WA8LMF Home Page | Main Ham Radio Page | Main Links Page | Updated 2 Feb 2025

TNC Test CDs

The files linked below contains disk images that can be used to re-create a compact disk containing audio files to test and compare the performance of standard 1200 baud VHF packet radio TNCs under various conditions.

Two versions are provided. The original version 1.1, released in 2009, creates an audio CD. The new version 2.0 creates a normal computer CD-ROM.

The Version 1.1 disk is a “CD-Extra” combination disk that contains standard CD audio files playable on any normal home or car audio CD player or boombox, and CD-ROM data files (including a copy of this page) viewable on a computer.

The CD-ROM part of this disk should autorun and display a directory of files automatically when inserted into a computer optical drive. Recent versions of Windows may offer to play the (hidden) audio part of the disk when inserted into a computer CD/DVD drive. On a computer CD drive, right-click the CD drive icon in the Windows File Explorer or “My Computer” and choose “Play” to force the audio part of this disk to play. This should launch your default audio player application. The audio part can also be played on home video DVD/Blueray players.

Playing back standard CD audio rather than CD-ROM .wav data files avoids the timing errors and incorrect playback sample rates that often accompany low-cost software-based (i.e. motherboard AC97) PC sound systems. It also avoids the mangling of data waveforms that may occur with MP3 or other lossy compression formats. Newer computers with the crystal-controlled "RealTek HD" audio chips should not have this problem.

The audio files could also be played on an old CD-ROM drive standalone, without a computer, by connecting the TNC under test to the drive's front panel earphone jack, or to the 4-pin analog audio jack on the drive's rear panel. (A CD-ROM drive normally doesn't need computer support to play audio CDs. A drive with a front panel volume control and track-select button is preferred.)
The Version 2 disk is a normal computer CD-ROM image with lossless FLAC files on it. For convenience playing the FLAC files, the installer for a lightweight audio player, the "VU Player", is included in the layout.

Both files are images of optical disks. The CD-audio Version 1.1 is in the .BIN/CUE file format. (Normal .ISO-format image files can't capture the multi-session mixed-format layout of this disk.) Version 2 is a normal CD-ROM layout in .ISO format. Either version can be used to burn a physical CD on a standard CD-R blank disk, using the freeware "ImgBurn" utility. The contents of the audio files in both versions are identical - they are lossless audio files, but in different formats.

Version 2 can also be "mounted" and used as a virtual CD-ROM using an unused drive letter on your system.

NOTE: Windows 8 and later, can mount an ISO as a virtual drive natively. Right-click the .ISO file name in the Windows File Explorer. Choose "Open With..." and select "Explorer". The contents of the ISO will "auto-magically" appear as a new drive letter on your system.
Older versions of Windows will require you to install a third-party mount utility such as "WinCDemu" . Once installed, you can right-click the ISO file in the File Explorer, and choose "Select Drive Letter and Mount..." from the pop-up context menu.

To aid in selecting the cuts on a CD-ROM drive that lacks a front-panel track-number indicator, voice announcements and cue tones have been added to the beginning and end of each track.

Track 1 has a DTMF digit "1" at the beginning and a DTMF digit "6" at the end.

Track 2 has a DTMF digit "2" at the beginning and a DTMF digit "7" at the end.

Track 3 has a DTMF digit "3" at the beginning and a DTMF digit "8" at the end.

Track 4 has a DTMF digit "4" at the beginning and a DTMF digit "9" at the end.

Track 5 has a DTMF digit "5" at the beginning and a DTMF digit "0" at the end

The differing digit values could possibly be used with a DTMF decoder to automatically start or stop data acquisition devices.

Note that all these recordings are taken directly from the discriminator. Tracks 1, 3 and 4 are not de-emphasized. Track 2 is de-emphasized (see below). If you wish to evaluate how various TNCs behave when connected to a radio's speaker or headphone output (rather than directly to the discriminator such as from a 6-pin mini-DIN "data" jack.), you will have to insert an RC de-emphasis network between the CD player and the device under test.

For an excellent discussion on FM pre-emphasis and de-emphasis, and how it relates to packet operating and TNCs, visit this website:

http://www.febo.com/packet/layer-one/transmit.html

The Tracks

Track 1 is an off-the-air recording of 40 minutes of activity on 144.39 MHz in Los Angeles, California, during the afternoon rush hour at about 5:00 PM when the channel is totally saturated to several hundred percent of the Aloha threshold. This recording was taken from the non-de-emphasized direct discriminator output of a Yaesu FT-1500 via the 6-pin mini-din data connector. It contains a variety of over- and under- deviated signals, packet collisions, rapid-fire packets with practically no pause between them, raw NMEA string trackers, TinyTraks, clueless idiots using CW ID on packet, etc. All periods of dead air over about 1 second have been edited out so that 40 minutes of real-life activity have been compressed to 25 minutes on the CD.

