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eHam Forums => Digital => Topic started by: NN2X on February 01, 2018, 04:39:20 AM



Title: Lets compare Digital modes...!
Post by: NN2X on February 01, 2018, 04:39:20 AM
Lets compare the digital modes... (And just for fun, have the SSB in there as well)!

Numbers don't lie!

Relative Sensitivity in a 2500 Hz Bandwidth

Mode SNR Threshold Power Equivalence

WSPR -27 dB  5 W (Only exchange Signal Report. etc..)

JT65 -24 dB   10 W (Only exchange Signal Report.etc..)

FT8 -  23 dB   11W (Only exchange Signal Report. etc..)

Olivia -17 dB   50 W (Rag Chew Mode) / this is for 500 / 8

PSK31 -7 dB   500 W (Macro / Some Rag chew)

CW -1 dB        2,000 W (Rag Chew)

RTTY +5 dB 8,000 W (Rag Chew)

SSB +10 dB 25,000 W (Rag Chew)

Source: by Dr. Carol F. Milazzo, KP4MD (Interpreting WSPR Data for Other Communication Modes – Aug 2013)

Interesting, why wonder, Olivia is the best for Rag Chew Mode...

NN2X...



Title: RE: Lets compare Digital modes...!
Post by: AA2UK on February 01, 2018, 01:32:25 PM
Well I see some issues already, not sure how an article can reference FT8 when it's not even a year old?

WSJT signal strength (regardless of mode) is given as dB relative to noise floor in 2500 Hz bandwidth.  However as you may or may not know there are some differences among the modes in terms of how it is calculated/reported.  

For example, taken from the most recent WSJTX documents:

"JT4 and JT65 signal reports are constrained to the range –1 to –30 dB. This range is more than adequate for EME purposes, but not enough for optimum use at HF. S/N values displayed by the JT4 and JT65 decoders are clamped at an upper limit –1 dB, and the S/N scale is nonlinear above –10 dB.

By comparison, JT9 allows for signal reports in the range –50 to +49 dB. It manages this by taking over a small portion of “message space” that would otherwise be used for grid locators within 1 degree of the south pole. The S/N scale of the present JT9 decoder is reasonably linear (although it’s not intended to be a precision measurement tool)".

Additional information, the WSJT signal strength number does NOT indicate an absolute signal strength.  Rather, it indicates signal strength relative to the noise floor in 2500 Hz bandwidth, as indicated above.  Thus even if the signal level is higher with the higher gain preamp, if the noise floor is raised more than the signal amplitude, then the WSJT signal strength will drop.

Bill, AA2UK


Title: RE: Lets compare Digital modes...!
Post by: AA4PB on February 01, 2018, 02:04:28 PM
PSK31 is listed as Macro / Some Rag chew. That's only by the operator's choice. PSK31 has the same ability to type all keyboard rag chew information the same as Olivia and RTTY.


Title: RE: Lets compare Digital modes...!
Post by: AA6YQ on February 01, 2018, 04:00:34 PM
Sensitivity is an important factor, but it's not the only factor, and for ragchewers it's not the most important factor.

Speed is also an important factor, but the requirement is simply  "fast enough".

The most important factor for ragchewers is "ability to quickly find a desirable QSO partner". The two biggest contributors to this are "panoramic reception" and "mode popularity". "Panoramic reception" is the ability to see all of the callsigns QRV in the mode on the current band, and easily call one of them.

The right combination of sensitivity, speed, and "panoramic reception" is what drove the PSK modes to critical mass and then dominance, and what is driving FT8 to dominance now.

The lack of "panoramic reception" is what's prevented Olivia from achieving critical mass, despite its other virtues, and despite several heroic attempts to bootstrap it.

Metcalfe's law states that the value of a network is proportional to the square of the number of nodes. A digital mode is effectively a network.

I don't think a digital mode can achieve and maintain critical mass without "panoramic reception".



Title: RE: Lets compare Digital modes...!
Post by: AA2UK on February 01, 2018, 04:12:30 PM
Really?
 
The law is also very much related to economics and business management, especially with competitive companies looking to merge with one another.
Bill, AA2UK


Title: RE: Lets compare Digital modes...!
Post by: NN2X on February 01, 2018, 04:19:47 PM
Please see below URL .Please look at slide 23....(Understand, the FT8 is about 1dB less sensitive the JT65, hence my calculations)

file:///C:/Digial_Modes/Digital-Modes-TBARC-19.pdf

There is the source of my information...

