NBEMS-Local

NBEMS-Local

Step 1.4: Interfacing your transceiver and fldigi device

Background

Step 1.4 of this course requires that you have an Amateur Radio license and an Amateur Radio VHF or UHF transceiver. If you don't meet those requirements, you can skip Step 1.4 and continue with the next step.

This step of the course deals with the "interface" between your radio transceiver and the device on which you are running fldigi. The only absolutely necessary elements of that "interface" are:

  1. moving audio effectively between the transceiver and fldigi, and
  2. switching the transceiver between receive and transmit at the correct times.

An "interface" can be as simple as your hand or a shelf or bracket holding an "HT" (handheld transceiver) in the correct position and your fingers pressing and releasing the PTT (push-to-talk) button at the correct times. You may be happier, however, using an electronic interface, with which audio travels by cables and PTT (putting the rig into transmit) is automatic.

In this step in the course, Step 1.4, you will first configure your transceiver (Exercise 4-1). Then you will operate fldigi on the air with yourself as the interface between your transceiver and your computer (Exercises 4-2 and 4-3). If you have a Tigertronics™ SignaLink interface device, you will go on to the later exercises in this step, configuring that device (Exercise 4-4) and using it on the air (Exercises 4-5 and 4-6).

Exercise 4-1

In this brief exercise, you will configure your transceiver to work properly with fldigi in the context of this course, using FM mode on the VHF and UHF bands. These settings apply to the use of any interface method.

Requirements

Settings

Exercises 4-2 and 4-3

In Exercises 4-2 and 4-3, you will learn how to "be your own interface" between your transceiver and the device on which you're running fldigi, probably your computer. You will see this technique called "acoustic coupling" or "audio coupling", because the digital signals travel through the air as sound between transceiver and computer. It does require some skill to push and release your transceiver's PTT button at the right time, and you will need to place or hold your transceiver's microphone near the computer's speaker and the transceiver's speaker near the computer's microphone as you operate. Even if you have electronic interface equipment like the SignaLink, I recommend learning and practicing these manual skills because you never know when, where, or with what equipment you may be called upon to manage a digital contact.

Requirements

Exercise 4-2

In this exercise, you will either receive actual digital signals on your transceiver or simulate receiving them by playing audio files on another device, such as a digital audio player or smartphone.

In preparation for this exercise, start fldigi. Use Configure|Sound Card. (See NBEMS menus and configuration for help with the "W|X" and "Y~Z" method of describing software menus and configuration.) PortAudio should be checked. In the Capture box, select the microphone of your computer that you plan to use. Click Save and then Close. At fldigi's lower right corner, turn off squelch (the light next to the letters SQL on the squelch button should be off). Clap your hands sharply in front of your computer's microphone. You should see horizontal blue bars moving down the waterfall.

On your transceiver, tune to any frequency and turn the squelch off. (On an HT, there may be a MON (monitor) button that you can press.) You should hear hiss from your transceiver's speaker. Move the transceiver as close to the computer's microphone as you can. You should see "blue snow" on fldigi's waterfall.

If you don't see anything on the waterfall, you may need to turn up the level of your computer's sound card for the microphone: In Windows, look at Sound|Recording. Click on the icon for the microphone you are using and press the Properties button. In the dialog box that opens, go to the Levels tab. Move the slider up, then press OK to close both boxes. Look again for blue snow or bars on the waterfall.

Over the air with another ham

Ideally, you can make an arrangement to meet on the air with a nearby ham you know who can transmit digitally with fldigi. Meet on a 2-meter simplex frequency that allows voice, and coordinate by voice. Have your friend prepare to transmit a few paragraphs of text with fldigi. Agree on an operating mode (I suggest MFSK-32) and a waterfall frequency (1500 is good). Tell your friend to transmit. Place your transceiver's speaker near your computer's microphone. As the transmission happens, adjust your transceiver's volume as necessary to see snow on the waterfall and text in the receive pane.

