Hi John and all,
On 8/8/2017 12:19 PM, John Zantek KE7B wrote:
This past weekend, I attended the Pacific NW DX Convention, where the buzz
of JT/FT was tangible. ... The
biggest news for me was the talk about the upcoming DXpedition to Mellish
Reef (VK9MA) and the stated intention to try JT65 and/or FT8 on one of the 5
positions. Of course, RATE is always the #1 issue with DXpeditioners and
Contesters. I believe this may be the first great opportunity for WSJT to
succeed for a major DXpedition. I spent some time talking with the team
leader and others about expectations. Not surprisingly, we cannot expect
the team to run QSOs conventionally.
Below is the summary of their thoughts. Again, we can't insist that they
run their Q-exchanges conventionally as WSJT is designed, but they are open
to some moderated feedback. I promised I would provide their input to the
Developers and get them a summarized response.
Thanks for bringing up this important topic for discussion. We (the
developers) have thought about these issues quite a bit, over the years;
but they are especially important now because of the rapidly growing
popularity of FT8. It's clear that in some circumstances FT8 can be a
very attractive mode for DXpeditions and contesting.
Here are some initial reactions to your summary ideas for VK9MA. Of
course they are subject to revision after further discussion here!
1. QSO rate is important, so use FT8, not JT65! (Four times faster,
only a few dB less sensitive; other characteristics mostly the same.)
2. Pick a nominal FT8 frequency for each band different from the
default, every-day FT8 window for that band. Plan to use at least 4 or
5 kHz of spectrum, and make sure you have an Rx filter that will support
this bandwidth.
3. My inclination is that VK9MA should call CQ (or maybe "CQ UP") near
the low end of the selected range. Callers should spread out anywhere
in the 4 or 5 kHz range above that frequency.
4. QSOs should proceed as in one of the following examples. Remember
that FT8 T/R sequences last for 15 seconds.
##########################################################################
1. CQ UP VK9MA QH72
2. VK9MA K1ABC -15 | VK9MA W9XYZ -13 | VK9MA WB6DEF -07
3. K1ABC VK9MA R-12
4. VK9MA K1ABC RRR | VK9MA W9XYZ -13 | VK9MA WB6DEF -07
5. W9XYZ VK9MA R-09
6. VK9MA W9XYZ RRR | VK9MA WB6DEF -07| VK9MA G4AAA -11
7. WB6DEF VK9MA R+01
##########################################################################
##########################################################################
1. CQ UP VK9MA QH72
2. VK9MA K1ABC FN42 | VK9MA W9XYZ EN37 | VK9MA WB6DEF CM88
3. K1ABC VK9MA R QH72
4. VK9MA K1ABC RRR | VK9MA W9XYZ EN37 | VK9MA WB6DEF CM88
5. W9XYZ VK9MA R QH72
6. VK9MA W9XYZ RRR | VK9MA WB6DEF CM88| VK9MA G4AAA IO90
7. WB6DEF VK9MA R QH72
##########################################################################
VK9MA starts a run by calling CQ (transmission #1). It's optional
whether this message should be "CQ VK9MA QH72" or "CQ UP VK9MA QH72".
Possible considerations include these:
- With the present FT8 decoder the first form (without "UP") can be
decoded at ~1 dB lower S/N than the second form.
- DXpedition instructions can tell everyone, in advance, to spread out
upward in frequency by (say) 4 or 5 kHz. In the above examples I've
shown three callers in each even-numbered sequence.
- Lids calling on VK7MA's frequency should not be a serious problem,
since they will be on the "other" timed sequence.
Note that as long as repeats are not needed, VK9MA makes only one
transmission to each caller: Tx#3, #5, #7, ... in the above lists. The
maximum possible QSO rate is therefore 2/minute or 120/hour.
Note that VK9MA does not proceed to the next caller until receiving
"RRR" and logging the QSO. In the first sequence of example QSOs, if
Tx#4 is not received then #5 should instead be a repeat of #3. This
message should continue to be sent until the "RRR" is received (or the
VK9MA op gives up and calls someone else).
Note that more information is being exchanged in these QSOs than in the
normal DXpedition QSO where everyone is "599". There's no reason not to
send either a real signal report or a locator -- as in the second list
of example QSOS. Space for these basic bits of information is anyway
reserved in the protocol. Although it's less familiar as a QSO
procedure to many HF ops, sending a locator rather than a report has one
big advantage: it allows reverse-beacon sites like PSK reporter to
display real-time maps showing where signals are being copied,
world-wide. Certainly this is much more useful information than signal
reports hardwired to "599".
The example message sequences shown above are not far from those already
supported by the FT8 "Auto Seq" facility. My preference, the forms
using 4-character locators as the "exchange", was in fact designed for
use in North American VHF contests -- and I think it already works as
outlined above when "Contest Mode" has been selected on the *Settings |
Advanced* tab. We'll check this, to make sure, and amend it if
necessary. If other operator convenience features can be built in that
would make it even easier for DXpedition ops or contesters to approach
the 120 QSO/hr limit, we'll be happy to work on those, as well.
A final piece of important advice for the DXpedition ops:
Get some experience with FT8 and its contest mode before you depart. We
think WSJT-X is easy to use -- but like any skill, top performance
requires dedicated practice.
Comments and suggestions are welcome.
-- 73, Joe, K1JT
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