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Diversity reception what is it

GeraldGerald Member
edited June 2020 in SmartSDR for Windows

Answers

  • Dwayne_AB6ADwayne_AB6A Member ✭✭
    edited November 2019
    A second receive slice ideally connected to a second receive antenna which tracks to the first slice - audio for the first slice is set to output the left channel (ear) and audio for the second slice is set to output to right channel (ear). Your brain puts the two receive sources back together. it can make a difference with a single receive antenna by playing with filtering for each slice.
  • Bob K8RCBob K8RC Old Guy Member ✭✭
    edited November 2019
    On units with 2 independent SCUs (6600, 6700), it's the ability to receive on separate antennas, one feeding each SCU, and combining the results.

    Fading (QSB) rarely happens identically on separate systems. Diversity reception makes use of this phenomenon to improve the reliability of the reception. 
  • PatrickPatrick WH6HI KauaiMember ✭✭✭
    edited June 2020
    The best way to describe what Diversity, is to use something that you may have experienced.  While approaching a stop light listening to a FM station in your car as you slow down the station suddenly fades away and as you continue forward it suddenly comes back.  The same thing happens in the HF frequencies.  If you add a second RX and antenna some distance away and link the two. And then process the two signals so that you keep the best of the two, that is Diversity Reception.  The effect of fading is some times described as selective fading or multi path, signal phase cancelation etc.
    Hope that helps...
  • RiaRia Member ✭✭
    edited November 2019
    As noted, it is quite different from how other manufacturers do it. Elecraft, for example has a voting receiver where it picks the signal with the better SNR. Flex depends on your brain to do it.

    A good use case is having horizontally and vertically polarized antennas for weak signal reception on bands like 160m, or even just different antennas (at different heights or locations) with the same polarization. Sometimes it's stronger on Horizontal and sometimes on vertical. 

    https://www.w8ji.com/polarization_and_diversity.htm
  • K3SFK3SF Member ✭✭
    edited March 2020
    hi ria  and all

    i will disagree about flex solution for diversity being done by only by ones own brain....

    All that is required is to place both signals in center of the audio position slider and NOT one channel left ear  (aka full left on audio slider) and one channel right ear (aka full right on the other audio slider)...

    With both signal in the center the radio audio mixes both signals together and in phase and you will notice NO to little fade issues...this works for ssb and cw...
    BUT
    a lot of operators would rather do the full left and full right
    and
    let the brains sort it out  and that causes a heavy cognitive overload
    and
    that cognitive overload is not necessary

    The real aspect of diversity besides the two receivers are the ideas of receive signal polarity and/or distance between receive antenna for each receiver.

    One thing i have noticed is that there is no DAX MIXER
    which would bring diversity reception to the digital modes...


    i would love to be able to have this Dax Mixer capability on FT8
    and
    really see how deep into the noise we could copy....

    that is just my 2cents which has been eroded by inflation ;-))

    Paul K3SF






  • Jim GilliamJim Gilliam Member ✭✭
    edited April 2020

    I use geographic diversity. One at the QTH and one 100 miles away at my cabin. I use a VPN to minimize the time lag between the two receivers. I get a slight echo effect, but listening to the same signal with a 100 miles span gives me a significant advantage when there is a lot of QSB. It is nice that one can run two instances of SmartSDR on the same computer at the same time.


    Jim, K6QE
  • RiaRia Member ✭✭
    edited November 2019
    In W8JI's article he explains why that doesn't work out, at least not as well as stereo diversity or true (voting receiver) diversity. I have tried it and went back to one in each ear... but I also tried it on a friend's K3S and I must admit that it is a better experience. 
  • RiaRia Member ✭✭
    edited November 2019
    Since I use diversity primarily for chasing DXCC, that option is out for me as it's against DXCC rules to use remote receivers. 
  • Neil D Friedman N3DFNeil D Friedman N3DF Member ✭✭
    edited November 2019
    As I revall, my Dovetron terminal unit circa 1970 had the capacity to utilize diversity reception to maximize RTTY copy in fading signals. 
  • GeraldGerald Member
    edited November 2019
    I was hoping the second receiver’s signal would be tuned to an area near the primary signal, receive near-signal noise and invert the noise 180 degrees. Then, if it were mixed with the primary receiver’s signal it would cancel out the noise. This may work much like noise canceling headphones. I misunderstood your purpose of ‘diversity’ reception, sorry.
  • Chris DL5NAMChris DL5NAM Member ✭✭
    edited November 2019
    Ham Radio is more much then DXCC !

    Geo diversity is one point on list of FRS - they have quietly forgotten :-( 
  • Dave-N9CHMDave-N9CHM Member ✭✭
    edited November 2019
    I agree with Paul, I use an inv V and an inv L on 160M with a 6600M, I prefer putting both signals (SSB) in the center position of the audio slider. It works great. I've read the article you mentioned several times, and I can't see (hear) the problem doing it this way. On signals >500 miles from me, the RX'd inv L signal can be from an S unit to +20db better than the inv V (as one would expect), and I can mute one signal or the other just to hear the difference (or use left-right speakers for either antenna). So, at least for me, I don't hear a problem if using both signals in the center position of the audio slider.
  • WA6FXT MikeWA6FXT Mike Member ✭✭

    I would still like to see FRS develop the true rf (dual SCU, phase) diversity that was being touted when I chose to send my $1000 ‘early adopter’ reservation in May 2012.


    mike WA6FXT

  • KF4HRKF4HR Member ✭✭

    I too do not separate the left and right Diversity channels, but rather center both during Diversity Reception. Seems to work better.

