Reflections about a remote mediumwave listeners station

Left: In the HT box at 4 m height is a Beverage Antenna matching set. The HT box was overhauled and re-waterproofed.

Middle: the CMCC was connected to the HT box with a 75 ohm coax cable at a distance of 5 meters. The ground rod is a discarded water pipe.

Right: a poplar serves as a holder for 3 long wire antennas, each 50 m in length. Not shown: a 2nd CMCC 5 m away from the receiver.

How are the CMCCs? First tests brought a significantly reduced QRN under thunderstorm disturbances.

Common mode choke coils act as a simple wire against push-pull current (signal), while acting as an inductor against common mode current (noise).

The kit, concerned on the HAM radio, contains all the necessary materials to quickly assemble a CMCC box. Only a 16mm drill for the PL jacks and another narrow drill bit for the screw feedthroughs are required, apart from the soldering iron. The box is IP55 certified and can be waterproof if you work carefully on the holes. The three central ferrite cores are shrink tubing sheathed, the associated thin coax cable is cut to the correct length sufficient. For a tech-savvy hobbyist, the assembly is easy, even if as in my case the instructions are missing and can not be delivered on request. The substitute transmitted by the manufacturer images of the open finished box could not help. In particular, I could only do the screwing with a number of washers at its own discretion. Since the screw connection also affects the water resistance of the box there are a few points deduction at this point. Also because the screws are not retractable as shown on the website, but come as slotted screws therefore. Another point loses the box due to an oversized wing nut that does not want to fit on any of the screws. Replacement by post was announced after a prolonged contact with the manufacturer.

Two of the boxes are inserted into the coax cable, one 5 m from the antenna's feed point, the other one 5 m from the receiver entrance. From the earth connection of the box a grounding line must be applied to the ground spike. These are not included in the kit. The earth connection is small in size, more than a 1 mm Ø line does not allow the eye with the pin. The wing nut would dress better if one had chosen a larger one. At this point, you can only rework yourself and realize your own ideas of a good ground connection.

The kit cost on the HAM radio 27 €, so 54 bucks for 2 CMCC boxes + a can of cold beer for free, which you can easily drink away while writing the many emails to the manufacturer.

Azimuthal Map
Center: 50°35'1"N 8°40'40"E
Courtesy of Tom (NS6T)



QTH: D-35390 Giessen/Germany

All 50 m Antennas are connected through a RPA-2 Preamplifier.
I am working on a 250°/ 70° direction.

Actually, everything was not a problem. The components were assembled, the elements assembled, the wire roll positioned in a bicycle trailer, and we went out to the neighboring meadow. There, first the earth piles with the connection components were cut into the dry soil, then the galvanized 300 m cable was towed from point A (NE) to B (SE), the 80 m long coax was laid out to the hut, and the RPA- 2 connected. The first test showed remarkably good signals over the entire medium wave, no additional amplified noise due to the preamplifier, in short: the perfect antenna for receiving from the NE direction. A two-hour recording showed me later, how good 300 m antenna cable can be.

I sat in my garden hut in front of the waterfall screen and listened intently, likening the reception to the now weak K9AY, it was around 1930z when I heard voices unknown from outside. When they did not stop, I left my seat, walked to the shack, and watched a person slam through the blackberry hedge. I would not want to go through that, I said. Police, was the answer. In the light of the flashlight I could see the lettering on the man's jacket. In fact, I said.

Displaced dog owners carrying their Fiffies on the meadow suspect a power cord, the policeman said, while his companion expertly examined the coaxial cable. It's an antenna, I confirmed, and that's guaranteed no electricity in it. Good - the law did not come to the dicuting. Now the identity card was checked, a radio check was made, and then I was allowed to roll up the quickly mounted antenna again. So that the dog owners can perform their Fiffies again the next morning. We'll check that later, they said before I let them out through the official entrance to the garden. No, we do not want to go through that again, they said, and disappeared in the darkness of the night.

Days later, I realized that the preferred direction of arrival from NE was not guaranteed at all, because one earth point was in the wrong position. So it is not even a pity that the experiment did not work out. It was exciting enough, from planning to firing.

40 safe meters remain me, NE 4-5 m pulled over the impenetrable blackberry hedge, soon. After all, it's my garden, and I do not keep dogs.

Antenna building material for a 350 m BOG. The line should run in NE / N direction, be largely invisible, and waterproof. Most of the material comes from a pasture fence shop, secret slogan: "Your partner for good MW-DX". The antenna is placed as soon as conditions permit on the neighboring meadow.

