John, there is a LOT of misunderstanding and plain wrong info out
there concerning the different modes available in K1JT's "WSJT"
package.
Joe has tried to match up different modulation techniques to different
propagation modes. The entire WSJT package was originally designed
for EME operation (JT-modes) with a digital nod toward the "high speed
meteor scatter" guys (FSK441). Be aware that the HF community was way
late to the WSJT party but has now seemed to 'hijack' the entire suite
of products. This is why we're seeing people touting modes on 6M and
above that really don't belong there. VHF/UHF guys have been using
WSJT for, I would guess, almost 15 years.
To be brief, the different 'products' in WSJT can be broken out into
two groups. A group for very low level but fairly constant signals
and a group for extremely quick bursts of energy. These groups are
very different and use very different types of digital techniques.
The "low level" group consists of JT6/JT9 and ISCAT modes (and others,
but these are the primary ones). The "quick burst" group is mainly
FSK441, but there are others. There is no technical reason one can
not use ANY of the "low level" modes for signal with those
characteristics. The same for the "quick burst" modes. However, as
stated earlier, K1JT has matched up the modulation schemes of the
various modes to the characteristics of certain propagation types and
bands. So, while any of a certain group may work, some work much
better then others.
Typically, if you are interested in meteor scatter, you will use
FSK441, no matter what band you are on. if you are trying to work
EME, you will use one of the JT65 subsets (a,b,c) depending on the
band. Each subset has different characteristics that better 'lines
up' with the targeted band. JT65a on 6M and JT65b or c on higher
bands (depending on the band). If you are looking to work weak tropo,
the EME type schemes work very well. After all, weak tropo has many
of the characteristics of EME. Also, as an alternative, I have found
ISCAT to be very valuable for tropo work, but be aware there are TWO
ISCAT modes, each one tailored for something a little different.
JT9 was designed for HF. Will it work on higher frequencies ? Yes,
probably. But, ask yourself this: When you are trying to work a guy
without a pre-arranged schedule - just some guy who might be calling
CQ - don't you want to be fairly certain you can guess what mode he
might be on ? Proliferation of modes is a negative when signals are
very weak. You want to be SURE you know what mode to use in a certain
circumstance on a certain band. STANDARDIZATION is key. "Flavor of
the week" digital modes mean nobody will know what the other guy might
be running. Not knowing means no QSO. You can't just listen to a
signal and say, 'Oh, he's running "PSJT9HF65X-441a", when that signal
is at the noise level (or below), which is where these modes excel.
Learn the standards for a band and choose the best digital modulation
for the job. K1JT has a pretty big head start on most everybody else
when it comes to deciding the best mode.
Jay W9RM
Keith J Morehouse
Managing Partner
Calmesa Partners G.P.
Montrose, CO
On Tue, Feb 18, 2014 at 7:29 PM, John Santillo <u1004467@warwick.net> wrote:
> Hello all,
>
>
>
> I understand that FSK441 is primarily used for meteor scatter and JT65 is
> for Tropo and HF too. But for VHF contesting especially on 2M and above
> isn't JT65 the preferred mode for weak signal work?
>
>
>
> I would think the ionization from small grained sized meteors don't produce
> enough ionization for 2M and above to reflect off the trail. I would think
> JT65 would be better for 2M tropo and above but I'm looking for opinions.
>
>
>
>
>
> 73,
>
>
>
> John
>
> N2HMM
>
>
>
> _______________________________________________
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