Other side band not properly suppressed

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  • (Edited)
My friends (F6500 owners) reported with not enough suppression of the other side band in SSB, i have not yet tested on my F6700, but in any way issue exist and need to be investigated, is anybody else can check it ?  at least 2 versions of the SSDR involved (has proved)  1.9.13 and 1.10.16
 Verification was done in FDX mode, RX not overloaded, unsufficient supression in low frequency bandwith. first screeshot with PROC OFF, second with PROC = NOR



Pink Noise  PEP   = -10dB
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Sergey, R5AU

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Posted 2 years ago

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David Livingston

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A low cut of 50 is unusually low. Most people use from 100 to 300. I use 200 and do not have this issue on my 6700. For dx and pile ups I use a low cut of 300 and a high cut of 2400. Put the energy where people can hear it.

I would also like to see what you get without your external audio equipment...!!!
(Edited)
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Sergey, R5AU

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Well David, no external equipment are involved in this test but only Rose Noise generator and Low Cut should not play here, example you running in DIGI and should also cut with 200Hz ? No way, this is not filtering superheterodyne but DDC and opposite side band must be well suppressed from >0Hz
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Bill -VA3WTB

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I know it is not a Flex problem, I have seen many Flex on the air and the sides of their signal drops perfectly down into the noise floor.
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Sergey, R5AU

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Bill, I keep my finger crossed with all perfect on Flex side , I'll be back tomorrow in my shack and able to look into my 6700, however still open question:
1. What are visible on screen shots above ?
2. Should we see or not artefacts with opposite side band on spectroscope ?
3. Can spectroscope be trustable for measure ?

My question to all - pls look into you radio on 2-3 min on such issue to report here.
May be that observation incorrect at all and correct statement completely different .
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Tim - W4TME, Customer Experience Manager

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Sergey,

We can’t duplicate this behavior here on a 6300.  The attached pics show both Pink Noise and Individual tones into the rig in Full Duplex mode with essentially the same bandwidth and setup as used by you.  We set the low freq cutoff at 50 Hz.

Observations: 

1.  With Pink Noise input, the opposite sideband suppression was nearly 80 dBm referenced to the peak in-band level

2.  With individual tones into the rig, the opposite sideband was in excess of 80 dBm referenced to the peak in-band level

3.  Your Pink Noise spectrum is suspect as is looks sinusoidal rather than a pseudo-random 1/f distribution.  With the Flex audio chain being essentially flat down to DC, and the 1/f characteristic of Pink Noise,  you may be inadvertently overdriving the radio with lots of low-frequency energy, thus the excessive opposite sideband energy.


Pink Noise:


Tone:

 
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Sergey, R5AU

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So Tim, jut reviewed original message from my friend , so you are right this is not a Pink Noise but a Human Voice with aaaaa- , nevertheless result clear enough. So on you screen could you make more wider (4-5 time)  passband of filter  and you can see artifacts in opposite side band
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Sergey, R5AU

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So , Tim, just reproduced it on my F6700 with playback tones into player with DAX TX output:

issue in zone below 300hz


1.  2 tones  50hz+150hz, good hearable on slice B




2. to compare (to check measure compatibility) IMD test with playback 1200Hz+1600HZ





Test in the initial post executed by George UA0IHZ 

last post with my radio  F6700, as you can see radio so far from overdriving here
but low freq tones are not suppressed 



SSDR 1.10.16
(Edited)
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Don Baughman

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Sergey-  I think you are confusing two different things here, and your screenshots demonstrate them.  The first is "opposite sideband rejection" and is primarily determined by the software algorithm used in the Flex.  It produces nearly perfect cancellation of the opposite sideband as demonstrated by Tim's response (80 db or greater).   The second is "transmit intermodulation distortion" and is a result of the mixing action of two tones introduced into the transmitter.  These tones are usually chosen to be non-harmonically related  (700 Hz and 1900 Hz for example)  and are a measure of the linearity of the transmitter's RF chain.  Your last screenshots are examples of this mixing (IMD) action. 

What is important in both of these areas (opposite sideband rejection and Transmit IMD) is that they are both referenced  (in -db) to their peak values in the desired region.  It's not clear what is going on in your original screenshots, but I suspect it is related to your test signal (Pink Noise) or input levels that are not accurately measured.  A good transmitter will show opposite sideband rejection of -60 db or greater.  Any Flex 6000 I have ever seen on the air or owned and tested have been significantly in excess of -60 db..

