<div dir="ltr"><div>I think what this demonstrated was not a lack of performance of the D700 but a lack of a match between the modulation of the tiny track and the D700,</div><div><br></div><div>I have found the D700 to be the best performer when used with the other kenwood radios. IE, they match the receiver to the transmitted waveform. So performance between kenwoods is the best baseline or benchmark I haven't found anything that can beat it. THen they decode all the way down to the FM threshold.</div><div><br></div><div>This test demonstrated what we all know. and that is packet is carried on an analog channel and performance will never be good unless all the analog parameters match the channel. It is amazing to see some of the signals on the air how badly they are modulated...</div><div><br></div><div>Two kenwoods will decode down to 3 bars.</div><div>Bob</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Aug 5, 2016 at 11:53 PM, Stephen H. Smith via aprssig <span dir="ltr"><<a href="mailto:aprssig@tapr.org" target="_blank">aprssig@tapr.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I had always assumed that the built-in TNC of the D700 was fairly optimized, due to being mated directly to the radio's discriminator, avoiding audio channel distortion, audio level issues, squelch rise times, de-emphasis issues, etc.<br>
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I just got back from a road trip to the Colorado Rockies for the annual Evergreen Jazz Festival. While there, I did some coverage testing in the mountains around Evergreen of a potential portable digipeater and tracker for the festival shuttle bus, that may be used next year.<br>
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This is very rugged mountain terrain with few line-of-sight paths and lots of multipath. I used the D700's internal TNC with one copy of UIview on my Panasonic CF-51 mobile Toughbook.<br>
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I also connected the 6-pin mini-DIN "data port" of the D700 through one of my homebrew sound card interfaces to a Behringer UCA-202 external USB "soundcard". In turn, the UCA-202 was used by the UZ7HO Soundmodem software TNC. The Soundmodem was linked to a second copy of UIview running on the same computer. (The Soundmodem faithfully emulates the AGW Packet Engine interface supported by most current APRS clients.)<br>
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The tests consisted of placing my FT-1500/TinyTrack 3 ammo-box tracker at the hillside location I picked for the digipeater, based on radials I drew on Delorme TopoUSA. The tracker was set to beacon every 20 seconds on 144.37 MHz. I then drove the 4-mile loop route taken by the shuttle bus during the event.<br>
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[The original intent of using the soft TNC on the mini-DIN port at all was to try using 300-baud HF-style packet on VHF/FM to gain 3-4 dB of noise margin compared to 1200 baud.]<br>
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I was completely shocked at the difference between the D700's hardware TNC and the software TNC, both at 1200 baud. When the signals were clean and fully-quieted, there was essentially no difference between the two TNCs. When the signals fell out of full quieting, or were "fuzzed up" with multipath distortion, the Soundmodem massively outperformed the D700 internal TNC.<br>
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Driving the 4-mile winding loop around Evergreen, only about a third of the loop showed on the D700 hardware TNC, while 100% of the beacon transmissions showed on the instance of UIview linked to the Soundmodem soft TNC.<br>
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When I saw how well the Soundmodem worked at 1200 baud, I abandoned the idea of going to 300 baud for this project. (Staying at 1200 means I can intermix off-the-shelf 1200-baud TNCs, radios and soft TNCs, while 300 baud would require that every node involve a PC of some sort running the 300-baud software Soundmodem.)<br>
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