[aprssig] weak signal ISS packet

Steve Dimse steve at dimse.com
Thu Jan 22 19:24:25 CST 2015


On Jan 22, 2015, at 7:21 PM, Bill Vodall <wa7nwp at gmail.com> wrote:
> 
> Perhaps if we'd invested more time on the RF Radio network side we'd
> have moved beyond technology that was outdated even in 1997.  That's
> the point of my suggestion - doing it easiest way isn't the best for
> the long run.

If there had been a more significant barrier to getting involved in APRS in the mid-90s - say $400 for a radio/modem per station, APRS would never have taken off. APRS became the success it is precisely because it worked with the TNCs and radios many hams already had or could buy used dirt cheap. People could experiment for free, and as they did some got hooked, and it reached a critical mass. 

To suggest it could have been done differently ignores the critical mass issue, and also assumes that someone spent the tens or hundreds of thousand of dollars to develop those radios and modems, you sure couldn't buy them then! TAPR spent a lot of money trying to build a point to point radio in the 500 kbps range in the late 90s. I personally threw thousands of dollars into that project. The problem was by the time we had turned the boards a few times one or more chips was discontinued because the technology was improving so fast. It was hopeless unless we spent enough to hire a full time team of engineers that could complete the project in a few months and buy a lifetime chip supply. TAPR couldn't afford that, no ham radio organization could.

>>> EuroHAMNET from the DCC on HamRadioNow - https://www.youtube.com/watch?v=ytuOqcYgOtg
> 
> This is one DCC presentation worth watching..     It shows what can be
> done building a independent networking using Ham ingenuity and modern
> hardware and software.
> 
And since you sent this I have watched it. Really, it is something very much like HAMWAN. And yes, it is interesting. If I lived in an area with one of these networks I'd play with it too. Sure, you could build an APRS-IS using these links. But right now these can do less than the commercial wired and wireless Internet links that get stronger every day, and they will never come close to reaching that level of service. They do nothing unique.

So yes, they are fun to play with. They have utility for putting our bandwidth to use and for possibly providing emergency TCP linkages. But they are not now replacements for the 1200 baud APRS network, nor will they ever be. 

We know that because of synchronization issues 9600 baud provides little improvement over 1200 in an ALOHA network for the short data packets APRS is concerned with, and faster modems really do not help. So even today, if I wanted to design something for the APRS network, I'd chose 1200 baud. It is cheap, easy, reliable, and proven. Nothing you have talked about comes close to matching it for what we need it to do! When linked with the Internet it is powerful and unique tool, but it never tried to, and never will, do everything.
> 
>> Something like "Seattle's HamWAN is an amateur network using commercial 802.11 equipment in the 5.9 Ghz band.
>> It has very limited coverage and is not suitable for mobile or portable operations."
> 
> Coverage is actually quite impressive

Looking at the map on their front page I'd disagree, it looks like tall rooftops and high ridges are the primary coverage areas.

> and I can see it working well
> for portable operations...  

Yes, for those areas with coverage, setting up a two foot dish is not too big of a hurdle.

> Mobile operation has been attempted but
> that's not a good fit (yet) for this technology.
> 
yet? You think there will ever be a day when an 802 technology will be good fit for mobile operation?
> 
> I'm the biggest APRS fan in the house - it's the Ham digital
> equivalent of what Facebook is for the rest of the world.  At least it
> could be if we move forward with all the missing potential
> functionality (email and bulletins, data files like the callsign
> database, custom icons, software updates) - and that's why I see these
> Internet clients as such distractions from what we could be doing.

Huh? You want to send software updates via APRS? That's really nuts! Even if we had a magic wand and every APRS radio and node had a dedicated 40Mbps bandwidth, the best you can come up with is matching what the internet has been doing for 20 years?

Here's the thing. If you want people to get excited about some high bandwidth ham radio network, you need to have a killer app, something that can't be done on the existing Internet. Otherwise you are just playing at making your own inferior version of the Internet. And interesting as that may be to some it is never going to attract a critical mass. And it is never going to replace the boring 1200 baud 144.39 network.

Steve K4HG




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