Diversity Reception for the 6700

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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?
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W5UN_Dave

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Posted 4 years ago

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Stu Phillips - K6TU, Elmer

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Though not to dispute the usefulness of what you describe for diversity, I think you have your logic wrong.

The title of this thread should be 6700 vs K3 - NO CONTEST...

Let me see...
The 6700 has...
  • 8 pan adaptors not requiring an add on product
  • Full screen pan adaptor(s) without requiring an expansion board with the add on product
  • 8 receivers - any where you like versus 2 if you add the second receiver
  • Digital audio support without a sound card or extra interface logic
  • 4 (count them... 1, 2, 3, 4) simultaneous IQ outputs versus.... ? None!
  • Receive audio that doesn't torture your ear drums in a contest
  • ... capabilities being added every release
You have it backward Dave - the 6700 is the hands down winner over the K3.

The K3 is a great radio to be sure and has its place in the world - but the state of the art is not static.

Folks here in the SF Bay Area are buying 6000 series radios and selling their K3s... you won't catch me doing the reverse.

There is a User Story in the system for synchronized slices and the guys will doubtless get to it when priorities merit.

In the meantime, I'm enjoying all the capabilities of the current 6700 and not missing a K3 in the slightest.

In closing, the 6000 series really is in a playing field on its own and its unfair to historic equipment to make a comparison.  I still fondly remember the Drake and Collins line equipment - great in their day, still great performers and fun to operate.  They are just NOT the tool for the jobs I need to do today in contesting or DXing today.

Stu K6TU



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Ernest - W4EG

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Stu,

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

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W5UN_Dave

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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!
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Greg

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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
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Stu Phillips - K6TU, Elmer

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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
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W5UN_Dave

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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
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Steve - N5AC, VP Engineering

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Official Response
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.
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W5UN_Dave

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Steve, receiver voting scares me. Call me outdated, but I still like my brain to do the voting.
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Steve - N5AC, VP Engineering

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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.
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Barry N1EU

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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.

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Steve - N5AC, VP Engineering

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Extremely useful comment, Barry. Thanks.
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Charles - K5UA

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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.

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