WSJT-X V v1.7.0 r7405 (New Release)

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The new release of WSJT-X coupled with the Flex-6700 seems to outperform other stations I am working, I've found that I need to run about 60 Watts to match signal reports. My 20 meter noise level is around -130 dBm and I can now decode JT-65 and JT-9 modes down to -27. Assuming that I am working stations that are running 10-20 Watts and using older versions of WSJT-X, I believe that the new WSJT-X release has a 1-2 dB improvement in decoding over the earlier beta release and that the Flex may have another dB or two advantage in reception which would explain what I am seeing. Have others found this to be true?
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WA6HTP - Juan Rivera

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Posted 2 years ago

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Kevin K4VD, Elroy

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Hi Juan.

Are you saying that to get JT signal reports similar to what you are giving you have to run 60 watts out? I have noticed pretty much the same thing though I keep it to 30ish watts normally.

A lot of my signal reports are a lot less than the reports I give. I haven't done the math in quite a while but I think I'm consistently getting reports about 6 dB less than what I send. Sometimes the spread is much bigger.

For the longest time I thought that meant something was wrong but if I read you correctly, it actually might be that my Flex receiver is just that much better than most other receivers? 

Kev K4VD
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NX6D Dave

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I know that the new code uses a new decoder for JT65 and that it uses a system in which it removes decoded signals from the raw data then makes a second decoding pass.  This allows it to find signals that would otherwise have been masked by the louder foreground signals.  All in all, it's a winning combination.  My favorite mode.

I'm giving a talk at Quartzfest next week on "how to get started in JT modes", and will be running live demonstrations on the special event station (usually W7Q) with my 6500 starting Sunday evening, probably on 20M.
(Edited)
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Bill W2PKY

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I don't think there is any explanation for the disparity of signal reports noticed when running this mode. Probably local man made noise could account for some of it. Some stations are still using JT65HF which does not have as good a decoder as the new one. The FLEX receiver has more dynamic range than most which can help decode the very weak stations. Hard to say how all these factors add up. When looking at PSKReporter a station maybe reporting a strong signal and then a station a short distance away is reporting a weak report. Some nights every station called answers and then sometimes no one answers. Just never know.
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Ria - N2RJ, Elmer

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A lot of stations are using compromise antennas and have high local noise, that's one reason.
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Kevin K4VD, Elroy

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OK on the noise but wouldn't a compromise antenna work both ways? If station B's antenna is poor at reception it is probably poor at transmission also. Then again, maybe he's running 100 watts against my 30.

I would expect to see over time some sort of a balance between positive and negative reports all balancing out around zero but I think - and I really should graph it again to be sure - I'm seeing better reports outbound than inbound.

Bottom line is that JT works very well for me. It's just curious the numbers appear to be lopsided.
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K1UO - Larry

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OK on the noise but wouldn't a compromise antenna work both ways? If station B's antenna is poor at reception it is probably poor at transmission also.

Not necessarily so Kevin....  My 160 and 80M verticals work very well on transmit but are terrible for RXing...  This is the case for most antennas actually.  Antennas made for receiving only (Beverages, phased vertical arrays, K9AY etc) are a necessity for low signal reception on the low bands.  I have even seen this all the way up to 10 meters at times.
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George Molnar, KF2T, Elmer

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Remember the "report" is not signal strength, but based on SNR. I have the same experience, though - I typically give better reports than I get. With the Flex receiver, dogged noise reduction in my house, and WSJT-X 1.7, life is very good. I can only imagine what a truly quiet location, far from my suburbs of Las Vegas, would be like.
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KY6LA - Howard, Elmer

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Theoretically you have a 3 dB gain advantage because DAX stays in the digital domain rather that going DISTORTION and Noise added thru an a digital to analog to digital conversion that happens with external interface devices.

