V1 Chapter 7
This chapter covers advances in SML, the Antenna Rotor repair task and the development of an Audio subsystem block diagram
Details
38. The Seti Markup Language (SML) 3/1/2001 to 2002-09-20 -
Notice that I have switched the way dates and time are represented to conform to the ISO 8601 recommendations. From now on Dates will be CCYY-MM-DD where CC is the century, YY the year, MM the month and DD the day. No left truncation (leading zeros are required). For example the first day of next year will be: 2003-01-01 Back in 1999 I started the development of a way to capture and display the data created by an Argus station such as my own. At that time Microsoft and many others had just started the XML initiative as a generalized way to capture and tag data. Using the XML guidelines I created the SETI Markup Language and its DTD. Right away I realized that I had much more work to do on my system before I could even understand the tasks necessary to tag the data. I had to develop a FFT for the system, a way to create waterfall displays the ability to set the antenna on a point in the heavens a way to save the audio data collected and a host of details about this station. So I put the SML part of the project on hold until I had a better handle on the whole task.
Since that time I have solved most of those problems and its now time to turn my attention back to the very important part of data collection and tagging. As it works out the rest of the XML community had a lot of work to do of there own and the wait was well worth it. Now the toolsneeded to develop SML are off the shelf and reliable, the schema creation process is better understood by every one and its now time to get going.
The SML task is large and deserves a set of pages of its own. I have created an entry page and others to be determined below that one. Jump to SML here...
Right now the first crack at a schema and one test file is complete...
37. The Seti Markup Language (SML) 2002-09-20
The first beta release of the SML Generator is available for download. It seems to create an acceptable XML file and conforms to the SML schema. At this point the association with the SETI data file (*.wav ) isn't working correctly but there is enough to get started.
36. Antenna Rotor Repair (2003-4-9 to 2003-4-18)
The elevation rotor motor can no longer raise the 200 pound SETI antenna and needs to be repaired. This is a difficult, heavy and dangerous job. My wife always wants me to find help with this kind of task but I would rather find a way to make a one man job out of what otherwise would have to be done by five or six strong backs. She say's I'm hard headed and she may be right. I think its something to do with the way a guy will never ask for help when he's lost - I know I'm that way. I would rather find my own way through the task.
2003-4-11- The antenna has been disconnected from the rotor and lowered to the deck. The rotor is also remove from the pole and is now in my work shop for repairs. As I was dropping it, using only a small winch, I realized that I could never get it back up that way and had to come up with some better way of doing it.
During a survey of the project I took some pictures of the LNA case and the effect of the sealing tape used to weather proof the type N connectors.
The LNA case looks a bit worse for ware after a year but is still water tight.
As you can see the tape does a good job of keeping moisture out of the type N connector.
This motor is rated at 24 volts but I run it at a higher voltage to generate the torque the antenna needs. At this point all the mechanical links have been remove, re-greased and re-installed.
I don't see the problem with the system but other things need to be fixed so I still could run into the main problem.
2003/4/16 - I did find several thing wrong with the rotor and rotor control box. Mostly wires that weren't a large enough gauge to handle the current to the elevation motor and other odds and ends - small problems. I fixed all of those and found a couple of other wiring joints that didn't look to good so I reworked them as well. I also replaced a SN7406 (hex open collector inverter) in the LNA control system that had blown out. This made it so that the filter after the LNA was always in the circuit and could not be switched out.
I put a 3 dB pad (fixed co-ax attenuator) between the LNA and the 25 dB line amplifier that I built (three MAR 6). I noticed that some noise spikes in the spectrum from the line amplifier that must have been self oscillation caused by a mismatch between the LNA and line amp. The co-ax SMA pad killed them and I really didn't need the full 25 dB anyway.
2003/4/18 - I had to construct a gin pole to rise the antenna and rotor back on the pole. The ladder in the next picture is 8' tall and the gin pole, behind the black 3" pipe that will hold the rotor and antenna, is about 15 foot. The gin pole itself is made from two 10 foot pieces of square steel tubing nested to 15 foot. The outside one is 2 1/2" the one inside it is 2 1/4". They are mounted to the side of the deck with 3 pieces of 1/2" threaded rod.
