How-To: Scope operation

    1. Introduction
    2. Character recognition without an oscilloscope
    3. Character recognition with an oscilloscope
1. Introduction

The oscilloscope in HOERWACHE (HW) was developed to better assess the quality of the input signal. Without this graphic representation, it is often difficult to analyze a problem if the decoding in HW does not work so well.
HOERWACHE receives the input signal via the audio interface of the web browser, which in turn reads in the signal from the sound card.

The audio signal is first passed through a bandpass with the bandwidth
400 – 1500 Hz. This increases this frequency range a little. The connected Morse code key or the associated tone generator should work in this frequency range. After the band pass, the signal is sent to a demodulator, which consists of a diode and a low pass. The signal behind the low pass is the input signal (InSig) as it is displayed in the oscilloscope. Bandpass, diode and lowpass are of course purely software-based (DSV: digital signal processing).
All values above an adjustable threshold value are raised to a maximum before decoding, all values below the threshold value are set to zero. The resulting square-wave signal (OutSig) is then decoded and sent character by character to the HOERWACHE server via the websocket interface. From there it is distributed to all connected stations.

2. Character recognition without an oscilloscope

Of course, the signal decoding also works without an oscilloscope. To do this, simply switch on the transmitter, select ‘Key’ on the mode selector and turn the MIC control up almost to the stop. This is how HOERWACHE receives the signal from the sound card and can decode it. Before the first transmission you should give a few V-groups until the characters are recognized and correctly displayed in the window for Receiver # 1. If everything goes correctly in the further course of the transmission, nothing further needs to be done. If too many ‘dirt marks’ are generated, it is time to turn on the oscilloscope and investigate the cause.

Sender für Key eingestellt

Morsetaste abstimmen

Picture 1: V-groups are already recognized, but there are still too many ‘dirt marks’.

3. Character recognition with an oscilloscope

To switch on the oscilloscope, we click on the scope switch at the top right under the activity indicator in the radio station.

Scope-Schalter

The oscilloscope appears in the activity monitor. So that the oscilloscope signal is not disturbed by the activity display, we temporarily switch on a band where usually little happens, here the 27M band.

Scope-Anzeige-Grundeinstellung

We now see the oscilloscope basic setting. The threshold is at the value 128, which stands for a zero signal and the signal value is at 223. This is the value that we previously set with the MIC control.

We saw in the text output above that some V-groups were interpreted as <SN>, a character string that is often used in practice to initiate a transmission, but which does not officially exist. In the following picture, which shows the output signal OutSig, we can see that HOERWACHE has actually not received any V-groups, but something like <SN>. The short filled rectangle after <SN> was interpreted by HW as a short fault and therefore was ignored:

OutSig

Now let’s look at the input signal InSig and then finally get to the point, i.e. I will then describe how the detection error can be cleared up.

InSig

We immediately recognize that the InSig signal is a V-group: The fact that the dots and lines are slightly flattened or dented does not bother us, because everything above the threshold value is raised to the maximum value. What should bother us, however, are the trailing ripple or spikes,  which is above the threshold value and is therefore interpreted as a point if the width is sufficient.

So let’s go to and use the slider to raise the threshold so that the peak value of these spikes is below the threshold value. In the previous picture (InSig) you can see that the peak is just slightly above the threshold value of 128. We set a threshold above 128 with the controller (the thick blue point at the top in the picture with the operating elements of the oscilloscope). An estimated value of about 140 is necessary to be safely above the spikes.

OutSig2

A new test with V-groups confirms this: After the threshold value has been raised to 143, we receive square-wave signals at the output (as a reminder: the square-wave signal OutSig is the input signal for the HW decoder) in which we can easily recognize V-groups.
By the way, don’t be confused: The threshold value regulator is displayed differently in the various web browsers: I use the Google Chrome web browser, which shows the handle for the regulator as a blue point.

Also important: The threshold value must never be above the signal value (the value that is set with MIC), otherwise the entire signal is suppressed and there is no signal at the output.

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Travelreport (TR)

Quotation from the "Handbuch Seefunk" from May 1981:

b) TR information, ETA and ETS reports

(2) Coastal radio stations can use the abbreviation TR to request maritime radio stations to transmit the following information:

– the ship’s name

– the location and, if possible, the route and the speed;

– the next port of call.

The maritime mobile radio stations should, whenever appropriate, transmit such TR information on their own initiative, i.e. without special request; especially if they come into the traffic area of a coast station.

TR information is only transmitted after the ship’s command has given its approval.

(3) Every maritime mobile station must notify the nearest coast radio station when the ship enters or leaves a port. If possible and expedient, the other coast radio stations with which the marine radio station generally operates should also be informed. In doing so, the regulations of the country concerned about sending in its territorial waters must be observed.

