How effective is diversity reception at extracting signals in high RFI environments?

Discussion in 'Software Defined Radio (SDR)' started by N5YPJ, Jul 13, 2021.

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  1. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Some Flex and Icom 7610 Actually have a diversity function on them/ not just 2 receivers.
    But if you have RFI near you diversity is probably not going to solve your problem.
    It helps improvement in reduction of QSB/fading. On HF as the ionospheric geometry changes with time, the arrival time, angle and polarization of incoming signals will also change. If one antenna is experiencing a deep fade, it is likely that another has a sufficient signal.

    I use Diversity most of the time on HF.
    73 from,
    The K0UO " Rhombic Antenna Farm" 2 miles of wire in the Air & On the daily
    PU2OZT likes this.
  2. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Not really diversity reception but I can often dramatically reduce the fairly small amount of local RFI I have by using a horizontal antenna vs a vertical, and vice versa in some cases
    PU2OZT and K6CLS like this.
  3. PU2OZT

    PU2OZT Ham Member QRZ Page

    Methink thread is actually built on unproper grounds.

    Facing harsh RFI environment you'd first rely on antennas not-prone to RFI e.g. quads,
    instead of complicating, just because «As it's complicated, should obviously be better.»

    To French-speaking hams "Pourquoi faire simple quand on peut faire compliqué."

    SWL37632 likes this.
  4. SWL37632

    SWL37632 QRZ Member

    K0UO....Wondering if you would share your diversity reception experience....benefits, set-up?

    20+ WPM 1970's Extra
  5. N2DTS

    N2DTS Ham Member QRZ Page

    The flex and anan radios can null out a lot of noise using the diversity feature.
    I used a zero 5 vertical and a dipole and you can move a pointer around on a chart and null noise out or peak a signal.
    Its fussy though, it takes fooling with every time you move frequency much.
    A small magnetic loop antenna works a lot like the same way, turning it you can null noises or peak signals.
    The MFJ loop is actually quite good as its a fat conduit not a thin wire and the amplifier is also quite good.
    But you have to be able to turn it...

    For QSB, the separate audio from two receivers into each ear using two different antennas works well.
    I often notice on 40 meters when the dipole signal fades the zero 5 signal comes up and it will go back and forth.
    I often just switch antenna's back and forth.
    Its amazing how well that works at times.

    For noise, the loop is best, then the dipole, the vertical picks up the most noise on the lower bands.
    WA3VJB and SWL37632 like this.
  6. K1VW

    K1VW Premium Subscriber QRZ Page

    I have an SDRduo with dual receivers, and the SDRUno software supports diversity reception. I've played with it a bit. I tried using my 80m dipole (runs East/West) on one channel and my 40m dipole (runs North/South) on the other channel. On the SDR screen there is a widget so you can adjust phase and amplitude. There was a weak signal I could not hear with either antenna alone, but I could hear it well in diversity, so it works as advertised. I was impressed! The reality is I found fiddling with the phase and amplitude widget too much of a bother, I wouldn't want to do that all the time. Luckily my QTH is pretty quiet, so there isn't a lot to be gained in my situation most of the time.

    BTW I realized I can't use it this way, listening with the SDRUno, and transmitting with my rig, not on phone anyway. When I'm transmitting a bit of it bleeds through to the SDR receiver, which doesn't auto-mute. So I hear myself speaking on my headphones, but with a wicked delay, the worst reverb ever. I would have to have PTT kill the audio feed to my headphones. With a real setup like a Flex or 7610 I presume it mutes the receive when you transmit.
    SWL37632 and K0UO like this.
  7. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Check my call on QRZ info there.
    The power is in the diversity, of course the kind of antennas you use helps a lot too.
    73 from,
    The K0UO " Rhombic Antenna Farm" 2 miles of wire in the Air & On the daily
    SWL37632 likes this.
  8. KI5FJ

    KI5FJ Ham Member QRZ Page

    Steve (K0UO), I mention your diversity operations in a local club presentation.

    Hopefully, my short Technical Correspondence article in the October QST opens up the concept to more operators.
    My residential Antenna Farm has limited space and polarization diversity possibilities.
    Two Antennas are better than one.
    If you want a copy of my PDF, drop a email to QRZ address. 73 & Be Well, Joe O, K I 5 F J, NNNN
  9. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    I emailed you and you can use any of my info on diversity RX anytime
  10. WA3VJB

    WA3VJB Ham Member QRZ Page

    Reception of wholesome AM voice communications on HF is enhanced by spatial diversity, in my experience. I've been at two stations where the operators configured two, military R390A receivers on different antennas, feeding a stereo audio system. The depth of differential audio, as perceived by the mind, enhanced the ability to pull out weak stations, but it also enhanced the quality of AM QSOs where signals were strong and well-modulated. In this second case, it seemed to be a matter of having your mind "select" the receiver that suffered the least amount of propagation distortion, or nearby interference from incompatible modes.

    If you have the gear, as did these ops, it's definitely a worthwhile experience.

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