As far as the IMD results that your last screenshots demonstrate, an average Amateur transceiver will range from the mid -20 db to -35db range for the 3rd order products.  Higher-order products are even further reduced  to the -50 to -70 db range.  The Flex 6000s I have owned (6300 and 6700) have both been in the range or -40 db for the 3rd order products.

In summary, I can't say for certain, but I think your testing method is providing you with erroneous results.

73
Don K7MX
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Ken - NM9P, Elmer

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What I have noticed , Sergei, is that in your first pair of graphs, you have a low frequency bass spike somewhere between 50 and 100 Hz that is about 20 dB louder than the rest of your signal. My guess is that even though your meter is not reading in the "red" that the hyper bass boost is overdriving your audio circuits and causing some IMD that is showing up below your USB signal. I would suggest reducing your bass boost, perhaps even moving your low-cut up to 65-100, and retesting.

Whenever I see a SSB signal with that much of a low frequency spike, I can tell just by looking at the panadapter that he is going to be difficult to understand unless he is very strong, because the low bass note drones on like a bagpipe in my ears. Many times I am forced to shift my RX filter up to about 150 before he is intelligible at all.
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Sergey, R5AU

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Don and Ken,
i am appreciate you notes and opinions however results can be easily duplicated.
  In my last post above i mix 2 measures because i also not believed at beginning such pity results what send by my friend from far east, and second picture with IMD test just show that PAN of my F6700 suitable for measures and trustable - at least RF detector and SW in this part works well !

So i repeat test with 100 Hz and 1000 Hz tones  to understand suppression of this frequencies.
NO overdrive, NO additional HW or SW in use both test are very clean. You can repeat this test so easily and in case missing Generator SW you can make you tone or pairs here :  http://www.audiocheck.net/audiofrequencysignalgenerator_dual.php for playback with you windows audio player, so results looks like:

1. Transmitter power = 1 watt




2. Transimmer power 40watt (slider on 40 watt)



Here we can see more harmonics and subharmonics but result so repeatble


I will very happy if my measure not repeatable at all and so appreciate you notes with your measures.



P.S. To compare and measure purpose your can download WAV file with pairs of the my test tones 100hz +1000hz here:
https://www.dropbox.com/s/ilfkef12271j6pb/audiocheck.net_100Hz_-10dBFS_1000Hz_-10dBFS_10s.wav?dl=0
(Edited)
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Sergey, R5AU

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So, just received corrected update from George UA0IHZ with pink noise as screen shots:


1. Flex-6500 Low Cut 100Hz_Pink Noise PROC OFF



2.  Flex-6500 Low Cut 100Hz_Pink Noise PROC ON




3. Flex-6500 Pink Noise PROC OFF



4. Flex-6500 Pink Noise PROC ON






--------------------------------------------------------------------------------------------------------

IMHO :  in my experience since July 2013 issues with opposite side band suppression 
appeared/disappeared periodically
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K2CB Eric Dobrowansky

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I have been running 0-3000hz , and occasionally 0-4000Hz (low end of 80m rag new) bandwidth, for some time now. I would regularly get good reports from the Flex users, and even the Anan ESSB guys.

However, after the second to last upgrade, I also received reports that my low end was blowing out and causing opposite sideband issues. Similar to the above reports, if I raised the low end to 100Hz, things got better. But something changed in the last two updates...... in the past running down to 0Hz was not an issue.
(Edited)
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Bill W2PKY

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In the Radio Setup panel clicking Filters there is a setting for Voice; Has anyone tried different settings to see if the problem can be solved with a different setting?
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Sergey, R5AU

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Bill, all tests with Auto=Off and Filters=Sharp, I love my radio but like Erik mentioned above , I received not so pretty reports from other SDR owners .
BTW that can be a problem in DIGI with wide bandwidth and others negative impacts.
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DH1RK

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@All,
this phenomenon was visible for a longer time, too!
First remark from other SDR user was 19.12.2016 => so version 1.10.8
So, it not an issue of 1.10.16 only.

Attached some pictures...

