Test and calibration CD created by Stephen Smith, WA8LMF.
File for TNC Test CD
recordings on this disk are intended to be used to test and compare the
performance of packet radio TNCs under various conditions.
disk is a “CD-Plus” combination disk that contains CD-ROM data files
this readme file) viewable on a computer, and standard CD audio
playable on any normal home or car audio CD player or boombox. The audio files could also be played on an
old CD-ROM drive standalone, without a computer, by connecting the TNC
test to the drive's front panel earphone jack, or to the 4-pin analog
jack on the 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.)
back standard CD audio rather than CD-ROM .wav data files avoids the
errors and incorrect playback sample rates that often accompany
software-based (i.e. motherboard AC97) PC sound systems.
Note that some recent PC CD-drives now
extract audio digitally rather than using the digital-to-analog
inside the CD drive for audio playback; i.e. there is no separate
output and cable from the CD drive. In
this case, take the audio directly from the front panel earphone jack
drive rather than from the computer sound system.
CD-ROM data area may be seen by some audio players as an un-playable
audio track. Use the hardware track
select button on an audio player or computer CD-ROM drive’s front panel
to the second track (first audio track) if the disk doesn’t play
a laptop CD drive that doesn’t have the hardware track select button,
Windows CD Player (not Media Player !) to create a software control
track selects, play, stop, etc. Normally
this is accessible from StartàProgramsàAccessoriesàEntertainmentàCD Player.
aid in selecting the cuts on a CD-ROM drive that lacks a front-panel
track-number indicator, voice annnouncements and cue tones have been
the beginning and end of each track to audibly identify it.
1 has a DTMF digit "1" at the beginning and a DTMF digit
"6" at the end.
2 has a DTMF digit "2" at the beginning and a DTMF digit
"7" at the end.
3 has a DTMF digit "3" at the beginning and a DTMF digit
"8" at the end.
4 has a DTMF digit "4" at the beginning and a DTMF digit
"9" at the end.
5 has a DTMF digit "5" at the beginning and a DTMF digit
"0" at the end
differing digit values could possibly be used with a DTMF decoder to
automatically start or stop data acquisition devices.
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 characterize how various TNCs behave when connected to a
speaker output, you will have to insert an RC de-emphasis network
CD player and the device under test.
very useful APRS program for this kind of testing is KH2Z's APRS+SA
"APRSplus" because it keeps a running count of the number of times
each station has been heard. Thus one
can easily compare the number of successful decodes different TNCs
produce. Both track 3 and track 4 are
recordings exclusively of a single callsign (WA8LMF), making this
number of decodes very simple.
Track 1 is an
recording of 40 minutes of activity in Los Angeles during the afternoon
hour at about 5:00 PM when the 144.39 channel is totally saturated to
hundred percent of the Aloha threshold.
This recording was taken from the non-de-emphasized direct
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
pause between them, raw NMEA string trackers, TinyTraks, clueless
CW ID on packet, etc. All periods of dead
air over about 1 second have been edited out so that 40 minutes of
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
the real world . The rapid pace of the
packets should be a good test of the ability of buffers in TNCs and
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
and 3000 Hz has been applied to simulate the typical de-emphasis found
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
de-emphasized speaker audio. The effectiveness of jumper-selected
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
land-mobile radio de-emphasis curve. See
the GIF image DeEmphEq.gif on this disk for a screen shot of the
setting. Note that a roll-off was also
applied below about 200 Hz to simulate the typical highpass filtering
keep CTCSS ("PL") tones out of the speaker of mobile radios.
Track 3 is a recording of a
Kenwood D700 transceiver making 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
audio editor. The result is 20 bursts
each minute, for 5 minutes, for a total of 100 absolutely identical
This track is intended to be used to
modulate the RF signal generator of a service monitor. Set
the playback level so that the data
bursts (not the white noise between them) deviate the generator about
KHz. While the recording is playing,
gradually decrease the generator RF output level until the TNC starts
to decode. Since the recording contains
exactly 100 bursts, counting the number of successful decodes can
the percent success rate at various RF carrier levels.
This track can also be used to compare the
weak-signal data performance of various receivers by connecting the
same TNC to
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
create some mobile flutter, multipath and loss of quieting. In several
stretches, several successive packets are audible on the recording but
to decode with the AGW packet engine.
Again, this recording was taken from the non-de-emphasized
discriminator output of a Yaesu FT-1500b via the 6-pin mini-din data
connector. The route driven is shown
on the map DriveTst.GIF in this directory.
The map was produced with UIview32, Precision Mapping 7.1 and
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
three following tracks are for TNC alignment rather than testing. They are intended to evaluate tolerance to
tone "skew" (unequal levels of the two tones)
Track 5 is a direct recording of
one minute of a KPC3+ TNC in the CAL mode sending the alternating 1/0
pattern (i.e. alternating between 1200 and 2200 Hz tones) with both
the same amplitude.
Track 6 is the same recording with
a precise 6 dB/octave 20 dB/decade pre-emphasis applied as in
Track 7 is the same recording with
a mirror-image precise 6 dB/octave 20
dB/decade de-emphasis applied.
shots of the Adobe Audition graphic equalizer settings, and the
waveforms are in GIF image format in the CD-ROM data area on this disk.
Smith WA8LMF wa8lmf.com 21 Oct 2006