Using an audio player

If you can't find anyone to send signals to you, you can use a digital audio player or smartphone as a substitute for your transceiver. In your workspace folder, locate files D1.2.2.wav, D1.2.3.wav, and D1.2.4.wav that you used in Step 1.2 of this course. Put them on your audio device or phone and try playing them to be sure sound is produced. (I hope you have an app that will play audio files in that format!) Now follow the same procedure as above, substituting your audio player or phone for your transceiver.

Exercise 4-3

In this exercise, you will transmit actual digital signals over the air using your transceiver.

In preparation for this exercise, start fldigi. Use Configure|Sound Card. PortAudio should be checked. In the Playback box, select the speaker of your computer that you wish to use. Click Save and then Close. Select an operating mode and waterfall tuning; I suggest MFSK-32 and 1500. Right-click in the transmit (blue) pane and select Clear if that command is not grayed out.

Making a test transmission

Turn on your transceiver and locate the frequency you wish to use. Listen to be sure it is not in use. If you hear nothing, press your microphone's PTT button and ask "Is this frequency in use? This is..." and conclude with your call sign. If you still hear nothing, announce "I will now transmit digital signals. This is..." and conclude with your call sign.

Press the microphone's PTT button down and hold it next to the computer speaker you selected. Now right-click again in the fldigi transmit pane and select Transmit. You should hear digital tones from your computer's speaker. Note where on your computer these tones are sounding -- that's the speaker you've selected in fldigi. (If you don't hear digital tones, or if tones are produced from a speaker you don't want to use, go back to Configure|Sound Card and try again.)

If you have a hand free, try typing the following into the transmit (blue) pane:

TESTING TESTING TESTING DE {yourcall} ^r

(Use upper or lower case as you wish except for the "^r", where the "r" must be lower case.) You should see your typed words appear in the receive (yellow) pane. In the transmit pane, your typed words will turn red as they are transferred up to the receive pane. When the "^r" characters are reached, fldigi should stop producing tones. When that happens, release the microphone's PTT button.

Regardless of how well that exercise went, press the PTT button on the mike and announce your call sign, then release the PTT.

You can make this exercise more rewarding, though it will be still more complicated. Use fldigi's TX Generate control as you learned in Step 1.3 to record your transmission, then use the Playback control that you learned in Step 1.2 to play back what you did.

Over the air with another ham

Ideally, you can make an arrangement to meet on the air with a nearby ham you know who can receive digitally with fldigi. Meet on a 2-meter simplex frequency that allows voice, and coordinate by voice. Repeat the instructions that you followed in "Making a test transmission" above while your ham colleague listens and receives your transmission with his or her copy of fldigi. When you've completed your transmission, compare notes with the other ham.

Exercises 4-4 through 4-6

In Exercises 4-4 through 4-6, you will configure your SignaLink interface device to your Amateur Radio transceiver and your fldigi device, most likely your computer, and will test reception and transmission. If you do not have access to a SignaLink or other interface device, you will not be able to follow these instructions, but it is still a good idea for you to read through them.

Exercise 4-4

In this exercise, you will configure a SignaLink interface device for use with your specific transceiver and computer. If you don't already own a SignaLink, this device can be purchased from Amateur Radio suppliers and also from Tigertronics™ itself. Your purchase will include cables to connect the device to your equipment as well as configuration instructions. The SignaLink device must be configured internally (with jumpers) for your specific transceiver, and the cable connecting it to your transceiver must also be correctly matched to the transceiver. Fortunately, once you have that done, it will not need to be changed ... for that transceiver. (If you switch to a different transceiver, you will need to do that again.)

Requirements

Once your have your SignaLink device and it is correctly configured internally, there are several adjustable configuration settings for you to consider. They are:

These settings interact with each other in various ways, and to some degree they are more art than science. There are surely disagreements among hams who are equally experienced and successful in digital operations on some of these points. In truth, you will need to experiment at least a little to find out what works for you. That's what I did.

