Latency 1.4.....Improvement?

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I just had a conversation with a "contesting" friend who said he avoids the Flex due to slow "turn-around" time particularly in SSB mode. It causes him to be one syllable behind the other radios in a contest thus loosing points. According to the QST review, the turnaround time is 138 ms for the 6300 and an even slower 140 ms for the 6700. Looking through reviews of other radios I see number like 38 etc. So I was wondering if ver 1.4 made any improvements in that area which we could pass along to others? I'm not a contester so I'm happy but apparently it is at least a perceived problem among contesters. 73  
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Steve N4LQ

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Posted 4 years ago

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Chris Tate - N6WM, Elmer

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This is an interesting thread.  I am going to run some comparative testing soon from the N6RO contest station where we will have my Flex 6500 and several other K3's and document it.  This may be a hard concept for some to swallow but this type of performance metric does make a difference in the minds of performance based radio ops, and perception is 9/10ths of the rule.  We need to try and have a solution in place when numbers like this appear.  Contesters are very performance conscious some times logically and some times not so much.  Contesting is skill.. and to maximize skill requires top performance.  think car racing as the mind set.   We are excited to start putting thousands of QSO's per year via the flex signature platform.. I have already started. providing filter sets and any latency reducing solutions(call it contest mode or whatever) will facilitate putting Signatures in contesting shacks. A lot of the platform is ready to rumble.. just a few details, and watch the Signatures start filling up 3830 reflector.  

Chris, N6WM

PS I Have dabbled in a contest or two...  :-)

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Burt Fisher

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Playing a video game is a skill. Counting blades of grass is a skill, not all skills contribute to the human condition. 
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KY6LA - Howard, Elmer

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@Burt

Playing Video Games makes for Skilled Drone Pilots

Counting Blades of Grass makes for skilled agricultural scientists...

Surprisingly Contesting also makes for very valuable EMCOMM Skills ...

I was a responder in the 2003 San Diego Fires and Net Control during the 2007 San Diego Fires.   The volume of EMCOMM traffic was huge because all normal and especially all Government Communications failed..  Hams picked up the slack and passed hundreds and hundreds of EMCOMM Traffic.

With the traffic volumes being so incredibly intense, it quickly became obvious that ARES was conspicuous by its absence because they were stuck manning hospitals and the CERT Ham responders just could not handle the volumes without creating life threatening errors..  Contesters and DX'ers checked in, quickly took control of the nets and soon smoothly handled the previously overwhelming traffic flows...

It was the hams that had practiced High Q rates under difficult conditions who saved the day....

BTW.. I have a write up of the 2007 San Diego Fires compiled from my station activity log that was published widely in the press if you ever want become aware of a real practical example where contesting training and experience proved invaluable....
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Burt Fisher

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If I accept all that as valid as it may be in your area, what percentage of contesters do you think do the above?
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KY6LA - Howard, Elmer

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All the major Contestors in San Diego county who hadn't been evacuated because of the fires pitched in to help. ....as the fires advanced mor nd more were evacuated. .. Several refused to be evacuated so that they could continue to pass traffic and direct rescue efforts in the area. All in all IIRC more than 300,000 were evacuated over a couple of days. ... In some cases minutes before firsts burned their homes.
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Burt Fisher

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Those deserved to be totally commended. That is what is amateur radio is supposed to be about.

That said, what percentage of contesters do you think do anything like the  above?

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Steve N4LQ

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Why does this bring to mind Foghorn Leghorn and Napoleon Dynamite?
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Steve N4LQ

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Note: The latency doubles between two Flex-6000 users. 
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Steve N4LQ

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Note: Latency doubles between two stations. 2 flex 6000 users experience 280 ms delay per exchange. A contest full of Flex rigs would slow the overall count for the entire contest. 
During Field Day 2014 there were 1, 268,916 QSOs. Someone do the math on how many fewer QSO there would be with an extra 200 ms delay per station.
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Barry N1EU

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You need to either call the other guy or call cq plus your exchange xmsn so you do 2 xmsns per contact.  Let's say an average contact is 15 seconds.  So you add .4 seconds (200msec x 2) to that so there's a 2.7% time penalty.

(I realize you were being facetious Steve ;-)  )
(Edited)
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Rich McCabe

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To me it doesn't matter. However I am not sure it has anything to do with math and less stations worked. Its all about getting the contact or not.  Losing 2/10 of a second for every connect is not going to add up to anything worth noting. Losing a contact because of delay is another thing.
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Dan -- KC4GO

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Unless you do what I did during the FRS net on  Sunday I monitored Dudley's stream and tried to reply to net control from my radio. I was way out of sync!!! Dudley's stream had a much better copy so i needed to be able to use his transmitter...
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Mike - N1MD

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I am a contester. Not a "big gun" but a steady,"little pistol" participant.
Frankly, I do not care about lab testing numbers.
What I am interested in are contest scores and finishes.
Those of us with FlexRadios who contest need to report scores and let the contest results determine the viability of the Flex 6000 as a tool for amateur radio contesters.

Scoring performance trumps theoretical argument.

Mike N1MD
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George - AB4FH

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For CW contesters, consider this. At only 30 wpm, which is not unusual in a contest, each code element takes 40 ms. The current latency of 140 ms is 3.5 code elements. My call goes from AB4FH to EB4FH if you truncate the first 3.5 elements including intracharacter element. Practically speaking, the other guy has already sent the first letter of his call while mine is making it to my antenna. This might explain why a 38 ms latency or one dit, is more acceptable.
(Edited)
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Steve - N5AC, VP Engineering / CTO

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The latency is reduced for CW, where the judgment was that it mattered more.  This is detailed in the manual.
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Paul Christensen, W9AC, Elmer

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Makes sense. I was wrongly thinking in terms of bandwidth and not shape factor.

Paul, W9AC
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George - AB4FH

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Thanks, Steve, I took the liberty of copying and pasting the table in a post below.  What do I need to do to the select the number of taps to achieve 43 ms on CW at <=400Hz?  This is a compromise I can live with in contest mode. Unless, of course,
you can pull some more magic out of the "lab experiment" that you all are conducting for SSDR V1.4.  :-)
(Edited)
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K6OZY, Elmer

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It certainly looks like a filter width of 401Hz would be a 43ms filter.
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George - AB4FH

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Good point.  I missed that.  Steve, N5AC, is that correct?  I'll use 401 Hz from now on.  Doesn't seem to work out for 100Hz to 250 Hz when things get really crowded.
(Edited)
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Stu Phillips - K6TU, Elmer

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Turn around time is an issue - perhaps less so in phone than in CW or RTTY but there is an issue.

