Diversity Reception for the 6700

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  • Idea
  • Updated 6 years ago
  • Under Consideration
  • (Edited)
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?
Photo of W5UN_Dave


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Posted 6 years ago

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Photo of Steve - N5AC

Steve - N5AC, VP Engineering / CTO

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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.