Stefan,
Transmitting unlis is no crime anymore.
It's comparable to illegal parking, nothing more...
Look on the so called free bands or eco Charlie bands on sw full of amateur
radio stns from DL, UK, F, PA0... Also German stns were active on 502 kHz in
QSO with UK in the beginning of mf amateur radio.
So why the story with the fundamental?
Just concentrate your tx power on 17 kHz !
:-)
Christian Groeger
Stefan Schäfer <[email protected]> schrieb:
>VLF,
>
>That 3rd harmonic is on the 17 km band. Do we have any experiences about
>local diurnal propagation?
>
>Sooner or later there will be misunderstandings and some will say i am
>transmitting on 17.265 kHz although the TX runs on 5.755 kHz!
>
>I had a thought about that. 3rd harmonics are generated by all HF
>amateurs, but we all ignore them. We actually can ignore them if they
>are well attenuated but that doesn't mean that they do not exist! BTW
>has someone ever tried to decode a 3HD signal (that name, 3HD, is just
>for fun, like the Dreamers band, a shortcut for 3rd harmonic detection,
>reminds on HD quality movies or 3D glasses ;-) ) in OPERA mode?
>
>_Example:_ When someone transmits a legal (!) QRO signal of 750W (in DL)
>on the 160m band using a typical lambda/4 vertical (which is radiating
>the 3HD signal because there it is lambda 3/4 and thus low impedant
>too), using a 60 dB attenuating low pass filter, which is quite a good
>supression, then there should be a 750uW signal on the 53m band, which
>could be detected in some distance, probably several 10km when using
>slow modes like OPERA-4 (WSPR will not work so easily here). Receiving
>this 3HD signal is certainly not absolutely strictly forbidden :-) So
>actually the amateurs can do legal QRPP tests in slow modes on 53m,
>can't they? Would you think that it is ethical unjustifiable to try to
>receive such a signal if it is there anyway and legally generated?
>
>_Example2_: PA0WMR is often TXing OP8 on 478.x kHz, making 2000km
>distance. If someone in say 30 km distance can receive him on 1434 kHz
>(if there would be no AM BCD stn), close to the decode limit, would
>something be wrong with this test?
>
>I know from WSPR QRP transmissions from DL to VK on 15m with 0.1 W TX
>power!! So i assume a 3HD signal could be detected in a few 100 km, maybe?
>
>Below 8.3 kHz there is no TX power limitation and we can certainly
>assume that no interference is caused to anyone at 3HD, just like in the
>above example (53m band ( i never tried it)).So why not trying to do
>tests like these today? The noise floor is much lower there which
>improves the situation :-)
>
>73, Stefan/DK7FC
>
>Am 02.02.2014 18:15, schrieb Markus Vester:
>> Stefan,
>> your third harmonic is clearly visible in Holland
>> http://www.qsl.net/pa1sdb/
>> and here
>> http://www.df6nm.de/vlf/vlfgrabber.htm
>> Started spot-on 17265 Hz, now another peak is coming up 15 mHz up.
>> Good luck,
>> Markus (DF6NM)
>>
>> *From:* Stefan Schäfer <mailto:[email protected]>
>> *Sent:* Sunday, February 02, 2014 3:27 PM
>> *To:* [email protected] <mailto:[email protected]>
>> *Subject:* Re: LF: DX VLF experiments in 3HD
>>
>> Markus,
>>
>> I am 16 dB stronger now!
>>
>>
>> Am 02.02.2014 14:52, schrieb Markus Vester:
>>> So what should be expected here? Scaling the fieldstrength from 1 km
>>> to 180 km (1/r^3 to lambda/2/pi, 1/r thereafter), the signal should
>>> be 82 dB weaker here on 5.755, and 63 dB weaker on 17.265 kHz.
>>> Neglecting ionospheric contributions (not really correct), and
>>> assuming similar noise levels (though 5.5 kHz is much affected by
>>> railway QRM here), my SNR in 0.47mHz should theoretically have been
>>> 35 - 82 + 10 dB = -37 dB on 5 kHz and
>>> 50 - 63 + 10 dB = -3 dB on 17 kHz.
>>> So while a detection on the fundamental seems pretty hopeless, the
>>> third harmonic should already be getting close.
>> Yes, the QRN and QRM is much lower in 3HD :-) Why didn't we get this
>> idea earlier???
>>
>>> What is the inductance of the loading coil?
>> Ehm , i didn't really measured it, it's just trial and error.