The ARRL review of the K3 says its turn around time is measured as 25 mS.  The same figure for the 6700 is 184 mS.  In both cases this is transmit to receive turnaround.  Some other numbers from ARRL review...  FTDX5000 - 66 mS, TS-590 - 30 mS, IC7800 - 15 mS...

Flex 5000 - 29 mS - and this has brick wall filters too...

Like Chris N6WM, I am a serious contester and I have a reasonably competitive mid-sized station. Whenever possible in all modes, I run a frequency - I call CQ and try to maximize my rate.

The issue with turn around time in both CW and RTTY is that I miss part of the call that is sent back to my CQ.  In RTTY, its common that someone sends their callsign twice - if both print ok, I don't have to ask for a repeat to verify that I have the call correctly.  Yes, there are other opportunities to verify the call but that's not the point.

Its not the additional 149 mS that is the sole issue - its whether I have to get a fill or miss copy the call as the result of the delay.  If I have to do this frequently enough, its an issue.  Why?  Because in a contest where I will make > 1500 QSO's, even a couple of seconds per Q translates into meaningful operating time in the course of a 48 hour contest when your rate is 60-100 Q's per hour...

I am competitive with my 6700 - in fact, I continue to exceed my previous personal bests in each contest where I make a concerted effort.  Some of this is modest skill improvement (I keep thinking after each contest how to do better in the next one) but I credit the radio for its reception capabilities as well as the much lower fatigue level that results from it's operation.

How much of an issue does the additional turn around time represent?  Hard to quantify but in RTTY I can SEE the issue - it audible in CW and Phone.

Chris rightly points out that contesters are heavily spec driven - it sure would be nice to see the turn around time addressed if for nothing other than the comfort level for the serious contester.  Even that said, I believe that getting into the 50mS range would significantly reduce the possibility of having to ask for a fill or repeat.

Stu K6TU
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Bill -VA3WTB

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What I know is Howard is one of the best contesters around and has won many. If he says latency is not an issue for him then that seals it for me. And Ken says the same. I'm sure if it were a problem they would have said so.......
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Stu Phillips - K6TU, Elmer

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Howard and Ken are serious contesters to be sure and perhaps its not an issue for them - they can add their own comments and also quantify their rates/QSO totals as part of the response if they wish.

I'm glad it seals the issue for you.

Alas, my personal experience doesn't for me.
Respectfully,
Stu K6TU
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George - AB4FH

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Ditto. Respectfully, George
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Barry N1EU

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Ditto, my experience says otherwise.

Barry N1EU
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Chris Tate - N6WM, Elmer

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Stu I agree 100%.  This is an issue that is going on my list as a problem requiring Optimization to reach the top bar.  Our racecars(signature rigs) need to be tuned for maximum performance. Think of the boost in QSO count Howard and Ken would get with the turnaround latency resolved! 5,10, 50?  This could be a winning difference. I want my flex to be my primary contest rig.  We have to have that level of optimization for mass adoption of the platform by the contest community.  They are a fickle group that obsess over numbers like cw rise times, easily selected optimized filters and, yes turn around times.

  My suggestion for Flex Radio would be to take some of the weaknesses being brought out by the testing lab and get them turned around Quickly.  The vendor of the current #1 preferred contest platform does this quite effectively.

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Ken - NM9P, Elmer

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Bill, Stu and others...
While I am flattered to be mentioned in the same sentence with contesting greats like Howard and Stu, I am not in the same league.  (Though, thanks to the 6500 I am getting better!)

However...here are some expanded thoughts after additional thought and feedback from others...

As a Phone & CW S&P-er..., the slightly higher latency hasn't hampered my rate nearly as much as the improved TX quality and superior RX sensitivity, selectivity, RX IMD/Blocking figures, reduced operator fatigue, and other improvements have added to my contesting experience.

Adjusting my timing and operating habits has eliminated any defect upon the beginning of my transmission.

I have had to make adjustments, however upon the end of my transmissions.  
In the beginning, I found that I was getting off the footswitch just a hair too early and cutting off the last half of the last letter in my call...."November Mike Nine Pa...."  instead of "papa."  This caused me to miss a few stations or required repeats until I learned to be a little faster on the press of the footswitch and a little slower on the release.  VOX operations wouldn't matter once you got the delay set correctly.

However... As Stu has mentioned, I can see how a longer latency-induced turnaround time could be a hindrance when running a frequency on RTTY or other Digital modes...perhaps even CW, though my CQ skills fer running a frequency rather than S&P would be the severe limiting factor at my station!

Long ago, when AMTOR was gaining popularity, they were trying to shave turn around times down to <25 ms, if I remember correctly.  Some were even trying for <15 ms?

I am a big fan of the brickwall filters...I almost always use 50 Hz when DXing or Contest S&P to give me the best chance of hearing a station.  When running split, I run the "much wider" 250 Hz filter on the "mob" frequency so I can get a better picture of what is around the station being worked and give me a better chance of finding a hole or hearing the next station up or down.   (I can't believe I am calling 250 Hz a "wider" filter!  It used to be the standard for "narrow.")

However, I can see that there might be some occasions where I might be willing to sacrifice a little bit of sharpness in order to gain some improvement in turn-around.  That might mean running 50 Hz reduced slope instead of 100 Hz, which would still be great compared to most other rigs.  IF... and it is a big IF... This could be selected and turned off at will.
I would not be willing to sacrifice my ultimate filter performance on CW & SSB permanently. 

Perhaps it could be implemented in DIGI only?  Or defined per-mode at the user's discretion?

This would be an interesting for the FRS staff to have as they work on V.1.5...
I don't know how much time could be shaved off of other procedures and timing loops, but it seems reasonable that while fine-tuning all the other functions they might do a complete sweep (again) of the timing elements and other things that contribute to latency and turn-around time.  (I am sure that they have swept this many times in the past already.)


Anyway... my $.02

Ken - NM9P
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Chris Tate - N6WM, Elmer

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"This would be an interesting for the FRS staff to have as they work on V.1.5...
I don't know how much time could be shaved off of other procedures and timing loops, but it seems reasonable that while fine-tuning all the other functions they might do a complete sweep (again) of the timing elements and other things that contribute to latency and turn-around time.  (I am sure that they have swept this many times in the past already.)"

