can we find somewhere an English version of the videoclip related to the Grimeton antenna (“The multiple antenna”) that is under “The Alexanderson transmitter” or at least its speech translation in English ?
Not so fluent in Swedish…
Question 1: The earth system is about 60 cm below the surface
Question 2: We guess that the reason is to obtain as low total antenna resistance as possible. The antenna current is lead to the earth system in 80 points, which means that the current in each connection was less than 10 A at full power. We have no simulation model of the antenna.
Thank-you so much for your clear explanation.
This suggests to abuse of your kindness for two related question more, if possible.
1) i have seen agricolture activities performed under the antenna : which is the depth of the buried ground network ?
2) the method that you have described for linking coils to ground network at tower 2-5 is really interesting. As the reason of this is not clear to me, do you have perhaps some simulation model (4nec, EZNEC, Feko…) of the antenna in order to play a bit around ?
In any case congratulation for the effort. I Will listen Grimeton in Christmas !!
Thank-you Fredrik for your so fast answer.
I have already read the document that you have pontented to my attention.
Unfortunately, differently from what shown in the clip, nothing seems to be there related to the antenna ground network (I was especially interested in it) and to the special settings of the first mast (elevated ground plane and – If I’m not wrong visiting it two weeks ago – different vertical radiator setup).
Do you have maybe some document in English to share related to this topics ?
Thank-you very much for any help
Best regards
Ugo Poddine (IU1IPB)
Dear Ugo,
Here’s a short desciption of the antenna and the ground network:
There are 6 antenna towers, each 127 meters tall, with a total distance of about 2000m between tower no 1 and no 6. The six towers are oriented for best radiation towards New York, though, we have not seen any document that confirms this. The radiation pattern of the antenna is almost omnidirectional, with a slight increase in NW-SE direction and a slight dip in the NE direction.
Along the entire antenna there is a 500 meter wide ground grid and the coils at the towers 2-6 are connected to the ground grid via overhead lines, 100m out from the towers, 7 connections on each side from each coil (no connection near the coils).
At tower no 1 it is a bit different. The coil is connected to the alternator and it is the alternator that is grounded. The alternator is connected via overhead lines to the ground line in 10 points, 5 on each side. The connection points closest to the station building are roughly 100-200 meters away from the buildning so you can assume that there is no ground grid close to the station building. Instead, overhead lines have been supplemented with extra lines closest to the station, which can then be seen as an elevated ground plane that replaces the missing ground line there.
The radiant parts of the antenna are almost vertical at towers 2-5. At towers 1 and 6, the top lines that goes up/down at about 45 degrees, is giving “useful” radiation.
Fredrik (with assistance from Ola Hernvall) / AlexanderSAQ
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