We ran some A/B tests a couple of years ago with an IC7700 and a microham interface vs a 6700 and internal DAX. Invariably the 6700 outperformed the 7700 by about 3-6 dB on JT-65. Some of the gain advantage was explained by the lower internal phase noise of the 6700 but the rest likely came from avoidance of the external interface.
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WA6HTP - Juan Rivera

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I think Howard has identified a large part of what I am seeing. The Flex / WSJT-X combination stays in the digital domain and gives us an advantage in receive performance over more traditional sound card configurations. If you are running the new release version of WSJT-X you get an additional boost in performance over older releases as the decoder is better. I am consistently decoding signals at a S/N of -27. I've never seen that with older version of WSJT-X. The result is that, if both stations are running the same output power, I can receive them much better than they can receive me. The overall improvement over most other stations seems to be 3-4 dB. The antenna should not be a factor as it will transmit and receive equally.
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Wayne VK4ACN

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Im finding with new wsjt 1.7 i can copy weak signals under very strong signals. A few hz difference in frequency but the weak one is still being decoded. Its much improved.
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NX6D Dave

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The signal strength reports are signal to noise reports, measured against 2500Hz worth of the local noise floor.  The point of these modes is to reliably fish very weak signals out of a lot of noise.  Here is the information from the documentation:

Signal reports are specified as signal-to-noise ratio (S/N) in dB, using a standard reference noise bandwidth of 2500 Hz. Thus, in example message at UTC 0003 above, K1ABC is telling G0XYZ that his signal is 19 dB below the noise power in bandwidth 2500 Hz. In the message at 0004, G0XYZ acknowledges receipt of that report and responds with a –22 dB signal report. JT65 reports are constrained to lie in the range –30 to –1 dB, and values are significantly compressed above about -10 dB. JT9 supports the extended range –50 to +49 dB and assigns more reliable numbers to relatively strong signals.

Signals become visible on the waterfall around S/N = –26 dB and audible (to someone with very good hearing) around –15 dB. Thresholds for decodability are around -23 dB for JT4, –24 dB for JT65, –26 dB for JT9.

Note that in JT65 mode the reports are compressed up against an artificial -1 dB ceiling.  This means that as the reported JT65 signal strength goes up, it means less and less.  This is not the case in JT9, where positive reports do occur.

Reported signal strength is entirely a matter of how the signal propagates and the local receiving conditions.  Pouring in lots of power may help a little, but brief band openings are probably more important.  I have a number of JT65 and JT9 DX QSOs in my log that suddenly popped up out of no where and just as suddenly collapsed.

I suspect that the new decoder performs better at the lowest signal power levels and the JT65 lower limit has been extended downward somewhat.

Regardless, I think its safe to say that Flex radios are just about the best possible choice for operating in this mode.
(Edited)
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wb7ond

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Regarding analog (old style) JT-65 decoding at the noise level, the quality of the sound card can determine how deep into the noise you can receive.  My best had been in the low -30db on a good Creative Xfi box with my KX3 portable with a well choked interface.  I typically do not drag my 6500 to the park (:-).    An interesting article that sums up the quality of the sound card with the old analog systems is the K9YC white paper here.  http://audiosystemsgroup.com/USB_Interfaces.pdf .   Also it is not fair to compare against a Signal Link, as some of them (circa 2009) have had problems detailed here:
http://www.frenning.dk/OZ1PIF_HOMEPAGE/SignaLinkUSB-mods.html,  but as noted before, staying in the digital realm is a bonus for deeper noise decoding.  I have yet to do long term listening on my Flex, as I am still in the "new radio" mode, and shut if off at bed time, rather than leaving it run all night, and see what I "catch" in the morning... 
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WA6HTP - Juan Rivera

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Howard,
what is the weakest station you've copied? I've seen several at -27 using the latest WSJT-X release. With the beta version the weakest I ever saw was -26. Local noise on 20 meters here is -130 dBm. I have very poor luck answering a CQ from anyone below about -20. I'm guessing that either they simply can't hear me or I'm getting stepped on by much stronger signals. I'll leave the rig on overnight and see what it captures...
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KY6LA - Howard, Elmer

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I regularly copy. -27.