Spot on.   I dont agree that some trade off is the best approach.   I would also add some specific ease of use filters, for example  a RTTY specific filter that would not require the invocation of the XIT/RIT, to be on qrg etc.  Click and run.  no time to mess or worry with stuff when logging at 300 qph.

~C./N6WM
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Paul Christensen, W9AC, Elmer

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Probably a good thing I'm not a contester!  My first and last was the 1972 Novice Roundup.  Hated it.   

Something is not adding up though... 

One year ago, I measured T=>R turn-around time in CW.  I measured approximately 50 ms in QSK mode.  I measured from the time of the actual CW key "key-up" (green trace) to the point of receive audio.  Not sure what that measures today with v1.4, but it needs measuring in multiple modes and multiple bandwidth settings and that takes a lot of  time.

https://community.flexradio.com/flexradio/topics/flex_6700_cw_keying_v_elecraft_k3

Scroll down to the section where I discuss the 50ms delay -- and N5AC responds.  Steve explains the delay in detail and discusses delay factors. 

As I recall, during my test, Rx bandwidth in CW mode was set to 2.8 kHz, my normal "ragchew" bandwidth setting.  That setting is close to a normal SSB receive bandwidth.  In CW at 30 WPM, the duration of one "dit" is approximately 40ms.  [T(ms)=1200/wpm] 

So, what we're talking about here is an audio delay of just over one dit at 30 WPM.  I'm not going to argue whether or not that affects a contester's  CW run rate, but I can say that the issue has never been noticed by me when trying to precisely time split DX contacts where "getting in" at the right moment is just as important.  I'm surprised the ARRL measured T=>R time of 184ms and R=>T time of 138ms, assuming a normal SSB receive bandwidth.  Why is SSB taking longer to turn around than CW?  I'm not disputing the ARRL's measurement, but I would like to know the exact test condition since my measurements in CW didn't show that kind of delay.  

This is an instance where the expanded QST Product Reviews would be a big help.  Not sure why that was discontinued, but as SDR dominates our shacks, the T/R and R/T turn-around times should be measured under varying conditions of mode, Rx bandwidth and other factors, including rigs that allow one to adjust filter tap settings where firmware/software must compensate for those changes. 

Paul, W9AC


 




  

(Edited)
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Stu Phillips - K6TU, Elmer

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Paul,

Excellent comments as always!  I had forgotten the thread you referenced and the 50 mS number!

Something about Lies, Lies and damned statistics comes to mind!

There is truth in numeric data but only when you understand the test conditions!

ARRL Labs document their test procedures - here's the link:

http://www.arrl.org/files/file/Technology/Procedure%20Manual%202011%20with%20page%20breaks.pdf

Page 27 provides the turnaround test measurement configuration - could you take a look and see how this compares to your test set up?  There is a very detailed description of this test even with scope pictures...

I know qualitatively that on RTTY I typically miss (not mis-print, miss as in NOT present) between 2 to three characters of a callsign on the first print.  If I have the math right...  at 45.45 bps, 5 data bits, 1 start bit and perhaps 1.5 stop bits - would translate to approximately 165 mS per character...  i'm assuming that the decoder itself has some "training" time as well.

Really curious now as to the correlation between the real world and the lab test numbers...

Stu K6TU
(Edited)
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Paul Christensen, W9AC, Elmer

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As a physics professor of mine once declared:  "One measurement is worth 10,000 words."

I'll have a look at the ARRL test procedures.

Paul, W9AC

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George - AB4FH

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As a former physics professor, I agree.  "First there is the measurement" Blaise Pascal circa 1640.  BTW, during my working career I often was in the hometown of Blaise Pascal, Clermont-Ferrand.  There is a school and a museum named after him.

Paul, I don't know if you ever talked to Katashi Nose, KH6IJ, but he was a physics teacher as well as a world renowned contester.  Amazing op who could easily copy 75 wpm in his head...very likeable, too.
(Edited)
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Steve N4LQ

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Mainly what I can't understand is why the huge difference between the Flex5k and 6k latency. 
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K6OZY, Elmer

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I would like to  know this too since they both have "brick wall" filters.
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Paul Christensen, W9AC, Elmer

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I just looked at the ARRL's Tx to Rx Turn-Around test procedure (Sec. 4.9) but note that: (1) Fig. 4-9 needs correction to show TRANSCEIVER and not TRANSMITTER.  At first, I could not understand why they wanted to sample audio from the transmitter to determine Rx recovery time; and (2) Fig. 4-9A needs a lot of clarification.  What is the upper trace?  Why is the trace delayed? Where exactly does key-up occur on the display?   I see two envelopes.  Is one RF and the other audio?   If so, which?   Those two figures need cleaning up to make any sense.

Paul, W9AC 

(Edited)
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Chris Tate - N6WM, Elmer

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Might be worth emailing the test lab.
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Stu Phillips - K6TU, Elmer

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Indeed!  I've not had much interaction with them but the little I've had, they are very responsive.  I think Ed W1RFI is the lab supervisor.

Paul - would you be willing to give Ed a call or an email since you have the context and comparable testing?

Stu K6TU
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Paul Christensen, W9AC, Elmer

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We should also keep in mind that latency is not the same as turn-around time.

Paul, W9AC
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George - AB4FH

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Paul,
In plain talk, I would like to know:
a.  Time from when my RF transmitted stops until the received audio starts - this would be pertinent for contesters while Running Q's
b.  Time from when I press the function key for the CWX macro that feeds N1MM+ until the RF starts  - this is more complicated I understand but would be pertinent for contesters while S&P'ing Q's

Others, please change the wording if you have a better way of expressing what you want.

Thanks in advance for chasing this down and performing the measurements.
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Ken - NM9P, Elmer

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Indeed, option 'b.' is more complicated, because it depends upon more things...If I have the focus on the Flex and hit 'F4' to send my call it is faster than when I hit the AUX1 button on my Flex Control Knob, which has more delay before sending.  And when I use a button on the Hercules DJControl LE MIDI controller that I am programming (with Help from William) it seems to be somewhere in between, or closer to the command directly to the Flex.  When running N1MM+  it seems to be a little bit different, but pretty fast.

