Andrew:
Thank you for your thoughtful memo! We are in violent agreement. This said
I must bring several points to your attention.
It would be unfortunate to limit ourselves to just use of these two
relatively simple pieces of DSP software which at the end of the day are
really just narrowband power detectors in not that narrow a bandwidth.
The piece from my announcement that mentions these two pieces of software
was for domestic Canadian consumption. I am dealing with many amateurs here
who have no exposure or experience with LF and specifically they have no
experience with LF and using either of the mentioned software packages.
I feel there is a lot more to be gained by coherent integration
techniques.
Yes, certainly, the work today needs to be rethought and redone enough to
make optimum of very fine frequency control and specific benefit from the
knowledge of time to a high degree of accuracy. I have been emailing with
Bill, VE2IQ on this subject seeking to find out if he feels it is time to
move to the next level. Our discussions are very preliminary at this point.
Use of the VE2IQ software and other slow BPSK modes goes
some way towards this, but all suffer badly from the need for clock
recovery and tracking. The need to get initial timing information
throws away much of the usefulness of this mode.
Well, it is not now optimum in terms of what can be done today, but we not
only need to see what can be done today but what the "reach" might be that
would give us a real push forward.
The ultimate solution is to use GPS timing. I know quite a number of
operators in the US are now using GPS locked frequency and time sources,
and they are begining to make an appearance here.
Well I am sitting here with an old HP 5248L frequency counter with the guts
slowing coming out and the Oscillator awaiting the arrival of one of Brooks
Shera's boards to let my OEM GPS receiver stabilize the HP Oscillator to a
few parts in 10 to the -11th or so.
Having the
transition points of the bit intervals known precisely to the
microsecond (if the path length is known) leaves the signal recovery
task to be merely an integration over whatever time is needed for the
bandwidth with no lockup or preamble phase.
Certainly. I understand the need, I do not have all the skills to pull it
off alone. But I can promise you that my transmitter here will meet all
such requirements. I have moved a Sulzer Labs high stability frequency
standard into my remote HF radio site, from which I will transmit LF signals
in Westport, and it will hold to a couple of parts in 10 to the -10th as it
is without further help.
TAPR have a range of GPS and frequency locking projects / kits. Who in
the US Lowfer community have the DSP hardware, even if not the
programming skills, to experiment with these techniques. Ideally, if a
Motorola DSP 56002EVM module, GPS receiver and carrier frequency known
accurately to milli Hz are availble software can be shared and
experiments made with known equipment capabilities.
Take this as offered, I am in an astonishingly high level of agreement with
you. My side here is ready, the basics are in place here to develop a
working system to a new level of accuracy. TAPR, as of a moment ago, do not
seem to have completed the work with the TAC2 to stabilize an oscillator.
Brooks Shera's work is available now and I am just waiting for him to let me
know the final price for the pieces and then he will ship be the bits I need
here. Please take a look at Brooks's site
http://www.rt66.com/~shera/index_fs.htm
I hope this will be useful to you.
Some people are going to spend lots of time/money/effort on antennas and
PAs, why not put a similar effort into signal processing as well. So
what if it takes 10 hours to send a message, at least it will have been
sent from a station that does not have a farm on which to erect huge
antennas.
Andy, if we co-ordinated this announcement and your response we could not be
in a stronger level of agreement.
Lets identify one thing. The TransAtlantic II effort this coming fall will
seek to do things with what we have now. We have no time to do more (in my
opinion), it is pushing us hard to get ready for November. I drove 150
miles round trip today to interview a chap who used to tune up LF and
Broadcast Band (ours) antennas. I have a tad more skill in this area
tonight - and a pile of notes.
When it comes to the next level, this is were I stand now. My friend Mitch,
VE3OT is working the issues with me. My station here is already taking
shape for the next level, I want to be part of this activity very much as it
is what attracted me to the LF scene in the first place. I have written
previously to David, G0MRF and to Dave, G3YXM about the use of AD9832,
AD9835, and AD9850 DDS devices so we could have milliHz control of the DDS.
David was kind enough to help me solve the exciter problem with one of his
boards so the situation for November is settled. Just this morning I have
had an offer from the US to get some boards that will fit the AD9835 device.
We are trying to see if we can fabricate a board here that will work with
the device. I have never worked with these thumb nail sized devices, but we
are going to keep going till we have RX's and TX's that are slaved to GPS
and we will have them here by this winter when we get back from VO1.
For a start, until we have something better, I will start with Bill, VE2IQ's
work. His system has let him hear the TEXAS LowFer beacon at his home north
of Montreal. His GRAB capability is working here now. In the next few days
we will start to test this system over some 300 mile path. If there is a
way to go further, I want to be part of it and will do my best to be ready
when anyone else is ready.
My last comment. On February 11th we missed a chance to probably bridge the
North Atlantic from here to the UK. I am not able to be here in the shack
during all hours of darkness but I sure would like to work you, computer to
computer, the next time we have a repeat of February 11th. I have a great
huge fire bell here in the basement that I would really like to hook up to a
computer that would go off when your signal is detected over here. Lets do
it.....
Larry
VA3LK
I am also sending a copy of this email to Mitch Powell and Bill de Carle,
please include them in any reply
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