Am 16.03.2010 14:08, schrieb Paul Nicholson:
Thanks,
that was a good field trip in the best amateur radio
tradition. Ironic how we are at the same time using the most
hi-tech, but also the simple batteries, kites, wires, big coils, etc
that Marconi would have been quite at home with. It is a nice
mixture.
Yes, this is a good analogy. I've never seen that before out of this
point of view ;-)
What is
the exciter you are using - the silver box with the LCD
display?
The silver box is the DDS-VFO. It has a rectangular and sinus output. I
integrated a ICL7667 MOS-FET driver to increase the output current and
voltage (12V/ abt 4A).
Since the duty cycle of the output is not exactly 50% i choose
17,9400kHz and added a CMOS 4013 as a frequency divider on the PA
board. The PA transistors are still IRFP064N (2 pcs).
And
when the kite is up and tied to the car, and the wind picks up,
how do you pull it down again - do you have a winch - or a knife?
Yes, i have a winch but you can also just take your hand since the
braid is rather big, no problem ;-)
Your
website mentions improvements for the next run, what do you
have in mind?
I plan to ease the link to key the PA. It will be an optical component
(SFH750V) that is driven by the RS232. On the PA i will use a SFH350V
just to drive a transistor that keyes the PA.
So i avoid EMC problems with the PC. That may be an issue when
operating with abt 20kV rms in a distance of some meters...
Furthermore i plan QRO, of course ;-) And i plan to integrate an
amperemeter into the water barrel, that good for adjusting to resonance.
Then, i plan to get the permission for a 300m vertical antenna!
With at least 10dB more ERP (+3dB due to QRO), the theoreticals can
calculate what will be possible :-) Maybe a signal at RN3AGC or in the
USA?
FSK
should be better than simple keying.
Yes, definitely but my VFO cannot simply be varied in the QRG by the
PC. There is an incremental wheel to change the QRG. Maybe i can modify
it so that it changes by one increment at the positive edge of the DFCW
signal and go back at the negative edge.
Alternatively i could use Spectrum Lab by DL4YHF as a frequency
generator but i assume that the output signal is not rectangular. If it
is sinousidial and i apply it to a high gain OP amp and/or a comparator
stage, the frequency may be not accurate any more!?? Wolf, any hints?
Feeding the frequency to the PA by an optical link wouldn't be a
problem at all...
I think
the ERP is about the same power as a small LED,
or less? Amazing to think that is detectable 850km away.
A standard LED has about 20mA and 1,8V, so 36mW but i don't know about
the ERP of it ;-) We have to keep in mind that we need a long time to
generate that dash in the grabbers.
This should be improved since transmitting a call sign or something
like "TNX LF GROUP 73" :-) would require a whole day and more in
QRSS240...
Paul, do you have ideas to even improve your RX or are you at the
limit? :-)
I am motivated to see what will happen at night and what DX can be
reached.
If
anyone is transmitting from home (uQRP?), I can set up very
long non-coherent averaging (days?). That is something else
to try for someone. An alternative to sending messages serially
is to send data bits in parallel, multi-frequency, the whole
message received in one long averaging. Many things to try!
Yes, a good idea! But there will be some problems for those with
antennas with less C to get a high-L coil that can handle the voltages.
But Markus showed us how it works! :-)
I am interested in what the others will do on the TX front...
73, Stefan/DK7FC
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