If I remember Paul's previous tests correctly, the key-up-to-receive-audio time was pretty good on CW.  It has to be, if they could run 100 WPM QSK with separate antennas.

Ken - NM9P
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George - AB4FH

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Steve, N5AC reminded me that there is a table of latency as a function of mode and bandwidth in the SSDR 1.4 Software Users Guide.  Here is a clip of the table:
This doesn't explain why ARRL measured 138 ms for SSB, though. In contest mode I could live with 43 ms with VG filtering and Med latency <=400 Hz.
(Edited)
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km9r.mike

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I do not have a great appreciation for the work that would be required to achieve the 43ms @ <=400 Hz target but I would appreciate this as well especially in the cw mode. At the same time, I am learning that many good cw testing ops better than I will open up the filter ( 500-1000Hz) while running to better catch all callers. However, many times crowded band conditions do not allow such wide filters so the 43ms @ <=400 Hz seems to be a good target and far better than 85ms.
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Chris Tate - N6WM, Elmer

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good point.
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KY6LA - Howard, Elmer

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Frankly as a Sometimes Very Serious Contester.. the one major drawback for S&P is the lack of integrated spots into the Flex Display..

Clearly not an issue when running a frequency but a definite limitation on S&P... 

Yes.. I know Writelog has a pretty good bandmap but it is static and does not correlate to the actual received signals on the Flex Display so one does not know if one should waste time listening on the spotted frequency or not..

If working S&P in contests we run NaP3 on a (Heaven Forbid) K3... the integrated spots into the Real Time display make a huge difference to rate as you can see immediately if the spot is actually there to work....
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Ken - NM9P, Elmer

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Howard,  I know your CW Key is tied to a brick at the bottom of Davy Jones' Locker....(;p) but...

On my last CW contests, CQ160CW and ARRLDXCW, I used N1MM+ and CW Skimmwe, which gave a wonderful band map of all the stations I could copy, and I could use the QSY technique that others have mentioned with the CTRL <&> buttons.  What a difference it made!  I wasn't limited only to the stations that were spotted by others, but I was able to have on my display and QSY controls the stations that my own receiver was actually hearing.  Next time I will open multiple skimmers on different bands and let them give me a head start for Band changes and multiplier hunting.  I haven't perfected this yet.  I figure that if I add one new tool to the contesting arsenal  each contest or two, then I will be making good progress.

To bad there isn't a Skimmer for voice modes yet!

Stu, et. al. Have you tested RTTY skimmer under the duress of contest situations yet?  
I need to know if it is worth the money....CQ Skimmer sure has been.

Ken - NM9P
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Stu Phillips - K6TU, Elmer

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Ken - haven't tried RTTY skimmer yet...
Stu K6TU
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George - AB4FH

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Howard, while I don't put in the butt-in-chair time to win contests because, frankly, I'm only interested in the exhilaration and intensity for a few hours, using N1MM+, CW Skimmer, SO2V  in S&P mode, I have achieved rates over 100 Q's per hour (peaked 70 Q's for 30 minutes once).  With N1MM+ 's keyboard shortcuts, I rarely look at the band map.  I just tap cntrl + up or down key to jump to the next unworked station.  The logger keeps track of everything else.  If the rig is a little off the station's frequency, I only have to tap control + "<" or ">" to move a user defined step.  Another reason to not use the visual band map is that it gets so crowded.  While you could use the mouse and "point & click", we both know that we need to keep our hands on the keyboard at all times for speed.

BTW, my hat's off to you for your achievements in winning contests.  [Back in the 1970's I was more serious and won SC section on occasions, if people remember WB4PDQ].
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Charles - K5UA

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One of the posts in this conversation implied a truncation of the first 3.5 elements of his call in CW at 30 wpm if the latency is 140 msec.

My question is this.... are any elements being being truncated?  That would seem to make QSK impossible, and we know that the 6000 series can do QSK at very high speeds.  Or are these elements simply being delayed?  If they are just delayed, that brings up a different question....

 Does the station with the quickest reply (let's say140 msec quicker) receive the prize of a return call from the DX station being pounced upon?  No, I would hazard a guess to say hardly ever in a pileup. So who does get the contact the vast majority of the time?  I'd say the station that is 3 dB (or more) above the pileup.  So unless YOU are that +3dB station above the pileup, you are not not affected by that 140 msec delay. Ever see what happens when the BIG DOG gets to the plate of food 140 msec behind the little dogs?

 In fact... in a pileup.... all stations being equal in strength, it is often the station that tail-ends after the horde makes their unintelligible racket for a second or two that gets the return call.  I have heard this consistently in pileups and contests for the past 56 years. So if you are not the BIG DOG, being 50 msec ahead of the horde is not going to make a difference.

 Since this 140 msec is so significant, shouldn't we also be talking about not eating or not taking bathroom breaks or not sleeping during contests :)

 I am not saying that reducing the turn around time has no merit, I just think justifying it based upon contest scores is really a stretch.  One would think the QSK ops would be the ones raising the issue of latency.

The trade-off between latency and filter shape factor that is now in SmartSDR has given the 6000 series the best filters in amateur radio.  All who want to give that up, keep complaining about latency.... but be careful, you may get what you ask for.  And you won't like it.

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Steve - N5AC, VP Engineering / CTO

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The paddle-down to RF out on the FLEX-6000 is a world-class ~8ms.  So this is not an issue.  It is on the receive side where there is filtering that you have the latency. The latency in CW is also less on receive because we adjust the filter based on the bandwidth of the passband to have a good shape factor, but not "overdo" the filter. 
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Stu Phillips - K6TU, Elmer

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I'm still not sure we are all talking about the same thing here...

Latency simply imparts a delay - what I hear happened some time back and as long as the time is small (100 mS is fine) its not an issue.

Turn around time is something else.  

Turn around time is the window of time from when the transmit PTT is raised and I can copy USABLE audio from the receiver.  I believe that is what the ARRL test measures.

The key question is from the point where PTT is raised, what is the DEAD TIME where nothing is copied by the receiver that can be used as usable audio?

If that dead time causes me to have to ask for a fill or a repeat, its not the size of the DEAD TIME that is the issue, its the time it takes for a repeat - that is seconds, not milliseconds.

Yes, I count seconds per QSO because over a full weekend it translates into a significant number of ADDITIONAL QSO's if I can save it.

