Hi MF,
Thanks to the many spotters and the discussion. Indeed, there were 53
stations detecting the signal. Those are the ones above 1000 km distance
| Timestamp |
Call |
MHz |
SNR |
Drift |
Grid |
Pwr |
Reporter |
RGrid |
km |
az |
# Spots |
| 2019-01-25 18:46 |
DK7FC |
0.475684 |
-26 |
0 |
JN49ik |
0.01 |
LA9IY |
JP53 |
1567 |
4 |
1 |
| 2019-01-25 19:16 |
DK7FC |
0.475683 |
-25 |
0 |
JN49ik |
0.01 |
LA2XPA |
JP33 |
1565 |
357 |
4 |
| 2019-01-25 21:22 |
DK7FC |
0.475683 |
-28 |
0 |
JN49ik |
0.01 |
GM4OAS |
IO76cx |
1274 |
317 |
8 |
| 2019-01-25 22:40 |
DK7FC |
0.475683 |
-30 |
0 |
JN49ik |
0.01 |
EI0CF |
IO65ih |
1263 |
307 |
18 |
| 2019-01-26 00:52 |
DK7FC |
0.475660 |
-23 |
0 |
JN49ik |
0.01 |
LA8AV |
JO59cs |
1153 |
4 |
1 |
| 2019-01-25 20:34 |
DK7FC |
0.475683 |
-28 |
0 |
JN49ik |
0.01 |
GM3YXM |
IO75xc |
1070 |
311 |
9 |
| 2019-01-25 18:10 |
DK7FC |
0.475683 |
-24 |
0 |
JN49ik |
0.01 |
LA3EQ |
JO28xj |
1012 |
351 |
22 |
So far the transmissions are still decoded, so the time offset seems to
be small enough.
I had to hurry building up the system last afternoon because i left the
QTH a few minutes later. So i just wanted to get some antenna current
and moderate TX power but i didn't match it accurately to 50 Ohm. The
PA losses are very small, maybe we can assume 40 W RF power. With the
measured 1.6 A we seem to have 15.6 Ohm on the primary side and then
0.2 Ohm on the secondary side, just as Rik estimated.
The antenna is in the 4th floor and it is an old house, with wooden
stairs and not to massive walls. I am quite sure that the wall which
carries the loop does not have internal steel grids. The loop is quite
close to the outside wall in north-west direction. So there is more
stuff causing some attenuation into the south-east direction. But i
would expect an overall attenuation by all the lossy stuff arround the
loop rather than a directivity given by the lossy stuff. Anyway, it
seems the loop performs is better into the north-west direction. Or is
it just because the QRN levels are likely to be higher in Italy than in
Scotland? And the Alps making an effect?
All in all we see that anyone can be QRV on MF, even with very poor
antenna possibilities. That is the good message :-) Oh and that system
is totally immune against rain, storm, and even thunderstorms! You can
even use the losses to heat the home, so is it a loss at all? ;-)
The limiting factor in that system is the capacitor! I use 2.2 nF +6.8
nF + 1090 pF variable C. Maybe it can be optimised by using 10 x 1 nF
WIMA-FKP-1-2000. The voltage is about 450 V, which is well below the
700 V limit.
Maybe two turns of litz (keeping the loop size) would make a better
antenna, with lower currents and lower losses in the capacitors. The
thermal capacity and surface of the loop is high so that will not limit
the system....
73, Stefan
Am 26.01.2019 08:49, schrieb [email protected]:
Hi
Stefan,
I just checked on WSPRnet and red you got plenty of reports from your
QRP activity so my 3 spots are a drop in the sea.. but
3 spots:
| Timestamp |
Call |
MHz |
SNR |
Drift |
Grid |
Pwr |
Reporter |
RGrid |
km |
az |
| 2019-01-26 03:34 |
DK7FC |
0.475683 |
-27 |
0 |
JN49ik |
0.01 |
IK1HSS |
JN35tb |
493 |
190 |
| 2019-01-26 03:28 |
DK7FC |
0.475683 |
-25 |
0 |
JN49ik |
0.01 |
IK1HSS |
JN35tb |
493 |
190 |
| 2019-01-25 16:10 |
DK7FC |
0.475683 |
-27 |
0 |
JN49ik |
0.01 |
IK1HSS |
JN35tb |
493 |
190 |
the rx is a direct conversion rx with a simple bandpass input filter..
it is sensitive but lacks of course of image rejection and other
features that make a real receiver another thing :-)
The strange point is how the 3 spots are spreaded in the period: 16:10
03:28 03:34..
Some years ago I made some trials on 137 kHz using an (outside) 2 turns
loop (5x5m) and it was funny
73, Marco IK1HSS
----Messaggio originale----
Da: [email protected]
Data: 25-gen-2019 15.23
A: <[email protected]>
Ogg: LF: TXing WSPR/MF on an indoor loop
Hi MF,
A few days ago i took some RF litz wire and built a loop that is now
hanging on the wall inside my home, just 1m besides the bed :-) (no XYL
here spoiling the fun). The loop is beaming to about 150/330 deg.
After playing some days on 160m (an unusual high frequency, witch feels
very strange. And the band is full of unknown callsigns!!) i did now
move down to more or less low frequencies, the 630m band!
About 10 nF is needed to series resonate the loop. It has about 2m x 2m
of size. The antenna current is not stable because the WIMA FKP-1
capacitor becomes warm during the 2 minute WSPR sequence. But the
maximum current in the loop is 14 A. That explains why the cap becomes
warm. A small parallel variable capacitor tunes to resonance. It is
tuned so that the upheating capacitor runs into the resonance point in
the middle of the WSPR sequence, then it runs out of the resonance by
upheating further. It can cool down during the following quiet periods..
14A into a 4 square meter loop at 475.7 kHz, how much ERP is that? The
PA consumes about 3.5 A at 13.8V, i.e. about 50 W.
The system will run over the weekend, even during daylight. The signal
generator is a Raspi which will have no internet connectivity from now
on, so let's hope the time offset stays inside the accepted range for
this experiment.
What will the best distance be? So far the band is closed but i'm
optimistic to crack the 1000 km distance with this QRP setup.
73, Stefan
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