So I think the best I can do is to offer here some respected sources of information for you to review and use as the basis of your experiments. Try them out. If you find other sources that are of value to you, suggest them to me for addition to this list.

The absolute basics

With your computer on, connect your cables to your SignaLink. One cable connects to the "USB" socket in back, and its other end plugs into a USB port on your computer. The other cable connects to the "radio" socket in back, and its other end connects to your transceiver. It is probably obvious from the SignaLink instructions just where on your transceiver that connection is made, but it does differ from radio to radio. Sometimes it is to a "data" port in back, sometimes it replaces your microphone, and sometimes it goes into a socket on the side.

Turn your transceiver on, then turn the SignaLink on by pressing the PWR button in front, lighting a green LED. If you are connecting the SignaLink for the first time, your computer may install a driver for the SignaLink at this point.

Always keep in mind that fldigi may not be able to locate audio equipment that was not connected to your computer and powered on when fldigi was launched.

With your interface device connected and powered up, launch fldigi. Configure fldigi as follows from this point:

  1. Use Configure|Soundcard, then Audio~Devices.
  2. Make sure that "Port Audio" is checked.
  3. Select the line that includes "USB Audio Codec" for Capture. ("USB Audio Codec" denotes the SignaLink sound card.)
  4. Select the line that includes "USB Audio Codec" for Playback.
  5. At bottom right in this dialog box, click SAVE and then CLOSE.

Here are other basic considerations for operating in the FM mode on the VHF/UHF bands, which may conflict with some instructions you may encounter that assume you will be on the HF bands using single sideband:

The settings

Making proper and mutually-compatible settings on your three devices takes a little work, but there is guidance. I suggest that you look at these sources of information. However, keep in mind that some of what is discussed here pertains to single-sideband operation on the HF bands. Information regarding ALC (automatic level control), for example, will not apply to you.

Exercise 4-5

In this exercise, you will receive actual digital signals on your transceiver as in Exercise 4-2 above. In this exercise, though, those signals will pass through your electronic interface device (such as the SignaLink) and be interpreted by fldigi.

Requirements

In preparation for this exercise, turn your transceiver on and turn squelch off; you should hear hiss from your transceiver's speaker. Connect your interface device, and then start fldigi and configure it and your interface device as described in Exercise 4-4 above.

On your transceiver, tune to any frequency. You should see "blue snow" on fldigi's waterfall.

If you don't see anything on the waterfall, you may need to turn up the level of your computer's sound card for your interface: In Windows, look at Sound|Recording. Click on the icon for your interface (named "USB Audio Codec" for a SignaLink) and press the Properties button. In the dialog box that opens, go to the Levels tab. Move the slider up, then press OK to close both boxes. Look again for blue snow or bars on the waterfall.

If you do see blue snow, you should then check to be sure the receive audio level is within an acceptable range by checking fldigi's receive level indicator diamond, just to the left of the AFC button near fldigi's lower right corner. Green is good, whereas black is too low, yellow is somewhat high, and red is excessively high. Adjust the sound card level up or down.

As an additional test, tune your transceiver to 144.390, which in most areas is the common frequency for APRS and therefore busy with packet transmissions. You should see horizontal variations in the waterfall's blue snow when APRS transmissions are received. (fldigi does not decode these transmissions, so you will not see anything appear in the receive panel.)

Over the air with another ham

Make an arrangement to meet on the air with a nearby ham you know who can transmit digitally with fldigi. Meet on a 2-meter simplex frequency that allows voice. If your interface device's connections allow you to use your transceiver's microphone, you can coordinate with your friend by voice on the air. If it does not, consider coordinating by telephone during this part of the exercise. Agree on an operating mode (I suggest MFSK-32) and a waterfall frequency (1500 is good). Have your friend transmit some text with fldigi. As the transmissions happen, you should see text in the receive pane.

If you do not see text, investigate the problem. With your interface device disconnected from your transeiver, can you hear the tones your friend is transmitting? With everything connected, agree on a few different operating modes to use (MFSK-32 is a good choice because it is slow and robust.)