As an example, I work really hard to only use phonetics when I have to and not endlessly repeat my callsign as KILO SIX TANGO UNIFORM but as K6TU - believe me, it all adds up.  

In the 2014 Cal QSO Party which is 24 operating hours out of a 30 hour contest, I made 1555 QSOs...  if I can avoid a second per Q, that's another 25-35 contacts I can make...

For me, this is significant.
Stu K6TU

PS: so what is the DEAD TIME in milliseconds?  Is it the 184mS ARRL claims?
Second question - why is PowerSDR so much better on the same measurement?
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Stu Phillips - K6TU, Elmer

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And as a follow-up...

Some web searching shows an average speaking rate of around 150 wpm and that's about 240 syllables  per minute or 4 per second.

So if the DEAD TIME is approaching 200 mS... that says I can miss a syllable like in Ki-Lo all I get to hear is the Lo...  Say the guy coming back to the CQ jumps the gun ever so slightly...  all I may here is "o"or perhaps just SIX TANGO UNIFORM.

My response?  TANGO UNIFORM again?  

GOLF is one sylllable so GOLF FIVE MIKE becomes FIVE MIKE...

My response?  FIVE MIKE AGAIN?

THIS is why this matters.

Those of you who have never run at high rate or had to deal with New York Air Traffic Controllers (who speak WAAAAYYYY faster than 150 wpm) are free to doubt.

Having done both...  I would still like the answer to what is the DEAD TIME before finding another morbid equine to flagellate.

Steve N5AC?  Any views???

Stu K6TU
(Edited)
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Steve N4LQ

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en four 
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km9r.mike

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New York Approach has nothing on Chicago nor Delhi but I will agree they are quick. After being invited to op at a station far better equipped than I can hope to achieve, I have gotten a great appreciation of just how tight final scores can be and 25-35 Q's / mults can make a whole world of difference in the world of big guns and others as well. And while it is not the sole strategy, running q's is definitely the biggest factor at such stations.

 I love the quoted 8ms time for pouncing but the potentially long turn around time while running is not good and that is if all goes well. If the running op has to repeatedly ask for a fill due to missing the first letter/number of a prefixe, well as the New Yorkers say fugeddaboutit.

From my own station, I have limited myself to qrp testing which limits me to mainly S&P. I have seen zero issues wrt latency time since 8ms is sierra hotel. 5w on the other hand is the bigger issue for me and a dipole at 35ft. : (

(Edited)
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KY6LA - Howard, Elmer

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I think we are confusing SSB vs CW vs RTTY Contesting...

140ms latency is not really a significant issue in SSB Contesting as the human brain can usually integrate the odd time you miss a 1/2 syllable.  Realistically most contesters are not EXPERTS so few S&P operators will jump onto your call within that 140ms latency delay....

I have actually (without knowing that it had less latency) run a few contests via DIGU and DAX.. did seem a tad quicker but not enough that I really felt a difference... I have used DIGU and DAX for Remote - where i did notice a quicker turn around.. but the Internet Latency was the real issue so every bit helped...

I can't comment on CW Contesting.  No experience whatsoever

On RTTY Contesting... I can see where latency could be a major issue.. but then I have never come in the top 10 in an RTTY contest.. so until I build my RTTY Skill levels to contest grade, I doubt that the latency will have that much effect on my scores..


Contesting Comments

This weekend is my favorite contest WPX SSB...  I am usually the only KY6 in the contest so I am a desirable multiplier which means that I can hold a frequency for the entire 48 hour contest and everyone comes to me.  easy to do 100-200 Q/hr for a while anyways....   IIRC I have done over 2K Q's a couple of times   Enough to dominate my area but Not as good as some of the Europeans who rack up 4-5K Q's 

HOWEVER..XYL is NOT traveling this weekend .. so butt in the chair time will likely be severely limited...  Likely only a very few hours of rates 100-200 Q/hr followed by intense silence...

My other favorite contests from my QTH are Asia Pacific and JIDX SSB Contests because my SteppIR MonstIR @85' @600' ASL 1KM from Pacific gives me about 30 minute longer openings at each end than anyone else in NA... Really helps to have a big station...as those contests seem to be like shooting fish in a barrel.. I tend to own the Pacific in contests.. I only wish I could same for Europe where the 1000' mountain in my backyard kills propagation....

BTW... love working the Japanese in contests.. they are so disciplined that I can get the rate up to almost 300 Q/hr by sitting on a frequency... I really wish some of the Europeans would take contest discipline lessons from the Japanese as everyone's rates would be better..

When we work ARRL Contests... I usually head up to the NX6T contest station which has the big gun to the East (I have a 1000' mountain in my backyard to the East)...  NX6T wins lots of contests every year..   Mainly with K3's albeit we have many different transceivers (K3, 6700, KX3, FT 5000, 7800 to name a few)....  

As i said the big difference maker for S&P is to use the NaP3 App to integrate Spots into the real time display on the K3.

By my estimates that can almost double S&P rates from 60Q/hr to over 100Q/Hr...

Why ......because you don't have to waste time trying to listen for spots you cannot see on the display as being workable...  the lack of integrated spots is the one major shortcoming of the 6700 for S&P Contesting...

Finally .. they run a Contest University, every year at the Visalia International DX Convention and at Dayton.. the crowd is much more sophisticated at Visalia...
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W7NGA

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I don't have much of a dog in this hunt as I believe contesting to be the bane of amateur radio .. but I digress. no dog, but I do have a research-grade electronics lab and took the time to make a few measurements.

latency AM   - 135.5ms
latency SSB - 146.5ms

remember too, that the sending station also has latency and switchover times that may help ameliorate the timing dependencies. geez .. I just want to call CQ and get an answer. any answer .. even if I have to wait an interminable 150ms!

I do have my Flex 6300 outputting a bodacious AM signal that I am very pleased with.

dan  W7NGA
San Juan Island, Wa.

(Edited)
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George - AB4FH

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Thanks for the measurements, Dan.  BTW, do you know Randall Benson?  He lives on San Juan Island, too.  He is one of the principals in BioCast Technologies, LLC.  I am also a principal.
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Marc-Andre

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Just my 2 cents but, on my desk, i have a FT-991, a FTDX-3000 and a Flex 6500. Tune all the 3 on the same RX frequency and the flex is receiving ANY station much faster then the 2 other, in fact, the FT-991 and FTDX 3000 sound like echo because the flex receive and send the operating station to my speakers ( ears ) few milisecond faster then the 2 other and to me, by MUCH MORE then a full syllabe then the 2 yaesu..... Beside the fact that the flex can hear poor signal that the 2 yaesu are even not aware of,  to me, if you RECEIVE faster you transmitt faster.... MUCH faster...