This track is intended to be played back directly into TNCs to compare the performance of various TNCs "under fire" in the real world . The rapid pace of the packets should be a good test of the ability of buffers in TNCs and associated applications to hand a rapid flow of data without overrunning.
Track 2 is identical to Track 3 except that a precise 6db-per-octave/20db-per-decade de-emphasis between 300 and 3000 Hz has been applied to simulate the typical de-emphasis found at the volume control or speaker output of the typical land-mobile receiver. This can used to evaluate the relative performance of TNCs in handling raw non-deemphasized discriminator audio vs de-emphasized speaker audio. The effectiveness of jumper-selected equalization networks available inside some TNCs can also be tested. This track was created by applying the graphic equalizer filter in Adobe Audition set to simulate the standard EIA land-mobile radio de-emphasis curve.

Note that a roll-off was also applied below about 200 Hz to simulate the typical highpass filtering used to keep CTCSS ("PL") tones out of the speaker of mobile radios.

Track 3 is a recording of a Kenwood D700 transceiver sending a Mic-E position report, taken from the wideband low-distortion discriminator output of an IFR1500 service monitor. The receiver was unsquelched and no de-emphasis was used. This recording of a single packet was then copied and pasted repeatedly in the Adobe Audition audio editor. The result is 20 bursts each minute, for 5 minutes, for a total of 100 absolutely identical packets.

This track is intended to modulate an RF signal generator, or the generator mode of a service monitor. Connect the CD player to the external modulation input of a generator, and set the playback level so that the data bursts deviate the generator about 3.5 KHz. Connect a radio's receive audio output to the TNC under test. Connect the RF generator to the radio's antenna input. While the recording is playing, gradually decrease the generator RF output level until the TNC starts failing to decode. Since the recording contains exactly 100 bursts, counting the number of successful decodes can directly indicate the percent success rate at various RF carrier levels.

Possible uses of this track:
1)     Compare different TNCs connected to the same radio.

2)     Connect the same TNC to different radios to compare the weak-signal data performance of various receivers.

3)     Evaluate the relative receive performance of audio taken from the radio's speaker versus audio taken from dedicated "data" or "packet" jacks or outputs. (De-emphasis and audio bandwidth may be different at these two sources.)
Track 4 is an off-air recording of 25 minutes of a single mobile D700 beaconing every 12 seconds (maximum beacon rate) on a quiet channel (no other stations) while driving around the San Gabriel Valley area of Los Angeles. The signals were monitored in Pasadena, California. Most of the drive test course was 8-10 miles from the fixed station, far enough away from the monitoring fixed station to create some mobile flutter, multipath and loss of quieting. In several stretches, several successive packets are audible on the recording but failed to decode with the AGW packet engine.

Again, this recording was taken from the non-de-emphasized direct discriminator output of a Yaesu FT-1500b via the 6-pin mini-din data connector. Click Here for a map of the route driven, produced with UIview32, Precision Mapping 7.1 and UI-HeightTrack (opens in new window).

This track is intended to be played back directly into TNCs under test. An APRS application running on a computer attached to the TNC should create a realistic moving object.

The three following tracks are for TNC alignment rather than testing. They are intended to evaluate TNC demodulator tolerance to tone "skew" (unequal levels of the 1200 and 2200 Hz tones).

Track 5 is a direct recording of one minute of a KPC3+ TNC in the "CAL" mode sending the alternating 1/0 test pattern (i.e. alternating between 1200 and 2200 Hz tones) with both tones at the same amplitude.
Track 6 is the same recording with a precise 6 dB/octave 20 dB/decade de-emphasis applied as in Track 3 above.
Track 7 is the same recording with a mirror-image precise 6 dB/octave 20 dB/decade pre-emphasis applied.

These are examples of what the flat response, pre-emphasized response and de-emphasized responses of the KAM test tones look like:. They were captured with the freeware "Visual Analyzer" soundcard software oscilloscope and a Behringer UCA-202 USB soundcard.

FLAT Response PRE-Emphasized DE-Emphasized

**WARNING! Please DO NOT play these test tracks over-the-air! My callsign is embedded in the beacons and will be igated. This will create false reports of where I was decades ago!**

Keep your testing confined to a dummy load.

File Download

READ THIS FIRST !!!

The image file contained in the first download link below produces a MIXED MODE disk that combines audio CD tracks and CD-ROM data tracks.

This is not a normal CD_ROM.
This is not a normal audio CD.
It is a combination of the two a.k.a. a "CD-Extra" disk. This disk format is often used on modern audio CDs to include song lyrics, artist bios, etc. When you place this disk in a computer CD drive, you will only see the CD-ROM data part of the disk.
The audio tracks should play automatically and normally in a car CD player, boombox or home stereo CD player.

The second link is to an ISO image of a normal CD-ROM

Most CD-recording applications, including Nero, CDburnerXP and others can re-create a physical disk from these types of image files. You do not place the .BIN or .ISO file in a list of files to be recorded as you typically do. Instead, pull down "File" from the menu bar, and look for something like "Record image file..." or "Make CD from image file...".

The original mixed-mode CD was created with the freeware program CD Burner XP available at:

http://cdburnerxp.se

The image file was created from the physical CD with the freeware program ImgBurn available at:

http://www.imgburn.com

WARNING! These are large downloads (over 530 megabytes for the BIN version and around 250 megabytes for the .ISO version).