Flex 6500 with 10.16.xx:


vs. ANAN-100D (different station,more bassy sound):


Best regards,
Ruediger
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Sergey, R5AU

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HI Ruediger !  you are completely right and really strange to listerning missing of issue by other hams. I do not wonna to talk concerning core of issue - i am not SW designer here but it should be investigated overwise it looks like classic superheterodyne with carrier on -10db on the low filter slop 
(Edited)
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DH1RK

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Hi Sergey,
I forgot to mention, the zero beat on the Anan was not from the Anan it was 3rd station carrier as you can see on the bottom part...
Okay, the 100Hz frequency parts in the other channel are for practical activities are not so highly important, they are down 25dB but for our competitor users visible.
I will only mention the missing pre-distortion feature.
For many hams I think it's the main topic not to buy a Flex!
Are there any news in the right direction?
Will follow the development.

Kind regards,
Ruediger, DH1RK
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Chris DL5NAM

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LOL

>> For many hams I think it's the main topic not to buy a Flex!<<
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Sergey, R5AU

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Chris   I wonna to make our radio better !
from here :  http://www.flexradio.com/downloads/flex-6000-family-datasheet-pdf/

(Edited)
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Chris DL5NAM

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Sergey, yes - making the Flex better is always great. There is always some space for that.
I am with you!

But not with KILLER phrase like Rüdiger. That's not helpful - it's for me attempt at blackmail.

Problem is now on table - FRS will give us a statement and if problem real - i trust in FRS that they bring a solution for us. (no, i am not a ELMER :-)

73 Chris
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Sergey, R5AU

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So , with other syntaxis  i also like to be focused on constructive  behaiviour.
Problem recognised and adressed and i hope will be solved by FRS in upcoming SW release, however issue not yet confirmed by FRS (  :-(  )
(Edited)
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K2CB Eric Dobrowansky

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Has Flex acknowledged this issue yet?
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Sergey, R5AU

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Not yet unfortunately
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Sergey, R5AU

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K2CB Eric Dobrowansky

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I'm surprised more users have not commented on this issue.

Tim, is Flex aware of this issue, or should one of us open a formal trouble report?
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Bill -VA3WTB

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The reason is because Flex has always had one of the cleanest TX anywhere. I have seen many 6000 Flex radios with amazing TX,,just like the Anan shown above.

If you are still having trouble, open a help ticket.
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Sergey, R5AU

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Bill, I am talking concerning very dedicated frequencies --> as you can see on pictures above all question regarding freq. below 300hz, in case you have cut off on you TX filter like 200 or 300 hz, reports will be more clean, however from my side question still open, example : why we have in SSDR EQ with 63 or 125 hz if that freq are not suppressed enough ?

In this thread above I placed links for WAV samples what can use by everyone to duplicate this issue.
Here in RU I got reports at least from 5 hams who are involved in ESSB or got reports from other SDR users based on PowerSDR SW.
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K2CB Eric Dobrowansky

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Huh?


One of the cleanest? Compared to what?


Other 12v PA radios? Maybe.


But like the ANAN with APD shown above?

I don't think so! Not even close.


Or compared to the 50v PA in the 7700/7800/7851 radios? Also not even close.


Anyway, back to the topic at hand - something has changed in the last release or two. This issue was corrected once before, early on in SSDR, but it has evidently resurfaced.


Tim - have there been any other additional reports of this issue recently?


Eric

K2CB
(Edited)
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Sergey, R5AU

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You are right Eric, that issue was before already and then solved
and
before enter the formal ticket I ask hams to repeat my test from above with report- 5 min effort.
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DH1RK

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Hello,
I think we are talking about the TX filter shaping factor / filter parameters.
It ́s digital and perhaps something with the calculation for the coefficients is not optimal...?

Ruediger, DH1RK
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Tim - W4TME, Customer Experience Manager

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No, we have not acknowledged this as a problem.  But I have entered an issue in our bug tracker (#4544) to investigate the reported behavior.
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K2CB Eric Dobrowansky

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Ok, thank you Tim.
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Sergey, R5AU

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Sounds good Tim, thank you !
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Ken - NM9P, Elmer

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My own testing results:

SET UP:

Testing was done using my 6500 in FDX mode.  Two pans, one slice in each pan.
Transmitting in Slice A  into the Transverter port on 75 Meters.  Receiving on Slice B with Antenna

Since this is a test of the SSB Generation and filtering, I didn't feel the need to test with any actual RF power output.