(Edited)
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W7NGA

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Marc-André, your observations don't match what would be expected from the architectures of the radios you mentioned. Perhaps you can perform additional testing and forward your results.
(Edited)
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Bill Roberts

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Speaking of Latency, I was just reminded of (stumbled into) a few simple performance enhancement tricks.  Best of all, they're free:

LatencyMon - Just for kicks, I installed this free software from Resplendence Software on my Flex PC.  In the PSDR days, I ran it on my shared I7 Windows 7/64 PC.  Now using a dedicated I7/Win 8 machine along with SSDR 1.4, I didn't think latency was much of an issue.  My machine did OK when receiving but going into transmit, LatencyMon said it was unsuitable for drop-out free audio.  Wow!

First, it suggested turning off "power saver" so my CPU would run at 100%, all the time.  (Control Panel, Power Management, etc.).  That kept everything green no matter what I did.  Who would have expected Dell to throttle back one of their faster machines, right from the factory.  Tree huggers!

LatencyMon also suggested checking the BIOS.  Pretty elementary but oh well.  Doing a BIOS refresh further reduced latency while using SSDR 1.4.

Surprisingly, it didn't complain about video drivers.  They were up to date.  Still, making sure your video drivers are current can also help reduce latency.

For whatever it's worth...

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Tim - W4TME, Customer Experience Manager

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Wayne, W5XD

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I would like to know whether this discussion about latency in the Flex audio--both for TX and for RX--is considered settled. I am trying to configure WriteLog for SSB operation and am unable to get latency for transmitted audio, especially, down to an acceptable delay, so far. I am also unsatisfied with the RX side. My interpretation of my measurements, so far, is that the latency is not inside WriteLog, but is inside the Flex itself, and even more is contributed by the DAX devices.

I am aware I am discussing a different, but related, spec than the "TX-to-RX" latency in this thread (or maybe they really are the same spec but using a different way to set the origin of the time measurement?) By latency on TX I mean the delay between the mic audio and the RF power in my dummy load (where I test), and, on RX, my standard of comparison is the delay between audio from two receivers, one being my 6500 and the other being any not-so-smart receiver, tuned to the same signal. An acceptable number, in my opinion for contesting, is something well below 100msec, and it has to be down below 50msec or so to be imperceptible. I see there is debate on this thread about whether 150msec Tx-to-Rx delay is acceptable for contesting. I personally am in the "50 msec is barely acceptable" camp. I am not sure how to convince a "150msec is OK" advocate, except maybe to suggest you engage in a rapid-fire VOX SSB conversation with another Flex user. The delays from the mic in one shack to the earphones on the other add: the TX antenna signal is roughly 150msec behind the mic, and the RX antenna to receiver headphone delay is another 150msec. (Speed of light between stations even at earth antipodes adds maybe 70msec antenna-to-antenna.) This is not Tx-to-Rx switching time, this is just a static measurement of how long it takes for a vibration in the transmitter's mic to be repeated in the receiver's headphones when a Flex is at both ends of the conversation. Anyone old enough to remember telephone calls through geosynchronous satellites will recognize this 300msec end-to-end delay, and I can testify its not easy to hold a conversation through it. You learn to say "over," ending every transmission. SSB contesters probably aren't going back to that anytime soon.

There is one posting on this thread that DAX might reduce the latency. My measurements indicate quite the opposite. DAX adds delay for either RX or TX compared to what the 6500 does with signals at its rear panel ACC connector. That is, I have a cable from my 6500's ACC connector with audio line in and line out to both line in&out of a physical sound board. If I configure WriteLog to use the TX and RX on the physical sound board, I get delays on both the TX path and the RX path I estimate in the 150msec range. If I switch to a DAX channel to repeat either the TX or RX delay measurement, add another 200msec (wow!) to make 350msec. Do this in the on-the-air experiment I mention above and its 700msec end-to-end. I am pretty certain I won't be able to sell that configuration to serious SSB contesters, nor do I think we want to cable a sound card to reduce the latency in our shiny new SDRs, so am looking for what can be done.

Wayne
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Stu Phillips - K6TU, Elmer

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Wayne,

I don't see the same additional delay you mention when using DAX either with Writelog or with N1MM+.  To be fair, I haven't measured it but from the point I push the function key when using either logging program, the RF starts out will minimal perceived delay.

Have you tried rebooting your PC?  I do see issues with DAX from time to time that seem to due to some buffer management issues in PortAudio.  A reboot or even forcing the deselection of the DAX device and re-selection generally removes  the issues.

I will say that as a serious contester, I haven't seen my SSB rate impacted other than positively by using the Flex 6700.  This past year I put in a personal best in SS Phone that was substantially higher than any of my prior efforts.

I'm not pushing back on the issue or TX-RX turn around time - quite the contrary - it is too long.

Stu K6TU
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km9r.mike

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As I posted above, I like the target of 43ms <=400 Hz that George AB4FH proposed but due to the architecture of the 6k I do not have a full appreciation if this is even possible. I saw where it was for the 5k but understand kinda that the 5k was a whole different animal.
(Edited)
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Tim - W4TME, Customer Experience Manager

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We can give you fast filters, but the shape factor will be high.  You can't have sharp filters with low latency.  This is the first rule of DSP thermodynamics.
(Edited)
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k0eoo

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Please NO NOT change the filters ...  FRS will be playing into our competitors hands if we reduce our GREAT filters.  We have contesters in the fold who have NEVER made this an issue so lets not spoil the porridge... This is one mans opinion, YMMV.
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George - AB4FH

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Thanks, Tim.  I would like to repeat my request for a "Fast Turnaround" option of
43 milliseconds at <=400 Hz.  I understand this will give Very Good filtering (less steep skirts) instead of Excellent.  What would be even better is a selectable "Taps"
setting for each filter width that allows us to choose the compromise of skirt vs. latency.
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Tim - W4TME, Customer Experience Manager

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I seriously doubt we will degrade the shape factor of the filters to reduce latency.  The filters rock like they are now.  If we can achieve lower latency without changing the shape factor, that would be considered.
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Stu Phillips - K6TU, Elmer

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PowerSDR had significantly lower tx to rx transition time and great filters so we know it can be done.