Exercise 4-6

In this exercise, you will transmit actual digital signals over the air using your transceiver as in Exercise 4-3 above. In this exercise, though, those signals will be created by fldigi, pass through your electronic interface device (such as the SignaLink) and be transmitted by your transceiver.

Requirements

If you have just completed Exercise 4-5 successfully, communicating over the air with another ham, you may wish to continue directly into this exercise. Otherwise, follow the instructions for that exercise to set up your equipment correctly.

One very critical thing about transmitting digital signals using an electronic interface device is that fldigi must automatically put your transeiver into transmit as it begins to produce its audio signals containing your transmission. This is called the "PTT" action, named for the Push-To-Talk button on a microphone. A perfectly-composed message in just the right operating mode is no good if your transceiver does not transmit it. So you should begin by making sure this happens.

In this part of the exercise, you will locate a clear frequency, test the PTT action on your setup, and if successful, identify with your call sign as required.

First, locate a clear frequency that you can use. If you have a ham friend who has transmitted to you and who is waiting to receive your transmissions, you already have this. Otherwise, a less-used VHF frequency designed for voice simplex is a good choice. Listen, or at least watch fldigi's waterfall, to be sure you will not interfere with another ham's activity. If you can use your transceiver's microphone, you may also wish to ask by voice whether the frequency is in use.

Click once in fldigi's transmit pane (blue). Right-click. If "Clear" is available as a choice, select it to remove text from that pane; otherwise, left-click in the pane. Now press your keyboard's Enter key twice, then type your FCC call sign, then press Enter two more times, then type "^r" and leave the insertion cursor (the "I" bar) where it is, to the right of the lower-case "r".

Near fldigi's upper right corner, locate the "TUNE" button and press it. If all is well, your transceiver will begin transmitting AND you should see a bright vertical bar appear on the waterfall at your tuning point (probably 1500). Whether or not both of these things happen, press the "TUNE" button again; this should stop your transmission. If your transceiver did go into transmit, you achieved success at this point (congratulations!) and you must now identify by call sign. To do this, right-click in fldigi's transmit pane and select "Transmit". Your transceiver should again go into transmit, you should see your call sign being transmitted, and when the "^r" characters are reached the transceiver should return to receive mode. (If your transceiver seems to be stuck in transmit mode at any point, you can right-click in the transmit panel and select "Abort" or you can press the "T/R" button near fldigi's lower right corner.) If you can use your transceiver's microphone, you may also wish to identify by voice. (If at any point your transceiver is stuck in transmit and all else fails, turn off your transceiver, then shut down fldigi, then turn your transceiver back on and identify by voice.)

If fldigi did not put your transceiver into transmit, you will have to diagnose and correct this. This problem can happen for a number of reasons, including a transmit level that is too low, mismatched cables, or erroneous settings. Review the sources of information cited in Exercise 4-4 above for clues.

Over the air with another ham

If you were successful in having fldigi put your transeiver into transmit, proceed to meet on the air with a nearby ham you know who can receive digitally with fldigi. Meet on a 2-meter simplex frequency that allows voice. If your interface device's connections allow you to use your transceiver's microphone, you can coordinate with your friend by voice on the air. If it does not, consider coordinating by telephone during this part of the exercise. Agree on an operating mode (I suggest MFSK-32) and a waterfall frequency (1500 is good). Transmit some text with fldigi (see the exercises in Step 1.3 for ideas). As the transmissions happen, you should see text move from the transmit pane to the receive pane, and your friend should report success in receiving your text. Remember to identify by call sign as required by the regulations; identifying in the digital operating mode you are using is perfectly adequate.

Summary

In Step 1.4 above, you learned how to configure one type of electronic interface device, the Tigertronics SignaLink, and also learned how to "be your own interface" and how to use your electronic interface device to receive and send messages over the air with fldigi.

Table of Contents

John Rabold KS6M
April 2020