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Author Topic: Lets compare Digital modes...!  (Read 6316 times)
NN2X
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Posts: 369




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« 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...

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AA2UK
Member

Posts: 928




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« Reply #1 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
« Last Edit: February 01, 2018, 01:34:41 PM by AA2UK » Logged
AA4PB
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Posts: 15067




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« Reply #2 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.
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Bob  AA4PB
Garrisonville, VA
AA6YQ
Member

Posts: 3277


WWW

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« Reply #3 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".

« Last Edit: February 01, 2018, 04:02:49 PM by AA6YQ » Logged

#1 DXCC Honor Roll, DXCC Challenge 3000
AA2UK
Member

Posts: 928




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« Reply #4 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
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NN2X
Member

Posts: 369




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« Reply #5 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
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AC7CW
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Posts: 1358




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« Reply #6 on: February 01, 2018, 04:20:31 PM »

CW will be higher on the list at narrow CW bandwidths.
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Novice 1958, 20WPM Extra now... (and get off my lawn)
AA2UK
Member

Posts: 928




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« Reply #7 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
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AA2UK
Member

Posts: 928




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« Reply #8 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
« Last Edit: February 01, 2018, 05:05:13 PM by AA2UK » Logged
N3QE
Member

Posts: 5598




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« Reply #9 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.
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AA2UK
Member

Posts: 928




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« Reply #10 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
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N9AOP
Member

Posts: 1174




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« Reply #11 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
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AA2UK
Member

Posts: 928




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« Reply #12 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
Huh?
https://www.fcc.gov/ecfs/search/filings?sort=date_disseminated,DESC&proceedings_name=RM-11708
Bill, AA2UK
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NN2X
Member

Posts: 369




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« Reply #13 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
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N9AOP
Member

Posts: 1174




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« Reply #14 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
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