There is the credibility verification


Title: RE: Lets compare Digital modes...!
Post by: AC7CW on February 01, 2018, 04:20:31 PM
CW will be higher on the list at narrow CW bandwidths.


Title: RE: Lets compare Digital modes...!
Post by: AA2UK on February 01, 2018, 04:33:54 PM
Please see below URL .Please look at slide 23....(Understand, the FT8 is about 1dB less sensitive the JT65, hence my calculations)

file:///C:/Digial_Modes/Digital-Modes-TBARC-19.pdf

There is the source of my information...

There is the credibility verification
Your not even close FT8 and JT65 are not w/in 1db of each other.

Bill, AA2UK


Title: RE: Lets compare Digital modes...!
Post by: AA2UK on February 01, 2018, 04:59:32 PM
"WSJT-X is a computer program designed to facilitate basic amateur radio communication using very weak signals. The first four letters in the program name stand for “Weak Signal communication by K1JT,” while the suffix “-X” indicates that WSJT-X started as an extended and experimental branch of the program WSJT.

WSJT-X Version 1.8 offers nine different protocols or modes: FT8, JT4, JT9, JT65, QRA64, ISCAT, MSK144, WSPR, and Echo. The first five are designed for making reliable QSOs under extreme weak-signal conditions. They use nearly identical message structure and source encoding. JT65 and QRA64 were designed for EME (“moonbounce”) on the VHF/UHF bands and have also proven very effective for worldwide QRP communication on the HF bands. QRA64 has a number of advantages over JT65, including better performance on the very weakest signals. We imagine that over time it may replace JT65 for EME use. JT9 was originally designed for the LF, MF, and lower HF bands. Its submode JT9A is 2 dB more sensitive than JT65 while using less than 10% of the bandwidth. JT4 offers a wide variety of tone spacings and has proven highly effective for EME on microwave bands up to 24 GHz. These four “slow” modes use one-minute timed sequences of alternating transmission and reception, so a minimal QSO takes four to six minutes — two or three transmissions by each station, one sending in odd UTC minutes and the other even. FT8 is operationally similar but four times faster (15-second T/R sequences) and less sensitive by a few dB. On the HF bands, world-wide QSOs are possible with any of these modes using power levels of a few watts (or even milliwatts) and compromise antennas. On VHF bands and higher, QSOs are possible (by EME and other propagation types) at signal levels 10 to 15 dB below those required for CW."
Joe Taylor K1JT

Bill, AA2UK


Title: RE: Lets compare Digital modes...!
Post by: N3QE on February 02, 2018, 06:00:25 AM
While I don't disagree with the overall point that KP4MD makes in that article, I believe there's some exaggeration going on with regards to S/N and power ratios.

A good operator in almost any of those modes, is going to be 10dB more effective than an average operator.


Title: RE: Lets compare Digital modes...!
Post by: AA2UK on February 02, 2018, 10:40:14 AM
While I don't disagree with the overall point that KP4MD makes in that article, I believe there's some exaggeration going on with regards to S/N and power ratios.

A good operator in almost any of those modes, is going to be 10dB more effective than an average operator.
My opinion FWIW, basing assumptions using flawed numbers = a flawed/ skewed result.
Bill, AA2UK


Title: RE: Lets compare Digital modes...!
Post by: N9AOP on February 02, 2018, 11:15:15 AM
Actually Pactor 3 & 4 are the best for rag chew under miserable conditions.  However that high price German modem keeps most hams away from this FB mode.
Art


Title: RE: Lets compare Digital modes...!
Post by: AA2UK on February 02, 2018, 11:35:17 AM
Actually Pactor 3 & 4 are the best for rag chew under miserable conditions.  However that high price German modem keeps most hams away from this FB mode.
Art
????
https://www.fcc.gov/ecfs/search/filings?sort=date_disseminated,DESC&proceedings_name=RM-11708
Bill, AA2UK


Title: RE: Lets compare Digital modes...!
Post by: NN2X on February 03, 2018, 07:15:23 AM
I had no idea I created such a explosive thread...This is like talking politics..All I was try to say, is the best digital mode to have a DX and a real QSO considering the least amount of power and a modest antenna is Olivia... (Many Hams on the post missed that, as they keep referring to FT8, (But with no QSO)..

Yes there are a ton of digital modes, But the graphs I seen, easily Olivia wins...And against QSB, might add..

Truth be told, I like the best SSB on 10 meters..but no play there...Since my desire is DX, AND A QSO , Olivia is the only choice..(By math, by practice, and by logic)...

Nothing more to say!