When you build a gin pole you must remember that it has to be a good bit higher than the assembly you want to lift. I miscalculated the overall height needed and was attempting to use only a single 10 foot tube. I couldn't raise the antenna high enough to place it on the rotor. I had to bring it all down again and go buy the second tube, climb up the pole and slide the second one inside the first. At one point I had a 10' piece of steel waving around over my head as I attempted to get them to slide together - damn near lost the whole thing down the hill.
If you ever have to build a thing like this don't skimp on the pulley. It has to be a strong 'V' shape that can keep the lifting cable in line and not get cut in half by the forces placed on it. The one I bought is a solid piece that can be directly lubricated with gear grease. There is nothing worse than having an antenna suspended in the air and the cable jam up in the pulley case. Its the critical part of a good gin pole - buy the best.
Rotor in place
With the gin pole ready to work raising the 60 pound rotor was a piece of cake. Now the antenna itself.
While the antenna is accessible I replaced all the galvanized hardware with stainless steel. The galvanized had started to rust and now is the time to replace it while I can. Ace Hardware made a tidy sum from all my purchases of 1/2 stainless fasteners.
Antenna ready to raise
Antenna on saw horse
I then hooked onto the antenna and raised it to the saw horse where it (and I) rested a bit. I drank a beer and admired my work so far.
Antenna on rotor
Moving the antenna to the top of the rotor was quite a trick. It kept getting hung up on the rotor housing and had to be lowered down a bit and horsed around until it cleared and went up. I then dropped in the first two of four of 1/2" stainless steel bolts through the connection plate and it was secure.
I then mounted the control box on the pole and got it all hooked up. Running the motors from the control box showed that everything was back in order.
I nudged the rotor abound using the motors in the rotor to make the last fine movements. I then put in the last two 1/2" bolts into the connection plate. The antenna was back in its proper place.
Gin pole comes down
To stow the gin pole I removed two of the three rods holding it to the side of the deck and then with the aid of the winch and pivoting on the third rod, lowered it to a stowed position.
I sure hope I don't have to bring the antenna down again - Its just to much work.
The RS-485 control line doesn't work for some reason but that's just electronics. I can fix that without a problem tomorrow. I also have to find a bag to cover the rotor head to keep it out of the weather. I usually use a 'stuff bag' that I get from the local sports shop. I cut the bottom out and fasten it around the rotor head with Velcro.
I mark this task complete.
Late Note: The reason the RS-485 control system didn't work was because I had remove a 3" piece of RS-485 cable that didn't appear to have a use. What is was doing was correcting a wire reversal I had somewhere else in the cable. The short piece was acting line a null modem cable that you might be familiar with.
35. Audio Connection Block Diagram (2003-05-03)
If your like me not understanding a basic component of your task drives you nuts. That's the way it is with the audio components of the SETI Net. They work but how do they work. I have always found that a good block diagram will do wonders in helping to understand something but there is no such diagram for the sound system in Windows - until now.
To get to the diagram I reverse engineered the behavior of the Microsoft volume control. Think its simple? Think again.
Open the Volume control on you computer with a single click and you get the simple master volume control slider. Double click it and you get the Volume Control itself.
If you double click it again the system puts a second volume control right on top of the first. This wasn't smart of Microsoft because, since it matches the first exactly and it appears that nothing has happened but there is a second one below. Select one and move one of them out a bit to see the other. Now select Options | Properties on one of them and then the Recording radio button then OK and you have the Recording Control.
If you work with them you can come up with the block diagram for your system as well but it should look a lot like mine.
The interesting things this shows are:
- The Recording Control is a record only one channel type of device. You can set it to the single thing you want to record to the disk.
- The Stereo Mixer input to the Recording Control comes from the Volume Control just ahead of the Master Volume slider and Master Mute. At that point its a mix of all the inputs to the Volume Control. This means that you can record anything coming into the Volume Control.
- The Microsoft Media Player will play any WAV file from the hard disk. Its output goes through the WAVE input to the Volume Control and then on to the Sound Blaster card. Since the output of the Volume Control component goes to the Recording Control Stereo Mixer input you can also record what the Media Player is playing.
- When you have Stereo Mix selected on the Recording Control muting any input to the Volume Control will shut off recording of that input. Sounds like a dumb arrangement but that's the way it works.