    And I agree with WA6FXT, a Diversity Phasing adjustment should have been implemented into SmartSDR by now. Lesser expensive competition has a leg up on this (along with Noise Reduction). Flex Programmers... get crackin'! :D


    Butch KF4HR

  • Dwayne_AB6ADwayne_AB6A Member ✭✭

    A logical AND operation on the audio from the two SCU's seems like a trivial programming exercise? It's something offered on a number of open source and commercial audio programs... Seems like some R&D is required.... (Ripoff and Duplicate)

  • Dan TrainorDan Trainor Member ✭✭

    The state of the art is diversity reception is that should INCLUDE the ability to do phasing between both signals to support the use case of having one of the antennas being a RX-only noise receptor and the other your main TX/RX antenna or other RX antenna. The purpose is to phase out the local noise from the main signal by adjusting the phase and amplitude using typically circular graphic display with a line control moved by the mouse, such as what is in SDRPlay RSP and also ANAN SDR radios to maximize S/N. This is only one use case of Diversity reception but a particularly valuable one when you live in a suburban noise. Receivers that don't have this capability today are seen as falling behind the state of art. Other forms of Diversity reception, not without standing. Such as geographic diversity where antennas are located farther apart, sometimes many miles apart. Or other use cases where antennas are on same property but have different orientations or polaritons. When you put all these use cases together, you have comprehensive diversity reception functionality. Flex is way behind. dan

  • KF4HRKF4HR Member ✭✭

    Dan - I'm curious what program allows the SDRPlay to use phase and amplitude for adjustable diversity receive?

    KF4HR

  • Dwayne_AB6ADwayne_AB6A Member ✭✭
    edited January 13

    Ralph - Since diversity reception on on the Flex outputs a left and right audio channel from the SCU's, they can be fed into any "audiophile" mixing program for post processing. Audacity as an example and using a  Nyquist recipe for post processing the left and right channel.

  • Dwayne_AB6ADwayne_AB6A Member ✭✭
    edited January 13

    Just to add and looking for feedback...

    For post processing the audio signal with left and right channels, what would be the best algorithm to use against the left and right channel? Take the lowest value from either channel, or some other approach?

  • Bill AB7AABill AB7AA Member ✭✭

    I have been doing diversity reception for about 18 years now and the whole station is set up for it. I originally started out by phase locking two IC-746's and using the binaural method of one antenna in each ear. I now use two 6700's on 4 diverse antenna systems. I agree with W8JI's page on the subject that one can hear thru the noise better with the binaural setup. I also have several JPS SNV-4 signal voters that work well because they vote the better S/N of 4 channels and eliminate the noise of the others, but, they were only designed for voice bandwidth.

    I like viewing diversity on separate panadapters. With the proper antennas, one can **** the band and immediately pick out lower angle DX from closer stations along with other characteristics.

    Bill AB7AA

  • KF4HRKF4HR Member ✭✭

    Dwayne - I'm not familiar with the Audacity program. Do you happen to know whether this program provides for both phasing as well as amplitude adjustments between L and R channeling?

    Butch KF4HR

  • Dwayne_AB6ADwayne_AB6A Member ✭✭
    edited January 13

    Ralph - There is much you can do with Audacity. To extend its capabilities you can use downloadable Nyquist filters to tweak your audio...

    This is as far as I have got at the moment - Playing with Audacity and Nyquist. I don't have the optimal receive only antenna set up at the moment but this dialog has prompted me to do something over the weekend. I have good programming skills, I just need to tweak my radio setup before I start too play with the programming aspects on Audacity.

  • Bill AB7AABill AB7AA Member ✭✭

    I have been doing diversity reception for about 18 years now and the whole station is set up for it. I originally started out by phase locking two IC-746's and using the binaural method of one antenna in each ear. I now use two 6700's on 4 diverse antenna systems. I agree with W8JI's page on the subject that one can hear thru the noise better with the binaural setup. I also have several JPS SNV-4 signal voters that work well because they vote the better S/N of 4 channels and eliminate the noise of the others, but, they were only designed for voice bandwidth.

    I like viewing diversity on separate panadapters. With the proper antennas, one can **** the band and immediately pick out lower angle DX from closer stations along with other characteristics.

    Bill AB7AA

  • K3SFK3SF Member ✭✭

    Dwanye


    The logicval AND of each SCU is easily accomplished by bringing Both to the center and not left ear and right ear...

    They combine in the center since they are in phase and the strongest( aka loudest channnel prevails)...


    The left ear/ right ear combo channel setup requires too much cognitoive loading to easily select the best signal

    i typically use two different antennas...sometimes ame polarity BUT spaced apart and other configuration is different polarity


    Paul K3SF

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