The abbreviation TR is also used to announce incoming and outgoing messages.

(4) Examples of Paragraphs 2 and 3:

  1. Radio telegraphy:
    TR Clio/DAKQ QTH Norderney fm Bremen bnd Rotterdam.

Meanings:

Clio/DAKQ     – Ship's name und callsign
QTH           - Position of the transmitting station,           
                here Norderney       
fm Bremen     – from Bremen
bnd Rotterdam – bound Rotterdam

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How-To: Receiver operation

The main receiver

has an on / off switch, several buttons for programmable fixed frequencies, one of which is permanently assigned to the frequency 500 kHz, a digital frequency setting, a large tuning button (VFO), and controls for RF gain (RF Gain) and volume (Volume).

Turn on the device

You can see whether the device is on or off by  the green light in the ON button . Immediately after switching on you will hear a noise in the loudspeaker, and the selected frequency will appear in the digital frequency display.

Frequency setting

There are different ways to set the frequency. First, directly at the digits of the frequency display, by placing the mouse pointer on a digit and scrolling forwards or backwards with the mouse wheel. However, there is no overflow, i.e. you have to set each digit individually.
Second, you can turn the frequency wheel (Tune, the big wheel on the right of the receiver). Based on the currently set frequency, you can set all frequencies over the entire range from 30 to 30,000 kHz. Since this would be a bit tedious  in 1 kHz steps, the following key combinations can be used:

Ctrl-mouse wheel: 100 kHz steps
Shift-mouse wheel: 10 kHz steps
Alt-mouse wheel: 100 Hz steps

Unfortunately, these key combinations are assigned differently by the browsers, so that the result is unpredictable. A suitable key combination will therefore only be available in a later version.
You can also set the frequency in the control panel using the band switch and the activity indicator.

Store and recall frequencies

The fastest way, of course, is to save the frequencies with which you mainly work in the memory and to call them up again when necessary. This is quite simple:

With the frequency set on the receiver, click one of the buttons 1 to 7 and hold down the Ctrl key at the same time (Ctrl-left mouse click). The frequency is then saved locally in your browser. To retrieve the frequency, click with the mouse on the corresponding memory button.

However, this setting only applies to the browser used on the same computer for the respective station (ship or coast station).

Adjusting the volume (Volume)

With the volume control you can adjust the volume within certain limits.

RF gain

currently without function

The HOERWACHE Radio station

Radiostation Overview

1 – Radio room clock
        with green and red sectors for the silence period

2 – Station panel
         Display of station data, ro name, time,  position and speed

3 – Main receiver
         All-wave receiver for the range from 30 kHz to 30 MHz. Seven
        Memory locations for any frequencies that can be selected, one fixed for          500 kHz.

4Transmitter
        Transmitter for all ship frequencies as well as one fixed frequency, if a
        Coast station was selected

5Control-Panel
        Multifunction control panel with band switch,
        activity indicator, display switch, oscilloscope, change of course
        and speed, server control display and an emergency receiver for 500 
        kHz.

6Steering compass
        Steering compass for displaying and changing the course (to change,
        using the mouse wheel when the mouse pointer is on the compass and
        the NAV button is off).

7 – Oscilloskop
         If the morse key is connected, an oscilloscope can be used
         to show the input and output signal (InSig / OutSig).

8Scrolling for receiving text
        Text display of decoded Morse code as rolling text (only if characters
        entered with the morse key or in morse chat)

9Display
        Alternating display after selection. Digital nautical charts with
        display of ships and coastal radio stations (OpenSeaMap), Morsechat
        as well as telegram form (more in progress).

      At this point I would like to thank the OpenSeaMap, OpenStreetMap
       and OpenLayers projects, without whose work the development of an digital nautical 
       chart would have been a real challenge for me!

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Who is online?

The display of all active ships and coastal radio stations gives you a quick overview of which stations are currently online. You can access the display via the “Radio station” menu.

If you are wondering why a coastal radio station you have called does not answer, you can quickly see here whether the station is actually occupied and is listening on 500 Khz (QRV = ‘YES’).

Go to “Who is online?

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Work as ship-station

In HOERWACHE you can participate as a ship or coastal radio station. To do this, select the appropriate menu item from the main menu and, after entering some form data, go to the radio station.

Menue: Work as Ship-Station

By selecting “Work as Ship-Station” in the “Radio station” menu item, you get to the selection form for ship radio stations.

Edit ship data and route

You only have to enter all data for the first entry. HOERWACHE notes the entry and saves it in a cookie. Therefore, you should definitely allow cookies for HOERWACHE, because the program cannot function properly without cookies.
All data fields must be filled. The program will ask you to fill in the fields until all data is complete and correct. Only then can you continue with “NEXT …”.

