Hi Stefan
In the past three years since I began prolonged 'low noise' listening
November has traditionally been the beginning of good opportunities for
EU/VE7 DX. However, DCF39 has surprised me this year with decent
showings already! A couple of nights ago it reached audible levels!
This isn't a new effort, G3PLX and I worked on a similar study about 6
years ago but I and he where limited by noise and a small TX antenna in
my case and him by a limited LF RX system.
I'd tweek out that system of yours and be ready to lobe some RF over
this way as I have a feeling that we may get some good opportunities
this season... Timing is key...! You need to be ahead of the curve here.
My personal goal is to see if it is possible to detect an amateur EU
station in VE7. I have no concerns about the usability of the signal
until we demonstrate that its even possible.
As a suggestion on how to get QRO with 100% keydown, consider using many
smaller stages combined to produce lots of power rather than one stage
pushed to the edge of meltdown. This strategy reduces the need to
stress a single stage when pushing everything you can out of it. My
MOALFA is capable of 2KW keydown all night long and uses 4 stages
combined into one output. I use a lumped four port Wilkinson Combiner.
As an added 'bonus' you get 'free' output filtering without the need
for more components (and loses). Jay, W1VD has a similar design in
which he uses a transformer arrangement to do the combining which allows
him to use it on 600m but does require additional output filtering for
each band, a classic engineering compromise!
With my combined stage amp the only time I lost a transistor was when I
melted the dummy load during qualification testing years ago... Since
then I've logged hundreds of hours on the same transistors.
I believe the DECCA TX also uses a combiner approach to achieve high
reliability at QRO.
Another advantage is you can build a couple of identical transmitters
and separate them for other tasks etc. VE7SL and I did this during one
of our first ZL attempts years back.
Just make sure you use one LO path and only ONE digital division device
to drive the driver ICs. The reason for only one digital division
device is based on the fact a Type D flip flop (or otherwise) can start
in any one of four phases on power up. If you have two as in the case
of a two complete TX combiner situation you'll need to reset the power
on one until it matches the other...
GL over there!
73 Scott
On 9/22/2011 6:10 PM, Stefan Schäfer wrote:
Hi Scott,
A "6000" grabber on LF. I never thought that this will come truth ;-)
Well, to leave a trace there i should TX at least 1 hour key down.
Currently DCF39 rather shows poor levels and i have to optimise my
variometer, so it will take some time until i'll try. But i'm watching
your DCF plot and will think about it. Actually the system can stand
such a veeery slow transmission but i don't want to leave it
unattended for that first test...
You said November is about the best month for DL_VE7 ?
73, Stefan/DK7FC
Am 23.09.2011 00:36, schrieb Scott Tilley:
Hi All
I've completed the preliminary configuration of the long integration
grabber.
Presently it can be found by clicking on the 'grabber 1' button of my
website and looking under the main grabber window.
It's running with a 424 uHz FFT bin width. Each pixel takes 600
seconds... You'll want to ensure you have a nice soft seat to be
sitting on the edge of to watch this grabber :-)
Center QRGs are presently:
136170 +/- 0.2Hz
137780 +/- 0.2Hz
Please advise if QRGs need adjustment to coordinate with
international activity.
Comments welcome.
73 es gl
Scott
VE7TIL CN89dk
http://www3.telus.net/sthed/argo/
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