[Lowfer] Modes, signaling, and data recovery

[Les Rayburn]

First of all, thanks to Jim for pointing out some of the specific 
differences. Very
helpful information. A few comments if you please...

1. I think lots of folks on both sides of the pond might be interested in a 
"weak signal
mode" version of Jason. As you correctly pointed out, the GUI interface 
makes it
much easier to adopt...but with our limited ERP, it will be a very limited 
tool
if it lacks the longer tone durations for weak signal work.

2. There is a lot of disagreement here over just how difficult it is to 
obtain the kind of
frequency accuracy required for modes like WOLF. In my mind, if you can buy 
a rig
off the rack (as I did) and do some simple calibration procedures to bring 
it in
line with WOLF that isn't too hard.

My rig, an Icom 746 is equipped with the high stability option, but several 
hams have
had good luck with stock rigs as well. I really think the GUI issue is the 
biggest
hurdle for most hams when it comes to WOLF.

Now, if we start talking about cesium time standards or locking to GPS 
references, etc.
I think we begin to get a little too exotic for most, myself included.

3. More questions: Any idea how much improvement we might expect if the tone
duration was lengthened? Would it be possible to approach the weak signal
performance of WOLF?

Thanks again, Jim!

73,







>Some differences between Wolf and Jason:
>
>Weak signal capability: Wolf will work at lower signal levels than Jason. 
>Of course, you could make a Jason version with longer tone duration that 
>would work at lower levels; but whether this is a good thing depends what 
>you want to use it for.
>
>Bandwidth: The "raw" Wolf BPSK signal has significant sidebands extending 
>over several hundred Hz bandwidth - not acceptable for European LF, but OK 
>in the US where powers are lower and more bandwidth is available. It 
>requires a few 10s of Hz bandwidth when the proper envelope shaping is 
>done, which is still a lot for the narrow Eu allocation, and adds 
>considerably to the complexity of the TX. The Jason signal essentially has 
>a bandwidth of 4Hz, without requiring envelope shaping.
>
>QSO capability: Jason has TX/RX capability built in, and works in "real 
>time", which makes it easy to have a Jason QSO. Wolf signal processing is 
>done off line, so is rather time consuming and tricky if you are 
>attempting a 2 way contact, although it allows for very flexible 
>post-processing of the signal.
>
>Timing and frequency accuracy: To achieve the benefits of integrating the 
>signal over a long period, Wolf requires accurate calibration within a few 
>parts per million - quite difficult to achieve when an amateur rig and 
>sound card is used, and requiring careful calibration procedures. Jason 
>can cope with a couple of orders of magnitude poorer accuracy, which means 
>normal Ham-type receivers and run-of -the-mill sound cards do not present 
>a problem. The Jason waterfall display allows you to make frequency 
>corrections on the fly.
>
>GUI: The Jason GUI is very easy to use; most people are used to having a 
>graphical presentation, although both programs transmit and receive text 
>messages.
>
>So Wolf and Jason are like chalk and cheese, and which one is better 
>depends what you are using it for. Wolf is currently better for extreme 
>weak signal use, Whilst Jason is much easier to implement and use, at 
>least from the European LF perspective.
>
>Cheers, Jim Moritz
>73 de M0BMU
>
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Les Rayburn, director
High Noon Films
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