Cheers

NN2X..Tom


Title: RE: Lets compare Digital modes...!
Post by: N9AOP on February 03, 2018, 09:56:25 AM
Bill,
The ham bands are not the only place I play.  P4 is legal outside the ham bands.  Hopefully the FCC will change those obsolete rules some year in the USA for amateur use.
Art


Title: RE: Lets compare Digital modes...!
Post by: AA6YQ on February 03, 2018, 10:01:47 AM
I had no idea I created such a explosive thread...This is like talking politics..All I was try to say, is the best digital mode to have a DX and a real QSO considering the least amount of power and a modest antenna is Olivia... (Many Hams on the post missed that, as they keep referring to FT8, (But with no QSO)..

Yes there are a ton of digital modes, But the graphs I seen, easily Olivia wins...And against QSB, might add..

Truth be told, I like the best SSB on 10 meters..but no play there...Since my desire is DX, AND A QSO , Olivia is the only choice..(By math, by practice, and by logic)...


Your conclusion is erroneous because you've ignored a critical factor: the probability that a station you wish to work is "available" via Olivia. That probability is low, which is why Olivia gets little use, despite its other virtues and despite several efforts over the years to bootstrap it -- like this one. If you want this to change, develop an application that provides panoramic reception for one or more effective Olivia submodes.


Title: RE: Lets compare Digital modes...!
Post by: K0UA on February 03, 2018, 10:33:57 AM
Then there is the little matter of bandwidth.  FT8 Bandwidth, about 50 hz.  Olivia 8/500 bandwidth, about 500hz. The faster versions are even wider.  Hm.. We put ALL of the FT8 QSO's in the world on 40 meters on 7074khz in a 2500hz bandwidth.  Sometimes you can't find an open spot to operate and operators are piled up on each other. How in the Heck are we going to operate Olivia in the same bandwidth?  Answer, we are not going to. We would all have to spread out, but the problem quickly becomes, spread out to where? Everyone has their favorite frequency's staked out already when you take into account ALL of the modes in use and the people that love them.

  I saw an "uninformed person" last night come on to the FT8 frequency with an Olivia 8/500 transmission.  He wiped out 1/5 of the entire worldwide FT8 usage frequency for 40 meters.  Right over the Malta station I was trying to work. And a bunch of others.  Right now there isnt a problem with Olivia, as not too many folks are on it. If everyone on FT8 tried to get on Olivia, there sure wouldn't be room for them in the digital subbands. You need to be thanking your lucky stars that NOT more people are on Olivia.  It is great when there are just a few people using it.  Olivia is a slow speed and bandwidth hog.  PSK31 was MUCH MUCH better even though it wont go as deep into the noise as Olivia can. BUT it uses 31hz of bandwidth for a good speed that is as fast as most guys can type anyway.

Be careful of what you wish for.! :)


Title: RE: Lets compare Digital modes...!
Post by: AA6YQ on February 03, 2018, 10:52:11 AM
Olivia 8/500 would need about 20 KHz of bandwidth to support an activity level comparable to FT8 or PSK31 (in its heydey).  14105-14125 and 7105-7125 don't get much use except during contests. So a new application that exploits wideband SDRs to provide panoramic Olivia 8/500 reception would have watering holes for daytime and night time operation; build it, and see if they come.


Title: RE: Lets compare Digital modes...!
Post by: K0UA on February 03, 2018, 12:43:31 PM
Olivia 8/500 would need about 20 KHz of bandwidth to support an activity level comparable to FT8 or PSK31 (in its heydey).  14105-14125 and 7105-7125 don't get much use except during contests. So a new application that exploits wideband SDRs to provide panoramic Olivia 8/500 reception would have watering holes for daytime and night time operation; build it, and see if they come.

Yes, but you have some pactor and all of the DX ssb qso's there already as well as the RTTY contests..  PSK31 was a good ragchew mode, and only takes 31hz, and is faster.  It just doesn't go as deep into the dirt, but it still works well.  Of course it is a moot point, at this point, and everyone is still on FT8.  At least for a while until everyone has worked everything.  :)


Title: RE: Lets compare Digital modes...!
Post by: VA3VF on February 03, 2018, 07:16:06 PM
Yes there are a ton of digital modes, But the graphs I seen, easily Olivia wins...And against QSB, might add..

How does it win when the number of QSOs are so limited. Put theory aside, look at reality. FT8 is the most used mode right now, by far. ClubLog put out a graph showing that a few months ago, the number of FT8 QSOs uploaded to the site was more than CW and SSB combined.

