Latency 1.4.....Improvement?

Steve N4LQ

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  

George KF2T

The 6000 uses relays to provide better signal quality, which may slow things down a bit. Perhaps up to 0.1 second per transmission. If a contest operator makes 1000 contacts, and transmits three times per contact, 3000 PTT times .1 second delay, or 300 seconds over the event. Five minutes. How is that costing contacts, really? Especially considering that the time from PTT to speech probably doesn't truncate anything from the exchange (what can you say in 0.1 second?) There are several contest ops here, and I believe the consensus is that the abilities the rig provides more than outweigh an imaginary fault. .

W7NGA

simply listen to your signal on an external receiver ... you might be surprised.

73's

dan  W7NGA

K2CM

An f 6.7 k, 2kw pep, a 10 element beam will certainly outweigh any small layency issue.

Steve N4LQ

According to the "contester"...The time lapse between when the other guy releases his PTT + time your Flex takes to reproduce his transmission in your ears + time to transmit your response is great enough that someone with a faster rig grabs the attention of the other guy first. It's a difference of over 100 milliseconds between the 6000 series and typical other rigs. I'm just quoting others here but I suspect it is a little more than just an "Imaginary fault". 
I thought maybe that maybe with ver 1.4, moving some of the cpu work to the 6000 might change the turn time?

W7NGA

latency - it's enough that you cannot realistically monitor and assess your signal real-time on an external receiver, and I suspect it could be an issue for the consummate contester.

dan  W7NGA

Ken - NM9P

The last time I looked, there is no interlock on the flex radio than prevents pressing the PTT before the other station's last syllable fades into the noise. A good contester knows his station and makes adjustments accordingly. One can press the PTT a split second before the other station finishes his "QRZ" and be right there on top of everyone else. In fact, I often see stations begin transmitting several seconds before the DX ends his transmission, presumably on order to get the drop on the competition. (I often wonder if they know that the other station cannot hear them until the DX station stops transmitting....) Yes, timing is often more important than raw power, and articulation is often better than compression, but much of that timing is in the footswitch or VOX, or even more..in the operator's mind.

Bill Roberts

Is this contester named Archie Bunker?  Does he come configured with preconscrewed ideas?

Steve N4LQ

The Flex-5000 turnaround time = 29ms
The Flex-6700 turnaround time = 140ms
Per QST reviews
We went from one of the fastest to by far the slowest. 

Steve N4LQ

Bill that is so funny. I'l just tell those ole contesters they are Archie Bunkers...Yea that will fix'em. Man why didn't I think of that? 

Lee - N2LEE

Steve what ever you do don't convince your contester friend to get a flex. Let him think the delay is a problem.

The last thing we need is another contester than can hear stations that the Flex users can hear.

Steve-N5AC

Relays have nothing to do with these measurements.  The measurements are a result of signals passing through the signal chain in the receiver and the transmitter.  As one of my radio mentors was fond of saying "all the delay comes from the quality of the final filter."  This is a hard concept to wrap your head around if you are not familiar with it, but the net-net is that the better filter you provide at the final sampling rate, the more latency is introduced.  The FLEX-6000 is the first radio I am aware of to provide variable-depth filters.  We can significantly reduce the delay by reducing the filtering and we can do this dynamically.  Even the FLEX-5000 with PowerSDR did not have this capability.

Our read when we designed the signal chain for sideband was that a little latency was less important than good filtering.  So we "maxed out" the filtering capabilities for sideband.  The filter dynamically changes width in DIGx modes and in CW.  If you would like to try out a shorter latency with reduced filtering capabilities, try running in DIGU instead of USB and set your filter width to greater than 2kHz.  The latency will go down to what we consider to be a very minimal level.  

