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Re: VLF: Long time transmission on earth antenna

To: [email protected]
Subject: Re: VLF: Long time transmission on earth antenna
From: Stefan Schäfer <[email protected]>
Date: Tue, 16 Nov 2010 21:11:29 +0100
Cc: Paul <[email protected]>, Bernd Grupe <[email protected]>
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Hello Markus, VLF,

Oh, indeed. Well, the earth antenna is a really broad band antenna, as seen. But the signal level at 134 kHz is rather small, when regarding distance and frequency ;-)
Anyway funny ;-)

Ok, there seems to be GPS in the forest, even when the GPS antenna is behind the car window. The TX power was arround 100W, the last 20 minutes even at about 200W. Distance to my grabber is 5 km. The antenna current was 440 mA at 100W, so the losses have been arround 520 Ohm, relatively low. The ground was wet.
The output transformer remained cold and the SMPS as well, the PA anyway. But i noted that the DC plug for my netbook is the wrong one so i have to exchange this, otherwise the netbook would shut down after some hours... Thus, the test was useful :-)

Ah, BTW, it was on 8970.00000, not on .00500

So, i hope i can do the 24 h transmission starting Thursday arround 16 UTC at 8970.00500 Hz, running 100W. Here i have attached a new usr file for this transmission (just a little change in the time stamp display), for those who want to participiate and need a usr file :-)

Well, 35 dB S/N, i just like it, even if its just 5 km :-)

73, Stefan/DK7FC

Am 16.11.2010 18:53, schrieb Markus Vester:
Hi Stefan,
since 16:54, you are painting a strong 8970 Hz trace on your own VLF grabber, about -69dB (35dB SNR) in the 4.5 mHz window. Interestingly, there is also a 15th harmonic at 134.55 kHz, which appears on your wideband LF grabber at - 80dB (20 dB SNR).
Nothing seen on the 0.95 mHz VLF grabber in Nuernberg yet, which may of course be due to me being near the null of your N-S oriented earth antenna.
Good luck,

-----Ursprüngliche Mitteilung-----
Von: Stefan Schäfer <[email protected]>
An: [email protected]
Cc: Paul <[email protected]>
Verschickt: Di., 16. Nov. 2010, 14:50
Thema: Re: VLF: Long time transmission on earth antenna

Dear VLF,

I will do some pre-tests today on the earth antenna (testing if GPS can be received in the forest and if the output transformer becomes warm in steady state when running 100 W RF key-down).

Before i will do a (new) short test on 1970 Hz. A loop antenna was built to receive on 1970 Hz. It has still no preamp but is directly fed into the soundcard, anyway... The antenna is now nulling out the strong QRM of the tram line near the institute and i hope for a better S/N.

After that about one hour or so on 8970.00500 Hz.

Starting time is in about 90 minutes.

If someone wants spontaneous to take part, you are invited. The 24 h transmission will then come hopefully in a few days, maybe wednesday/thursday...

73, Stefan/DK7FC

PS: Again note that this is a very weak signal test and cannot be compared with a kite antenna transmission. So do not wonder if the signal doesn't appear at 25 dB S/N in 4.5 mHz ;-)

Attachment: 24hExperiment on 8970 in 141uHz.USR
Description: Text document

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