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[aprssig] *** APRS TNC Test CD Now Available ***

Dave Baxter dave at emv.co.uk
Tue Oct 31 09:13:08 UTC 2006


Downloaded it last night, all 500MEG+ zip file, two hours over 2MEG DSL
(I know, overheads etc) but not a problem.

Burnt it to a CD this morning, just to check, then had a quick listen
with mk1 ear-ole, just to check the disk burnt OK.

The track numbering is a bit odd.  Track 1 is very short and blank,
track two announces itself as "Track One" , track 3 announcement is
"Track Two" and so on....

The "De-emphasised" audio is "very" muffled, compared to what comes out
of the rig speaker jacks hear in the UK.  I'm not aware of any US/EU
differences in Ham FM radio charactersisics, but I suspect some TNC's
will struggle with the "De-emphasised" tracks, where as they will work
just fine with a real FM radio speaker jack feed.  I have a collection
of TNC-220's, none have a problem with radio speaker feeds, so long as
you load the radio with say a 10r resistor, and that's more like keeping
the radio's speaker output chip bias point in the right place.

The "Non de-emphasised" audio examples are as expected very "bright" to
say the least.

I was playing it on a true audio CD player (a 10 year old discman) into
'phones, with all the audio enhancements turned off, just a flat
response, as near as.  I'll feed it to a TNC tonight, and see what
happens.  Let you know.

Overall, a nice idea, well done that man...

Dave G0WBX.


> -----Original Message-----
> From: Stephen H. Smith [mailto:wa8lmf2 at aol.com] 
> Sent: Monday, October 30, 2006 7:18 AM
> To: TAPR APRS Mailing List
> Subject: [aprssig] *** APRS TNC Test CD Now Available ***
> 
> ***   APRS TNC Test CD Now Available   ***
> 
> 
> I have produced a CD containing signals for testing and 
> comparing the performance of different packet TNCs, and 
> radios that might be used with these TNCs.  The recordings of 
> live off-the-air APRS activity are also useful for 
> demonstrations in locations where live signals aren't 
> available, such as a basement conference room.
> 
> This disk is a "CD-Plus" combination disk that contains 
> CD-ROM data files viewable on a computer, and standard CD 
> audio files playable on any normal home or car audio CD 
> player, boombox or DiskMan.
> 
> 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.)
> 
> Playing back standard CD audio rather than CD-ROM .wav or 
> .aiff audio data files avoids the timing errors and incorrect 
> playback sample rates that often accompany low-cost 
> software-based  PC sound systems (i.e. 
> motherboard AC97-based systems).
> 
> Details on the disk, links for downloading the 530MB image 
> file for creating this CD, and a link for purchasing a 
> ready-made CD, are located on my website at:
> 
>       http://wa8lmf.net/TNCtest
> 
> Scott, N1VG, of OpenTrac fame ( http://opentrac.org ) is 
> handling the sale of recorded disks on his Argentdata 
> e-commerce site, and has also graciously volunteered to host 
> the large downloadable CD image files on his server.  
> 
> 
> 
> 
> 
> About 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. 
> 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.
> 
> 
> 
> ---- 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.  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. 
> 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.
> 
> 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.
> 
> 
> 
> 
> 
> 
> --
> 
> Stephen H. Smith    wa8lmf (at) aol.com
> EchoLink Node:      14400    [Think bottom of the 2M band]
> Home Page:          http://wa8lmf.com  --OR--   http://wa8lmf.net
> 
> 
> NEW!  TNC Test CD
>   http://wa8lmf.net/TNCtest
> 
> JavAPRS Filter Port 14580 Guide
>   http://wa8lmf.net/aprs/JAVaprsFilters.htm
> 
> UI-View Misc Notes and FAQ
>   http://wa8lmf.net/aprs/UIview_Notes.htm
> 
> "APRS 101"  Explanation of APRS Path Selection & Digipeating
>   http://wa8lmf.net/DigiPaths
> 
> Updated "Rev G" APRS            http://wa8lmf.net/aprs
> Symbols Set for UI-View,
> UIpoint and APRSplus:
> 
> 
> 
> 
> 
> 

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