For folks to say that contesters have never raised this issue is simply incorrect - I raised the issue a long time ago.

Lower latency is a key requirement for me as a contester.  So are excellent filters...

I don't want one or the other - I want both.  There are likely trade offs in functionality or capacity that result but that would be a fine alternative for me.

Stu K6TU
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George - AB4FH

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As a clarifying note, this compromise would still give the user the same skirt at <=400 Hz as they currently have at <=1 kHz per the user's guide clip above.  
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Bill -VA3WTB

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Leave it alone Tim. as you said we can't have both. If you trade off soon others will complain about the trade off. My vote? just leave it .
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George - AB4FH

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Final comment to allay the fears of non-contesters.  I was asking for an optional "Fast turnaround" selection, perhaps in the CW tab when first turning on SSDR.  The default would be exactly as today.
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Wayne, W5XD

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W4TME said: I seriously doubt we will degrade the shape factor of the filters to reduce latency.  The filters rock like they are now.  If we can achieve lower latency without changing the shape factor, that would be considered.

Some users request lower latency at the cost of filter shape. I, for one, am not satisfied with "filters rock as they are now" as a reason that no users can make that tradeoff. Sure, there are users saying, to paraphrase, "I cannot see why anyone would want that." But that does not reduce the number of contesters saying, "I won't use the Flex because the latency is too high." My own assessment, for now, is that I am getting too much delay in the Flex for the really snappy SSB QSOs that happen among the very best ops (which, by the way, does not include me, although I try to not slow them down when I work them.)

I haven't yet looked into the Waveform API's, but am willing to build my own filters to reduce latency if that is an option? (I appreciate any pointers.)

I limit my comments, for the moment to SSB. I have not done enough work to say anything about CW or RTTY contesting on the Flex.
Wayne
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Mark Griffin

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I am a K3 owner, but looking to purchase a Flex in the next 6 months or so. I am a day to day operator as well as I operate in the major contests. With my K3 I have 2 cw filters, a 250 Hz and 400 Hz 8 pole filters. For SSB I have a 2.8 Khz and 1.8 Khz 8 pole filters. These filters serve my needs very well for both kinds of operating. I realize that with the Flex you can have unlimited filter combinations. That is great, but in a nut shell how many filter alternatives does one need to operate?

From what I am reading here, it seems the issue with the latency delays is more software then hardware. If I had my choice, I would like to have less filters but a better latency time. Because it not only effects those who contest, but day to day operating also.
(Edited)
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Charles - K5UA

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Give me 1:1 shape factor filters or give me.........uh.....1.04 :1 shape factors.
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Mark Griffin

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What is a shape factor filter?
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Lee - N2LEE

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Google or buy an Amateur Radio Handbook.
(Edited)
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Charles - K5UA

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Hi Mark,
The shape factor of a filter is defined as the width of the filter at its -60 dB points divided by the width of the filter at its -6 dB points. A "perfect" filter would have vertical sides because its -60 dB points would have the same width of its -6 dB points, i.e., a "brick wall" filter. Such a filter is impossible in the real world because it would have infinite latency, but the engineers at FRS have managed to design filters with incredible 1.04:1 shape factors with reasonable latency. Hence my tongue in cheek post "give me 1:1 shape factor filters" earlier to state my objection to degrading the shape factor of these beautiful FRS filters to shave off a few milliseconds of latency. I would not object to some future version of SSDR giving the user an option to degrade the filter shape factor to decrease latency, BUT I strongly object to simply degrading the filter shape factors to decrease latency as a default condition of SSDR.

By comparasion, the best analog filters have shape factors of about 1.4:1. Plot out a 1.4:1 filter versus a 1.04:1 filter and you'll see why I don't want to give up those filter skirts for the sake of a few milliseconds of latency. In the CW world filter shape factor is much more critical than for the SSB world. That's why you will hear mny more CW operators talking about filter shape factor than SSB operators.
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Walt - KZ1F

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I didn't even ask the question, but thanks for the explanation Charles! Way more informative than the previous 'look it up' response.
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k3Tim

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agreed..  thanks Charles....
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Ken - NM9P, Elmer

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Good explanation, Charles. If I remember correctly what I have heard before, the latency is a function of shape factor and width, which is why latency is more of a problem with the contesters, because they often use more narrow filters in the battleground.

On the other hand, I don't think any of those proposing a change are suggesting that the solution become standard, only a selectable option. I would welcome a "low latency" option for that purpose as long as it didn't degrade the standard filter slopes, which are the best in the business!
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Lee - N2LEE

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Walt, the reason for my "look it up" is because frankly I am frustrated with so called hams who are too lazy to learn. It took longer to enter the question than it did to do a search.

If we keep handing people the answer instead of encouraging them to at least TRY to learn then our hobby will die. Sorry for being so terse but it is discouraging to see forum after forum of "licensed" hams who will not lift (literally) a finger educate themselves.

There is no one here to has all the answers, we are all learning no matter our age. But, if our hobby is to survive we have to push back some times and help others by teaching them how to find the answers on their own.
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Charles - K5UA

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Yes Ken, just wanted to make sure the Community understands why low latency filters should be an OPTION, and not the default condition of the 6000 series filters.

Degrading the shape factor of a 2.9 kHz wide SSB filter for the sake of latency is not going to affect its performance in a crowded band AS MUCH as degrading the shape factor of a narrow 100 Hz CW filter in a crowded CW band. In my opinion, I would rather have a 1.04:1 shape factor 200 Hz CW filter than a 2:1 shape factor 100 Hz CW filter. It sounds counter-intuitive, but if these two filters are plotted out it will become apparent why the wider filter with the better shape factor gives superior selectivity in a crowded CW pileup.

"Where the rubber meets the road".... "In the final analysis"....... "After all the smoke has cleared" ..... it is always selectivity, selectivity, selectivity that decides if that rare one gets in your log.
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Stan - VA7NF

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The shape factor is just a number that varies with the bandwidth. 

For example, Charles you referenced 1.04:1 at 2.9Khz - 2900*1.04 = 3016 or 58 Hz difference from -6 to -60 on each side.  Take that same filter slope to a 200Hz filter then the shape factor will be (200 + 58 + 58) / 200 =  1.58 slope factor.  Both are the same filter requiring the same processing overhead and the same latency, just the slope factor number changed.

