    Thanks!
  • WA2ZKDWA2ZKD
    more on Loops...

    The Pixel/DX Eng. uses a 24VAC wall wart whereas the other 2 use 12VDC or lower supplies.  The higher voltage suggests a better (higher voltage) drain supply and and better big signal performance.  Measuring things like the IMD etc of the preamp would confirm but I don't intend to do a bench eval of them.  
  • G8JNJG8JNJ
    Hi James,

    You misunderstand, my suggestion was to place the ferrite bead and resistor at the amplifier input (in series with the whip) as shown in the link that was later posted by John. 


    This method works very well.

    Regards,

    Martin - G8JNJ



  • WA2ZKDWA2ZKD
    OK.... well the whip is in my review mirror so....  will keep it in mind for the future
  • KA7UKA7U
    I currently have the W6LVP magnetic loop running @ http://ka7u.no-ip.org:8073

    So a heads up comparison is underway between these two antennas.
    Ron
    KA7U
  • KA7UKA7U
    The W6LVP antenna running on http://ka7u.us.no-ip.org:8074 is doing almost as good a job as the 210' G5RV dipole. The dipole gets down to 15KHz whereas the W6LVP gets down to 60KHz. Generally the G5RV provides better S/N ratios up to 14MHz and the W6LVP does better above 14MHz. This is not a rule though, merely a perception based on observation since it has been up. At any given time either antenna might seem better than the other on a given frequency.

    The result for me is that the small footprint W6LVP Magnetic Loop provides almost as good a signal to the KiwiSDR as the very large footprint G5RV. In my mind this makes the W6LVP the more desirable antenna for aesthetic reasons and still provides excellent 60KHz through 30MHz reception.

    Nice little antenna.
    Ron
    KA7U
    WA2ZKD
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