The ARRL and others are not used to measuring radios that have complete flexibility in how things like this are controlled and so they put the radio in a given position and took a measurement.  The measurement is accurate for that one setting, but is not a complete picture of what the radio can do (and in this case doesn't explain the tradeoff that we made).  I'm sure I would have done just what they did.  As you guys probably know by now, if you provide a compelling case for making a change in the radio there are very few things we cannot change.  You can try using DIGU and let us know if you prefer it like this.  There is actually a table in the owners manual with this information along with a description of how it works (see 29.6.4 on page 140).  

Steve N4LQ

Steve
Thanks for the informative reply and I now understand. So to answer our contesting friends concerns we need to explain to them that excellent filtering is more important than longer delay. 
I guess a "contest mode" would be a nice marketing tool. )
72

K6OZY

I think a "contest" mode for USB/LSB filters is a great idea.  We can test latency using DIGU/DIGL but the PROC is disabled so it's not a long term solution.

Steve-N5AC

If you guys truly feel you are missing contacts due to the latency I want to hear about it.  If not, I would argue that the filtering is more important.  Agreed that DIGU is not a long term solution -- I just wanted to show you an easy way to test the difference.

KY6LA_Howard

You actually do not need to do that much to achieve a "Contest" Mode with the lowest latency in the market...

All you need to do is to route your TX and RX audio via a DAX Channel.. and then have your device (speaker and mike) listen to those channels..

I could provide your friend with screen shots as to how to do it as that is how I do it with iPad Remoting via DAX..before Remote was available in 1.4

BTW,,, at times I get hit with the contesting bug and I can be a serious contestor... I have won my ARRL section using SDR's and have placed 2nd in World and #1 NA in a JIDX SSB Contest... so I can speak with some authority about contesting..... 

It always helps to have a contesting station.. I have a 6700. SPE 2K-FA and a SteppIR MonstIR @85' located 600'ASL 1KM from the Pacific Ocean.. so by definition I will always do well in an Asia Pacific Contest without trying too hard.

So what is the difference between #2 in the world and #10 in the world when I was not trying too hard......

Basically its the operator's skill...

that 100ms latency is a mental factor.. if no one had pointed it out there is absolutely not doubt that  it would not be an issue..as a great operator can win with even a lowly ICOM IC-756 Pro3...

Charles - K5UA

Woudn't a contest mode with poor filter skirts be counterproductive ? If there is one situation where you need good filter skirts ... It's in a contest. Surely no contester would give up these fantastic shape factors for a few msec less latency. How many seconds would be lost in a 48 hour contest asking for a repeat of the exchange because a poor filter skirt made copy impossible?

George - AB4FH

Steve, Could you give us some data that compares latency to filter skirts? While I'm not the contester that I used to be in my younger days, with the call WB4PDQ, I think this is worth further discussion. On CW a difference of 100 ms is very noticeable at 40 wpm contest speed.

Mike va3mw

I am calling BS on this and he is just looking for an excuse. I have done hundreds of SSB contests both with and without the Flex and there is no difference that would ever make a difference in my score. If he really knew contesting and it was a pile up, it isn't about being first in, but being heard when there are less people calling. I also contest with a remote base with about 100ms latency (and I have been for almost 10 years) and I have never noticed a difference where it would make an impact on my score. It is 100% operator skill and nothing to do with the change over time. va3mw

Barry N1EU

What's clearly needed here is hard data, not words - what are the rx and tx latency measurements in milliseconds for the range of filter slope and audio connection settings?  I'd for one appreciate seeing that for the 6300 and 6500.

Barry N1EU

Steve-N5AC

We'd have to go plot them, George, which we could do.  I don't have the plots ready today.  I can tell you that with the highest latency and number of taps, the filters are virtual brick walls.  If you compare the filters in CW mode to the finest crystal filters available in other radios, the shape factors we produce are significantly better.  Here's a post where several folks chimed in, did some plots and talked about the filters:

https://community.flexradio.com/flexradio/topics/cw_filter_shape_factors?topic-reply-list%5Bsettings...

The same filters used in CW are also used in sideband so the same numbers apply.