Using Audacity, I created four different test .wav files for this test.
(Audacity signal level of .35, because any higher wold overdrive my transmit audio)

1) Using the standard IMD testing tones of 700 & 1900 Hz.  
2) Using Sergey's tones of 100 & 1000 Hz.
3) 30 seconds of "Pink Noise."
4) 30 Seconds of "White Noise."

I was skeptical of the 100/1000 tones because they are harmonically related and might generate in-band distortion that might not give a good picture of what is really going on.  But I tried them anyway.

The tones were sent via the voice keyer feature in ACLog 5.8, which allows sending tones via the DAX TX Audio channel.  I tested using 4 or 5 of my standard Mic Profiles, including my ESSB 6K, Rag Chew 3K, DX 2.7K, and Contesting 2.3K.  I also turned PROC On & OFF, and rolled the low cut filter setting up and down from 0 to 350 Hz on all tests.

I set the DAX TX Audio level so that the tones would drive the rig one notch below the "red" audio level on the TX Panel.

I realized that the one test I didn't do was with the TX EQ completely FLAT.  (How did I forget THAT one?)  But I DID try all manner of LO CUT settings.

Test 1:
Using tone set #1.  (700 & 1900 Hz)
I detected NO undue IMD or opposite sidebands and could not produce any.

Test 2:
Using tone set #2 (100 & 1000 Hz)

If I took the TX filter Lo Cut all the way to 0 (Which I never use) I was able to get a pattern similar to what Sergey posted, although my 100 Hz opposite sideband was down 25 dB from the main sideband.

If I rolled the Lo Cut up in frequency, by the time I got to 250 Hz, there was no significant opposite sideband tone.

THIS SURPRISED ME a bit:  If it turned PROC OFF, then the rejection was a little worse.  With Lo Cut of 0, the rejection was perhaps 20 or 15 dB down.  (My experience with most rigs is that PROC actually makes things WORSE, not better.  It must be the PROC algorithm.)  

But even with PROC OFF, if I turned LO Cut up past 200-250 Hz, the opposite sideband disappeared.

At no time were there any opposite sideband products beyond about 250 Hz, 


Test 3 - Pink Noise.

With pink noise running, and the Lo Cut at 0 Hz, there was a little bit of opposite sideband mostly 30 dB down, declining rapidly as the audio frequency increased, and NONE of it extending beyond about 200-250 Hz.

As I moved the Lo Cut up, the opposite sideband quickly attenuated.  By the time I got to 250 Hz, there was none at all.

Test 4 - White noise.

Test results basically the same as with Pink noise.


SUMMARY AND CONJECTURE:

I do not think this is an IMD problem.  

So I don't think it would be remedied with Adaptive Pre-Distortion routines.  (To prevent that argument spilling over into this thread.  APD will have its own benefits when it arrives, but this is not that.) 

I think it is a filtering skirt issue.

It seems to be real, but I wouldn't classify it "serious" under most normal situations.

With my "normal" usage, with my PR-22 mic and my particular mic settings (My usual Rag Chew Mic Profile setting has a low cut of 65 Hz, and even my ESSB Mic Profile only goes down to 50 Hz) I do not see any significant opposite sideband problems.

BUT....

If the audio has a VERY strong bass presence, the Lo-Cut of the filter is not filtering it all out.

I suspect that when the TX filters were redesigned for lower TX latency and better turn around time, that the skirts were loosed up enough that they are letting a little through, especially if the user is using a "hyper-bass" profile.  

The worst case scenario was with the 100/1000 two-tones, with PROC OFF, and Lo-Cut at 0 Hz.
By increasing drive to the absolute limit, at the edge of the "red" I could generate an opposite sideband signal of the 100 Hz tone that was 15-25 dB down.  But It quickly improved with more normal settings of the Lo-Cut filter.  At 50-100 it was still there, but reducing to about 25 dB down.
Between 100-200, it moved to about 25-35 dB down.  at Lo-cut of 250 Hz, it was gone completely.

