Lorem Ipsum

I spent some time this week tracking down a bug in the firmware I wrote for the Steven's GHT. Most of the time was taken up with refamiliarizing myself with the code. If has been over a year since I last worked on this project. The GHT is a specialized satellite transmitter: GOES HDR Transmitter, where GOES is the US weather satellite system, and HDR means it is the new, advanced version. If you spell it all out GHT stands for "Geostationary Operational Environmental Satellite High Data Rate Transmitter". Geez, what a name. No wonder we call it the GHT.

Anyway, once I found my way back into the depths of the encoding algorithm, it wasn't too difficult to find and fix the bug. The bug hadn't shown up before because no one had tried to send any messages longer than 256 bytes. Most were under 100, but now there is a customer is Austria and he wants to send 600 byte messages. Durn Austrians anyway, always trying to make the machine perform up to it's advertised specs.

Now we need to verify that it is fixed and that means testing. The GHT has three canned test messages it can send: short, long, and extremely long. They are roughly 100, 200 and 500 characters long. The first two are pithy sayings, which are okay, though they were getting a little old. I tried once to come up with something different, but I drew a blank. I come across pithy sayings occasionally, but they never stick. I guess my mind just doesn't work like that.

The third test message is simply the ten digits followed by the alphabet in uppercase and lowercase repeated several times. Looking at this message on the screen it forms a nice orderly block. In one case this is very good. A quick glance at the received message will show you whether it was received intact or whether characters were dropped or garbled. However, in another case, this could have been bad. As the contents repeat after a fixed number of characters, if you have a buffering problem (like we had), and the buffer happens to have the same number of slots as the length of the repeating string, you might never know that you had a problem. The message still looks fine. This did not happen to us, and it would be a very odd situation, but it just illustrates the kind of traps that are waiting out there for the unwary.

Another kind of test message is "Lorem Ipsum". I had seen this stuff before, but I did not know there was a name for it. It is the Latin name of a Latin phrase that is often used for filler on a page where you need some text to make the page look good, or to see what the page is going to look like, but you don't want anybody actually paying any attention to what is written. As few people learn Latin, few people will attempt to read it. Problem with this kind of test message is that it is difficult to tell whether it came through intact, or not. If you use one particular phrase, you might, through osmosis, memorize it, and then be able to recognize it on sight, but that would take some time.

I have seen this stuff, or something similar, on pictures of fake newspaper pages. Someone wants to highlight an article by making it look like it was printed in a newspaper, so they show you a picture of the article in the middle of what appears to be a page of a newspaper. If you look at the text surrounding the article you will find it is gibberish. Quite startling, the first time I noticed it.

Update December 2016 replaced missing picture.

New Guy

We have a new radio man: Mike B. He is here for three weeks, maybe longer if things work out. He is going to be working on GHT's (GOES High data rate Transmitters). Former military man, moved here three weeks ago from Ft. Bragg, North Carolina. His wife is from Oregon, she is a Native American from the Warm Springs Indian Reservation.

As one might expect of a military man, he has an interest in firearms and shooting. Recently he has taken up black powder shooting, and has been teaching his kids to shoot. It is one thing to take shooting seriously and make every shot count, but with modern rapid fire firearms, it is very easy to just start blasting away for the fun of it. Shooting muzzle loaders means you have to work for every shot, which means you are more likely to make every shot count. You can spend all day shooting 20 or 30 rounds from a muzzle loader, whereas with a modern semi-automatic rifle you can whip off that many in a few seconds. And if you are shooting a high powered rifle, it can get very expensive.

He has taught his 15 year old daughter and younger son to shoot. His daughter has gotten quite good. She wanted to go shopping, so he gave her a goal. If she met the goal, he would take her shopping. The goal was to put a hole in a 308 shell casing at 100 yards using only four cartridges using a modern center fire rifle with a scope. He taped the shell to target board. A 308 shell is about one half of inch in diameter and maybe two inches long. She knicked it on the first shot, and managed to put holes in it with the next three. Mike took her shopping.

Monday

Woke up around 6:30am. Tried to sleep till 7, but ended up getting up about 15 minutes till. Had a bowl of cereal with blueberries, small glass of orange juice and a cup of decaffeinated tea for breakfast. Had a couple of chores to do: move the presents from the car, set out cash for Mohan (Johnny's guitar teacher), payed the credit card bills. Hope I am not too late. Left the house about 8:15.

Jack and I went to Buster's for lunch today. I had a brisket poorboy, a dish of potato salad and a glass of water. Penny is still a happy puppy, though Jack did get a notice in the mail from Multnomah county. One of his neighbors was complaining about Penny barking, so now she has to stay in the house when he is gone. So he put his wind chimes back up.

Roger stopped by this afternoon to troubleshoot the broken GHT's. Turns out there was a via that was not plated all the way through. I am not sure if this is fault of the board house (the company that made the bare circuit boards) or the assembly house (CB Ram, the company that placed and soldered all the components). It is surely Christopher's fault that we had to call Roger, but do we really care? No, not really. But it would have been simple enough to check to see if we were getting power to the power amp, and he didn't do that. I checked it on one of those that was sort of working, and I didn't see any trouble. I put test leads on the I and Q lines coming out of the filters, and with the voltage scale turned way down on the scope, I was able to get a small constellation. But then while I was looking for another micro clip, Roger showed up and took over. He brought a co-worker with him, a hydrologist by the name of Rod. Evidently they work together. Roger is the hands on kind of guy, I get the impression Rod is more theoretical. I introduced him to Keith, they seem to be two of a kind.

Picked Anne up at the transit center, drove to Sue's and picked up her gang and took them all to the Blue Hour bar downtown so they could celebrate Anne's 50th birthday, which is tomorrow. Stopped to gas up on the way to Sue's. Round trip took one hour and ten minutes.

Stevens Chart Recorders

Stevens Chart Recorders
Got an email from my old employer - Stevens Water Monitoring Systems, Inc. announcing the last build of their chart recorders. Chart recorders were the mainstay of their business for most of the last century, but electronical gizmos are pushing them off the stage.

Drawing of complete chart recorder

These old chart recorders were little marvels of mechanical engineering. The pen moves back and forth, driven by a wheel connected to a float. The paper is driven by a clockwork mechanism that only needed to be wound every six months, when the USGS field guy came by to change the paper. It was conceptually simple, but there are hundreds of little details that made the machine reliable and effective. They are also expensive. I think they cost something like five or ten thousand dollars.

The have been mostly replaced by electronic sensors, electronic data loggers, like the DOT Logger, and radios, like the GHT. Loggers and radios are fairly commonplace these days, but the sensors are still something of a black art. Mostly they use water pressure, and when you want to know the level of a body of water to within an inch, your pressure sensitivity needs to be very high. One inch of water spread over ten square miles of lake is a stink load of water.