Month: April 2021

DIY Antenna Tuner 1 – 30 MHz

In China you can get a kit for an antenna tuner for about 10 €, which I once assembled for fun. Here is the link to buy it: Manuel Antenna Tuner DIY Kit 1-3 0 MHz

The build was a little tricky because there wasn’t much room in the case. In addition to the parts included in the kit, I added two banana sockets. This is what my finished kit looks like.

Matching the antennas actually works quite well: tested from 160m to 12m.

Mini-Whip – DL4ZAO BlueWhip Megawhip

DL4ZAO has further developed and modified the circuit of the Mini-Whip antenna and published a number of variants. Here you can find the website of DL4ZAO:

DL4ZAO BlueWhip MegaWhip

I have rebuilt the MegaWhip from DL4ZAO. The reception is much less sensitive to interference compared to the Mini-Whip from pa0rdt. Link to the building instruction:

Features of the BlueWhip MegaWhip

  • It is an active receiving antenna that cannot transmit
  • The antenna is very broadband and you can easily overlook several mHz with the SDR
  • By jumper you can add a FM band stop

DL4ZAO BiasTee Basic

I have also rebuilt the BiasTee. On the same website you can find a building instruction for a BiasTee. Link to the building instruction:

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.

SDRConsole – Digital Decoder (PSK / RTTY)

Since version 3.0.4 the SDR console comes with a decoder for the digital modes RTTY and PSK. However, the digital decoder must first be activated or displayed.

Show Digital Decoder and configuration

In the SDR console, under the “View” tab on the far right, click on the “Select” button.

I have activated the “Analyzer”, “CW Skimmer” and the “Digital Decoder”.

Now the SDCConsole must be restarted once.

Now the new buttons are available in the “View” tab and with a click on “Digital Decoder”, this is displayed. I have docked the window at the bottom of the SDR console.

Now the digital decoder must be activated. With a click on the button with the round circle, as marked on the picture, this is activated.

As modes I have selected USB. Sometimes LSB is also used, but this does not have to be changed, because in the digital decoder, as marked, you can also switch on a reverse mode.

In addition, the speed and the bandwidth must be selected. On 40m I decoded most of the signals with the following settings:

  • Speed: 45
  • Bandwith: 170

The bandwidth must be set so that the marking lies exactly on the two end lines of the signal. If in doubt, simply try out several bandwidths until it fits.

If there is still no readable result, switch on the reverse mode once, if the transmission is on LSB.

Lastly, two optimizations can be made: AFC and Squelch

I have always deactivated AFC. The squelch can be adjusted to the strength of the signal so that no noise is decoded between the transmissions. I then move the slider just before the strength of the emission, which is marked in red.

Decode German Weather Service (DWD) on 4.482.5 mHz

To decode the RTTY transmission from the German Weather Service on 4.482.5 mHz, the following settings must be made:

  • Modulation: USB
  • Reverse Mode: on
  • Speed: 50
  • Bandwith: 450
  • Set the selection at the bottom of the digital decoder to the two sides of the transmission

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:

  • 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.

NanoVNA H / H4 – Firmware Update

Today the NanoVNA H / H4 came to me and the first thing I did was to update the firmware. How this works, you can read here. Among other things, you can now cover up to 2 GHz.

DfuSE – The program to flash the firmware

The first thing to do is to download DfuSE. The software is free and can be downloaded against registration. You can find the software here: STSW-STM32080 – DfuSe USB device firmware upgrade

By clicking on “Get Software”, you can then register and will receive the download link by e-mail.

NanoVNA H / H4 Firmware

Now you have to download the firmware. You can find it on Github under the following Link DiSLord NanoVNA: DiSLord NanoVNA-H4 Firmware

Make sure to select the correct version, depending on whether you have the H or H4 variant. The wrong firmware makes the device unusable for the time being. You can still write the firmware directly on the chip, but you will need the appropriate hardware.

At the time of this post, version 1.0.64 was current. Here you need to download the file with the extension .dfu:

NanoVNA H / H4 in DFU mode and install driver

  1. First, the NanoVNA H4 must be set to DFU mode: To do this, press the joystick in the middle and switch on the device. The screen should now remain black.
  2. With the NanoVNA H, the DFU mode is started via the Config Menu.
  3. Now the NanoVNA H4 can be connected to the computer via USB. Probably the USB driver is missing in the Device Manager.
  4. Then the driver must be installed in the device manager from the DFU installation path via the device manager. You can find it here: C:\Program Files (x86)\STMicroelectronics\Software\DfuSe v3.0.6\Bin\Driver\Win10
  5. Now DfuSeDemo can be started from the start menu.

Firmware Flash with DfuSE

In the DfuSE, the lower “Choose Button” must then be clicked:

Now the just downloaded firmware file can be selected:

With a click on “Upgrade” the firmware is now updated:

Please make sure to select the correct firmware. If you flash the firmware without H4 on a NanoVNA H4, the device is defective for the time being. You can still write the firmware directly on the chip, but then you need the appropriate hardware.