Combining output of dual SCU for signal peaking and nulling

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  • Updated 2 years ago
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One way hams handle gain and noise issues (on the lower frequency bands in particular) is to phase antennas.  Frequently this involves a two or even more antennas some significant portion of a wavelength away from each other and use various switches and phasing lines to yield several different patterns.

It occurs to me that if the output of two SCUs were to be added together with each antenna connected to a different SCU, one could do all this phasing stuff in the digital domain.  That it should be pretty simple (always easy for a user to say) to provide an addition function with a controllable phase offset that could be adjusted between +/- 180 degrees.  Thus with the correct antenna setup one could effectively adjust intuitive for the best signal peaking or adjust for maximum nulling of a noise source/QRMing signal.

Unlike a phased antenna this wouldn't help on transmit, but it could be a very handy receive feature.

This thought isn't entirely my own and was inspired by a discussion about things that could be done with multiple sampled data streams.  Most of which seemed very complex, but this basic feature seems like something that may not be too difficult to implement for the models that have dual SCUs.

Thanks

Andrea, K2EZ

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Andrea

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Posted 2 years ago

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Photo of Ria - N2RJ

Ria - N2RJ, Elmer

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Welcome, Andrea! This is certainly a topic worthy of future consideration, I hope. I really enjoyed using the Flex-6700 in our rover operation for the 6m contest. 
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Al / NN4ZZ

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Hi Andrea,
Would the software phasing be the same or similar to diversity reception?  The basic diversity is currently available on the 6700 using both SCUs and 2 antennas.  It requires you to use headphones to mix the signals using your brain.  They said other diversity modes  (geo diversity, etc) might be available in the future.   I have tried it a few times on my 6700 but probably don't have the best antenna setup as it doesn't seem to do much.  My antennas are about 100 feet apart and one is a 3el quad, the other is a hexbeam.  

Here is a snapshot from the manual in case you haven't seen it.  

  

Regards, Al / NN4ZZ  
al (at) nn4zz (dot) com
SSDR / DAX / CAT/ 6700 -  V 1.10.16
Win10
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Andrea

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Not diversity reception Al.

Diversity reception as described there provides a means by which the brain can either focus on the one ear which receives the signal stronger or if signals are about equal hear them better over background noise which will not have the same sort of coherence.  While this can be effective, and in some circumstances, allow one to copy a signal that they couldn't copy in either receive port.

What I was describing is a true phasing system that could give up to 3dB of desired signal to noise.  Nulls on the other hand could be far deeper so the real power is ability to notch out the noise.

Essentially it is a very simplistic take on what is done for electronically steerable arrays.  What I described won't give a strong receive peak that one can simply point in an arbitrary direction or a single null.  A cardioid pattern could be set in two directions but mostly there would be a couple peaks and couple nulls.  The ability to twiddle the phase could be very powerful in some circumstances.


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Al / NN4ZZ

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I got the impression that the current diversity feature was just the start and that other more sophisticated implementations would be done eventually.  Anything to utilize the 2 SCUs and give us more options to pull out a weak DX signal would be nice to have.  
That future capability is the main reason I decided on the 6700.

Regards, Al / NN4ZZ  
al (at) nn4zz (dot) com
SSDR / DAX / CAT/ 6700 -  V 1.10.16
Win10

 
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Brad A. Steffler

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Same for my decision on the 6700, AL.

Brad
KE4XJ
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HCampbell WB4IVF

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RX antenna phasing or beam steering via the Flex has been previously discussed, including:

https://community.flexradio.com/flexradio/topics/frs-should-add-feature-to-flex6700-to-noise-nulling-ability-like-the-anan-radios-see-hpsdr-phase-noise-cancellation-nb

Some of us use the DX Engineering NCC-1/2 or MFJ 1026 boxes but yes, integrating the capability into the radio makes sense.

Howard

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Andrea

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Not quite the same thing, but what is needed to do that could probably do what I describe too.  I am not asking for something that can automatically just reduce noise but rather an addition function with a phase control and let operator decide how to use

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Don WB3FTQ

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if you want a good implementation of diversity buy a used Flex 5000 with 2nd receiver. the diversity algorithm in PowerSDR is VERY good. hopefully SmartSDR will someday catch up. 73
WB3FTQ