U of MD Computer Science dish (was Ham IP addresses?)

[Mark Bulla]

On a related subject - the dish on the computer science building was a 3.5m Andrew.  I was working at U of MD College Park at Instructional Television (part of the School of Engineering) in 1991, and I noticed this nice, dish on the roof of Computer Science, and saw that it never moved.  Looking into it a bit, I found that it wasn't being used, so I talked them into letting us take it.  
We used it as a TVRO dish because, although we already had an uplink dish at the end of the building, we didn't have a good steerable downlink.  It was a nice dish!
The dish was installed on a steel structure behind the ITV building between the EE and T lots.  It looks as though they have since built a building in the T lot, so the dish may no longer be there.
MarkKB3OGD

> Message: 1
> Date: Wed, 15 Jan 2014 00:28:57 -0500
> From: louie <louie at transsys.com>
> To: tacos at amrad.org
> Subject: Re: Ham IP addresses?
> Message-ID: <52D61C99.8070703 at transsys.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> 
> There was a wormhole in the sky that I was involved with back around 1987.
> 
> I was working at the University of Maryland Computer Science Center in 
> College Park at the time, on the staff at the computer center there.  We 
> had a couple of satellite antennas on the roof that we used for various 
> purposes.  One of them was otherwise "idle" as the project in question 
> has come to a merciful end.
> 
> Now this satellite dish and feed, etc. were still up on the roof. It was 
> a pretty good size, maybe around 3 or 4 meters?  It was relatively 
> expensive and painful to get installed, both because of the weight of 
> the structure, as well as needing to run conduits for the signal runs as 
> well as non-trivial power to run heaters for the feed and dish so that 
> the link would continue to operate during snow storms.  While there was 
> money to install it, there was no obvious money at hand to remove it, 
> and I think we were all hoping to leverage it as part of some future 
> project or grant..
> 
> There was a ham at the company that ran the actualy satellite operations 
> for this link.  I wish I can recall who it was at Vitalink in the SF bar 
> area, but I can't at this point.  We managed to hook up somehow, and he 
> had the idea to set up an AX.25 packet radio wormhole.  It was done in a 
> fairly interesting way, at least given what was available at the time.  
> He shipped out some hardware that produced the ability to transmit audio 
> over the data link.  I think the capacity of the full-duplex data 
> circuit was 19.2-50 kb/s; and he had some hardware with a (as I recall) 
> CVSD audio code.  We installed a 2m antenna on the roof of the building 
> in a quasi-official manner and scraped up 2m radio and TNC.   Likewise, 
> a similar configuration at the far end.  We ended up sending audio from 
> each end to the other with the effect of having this crazy digipeater.  
> It suffered a bit from a hidden terminal problem, since local 
> transmitters on 2m in the MD/DC end couldn't hear the audio being 
> received from california, and vice-versa.  But it worked after a fashion.
> 
> It was up and running for some number of months, maybe a year or so, 
> using WA3YMH-1 (or some other suffix) as the callsign of the 
> digipeater.  I'm sure it was all perfectly legal, and I'm pretty hopeful 
> any statute of limitations has since expired, if not :-)
> 
> There's an article here: 
> http://ncpa.n0ary.org/13_Downlink_1994_summer.pdf starting about page 
> 13, describing that experiment, including the later conversion of the 
> audio bridging to using the link  between two NET/ROM nodes, one at each 
> end.  As I recall, we just shoved the 9600 bgp async serial data into 
> the 56k synchronous satellite modems and there were enough samples per 
> bit to get the async characters shoved over to the other end!
> 
> I also recall random flame wars at the time about the impurity of 
> tunneling amateur packet radio over non-amateur radio facilities, 
> because, you know, that's just wrong.  Like phone patches are all 
> different.  Like we do with many ARISS contacts these days.  Oh well.
> 
> I don't know if any AMPR IP traffic ever got shoved over this. Around 
> the same time, early KA9Q NET or NOS code has the ability to tunnel over 
> the Internet, so maybe that was going on at the same time?
> 
> louie
> wa3ymh
 		 	   		  
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