Michael - N5TGL

I'm in the camp that the 140ms delay is just an excuse.  It truly is all about timing, understanding how the other operator is operating and jumping in at the right time.  Unless you have a big gun station, being the first to rattle off your call after "QRZ?" is likely to not get you an answer.

WA2SQQ

In the digital photography world people who scrutinize image quality by viewing images at 400%, or quote numbers that just are not "visible" are called "pixel peepers". My take on this is they are complaining about this "spec" and using it as ammunition to support their decision to purchase the brand they have, over a Flex. Most of them probably wish they waited and bought a Flex! My Flex 6500 allows me to enjoy the hobby which is what it should be about.

Barry N1EU

I would suggest that where this becomes a real issue in serious (i.e., high rate) ssb contesting is when the latency (sum of rx plus tx latency) is equivalent to a single spoken syllable.  In one likely scenario, what happens is that the dx will hear a quicker responder's signal and then your signal come in with that syllable (or character) delay and the dx gets your callsign wrong.  

Latency is a trade-off with filter slope steepness.  To throw out a number, perhaps a 2:1 minimum filter slope is needed for serious ssb contesting when the least amount of latency is desired (i.e., sacrificing filter slope steepness for less latency). 

Barry N1EU

Steve W6SDM

There are some really detailed high tech explanations here.  Here's my low tech view of the matter.  We're talking syllables and milliseconds here.  As a mediocre contester myself, I don't see how that can possibly impact your score unless you are one of the top three contenders and the winning difference comes down to that last single contact.  My guess is that this guy scores somewhere in the middle of the pack - otherwise he would be developing contest skills that worked around whatever characteristics the radio had.

This reminds me of the guys who speed the "5nn" up to 65 WPM in a CW response - how much time did they really save and did it make a difference?

Whatever latency may be characteristic of the Flex is much outweighed by the various advantages that a Flex offers to contesters.  I wouldn't be surprised if they didn't come out with a SDR-assisted category to level the playing field.

KY6LA_Howard

Winning Contests is about Rate. You don't run high rates by running Search and Pounce. You run rate by holding a frequency and letting everyone come to you. When holding a frequency the 100ms latency is not an issue PERIOD I can see where 100 ms might slow u down in S&P But As I said you are not running high rates in S&P. Even then a BIg Station will easily dominate most everyone else who beat you to the 100MS punch. So I can only surmise that the Latency issue is. Not an issue for Big contest winning stations but might be an issue for someone in the middle of the oack.

George - AB4FH

For clarification, I think the situation that latency becomes important in a contest is when you are doing Search and Pounce, i.e. moving frequency looking for the next station calling "test". In this mode, the other station will respond to the first, readable station that answers his call. I'm sure that being one tenth of a second behind, given equal readability, will cause you to not get the contact. So, now, you either have to find another station or wait to call the same station again. As Howard has said before, everything in a contest is about rate or contacts per hour. Each missed contact slows the rate. Imagine missing 10 such contacts per hour at a 100 contact per hour rate.

George - AB4FH

Sorry, Howard, we "doubled". Lol

George - AB4FH

BTW when Running a frequency, I often widen my receive slice bandwidth to make sure I don't miss any callers. Katashi Nose, the former KH6IJ, contester of fame, would often copy multiple stations in his head and answer them in rapid fire. I know, because I was one of the callers back in the '70s. Now that's a way to up your rate...but few of us mortal can achieve that.

Bill -VA3WTB

Perhaps his mind has to much latency. What do you do about that? Latency problems, I just can't buy it....

George - AB4FH

Howard, when using N1MM+ in CW as SOA, I've hit 100 contacts per hour rate in S&P for the first hour on a good band. The trick is to use CW Skimmer to load up the bandmap. Then to get to the next frequency, you just tap Ctrl < or > and it takes you to the next unworked station on the map. You only have to wait long enough for him to finish his call. I'm sure to win you need to Run some too.