Charles comparison of a 1.04:1 SSB and 2:1 at 100Hz is correctly comparing the same filter.  Latency will drop as more processing power is brought to the algorithm, or an improved algorithm.  Since this software is quite refined and the hardware is fixed for this generation, it appears what is left is slope vs. latency.  Assumption: Processing is already done on the gate array.

Pushing this option to the user would be a slider  "Slope <-- . . . . --> Latency"  Squeeze the marshmallow on the Slope side and the Latency side grows.


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Charles - K5UA

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Hi Stan,

I may be going out on a limb here, so I don't want to sound too dogmatic about the this filter shape factor discussion. I hope that Paul Christensen, W9AC, will weigh in on this discussion.

It appears that you are implying that the slope of the filter skirt of a 2900 Hz, 1.04:1 shape factor SSB filter is the same as the slope of a filter skirt of a 200 Hz, 1.04:1 shape factor CW filter.  I think you are confusing slope of the skirt with the definition of shape factor of a filter.  Let's look at the math....

As you correctly stated, a 2900 Hz, 1.04:1 shape factor SSB filter would be 2900 Hz wide at its 6 dB points and 3016 hz wide at its -60 dB points.  The slope of the skirt from the -6 dB point to the -60 dB point would be (change in db) divided by (change in frequency), or 54dB/58Hz = 0.93 dB per Hz.

However, a 200 Hz, 1.04:1 shape factor CW filter would be 200 Hz wide at its -6 dB points and 208 Hz wide at its -60 dB points.  The slope of the skirt from the -6 dB point to the -60 dB point would be (change in db) divided by (change in frequency), or 54dB/4Hz = 13.5 dB per Hz.

As you can see, the difference in the SLOPE of the filter skirt of the 200 Hz, 1.04 shape factor CW filter is much steeper than the SLOPE of the filter skirt of the 2900 Hz, 1.04:1 shape factor SSB filter. I think you are correct when you say "it appears what is left is slope vs. latency", but from the above calculations it should be clear that the SLOPE of the two filters are dramatically different.

Only Steve from FRS engineering can confirm or deny your statement that ..... " Both are the same filter requiring the same processing overhead and the same latency".  My guess is that they are NOT, based upon the above calculations. However, I do not claim any knowledge about Gate Arrays or DSP programming, soooooooo...........

Steve, please help us with this thread, we always learn a lot when you clarify things for us.
(Edited)
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Walt - KZ1F

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@Lee, you never taught or mentored, did you? That's not how one encourages another to research. It is likely, very likely, not everyone is as knowledgeable about online resources as others are. This doesn't require a conversation between you and I, nor does it require you to defend your remark. I,merely, drew a comparison between your answer and Charles's.
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Lee - N2LEE

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I actually mentor and speak to class rooms all the time in another industry, but not ham radio.

I will do everything I can to help someone who wants to learn. But, when they are too lazy to open a book, do a simple search or at least try then NO, I will not spoon feeding those that just want the answer.

A teachers job is to teach students how to learn, how to find solutions to questions and to retain that information. I wonder how many people who hand out answers are actually do this for their own self gratification and ego vs those that are actually trying to teach ?

I am honestly not picking on Mark because I see this on every forum. But if he would have posted a question along the lines of "I read a WIKI page and now have a better understand of shape factor but still not see how DSP filters achieve this, you can help me understand ?"  that would have totally different.

There are a percentage of hams who are formally trained engineers. I am not one of those. I believe many hams get into the hobby because they are inquisitive people who love to learn how things work. And a huge percentage are self taught through trial and error, reading, mentors or asking questions.

  • How would handle a new ham that came to you and said I want to get on the air, can you give me radio ?
  • I don't know anything about antennas, will you build me one and come put it up ?
  • Don't know a lot about computers, can you install logging software and then show me how to use it ?
  • Then called you day after day asking question after question, would you consider this mentoring ?
I will restate me initial point. If we don't teach hams how to learn, find the answers and make mistakes, then our hobby will die.
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Walt - KZ1F

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And, implicit in what you just said, (I am really surprised you dbl'd down on this), it is YOUR job to 'teach' them. Actually, Lee, maybe I am not surprised. But it is good for all to hear it from you that you are the new sheriff in town. Lee, my wife and I both have MEd degree, I suspect we have the 'what does teaching involve' covered. Do you?
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Lee - N2LEE

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Darn Walt, I give up, I thought I had some good points but you win :(

I admit defeat and I am certainly no match for an over educated know it all that insist on contributing to the dumbing down of the the hobby.

The hobby is all yours. Go for it.
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James Whiteway

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Lee, having had Walt offer me guidance on several things I have asked about concerning the Flexlib api, I can truthfully say, he is NOT "contributing to the dumbing down of the hobby". Instead, he has encouraged me to take things one step at a time and given hints instead of outright answers.
  If there is any "dumbing down" in that, I fail to see it. 
james
WD5GWY
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Bill -VA3WTB

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Lee, I do understand you, but is this not what we do here, or is this place only for the astute?
Some times I like someone explain things to me, If I look it up I may find it confusing if I don't understand what they are saying. We are all on different levels here, sorry to say I'm on the lowest level I think....

But I agree, most things can be researched on line to increase understanding.
(Edited)
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Walt - KZ1F

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But to reiterate what you said Bill, sometimes the Wikipedia answer was drafted by an engineer, not what does it mean to the average person. Not every ham is a EE. It's akin to "ok, could somebody say that again, in English this time?".  I understood what Lee meant too and sometimes I catch myself before I say, um, less than gracious things because I am not in the mood. Rarely, I don't catch myself before I commit it to type. I merely wanted to give a shoutout to Charles for, what I thought, was a really good English answer.
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KY6LA - Howard, Elmer

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What relevance has any of the above nonsens to ADP.
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Walt - KZ1F

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Howard, I believe it has to do with the question about a shape filter. You are, of course, welcome to read the thread in order to answer your question. I should point out, as I know you would, your post just now added zero value.
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KY6LA - Howard, Elmer

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I stand corrected
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Jay / NO5J

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I tried reading this thread "in order."  I failed! Too much time traveling required. 
73, Jay - NO5J
(Edited)
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Walt - KZ1F

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I totally agree Jay. Posts 9 mins old nestled between two posts 6 months old. It would be nice if the software prevented that, it is, after all, just software.

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