The weakest QSO was a DL @ -29. I ran a KW into a beam (ERP 10KW) and he gave me a -19
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KY6LA - Howard, Elmer

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I suspect that most of the weak signals can't hear you because their radios have significant internal phase noise and use analog interfaces that masks the weaker signals.
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wb7ond

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I remember the first time, one morning, I saw and Australian station on JT-65 and tried to get him on 30M with my 10W.  I could see on the PSKreporter I was only getting to the West Coast with 100W.  So I fired up the linear, and I thought it was heresy to run 300W on JT-65, but it was morning, most everybody was asleep (:-), and I got him.  Did not know others ran power on JT also... 
(Edited)
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KY6LA - Howard, Elmer

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JT-65 is a weak signal mode NOT a low power mode. As long as you do not splatter (overdrive the audio) you can run high power to work the weakerstations who could not hear you otherwise.
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Paul

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I don't (as yet) have a 6x00 with its superior receive performance. However, I have still made worldwide contacts with WSJTX 1.7 and just 10W into a 160m wire loop antenna. The best signal report exchange was -26 dB (his sig) / -23dB (my sig). I don't believe this was down to any skill on my part, unless of course you count patience.

The "band police" would probably disapprove of 1kW on a JT mode whereas I prefer to run the lowest power necessary to maintain communications. I find 10W + patience for these modes is sufficient. Other operators may require more of each ;)
(Edited)
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Ken - NM9P, Elmer

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It is all a matter of signal path attenuation and receiver noise floor. The same as running EME. Whenever total path loss is less than the total power being transmitted, then you have a contact, otherwise you hear only noise.

Path loss can be improved with better receiving equipment, antennas, reducing man-made noise, and using modes and processing software that negate noise (such as JT65/9... the option on the other end is to improve antennas or increase power..

It doesn't matter which end the improvement occurs, the result is the same.
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WA6HTP - Juan Rivera

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Recent rains in California seem to have cleaned off the power line insulators and my local noise level dropped from -115 to -130. Now that I've upgraded to WSJT-X v1.7.0 I think my station is as good as its going to get. I' like to do some experimentation with one of you to see just how far into the noise we can go on JT-9. I'm wondering if narrowing the receiver slice bandwidth down to a minimum would improve reception - set the transmit offset to zero and meet on 14.078500 for example.
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Ken - NM9P, Elmer

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Alternately, for JT9, you can simply drag your filter sides in to narrow the filter during a contact.  Then hit the filter = 5K button when finished and go back to normal use.

Either method would also solve the issue of the passband and AGC being captured or overloaded by strong nearby signals.  I have done this successfully on PSK31, but haven't tried it on JT9.

Ken - NM9P
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Paul

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For me, reducing the RX filter bandwidth works very well Ken. The resulting noise power is reduced as well as gaining an AGC advantage (one of the reasons I have no issue with people who use QRO on adjacent frequencies ;)

I find when doing this, the results in WSJTX are better without the "flatten" box being ticked. A very interesting mode for propagation experiments but not one I use that much due to the inherently limited exchanges available.
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KY6LA - Howard, Elmer

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Interesting Experiment using PSKReports

1. Run CQ at Low Power... see how far they hear you

2.  Run CQ at High Power (Tight XMT Filters and Low Drive Audio to reduce splatter) - See how far they hear you

3   Run CQ at High Power but don't adjust the filters or drive...see how far they hear you

I found that #2 easily went the furthest.  YMMV


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wb7ond

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This is an interesting post, I discovered to my dismay, I was running PSK-31, adjusted the DAX Tx level according to the prescribed display (green peaking into orange), and got a call from my friend across town I was splattering.  He sent me a pix and sure enough...  I backed the audio down into the green, and of course, the power out dropped below my slider setting...  I will have to investigate how to adjust the tx bandwidth, thanks for the tips...
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Paul

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Or better still? :
1) if a band is open; call cq using QRP and see how far away you get on PSK reporter.

Note the worldwide coverage, be happy and keep at QRP.

2) If a band 'appears' to be closed; call cq using QRO and look at psk reporter....

(a) if no reports from regions of interest, wait until band is open and go back to 1)

(b) if reports from regions of interest are around minimum decodable signal, keep QRO and try to make some contacts. Periodically go back to 1)

(c) If reports are above minimum decodable signal, drop power by an equivalent number of dB, then make contacts. Periodically go back to 1)
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KY6LA - Howard, Elmer

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Most IMPORTANT

I f running QRO. Trim your transmit bandwidth AND reduce audio drive so you do not splatter.

Splatter defeats QRO benefits.