Ship selected

The completed form is displayed again and you can now access the HOERWACHE radio station by clicking on the “ZUR FUNKSTATION” button. To indicate that the fields can no longer be edited, the input fields are highlighted in gray. If you still want to change something, you can return to the entry with “ZURÜCK”.
As already mentioned, the name of the radio operator must be entered. For data protection reasons, however, any name or nickname can be entered. This will keep you anonymous if you want to.

If the selected station is already occupied by a colleague, you will receive an error message and will be asked to select another station. Unfortunately, this does not prevent someone from using your callsign incorrectly, but it was no different in “real life”.

Fehler Shipstation

Only the call sign has to be unique, ship names can be registered in HOERWACHE as often as required.

As long as you are online, the position data is recalculated on the basis of the data for position, direction and speed and displayed on the map. After leaving the station, the current position data is saved in a cookie (or in the local memory of your browser) so that it is available again the next time you visit. This assumes, however, that you use the same computer and internet browser, because this data is stored in the browser.

The radio station has a transmitter with all MF ship frequencies and a main receiver with all frequencies between 30 and 30,000 kHz as well as an emergency receiver for 500 kHz.

Now go to “Work as ship-station“.

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Work as coast station

In HOERWACHE you can participate as a ship or coastal radio station. To do this, select the appropriate menu item from the main menu and, after entering some form data, go to the radio station.

Coaststation Auswahl

By selecting “Work as Coast-Station” in the “Radio station” menu item, you get to the form for the selection of coastal radio stations.

coaststation form

The coast station is selected by selecting it in the list on the left. In addition, you have to decide on which frequency you want to work, because each frequency of a coast station can only be used once. In this way, several radio operators can share the operation of a coast radio station without interfering with one another.
If you can’t find a colleague who would like to use a different frequency, you can of course open additional windows in the browser and use them to assign additional frequencies. But you should proceed with caution because every open radio station is quite a burden for the computer. In any case, it is better to use a second computer for this.
In this way it is possible to take calls on 500 kHz and then carry out further traffic processing on a working frequency.
Incidentally, ship radio stations have a transmitter with all MW ship frequencies, i.e. 410, 425, 456, 463, 480, 500 and 512 kHz.

Coaststation-Zur-Funkstation

After clicking on “Next”, the completed form is displayed again and you can now click on the “To radio station” button to go to the HOERWACHE radio station.
The name of the radio operator, in the input form on the right, must be entered, otherwise you will be asked by the program to do this if you try to continue without a name. For data protection reasons, any name or nickname can be entered. This will keep you anonymous if you want to.

If the selected station is already occupied by a colleague, you will receive an error message and will be asked to select another station. Unfortunately, this does not prevent someone from using your callsign incorrectly, but it was no different in “real life”.

Fehler-Station-besetzt-CSt

If everything has been entered completely and the station is free, the call to the radio station should succeed.

Now go to  “Work as Coast-Station“.

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Connecting a morsekey

The program recognizes when a tone generator with a Morse code key is connected to the sound card.

A problem are newer, simple laptops that have a built-in microphone but often no longer have a seperate microphone input at all. For this, there are external sound cards for connection to a USB interface (e.g. USB sound card from UGREEN for 14.00 euros on Amazon (Amazon Germany as of March 2021)).

USB-Soundcard
USB-Sound

You also need a tone generator to which the Morse code key can be connected. For example, on the market there are keys for beginners with a connected tone generator.

MFJ-557
Morsekey with integrated tone generator MFJ-557

The “Ear Phone” output of the key respectively the tone generator is connected to the microphone input of the sound card with a jack plug. The volume and pitch can be adjusted with the controls. A 9 volt block battery is used as the voltage source, but the device can also be operated with a power supply unit.

If you don’t want to work with a simple beginners key (in my experience the lever arm is a bit too flexible when keying), a better key can be connected to it. In the next picture you can see a K-64 (GDR), which was connected to the tone generator with alligator clips. You can do this to try it out, but later you should not only connect the second button provisionally.

MFJ-557 und K64
Connecting a k-64 to the tone generator

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Supported Internet Browsers

The program (the radio station) now runs equally well on the various Internet browsers. The following table gives an overview:

System Browser Rx Tx (Text) Tx (Key) Remarks
Windows Chrome X X X  
  Firefox X X X  
  Edge X X X  
  Opera X X X  
  Windows
Explorer
      outdated, not supported
Linux          
  Chromium X X X  
  Firefox X X X  

It works best with the Chrome browser on Windows.

HOERWACHE does not work on smartphones and tablet PCs.

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