Tag: Antenne

MLA 30 Plus – Experience with reception

Since I live in the middle of Berlin and am surrounded by 6-story apartment buildings, my reception conditions are very poor. The sources of interference are extremely diverse. In addition, there is an LED street light directly in front of my balcony.

I have provisionally set up the MLA 30 Plus on the balcony on the second floor, on a two-meter high bar, which points diagonally to the street. I have noticed that the further the antenna is from the apartment, the better the reception.

Receiving on 40m

Receiving on 80m

Reception on 20m with FT8 over 2 hours

Currently I am working on a modification of the MLA 30 Plus: I have a 2m long copper tube, with 6mm diameter bent into a circle and mounted on the antenna. Provisionally, I have insulated the upper end of the stainless steel rod with self-welding tape and attached the MLA 30 Plus, with cable ties to these. This will later become the final mounting on the balcony.

ADS-B – Groundplane Antenna DIY

ADS-B for receiving the flight data is on 1090 MHz. So a quarter wavelength is about 6.8 cm. However, I cut my copper wires a little longer so that I can still tune afterwards.

What do you need:

  • A socket,perhaps a PL, BNC or SMA
  • Rigid copper wire, 5 x 8 cm (I stripped mine from a 3 core power cable).
  • optional are cable lugs and screws (instead you can solder the copper wires directly to the socket)

I have decided for the SMA socket, because I want to go later anyway on SMA. Otherwise, I have found four different screws and nuts, in the same diameter.

  • Next, I attached the cable lugs to the SMA socket with the screws. Alternatively, you can solder the copper wires directly to the socket.
  • Then I stripped 5 chum wires from a power cable and shortened them to 8 cm.
  • Then I wetted all the copper wires with tin.
  • Next, I soldered four copper wires to the lugs.
  • After that I soldered the fifth copper wire to the inner conductor of the SMA socket.
  • Finally, I connected the antenna to an analyzer and found that the copper wires were too long.
  • I shortened all copper wires to 6.7 cm and had a SWR of 1:21 on 1090 MHz. I measured including the cable lugs.
  • The antenna is located in the middle of Berlin on the balcony on the second floor and has a range of about 280 km.

MLA 30 Plus – SMA socket

I’ll skip the first steps, because I had already described them in the instructions for the BNC socket. You can read that here: http://mini-whip.de/2021/04/08/mla-30-plus-bnc-buchse/

  • I stripped the cable a few cm, almost as long as the SMA socket is.
  • Now I have bent the outer conductor backwards.
  • Then I soldered the inner conductor.
  • Since I decided to use the crimp variant of the SMA socket, I now have to pull the heat shrink tubing and crimp sleeve onto the cable
  • Now the inner conductor can be inserted.
  • Next, the outer conductor must be bent forward again and the crimp sleeve put on.
  • Now the connector can be crimped.
  • The whole thing should then look like this.
  • Finally, I pulled a heat shrink tube over the connection.
  • It should then look like this.
  • Finally I glued the bushing and the screws for the loop with epoxy.
  • Before that, I roughened the areas with a file so that the epoxy would sit better.
  • The last thing to do is to fold the cable and close the lid.
  • I left the cable extra longer in case I still want to make adjustments.

MLA 30 Plus – BNC socket

Since the cable on the MLA 30 Plus is fixed, quite thin and 5m long, I decided to install a BNC socket. I had these two BNC sockets in stock. I would have liked the larger with the rubber verbau, but the diameter seemed too thick, so I have the left variant use.

  • When you open the lid, you will see the cable, which is attached to the housing with hot glue.
  • The cable can be pulled 20 cm inwards with a little force and then the cable can be clipped off and the adhesive carefully removed.
  • Now the hole can be drilled out. I did this with a hand drill, because otherwise you can hit the coil in the middle very quickly. I have seen some videos where the coil was striped with the drill.
  • In my case, the diameter of the smaller BNC socket was 9 mm.
  • Then the rubber must be removed a few cm. After that I bent the screen backwards.
  • Twist the shield together and tin it.
  • Tin inner conductor.
  • Install the BNC socket. Depending on how much black epoxy was poured, it may be very tight with the nut. It may be necessary to scrape or file the black epoxy down to the board.
  • Solder the sheath and inner conductor to the socket. I left the cable longer on purpose in case I want to make adjustments in the future.
  • If you still have a ferrite core / folding ferrite, you can still attach it to the coax cable in the housing.
  • It might make sense to adjust the blue potentiometer in the upper left corner. With the included wire loop, you can definitely raise the sensitivity a bit. In my case, I had to turn it counterclockwise.
  • If you use a longer or thicker loop, you should reduce the sensitivity, otherwise too much interference will be amplified.