[aprssig] Kenwood D700 Internal TNC Amazingly Mediocre!

Steve Noskowicz noskosteve at yahoo.com
Sun Aug 7 08:10:42 CDT 2016


Ah!  Sorry Stephen.  I think I get it now. I scanned your post a little too quickly. (I'm in the last of an estate sale and feel rushed)

 The difference showed up only with the bad cable/poor signals; but with a good cable/signals the D700 still performs well on the target route.  

Therefore, the D700 will work for you, but you still saw the weak signal difference.

So, my comment still applies, but to the Amo-Can Tracker modulation being 'off'.. 

A) It could be that the SoundModem is more acceptable of 'off' modulation and performs better all around; a good thing for the SoundModem, shame on the D700.

B) It could be that the SoundModem's 'ear' is "off" the same way the Amo-Can is (if you know what I mean).  This may mean that the SoundModem will be poorer on 'correct' modulation.  Good for the D700, but shame on the SoundModem.

...OR...

C) Nobody want to hear that the ole' D700 is inferrior...  (:-o)  Boo Hoo.

-- 
 Cheers, Steve Noskowicz K9DCI
 Science & Technical Advisor
 http://www.challengerillinois.org/

--------------------------------------------
On Sat, 8/6/16, Stephen H. Smith <wa8lmf2 at aol.com> wrote:

 Subject: Re: [aprssig] Kenwood D700 Internal TNC Amazingly Mediocre!
 To: "Steve Noskowicz" <noskosteve at yahoo.com>, "TAPR APRS Mailing List" <aprssig at tapr.org>
 Date: Saturday, August 6, 2016, 11:07 PM
 
 On 8/6/2016 10:19 PM,
 Steve Noskowicz via aprssig wrote:
 >
 >
 Hold on.  (I know Stephen is quite astute).  However, Keep
 in mind guys.  This test also
  > depends
 on the signal transmitted from the digi.  Set up the digi
 
 differently and you can
 
 >skew the data.  Perhaps the digi is setup
 wrong/differently....
 >
 
 There was no digi involved in
 my test.   I had the FT-1500/TT3 ammo-can 
 tracker, equipped with a Diamond 770
 no-ground-plane half-wave whip, located at 
 the PROPOSED digi site, beaconing direct to my
 mobile down below.
 
 The
 purpose was to evaluate whether the proposed digi location
 could actually 
 cover the entire area I need
 to cover with enough RF. This after playing with 
 terrain profiles in Delorme Topo North America
 in my motel room the night 
 before, to
 select a "magic location" to cover what amounts to
 two canyons 
 joined at right angles.
 
 The discovery of how much
 poorer the D700's internal TNC was than the 
 Soundmodem soft TNC was purely by accident.
 
 On the first drive-test run,
 the signals from the hill-top beacon to the mobile 
 on my selected route down below were very poor,
 resulting in 
 less-than-fully-quieted
 signals any time I was more than about a third-mile 
 from the transmitter.  It was then that I was
 surprised to see the Soundmodem 
 way way
 out-copying the D700 TNC on these noisy signals.
 
 After wondering why I had so
 little signal, I returned to the transmit site, 
 disassembled the ammo-can tracker, and
 discovered that a coax cable assembly in 
 my
 tracker box was defective (bad crimp in a commercially-made
 cable assembly) 
 resulting in extremely low
 ERP.   [Bench-testing the setup at home before
 the 
 trip, I never had the tracker box more
 than about 25 feet from my mobile so I 
 never realized I had 20+ dB loss on transmit!
 Next time, this thing goes into a 
 wattmeter
 and dummy load before hitting the field...]
 
 I bypassed the bad cable, and
 re-ran the test.  This time I was getting "full 
 smash" completely-quieted signals around
 the entire 4-mile loop test course. 
 The
 signals were good enough that my even TH-D72 handheld lying
 horizontally on 
 the seat INSIDE the car (no
 external antenna - just a 19" whip) copied 
 virtually every transmission as well.
 
 The result of these
 investigations is that the difference in the receive 
 capabilities of the D700 hardware TNC and the
 soft TNC will be insignificant in 
 the
 actual application next year. (I have full-quieting signals
 everywhere on 
 the loop with the
 FT-1500's 40-50 watts out.)
 
 Next year the "magic location" on the
 hillside will be occupied by an "ammo-can 
 digi" containing another FT-1500 mated to
 a KPC3+ and another Diamond 770 
 half-wave
 no-ground-plane whip.  The current FT-1500/TT3 ammo box
 tracker will 
 be strapped to the shuttle
 bus.
 
 The 4 receive
 locations for the digi's downlinks (one at each venue)
 will each 
 be Wouxun KG-UV8D handhelds with
 19" whips, mated to the sound input of 
 Microcenter 7" "Winbook" tablets
 running the Soundmodem and mapping software. 
 In turn the tablets will be Velcro'ed to
 the back of 23" HDMI monitors (the 
 tablets have a full high-def 1080p HDMI
 output)  placed at the entrance of each 
 venue.
 
 The
 KG-UV8Ds come with a nice drop-in charger with built-in AC
 supply as 
 standard equipment. (no wall wart
 - just a lightweight 18/2 "shaver" cord) The 
 charger holds the radio very stably in a
 vertical position, making for a very 
 compact and tidy receive setup.]   I
 actually took my TH-D72 inside each venue 
 during the drive test, to verify that I have
 enough RF -INSIDE- each building 
 for this
 modest receive setup to work reliably.
 ______________________________________________________________________
 Stephen H. Smith    wa8lmf (at) aol.com
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