Message-ID: <4CF6813A.7030600@telus.net>
Date: Wed, 01 Dec 2010 17:09:14 +0000
From: Scott Tilley <sthed475@telus.net>
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References: <4CF65D62.21930.96EDB2@mike.dennison.ntlworld.com> <4CF672A2.6040506@iup.uni-heidelberg.de>
In-Reply-To: <4CF672A2.6040506@iup.uni-heidelberg.de>
Subject: Re: LF: QRSS120 and grabbers
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Hi Gents

The secret to these long haul QSOs is using fairly fast speeds to=20
exchange calls and timing the exchanges to known periods of good prop.

JA7NI and I felt that faster speeds would have been possible based on=20
our observations during the QSO and beaconing tests.  In fact, I was=20
copying him on an Argo 3sec dot screen with O results during parts of=20
our QSO!  However, the big issue is destructive interference and other=20
variations in propagation this is what killed our QSO a couple of times=20
before we where successful.  The solution for me was to slow down the=20
final bit of the exchange to 120second dot and watch very closely=20
everytime the TX stopped to see if NI copied my RO.  As we are all aware=
=20
there is usually a time between two stations when prop will lift to the=20
best of the night, this is usually repeatable from night to night.  This=
=20
is the time to try and exchange at a higher datarate (ie. exhange=20
calls...)  the tough part is pulling together the final bit as often you=
=20
will run out of propagation or a deep fade occurs...  During our QSO=20
three hours passed before NI copied my RO at 120sec dot DFCW!

Beaconing before attempting the QSO helped us determine what would be an=
=20
optimum 'data rate' for each station should be and the best time of=20
night.  NI's TX rate was 30sec dot DFCW and mine was 60 sec dot DFCW.

So the moral of the story on 2200m is that nightly beaconing on a path=20
is the beginning of a QSO attempt as it provides useful information on=20
what the path will support and how each station's setup performs. Fast=20
dot lengths should be used to try and exchange the bulk of the=20
information and final RO, 73s etc can be pushed out to greater dot=20
lenghts to ensure correct copy even if conditions don't recover to=20
earlier levels during the attempt window.

So dynamic TX speed changes are good, and running multiple waterfall=20
speeds on RX allows you to be very adaptable as well.

73 Scott
VE7TIL CN89dk
http://www3.telus.net/sthed/argo/

On 12/1/2010 4:06 PM, Stefan Sch=E4fer wrote:
> Hi Mike,
>
> Yes, some thoughts:
>
> Am 01.12.2010 15:36, schrieb Mike Dennison
>> I believe the danger is to regard this as the 'optimum' speed for DX
>> working, simply because the S/N ratio is good.
> Is that really a danger?
>>   In practice, there is
>> another factor in play. There is often rapid and deep fading on a DX
>> path, often resulting in only parts of letters being received at this
>> speed, even though the peak signal is quite strong (see many of the
>> pictures of transatlantic reception regularly posted on this group).
>>
>> The situation becomes worse if the final aim of experimenting with a
>> path is to have a two-way DX QSO. Even exchanging minimal
>> information, a QSO will take several hours, during which time the
>> conditions must hold up.
> When was the last real QSO done in QRSS >=3D 30? I rember the contact=20
> between VE7TIL and JA7NI but most of the active people are just=20
> transmitting a character (representing their callsign) in beacon mode.=
=20
> I have never seen a "CQ ... K" in 60 or 120.
> So if one just wants to transmit a beacon signal it doesn't matter if=20
> there is some QSB. As an example, XGJ is monitored very often most of=20
> the nights. If the G would be lost (X_J)and in the next turn the J=20
> would be lost (XG_), anyway everbody would know it't (XGJ).=20
> Furthermore the DX interested OMs gets the confirmation on the other=20
> grabbers.
> If a QSO is wanted, i fully agree with your opinion. But a QSO means=20
> that both stations are sitting in front of the PC, so they can change=20
> the RX to the wanted QRSS/DFCW mode.
> Anyway, i am providing both QRSS-60 and QRSS-120 for TA and EU, so=20
> people may chosse what they like :-)
>> Take a look at VE7TIL's excellent DCF39
>> graph to see how short a good DX opening usually is - perhaps an hour
>> if you are lucky.
> ...which wouldn't be enough for a (real) QSO in QRSS-60 but enough for=
=20
> "FC" or "NM" or "NI" in QRSS-120.
>>
>>
>> The very few who have had transatlantic QSOs have used QRSS30 or at
>> most QRSS60. I am not aware of a successful two-way involving a
>> longer dot length.
>>
>> I would suggest that DX beacons and grabbers use a =3Dmaximum=3D of 60s
>> dot length (though a second grabber screen could be provided for 120
>> etc if desired). In my opinion this would be more likely to result in
>> useful propagation data.
> Done.
>> Any thoughts?
>>
>> Mike, G3XDV
>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>
> 73, Stefan
>
>