If you're just interested in the technical aspects of a mode, there may be others even better than Olivia, who knows. They are so good they are a secret. :o


Title: RE: Lets compare Digital modes...!
Post by: HS0ZIB on February 06, 2018, 03:06:42 AM
Quote
the probability that a station you wish to work is "available" via Olivia

Suppose a rare DXCC or Dxpedition (Bouvet next time?) announced that they were going to use Olivia and not FT-8?

What do you think hams would do?  Refuse to use Olivia and not make that QSO? :)


Title: RE: Lets compare Digital modes...!
Post by: VA3VF on February 06, 2018, 05:04:15 AM
Quote
Suppose a rare DXCC or Dxpedition (Bouvet next time?) announced that they were going to use Olivia and not FT-8?

What do you think hams would do?  Refuse to use Olivia and not make that QSO? :)

Make no mistake about it. They will use whatever is needed for an ATNO. Don't believe the pontificating.


Title: RE: Lets compare Digital modes...!
Post by: AA2UK on February 06, 2018, 09:17:20 AM
Quote
the probability that a station you wish to work is "available" via Olivia

Suppose a rare DXCC or Dxpedition (Bouvet next time?) announced that they were going to use Olivia and not FT-8?

What do you think hams would do?  Refuse to use Olivia and not make that QSO? :)
I doubt that will happen however I'm not sure why a DX'pedition wouldn't want to maximize the Q rate so FT8 would by default be the digital go to...
Bill, AA2UK


Title: RE: Lets compare Digital modes...!
Post by: AA6YQ on February 06, 2018, 10:35:03 AM
Quote
the probability that a station you wish to work is "available" via Olivia

Suppose a rare DXCC or Dxpedition (Bouvet next time?) announced that they were going to use Olivia and not FT-8?

What do you think hams would do?  Refuse to use Olivia and not make that QSO? :)

DXers in need of QSOs would of course use Olivia to make contacts with the Dxpedition. After the operation was over, they'd stop using Olivia for the same reasons they hadn't been using it beforehand.



Title: RE: Lets compare Digital modes...!
Post by: N3QE on February 06, 2018, 11:46:24 AM
I doubt that will happen however I'm not sure why a DX'pedition wouldn't want to maximize the Q rate so FT8 would by default be the digital go to...

Do we have actual FT8 rates recorded by a DXpedition in excess of 20 per hour?

I regularly achieve 100+ an hour on RTTY simplex and have heard DXpeditions doing at least 60 an hour on RTTY with split pileups. Admittedly that's above average operators in decent bands.


Title: RE: Lets compare Digital modes...!
Post by: VA3VF on February 06, 2018, 11:49:15 AM
I doubt that will happen however I'm not sure why a DX'pedition wouldn't want to maximize the Q rate so FT8 would by default be the digital go to...

Do we have actual FT8 rates recorded by a DXpedition in excess of 20 per hour?

I regularly achieve 100+ an hour on RTTY simplex and have heard DXpeditions doing at least 60 an hour on RTTY with split pileups. Admittedly that's above average operators in decent bands.


No, we don't. The 'hope' is the new Dxpedition mode to be included in WSJT-X version 1.9. A theoretical 600 Qs per hour, more like 200-250 in actual use.


Title: RE: Lets compare Digital modes...!
Post by: K0UA on February 06, 2018, 01:01:09 PM
I doubt that will happen however I'm not sure why a DX'pedition wouldn't want to maximize the Q rate so FT8 would by default be the digital go to...

Do we have actual FT8 rates recorded by a DXpedition in excess of 20 per hour?

I regularly achieve 100+ an hour on RTTY simplex and have heard DXpeditions doing at least 60 an hour on RTTY with split pileups. Admittedly that's above average operators in decent bands.


No, we don't. The 'hope' is the new Dxpedition mode to be included in WSJT-X version 1.9. A theoretical 600 Qs per hour, more like 200-250 in actual use.

I am very eager and optimistic about the new Expedition mode of FT8.  I will finally give us "little pistols" a shot at some of these rarer countries.  especially in these "not so good" propagation times.


Title: RE: Lets compare Digital modes...!
Post by: AA2UK on February 06, 2018, 01:12:49 PM
I've been testing recent developers versions of FT8 w/Fox and hound.
I think the capacity to support high Q rates is there.
It's still difficult to predict real rates. During the January VHF contest I did manage to work 80 Q's using FT8 in the 2nd hour using NA Contest mode w/RR73 on 6 meters.
Without much prop this is not sustainable but that wasn't FT8's fault.
Bill AA2UK