locked Re: Use of Q65 on 2m #Q65


Hasan Schiers N0AN
 

Amos,

There isn't any 'one size fits all' answer, but a lot of experimenting in the real world, as well as Joe's more carefully controlled tests have shown for the following on 6 meters:
(most of which is also true for 2m)

At any given moment, there are multiple propagation modes taking place while conducting a Q65 QSO. They often vary inside EACH 30 second sequence, i.e., you may have Es for 10 seconds, followed by troposcatter for 5 seconds, followed by 3 meteor pings, followed by some low level ionoscatter, followed by some long term ducting, and an aircraft or two, etc.

By looking carefully and analyzing the signal history from the SDRC (Simon's) program, you can see a 'tell-tale' signature for each propagation mode, often changing within the 30 seconds of a sequence. You can see the propagation modality changes in real time.

The ability to determine the mode from the signature is not quite like reading tea leaves, but neither is it so definitive that you can tell each mode definitively from each signature with every variation.

We have observed the following modes (many times, but not always within the same hour or two of continuous sequences)

Meteor Scatter
Sporadic E
Ionoscatter
Tropospheric Ducting

On shorter paths, we see the same variety of signatures, but for different propagation modes:

Tropospheric Scatter
Ground Wave
Localized Tropo-Ducting (morning and evening extensions as air settles)
Aircraft Scatter

As Joe has stated many times Q65-30A is the best overall starting point for terrestrial on 6 meters. For 2 meters, a lot more testing needs to be done, but all it takes is a pair of stations and some time each day to evaluate 30A vs 30B vs 30C for 2 meters (or other variations)

Q65 cannot replace FT8, period. They are designed with completely different purposes in mind. 

If you are going to schedule a terrestrial contact, in an interference (multi-signal)  free environment, Q65 in virtually any of its modes is superior to FT8. The same is true for EME.

Our QRP tests have reliably demonstrated that we can decode at well above 50% of the sequences with a well-equipped station at distances of 670 to 870 miles , every morning. The distant station (670 miles) is running 2 watts output to a 7 EL LFA at 40 feet, fed with 1/2" hardline. Another station is running 10 watts output to a 5 EL M2 @ 25'. We started the qrp testing for maximum performance running Q65-120E, which performed like magic, but was hard on equipment (2 min xmit time). We ended up using Q65-30A (funny how that matches what K1JT has been recommending), and could produce the results listed above. Did 120E work better...clearly, yes it did , but at what point do you give up the time and equipment issues that can accompany 120E ?

The receiving station in these tests was my own:

5 EL LFA At 55', fed with 80' of 1/2" hardline. GAsFET preamp in the shack
TS-590sg (internal preamp off)
Airspy R2 SDR (fed by TS-590sg splitter output AFTER the GAsFET preamp)
SDR-Radio SDR Console v 3.x


The good news is that Q65 will take advantage of ANY propagation mode that exists for any given moment, while some of the other modes cannot do that (FT8) or do not have the same low sensitivity (MSK144). 

That is not to say Q65 does a better job of making use of meteor bursts than MSK144 does. It most certainly does not.

If you are going to randomly seek qsos, Q65 is not the answer except perhaps to a limited extent on 6 meters 50.275-30A , which can accomodate quite a few non-overlapping signals. We see people calling CQ and having qsos every morning on this freq and mode...but, will it work in the face of a major Es opening with dozens of stations....no, it won't, at least nowhere nearly as well as FT8 already does.

Fit the mode to the intended use, coordinate with others for Q65 qsos, and establish your own watering holes. We are hams, we are supposed to be good at communicating. Here in the USA, we have established 50.275 for 30A and 235 for more experimental stuff, especially 120E. There are similar watering holes for 2m terrestrial that have been mentioned on this list many times. Joe didn't create them, users did. EME stuff is coordinated on the ON4KST web site.

The rest is just 'doing it'
73, N0AN

Hasan


On Sun, Jul 25, 2021 at 11:38 PM Amos Sobel 4X4MF <asobel@...> wrote:

2m FT8 is dead here because of severe interference on 144.174 Mhz. Can Q65 replace it?

  1. Is  Q65 15A equal or better then  FT8 for terrestrial and Troposcatter  work? What is?
  2. A default frequency for such service must be set.

 

Amos 4X4MF

 

From: main@WSJTX.groups.io <main@WSJTX.groups.io> On Behalf Of Jeff Townsend
Sent: Monday, July 26, 2021 2:42 AM
To: main@WSJTX.groups.io
Subject: Re: [WSJTX] Use of Q65 on 2m #Q65

 

What is the difference between the submodes?

From reading the quickstart It seems that as you go up from A that they are more and more resistant to doppler spreading.

Is there more?

And increasing the sequence time allows for weaker signals to be decoded.

Am I getting that right?

 

On Jul 25, 2021, at 11:30 AM, Joe <joe@...> wrote:

 

Hi Amos,

It makes no sense to define default submodes on a band-by-band basis, independent of propagation mode.  Many submodes are available for Q65 precisely because different propagation modes and paths have different requirements.

We do not define default frequencies for WSJT-X modes.  They are determined by community usage and then incorporated into WSJT-X.

EME on 2 meters has plenty of Q65 activity.  The preferred EME mode is Q65-60A, and frequencies generally fall in the range 144.100 to 144.160.

For other propagation types: find some potential QSO partners at suitable distances, decide with them what submode(s) you want to experiment with, and decide on a frequency.  When enough activity is accumulated, your choices could then become general recommendations.

  -- 73, Joe, K1JT

 

Jeff Townsend

WB8LYJ/R

 

 

 




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