>>
>>> Would be interesting to see a picture of the scope trace picked up
>>> near the antenna ;-)
>> Looks quite good but could cause misunderstandings...
>>
>> The amperemeter in the coil shows 350 mA now! There is some kind of
>> selfoscillations, audible. Thus i do not rise the power even more.
>> Have to search, find and fix this problem later. The AC voltage from
>> the vari-transformer is 110V now, so there is room for at least
>> another 6 dB. Power is in the range of 100W now.
>>
>> I'm going to measure the strength at home now. Hopefully the signal is
>> audible :-) Yesterday it was still weaker than the mains hum, so far
>> away from any interferences!
>>
>> 73, Stefan
>>
>>> Best 73,
>>> Markus (DF6NM)
>>>
>>> *From:* Stefan Schäfer <mailto:[email protected]>
>>> *Sent:* Sunday, February 02, 2014 2:06 PM
>>> *To:* [email protected] <mailto:[email protected]>
>>> *Subject:* Re: LF: DX VLF experiments in 3HD
>>>
>>> Markus, VLF,
>>>
>>> Am 01.02.2014 20:34, schrieb Markus Vester:
>>>> Stefan,
>>>> running two 478 µHz "6000" windows centered on 5755 Hz (on the
>>>> grabber, but much QRM here) and also 17265 Hz (offline) which seems
>>>> more quiet. So hoping for a long carrier...
>>> Well, i hope that 16 hours key down were long enough ;-)
>>>
>>>> On which of the two frequencies would you expect to radiate more power?
>>> I don't know. But the harmonic signal is very weak and cannot cause
>>> interferences for JXN or HWU or SAQ or GBZ...
>>>
>>> I've done measurements at home, 950m distance, of that _5.755 kHz_
>>> transmission and saw that the signal was very weak, see attachment.
>>> Just 50 dB SNR in 4.5 mHz at 3HD. The TX power was just 15W at the
>>> end. Also the frequency response of the active antenna + soundcard is
>>> attached.
>>>
>>> The experiments are very interesting here and i like to do the
>>> measurements. Despite rain the coil was on the top of the building
>>> and on air. It was just covered by a trash bag. The voltages are very
>>> small...
>>> I just hang out a 30cm long wire connected to a probe of the
>>> oscilloscope and so the voltage waveform of the antenna wire. It
>>> nearly looks as expected :-)
>>>
>>> Now i got another idea. There is a 2.2 uF WIMA MKP-10 capacitor in
>>> series to the output of the H bridge, just to protect it against
>>> damage in case of a DC output. Now i've disconnected the antenna and
>>> tuned for the series resonance of this C and the L of the primary
>>> winding of the loading coil. The resonance is at 1.77 kHz. This
>>> allowed me to calculate a much smaller additional series C which
>>> helps to attenuate unwanted frequency components, i.e. makes the
>>> spectrum cleaner and provides a lower impedance on the wanted
>>> frequency :-)
>>>
>>> There is really no alternative to that H bride PA which works from 10
>>> Hz to 100 kHz :-)
>>>
>>> in a few minutes i will be on air again for a longer time, hopefully
>>> with a much stronger signal.
>>>
>>> Maybe you can detect something of that 5.755 kHz transmission.
>>>
>>> 73,GL, Stefan/DK7FC
>>>
>>>
>>>> BTW Today I have updated SpecLab from version 2.79 b08 to b10 (Jan
>>>> 26), and it seems that GPS 1-pps sync is finally working well now,
>>>> even with 42 µHz resolution.
>>>> Good luck for the test!
>>>> 73, Markus (DF6NM)
>>>>
>>>> *From:* Stefan Schäfer <mailto:[email protected]>
>>>> *Sent:* Saturday, February 01, 2014 5:46 PM
>>>> *To:* [email protected]
>>>> <mailto:[email protected]>
>>>> *Subject:* LF: DXl VLF experiments in 3HD
>>>>
>>>> VLF,
>>>>
>>>> This evening and night i'm planning to transmit on _*5.755 kHz*_,
>>>> using the large antenna, the large coil and the large PA :-)
>>>> I don't know what can be expected and how the system works at that
>>>> frequency. Actually it is just _a first test for playing arround and
>>>> doing some measurements_ :-)
>>>> If some nearby stations want to give it a try, maybe even in *3HD*,
>>>> then don't hesitate :-)
>>>>
>>>> 73, Stefan/DK7FC
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