25 May 2013

MF station setup at PA3ABK

Just a small overview of the MF antenna and MF transmitter.

The antenna picture gives you an idea. Click for enlargement. In total 54m of wire is used. The topwires are not connected together but it's one wire which goes back and forth. Read this item to learn the background.  Both roofpoles have a length of 5m, and distance is 7,5m. The backyardpole is 10m.
Besides the "waterworks" earth, there is also an  "earthprobe" in the garden, 3m pipe driven into the soil. For reception I use the garden counterpoise which has less "noise". A reed switch arrangement takes care of switching the correct "earth"


The whole trick isn't the antenna itself but the earth system.
Having a garden with only 12m space doesn't leave much left for a decent radial system. My house is part of a terrace arrangement. Every house has his own "earthprobe"All these earthprobes are connected together, Over the whole range of 100m  I have a firm counterpoise. Needless to say that other cables, pipes of all kind of services are connected to it. In the Netherlands all cables pipes in teh city are buried.
The toppart  of the antenna poles holding the arrangement are of glass fiber. This is important to avoid that radiation is not absorbed.
The system is tuned by a "large" variometer ex merchant transmitter S-1250, which is capable to handle over 600W. The impedance matching is done by a core 3C65 material. Primary 15 windings litze secondary is a flexible wire of  5. It's easy to increase or decrease the windings by simply  adding more or less turns thru the core. The system seems to have a total impedance of 7 Ohms, which is rather low for this given situation. Most amateurs in this environment have around 50 Ohms. The variometer is placed as close a possible to the window. A feedthru arrangement of a few centimeters is done to keep leakage a as low as possible. The wiring is leaving the house almost horizontal. This maintained by a horizontal glass fibre holder. Connection to "earth" is done  by "disposed, old" fat coax cable in order to keep the skin-effect as low as possible.
Another advantage of my location is the lack of high trees which give me a reasonable  free take-off.

The system has a basic resonance of 1430kHz. I also use it for 160, 80, 60 and 40m. Other bands are covered with a  ladderline feeded 2x 7,5m Inverted V. Which is also visible on the picture above. Note that this antenna must be "isolated" when using the 630m otherwise it will suck a lot of energy to the ground.
Below is sketch of the whole technical setup. It is not updated to the present situation.


WSPR is produced with a MP3 player and a timer. The shift has been multiplied by 4 and was created with Audicity. This to survive de DIV/4 sequence of the GW3UEP PA. Details can be found here.
To avoid "hiss" during silent periods, there is a squelch to make sure that the drive has reached a certain level. Without it, the PA will behave erratic, transmitting broadband noise.

3 comments:

  1. Hallo Jan ik heb nu the annother tuning methode in gebruik het lijkt beter te werken. Bedankt voor je tips. mijn mail is jaapoosten (op) gmail.com
    ik ben ook op Facebook te bereiken 73 Jaap

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  2. Hallo Jaap.
    Ik heb hier een furuno AT 1560 die ik aan de Icom IC 706 MK2G wil knopen. Maar hier mis ik de aansluitgegevens voor en de icom heeft 4 pennen en de Furuno 7... ik vond jouw site toen ik hongerig naar oinfo op het www aan het speuren was.
    Kan jij mij op weg helpen?
    Eddy,
    LB9ZG

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    Replies
    1. Mogelijk dat het service manual van de FS1562 je kan helpen?
      http://www.radioscanner.ru/files/download/file14171/fs-1562-15-ms.pdf

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