[aprssig] Multi control station situational awareness - (kenwoods)

Stephen H. Smith wa8lmf2 at aol.com
Wed Dec 4 11:05:47 EST 2019

On 12/4/2019 10:04 AM, Robert Bruninga wrote:
> ØBy the way, the D700 TNC is a REALLY mediocre-performing device as well.    
> In several test runs, Direwolf and the UZ7HO "Soundmodem" software TNCs 
> copied almost THREE times as many beacons as the D700 hardware TNC.
> The problem in this case was what was doing the transmitting?  A typically 
> non-tweaked packet transmitter can be FULL Scale on a kenwood and some other 
> TNC’s and not decoded.  But a properly balanced packet can be fully dedoded 
> on a kenwood down to only 3 bars on the s units.
> The problem is that 90% of all packets on the air were never properly tweaked 
> for optimum performance.  Just put it up and it works!  (but fails miserably 
> in weak signals).
> Repeat your test with a kenwood doing the transmitting (known factory good 
> signal) and a kenwood doing the receiving and you will see an order of 
> magnitude improvement in performance comparted to most signals on the air.
Are you then suggesting that only Kenwood devices be allowed in organized APRS 

In this test, the transmitter ("ammo-box" tracker) was a TinyTrack III 
connected to a Yaesu FT-1500 2-meter monobander's 6-pin mini-DIN data port.    
The FT-1500's data port yields flat (not pre-emphasized) TX audio response,  
just like a D700.   The transmitting  FM deviation was monitored and set to 
exactly 3.5 KHz peak, using my IFR-1500 communications service monitor.

This test reflected the receive decode performance of signals sent from a 
single transmitting device.   In casual monitoring while on cross-country road 
trips, listening to many different transmitters from different users, some 
fully-quieted and some noisy & scratchy, I see the same pattern.   It is clear 
that the soundcard soft TNCs, fed raw discriminator audio from the mini-DIN 
data port, are far more tolerant of malformed, over-deviated, under-deviated, 
incorrectly equalized, or just plain weak and noisy TX signals than the D700's 
own TNC.

In the real world, the great majority of APRS signals are being originated by 
NON-Kenwood devices, with a wide range of optimal and not-so-optimal settings 
that you have no control over. Having a demodulator that can tolerate these 
marginal signals successfully is a HUGE advantage.

This is NOT a case of the D700 transmitter somehow being magically "tweaked".  
It is a case of the D700 hardware TNC being an inferior DECODER of marginal 
real-world signals than the soundcard software TNCs.

Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
EchoLink:  Node #  14400  [Think bottom of the 2-meter band]
Home Page:          http://wa8lmf.net

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