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Diversity Reception for the 6700

W5UN_Dave Member ✭✭
edited May 2020 in New Ideas
Until FRS can come up with a good, simple way of running full diversity, the Flex 6700 cannot compete with the Elecraft K3. I base this on dual comparisons  of the two radios on 160 and 80 meters for the past several months, where I use full size 4-square antennas and Beverage antennas for full receive diversity. The K3 has a very simple way of enabling DIVERSITY mode by the press of a single button, which locks the two internal receivers in tracking diversity mode. Flex will need to make this just as simple to setup in order to compete. Then I will need to evaluate both receivers again to see if performance in Diversity mode of the 6700 can match (or exceed) the K3 performance.

What say FRS; is this in the cards?
1 votes

Open for Comments · Last Updated


  • Barry N1EU
    Barry N1EU Member ✭✭
    edited February 2017
    I think the subject line of the thread probably should have included "diversity" to qualify the comparison.  But I hear you Dave.  Besides the obvious vfo/oscillator tracking, you really need many of the controls in the two receivers to track so the operator doesn't have to continually adjust TWO sets of controls. To name a few: mode, bandwidth, shift, AGC should all track in diversity mode and ideally RF and AF gain controls in the two receivers can be ganged together with a balance control.  K3 and Orion both provide these now (they didn't initially) and hopefully the Flex 6K will eventually (?).
  • Ernest - W4EG
    Ernest - W4EG Member ✭✭
    edited January 2015


    You hit it right on the nose.

    My findings last summer side by side test perform by the SDDXC* proved that the K3 was not going to be a challenge to the Flex-6X00 radios. As a matter of fact we found the KX3 to out performed the K3.

    Mind you, the Flex 6x000 radios were just released running Flex SmartSDR first beta version: The radio was in my possession less than 2 weeks: And I barely knew how to turn it on.

    *CW DX Contest 2013. Test findings and results can be found in Facebook

  • k0eoo
    k0eoo Member ✭✭
    edited March 2017
    At the risk of raising some eyebrows, the only items I would add to Stu's list are separate CW/SSB/AM filters at $140ea, low noise preamp at $160 and general coverage RX module at $160 plus many other options not mentioned here....
  • Greg
    Greg Member ✭✭
    edited May 2020
    Like Barry pointed out, I think the orig post was focused on diversity RX. That is something obviously important to him so his remarks are valid...for him. It is not going to be the same for everyone. As Barry knows, I'm a very early field tester for the K3 (ser #9) and still have the radio. It is very simple to use and provides great performance. That said...I had become tired of kludges for a good panadapter for it; though I had come to really appreciate a panadapter and decided for me, I want a radio that has that as part of its integral design, not an add-on. I also wanted something easy to use on my LAN so I can operate from the house. I tried the remoterig setup and though it worked. It was a pain to setup. With the 6700 it is automatic now with the DAX functionality. Everyone's needs or desires are different and what is best, or important to one may not be for another. So pointing out myriad other features is meaningless to someone whose main focus needs to be diversity rx....which the K3 does exceedingly well....probably better than any other ham rig as it has both receiver synthisizers tied to the same LO. 73 Greg
  • W5UN_Dave
    W5UN_Dave Member ✭✭
    edited November 2016
    Stu, I fully understand and appreciate all the great features of the 6700. However, I have both the 6700 and K3 side by side here. Every time there is weak DX on 160, I listen on my 6700 and try to pull the signal out. Failing to do so, I jump to my K3 with DIVERSITY and have no problem reading the signal. What I am saying is that the 6700 needs the same capability to let me quickly switch to DIVERSITY mode. Once this is possible, I believe the performance can equal or exceed that of the K3. My point is to motivate FRS to provide this capability. I look forward to the day when I will not have to "jump" back to my K3 in order to hear and work the DX. That day is not today!
  • Stu Phillips - K6TU
    Stu Phillips - K6TU Member ✭✭
    edited August 2016
    Though not to dispute the usefulness of what you describe for diversity, I think you have your logic wrong.

    My opening comment in the initial response to Dave...  the title of this post was poorly stated.  "Need diversity reception for 160m DXing" would have been better than the one chosen.

    I totally agree that different folks have different needs but a casual reader of this thread could get the wrong perspective and a balance was only fair.

    I totally get the need for diversity BTW.

    Stu K6TU
  • Steve-N5AC
    Steve-N5AC Community Manager admin
    edited February 2019
    The situation is this -- not only is the FLEX-6700 capable of what I would call "antenna diversity with human decoder" where you stick two receivers that are locked, one in each ear (a.k.a. poor man's diversity), the FLEX-6000 has the necessary hardware to support MRC/optimal combining.  Poor man's diversity is essentially a form of what is called selection diversity where two ears are used to actively select the best of the signal at any point in time. This is how classic voting receiver systems worked on repeaters as implemented by GE and Motorola in the day. With selective diversity, two signals with different SNRs are presented to a voting system (electrical or your ear) for the selection of best SNR at any point in time. 

    In contrast, MRC/optimal combining is different in that DSP is used to look at the correlated signals (the ones you want) and non-correlated signals (noise) and then subtract out the noise. This nominally provides a 3dB SNR improvement on the signal you give to your brain. This is really a big difference -- it can essentially lower the noise floor by 3dB at your location. Again, this can be 3dB better than the BEST of the two signals you get off the two antennas which is not possible with selection diversity.

    Additionally, we have a mechanism in the FLEX-6700 to take a single antenna and run it to two data converters.  This is also another form of diversity, but it aims to lower the noise floor of the data converters.  

    So the FLEX-6700 is built for diversity -- we just need to complete the software to make it happen.  The proof is obviously in the pudding, but we built the radio to have the best diversity you can get in a one or two antenna system.
  • W5UN_Dave
    W5UN_Dave Member ✭✭
    edited November 2016
    Stu, with all due respect, my original title stands. Let it happen, as Steve mentions below. Then we shall see which system wins with respect to diversity reception
  • W5UN_Dave
    W5UN_Dave Member ✭✭
    edited November 2016
    Steve, receiver voting scares me. Call me outdated, but I still like my brain to do the voting.
  • Steve-N5AC
    Steve-N5AC Community Manager admin
    edited December 2016
    No problem, Dave.  We aim to please.  If for no other reason that to give everyone the opportunity to compare, we'll enable selection diversity at the same time.
  • Barry N1EU
    Barry N1EU Member ✭✭
    edited December 2016
    My most common use case on the low bands for diversity is to similtaneously  listen to two Beverage antennas pointing in different directions when listening for callers or tuning for dx - no special combining/processing needed there.  I do like the idea of optimal combining on a single signal, but I would use that far less often.

  • Steve-N5AC
    Steve-N5AC Community Manager admin
    edited December 2016
    Extremely useful comment, Barry. Thanks.
  • Charles - K5UA
    Charles - K5UA Member ✭✭
    edited March 2015
    I personally would like to off-load as much of the brain stuff to the radio. At 67 my brain has enough to do without adding spatial diversity to the list. Turn the coders loose Steve, its what they were born to do.
  • Ilan Grosman
    Ilan Grosman Member
    edited April 2022
    It should be implemented as an internal function in the radio. It's just that it's cheaper not to develop this, and instead send the steams to the user. Add to that the the API does not allow you to build that; you need access to the code running the radio. If they built a plugin mechanism to add that it would be good and very low risk to modify the internal software so that it bricks the radio.

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