For construction: The Beverage boxes are installed in watertight HT tubes, the cables are routed through watertight cable feedthroughs. The ground wires at both ends are bolted to the ground rods. An approximately 60 m long coaxial cable is laid underground to the shack. If necessary, the ring insulators are placed in the ground at long intervals, bolted to wooden bars to keep the BOG flat and tight.

The BOG is connected to an RPA-2 Modular Receive Preamplifier by DX-Engineering.

Summer is the time to check or repair the station and antennas. The Beverage Antenna matching Set from lowbandsystems has been in a waterproof plastic box for over a year. Fortunately, no rust has formed, although - after opening - the waterproofness must be questioned. A new grounding rod was inserted and connected with thick copper wire. All openings for the pipes were re-sealed. Next check is in a year.

The 60 m long wire antenna, mounted in the direction of NW, works perfectly. The noise floor is about -120 dBm. It apparently has no pronounced directivity and can also be used very well as a South American antenna. However, signals from NE / SE are correspondingly quiet.

The new K9AY with extended circumference has a height of 9.50 m, the single wire a total length of 26 m, which corresponds to a limb of 8 m or 5 m. No problem was the erection of the mast. Most of the work fell as wires had to be entangled and the almost ailing tree crown was felled. A first hearing test showed that it is not worse than v1.0. The freestanding position without disturbing tree crowns, better copper lines, improved grounding and other dimensions provided a more rounded sound picture. Better separation accuracy and better forward / reverse ratio are the decisive factors in my assessment.

The masthead of the tree on which the two antenna wires of the K9AY crossed broke at one of the last storms. The reconstruction is now done with stable material and even better antenna wires. The felled tree will also serve as a "scaffold". It is sheathed over a length of 4 m with a 75 mm HT pipe (plastic water pipe) and is thereby brought to a total height of 9,50 m. It replaces the original height of 7.50 m. This results in other lengths, namely longer wire lengths.

Running a remote station means there is always something to do.

I checked the antennas after some storms and noticed that the top of the K9AY was broken. This looks like a difficult work in a height of about 8 m. I have to fix this in the coming weeks. Another antenna - the horizontal loop - doesn't work as good as before and I have to check if there is a cable break in only 5m height. [fixed: a badly connected wire]

Another duty is the connection of the big notebook, which consumes 5-7 Ah, to the solar energy circle. Connecting this notebook is not as easy as you might think. I bought a 19 V powerbank which delivers 2,5 h additionally to the notebook accu cell. But, for timed recordings with SDR Console software, the USB connection always failes if coming from a sleep state. This problem comes with Windows 8.1 and I don't know how to solve it yet. Another problem was coming up: the powerbank creates disturbances. So I wan't be able to record with the notebook. Very sad.

The Rocketec voltage converter is meanwhile broken, which is not so bad because it delivers always some noise on some bands. So returning to accu energy might be the better way. As you know the small Tablet can only run with a limited bandwidht so I am looking foreward to have a stable connection of the notebook which can run up to 6 MHz broad recordings.

I am also looking for falling prices of SSD discs to get more space on night recordings. My Toshiba 2 TB HD denies since some time to work properly.

Further plans are to connect another 100 Ah solar battery to the system and to get another 100 Wp solar panel. Charging the batteries with 1.5 Ah in average takes a long time, so a second panel and battery may help coming better through the winter. A WiFi-connection is also in planning which could mean to run the station really remote in some time from now.

Hope to get the right stuff on the Ham Radio Fair in Friedrichshafen and to see the one or another of you guys there.

73's and cugn from Giessen!

A new project was started this week, the construction of a K9AY array with adjustable termination resistance, controller unit and relays. As you can see in the picture, the mast still causes problems. The heavy pole should be mounted nearby the other tree and still has to be passed by the tree crown. The white seat in the middle is the directors chair.

The screenshots show the range from 4.5 to 6.3 Mhz and part of MW. There was a lot of noise from thunderstorms on the bands. The performance of the horizontal loop was exciting. Compared to the 8-m wire which hangs around the trees was an increase of more than 10 dBm or 2 S-units on the tropical bands and on MW. Under this constellation it's really sad to return @ home to my ALA 1530s+ .... At the end of the loop construction a balun was sunk in a pipe with waterproof hats. The lead-in is a RG-58 coaxcable.

The horizontal loop is my second antenna type in the garden. The closely placed, meanwhile leafy trees, additionally complicate the mounting. The wire is 2 mm green-clad steel wire, which proved to be excellent tensile strength. He was purchased at the hardware store for 0,06 € / meters.