Note.....If one is using what I have called a "Hyper-Bass" profile strong enough to cause significant blast-through to the opposite sideband, I wonder how intelligible the signal would be, especially at lower signal levels (see my you tube tutorial on my Audio Profiles), but that is a different story.

It might be that on SSB/Digi we may want to have a latency or filter skirt option for transmit similar to the one on receive that lets us select between two modes:

1) "Standard" mode (the way it is now) with lower latency & quicker faster turn around time, and 
2) "Brick Wall" mode (The way it used to be)  with higher latency, but sharper filters for those who want them.

I will need to test these tones again with a completely FLAT audio profile to see if there are any changes from these initial observations.
 
Hope this helps...

Ken - NM9P
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Chris Tate - N6WM, Elmer

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Eric D.  Please dont turn this into a bashing of a particular group.  Its probably not the healthiest approach to suggest things are done because who got flex where.  There are multiple communities withing the community and the team does their best to balance those needs.  The team will come up with a solution but hopefully one that will work for everyone.
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Ken - NM9P, Elmer

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I think the idea of variable skirts (and consequentially higher latency), based upon proximity to the Zero-beat line is potentially a good solution.  As one who does almost EVERYTHING in the hobby with my 6500, I find that I seldom engage in "Rapid QSO" situations with my ESSB or Rag Chew profiles that have Lo-Cut set below 100 Hz.  So a little more latency wouldn't bother me at all.  A few more milliseconds is nothing in a long Rag-Chew.  My Main Rag-Chew profile is 65-3000 Hz

My various "High Performance/High Intelligibility" or weak signal Mic Profiles have the Lo-Cut anywhere from 115-300 Hz, depending upon the conditions.  My Main 2.3 KHz Contest profile is 300-2600 Hz.  My Main DX_2.7 Profile is 165-2900 Hz. 

I would not want to sacrifice turn around time in a contest or DXing situation using those profiles.  But chances are, with the testing I have done, they aren't a problem even with the current filtering.  

The "sticky wicket" here might be Digital.  I have already been setting my Lo-Cut to 25 or 50 Hz for WSJT-X and other modes that use a wide bandwidth.  On 160 Meters, I even roll the low end of my receiver filter up to about 150-175 to block the WSPR signals when I am using JT-65/9.  Finding a compromise between digital turn around time and proper filter sharpness is going to be a challenge.
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Chris Tate - N6WM, Elmer

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Yep seems like there are some options out there that will fit the bill for everyone.. the right solution will work for all.  Its great these guys identified this and made the data point available and from what I can see it looks like an equitable solution is on the table to re-mediate it.  Not sure about the digital stuff tho..

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K2CB Eric Dobrowansky

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Chris, I am not bashing anyone.

I'm not the only one who has valid concerns. To many, it appears Flex's main focus shifted from the development of SSDR to the Maestro, and from the Maestro on to the Power Genius XL. And let's be honest, the last few SSDR releases have been mostly long overdue fixes and tweaks, and no new earth shattering features, sans the USB cables. And there are still items that have not been addressed yet, like something as simple as the screen formatting issue where the five right most boxes don't display properly, and the right edge not going full screen. Yes, simple things, but things that should have been fixed long ago. So no, I'm not bashing, I'm just being honest.

The real question is, how did this issue slip thru the Alpha and Beta process? It's not the first time things like this have happened. It seems like two steps forward, one step back, on numerous occasions. Maybe Fkex should re-evaluate their testing teams and look to add some of the more technically astute users, such as the ones here who are discovering these sort of issues after the fact. When new features are added, have select testers who continue to test and ensure previous portions still function properly, in addition to those testing the new functions.
(Edited)
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Tim - W4TME, Customer Experience Manager

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Eric,

We appreciate your concerns.  And I can assure you that the solutions we provide to issues are balanced and accommodate all users and operating styles.
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DH1RK

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@Eric - KE5DTO
Can you give more details about the filter (type, order, data type, etc.).
Did you investigate different calculations for the filter coefficients (denominator base, calculation iteration with multiplication / division)?
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Eric - KE5DTO, Official Rep

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They are FIR filters of varying size (e.g. 256-2048 samples).  Lots of effort has gone into optimizing the performance of these filters both computationally and to balance the sharpness (skirts) with latency/delay.

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