V1 Chapter 1
Covers work from late 1998 to mid 1999. Mostly centered on the rotor and antenna build out.
- Rotor Servo Problem 12/26/98,
- Move Rotor to the Pole 12/28/98,
- Ready Antenna and Control Box 12/29/98,
- Antenna in place and working 1/22/98,
- Antenna Monitor AS Of1/29/99,
- Feed Horn and LNA AS Of 1/25/98,
- FFT AS Of 1/15/99', Scope Repair AS Of1/25/99,
- Giant Leap Forward 3/2/99,
- More Rotor Problems 3/14/99,
- Horn and LNA Installed 3/30/99,
- First Drip 4/2/99
15. First Drip 4/2/99 - The first output from the LNA as seen on the Spectrum Analyzer was completed today. Task Complete..
14. Horn and LNA Installed 3/30/99 - I was able to mount the LNA tube, Horn, and LNA to the dish and route the co-ax down to the computer room. The LNA cover has been painted and is in place but not sealed completely yet. The distance from the surface of the dish to the horn was computed from a spreadsheet retrieved from the SETI League website and the distance set. Next step is to build a +15 Volt power supply for the LNA and mount it in the control box. This should get the first squirt of water hole down to the shack where the H/P 141 spectrum analyzer is ready to look at it. Task Complete.
13. Antenna Control Software 3/25/99 - The Delphi application is coming together now. I have the form for the antenna control module designed and am working on the homing logic for the Az/El motors. This requires slewing the antenna until limit switches are detected and then shutting down the motors before they hit the mechanical stops. Software seems to work OK now. Az and El positions are slewed too using a trapezoidal acceleration curve, to lessen the shock on the system at start and stop, and the location counters are working now. I now have to add the initial conditions for the elevation wedge and the azimuth home position. Although I have to add more capability to the Homing Function for now I can call this problem ...Task Complete.
12. More Rotor Problems 3/14/99 - While developing the antenna control software I noticed instability in the RS-485 control network. This was traced to a malfunctioning +5 Volt power supply in the control box. The original was a switcher supply that I always felt uncomfortable with because of the noise that this type of supply generates. I replaced it with a dissipative supply and put 5 volt regulators in both of the KERR control modules (I had left them out of the original build). I also replaced the +24 Volt Az/El motor power supply with a dissipative supply as well. The supplies seem to have solved the instability problems. Task Complete.
11. Giant Leap Forward 3/2/99 - Pulling the antenna off the rotor, the rotor off the pole and unbolting the pole from the wooden deck reveled a plastic trip for the limit switch that had fallen off. This accounts for the failure to find the Az limit position. The elevation encoder problem turned out to be a plug that had come loose in the bowls of the rotor. These two items fixed and the rotor (but not the antenna) is back in place. Every thing is now tied down with lacing tape to prevent more plugs from coming loose. I'll finish development of the rotor software before I remount the 500 lb dish on the rotor. Task Complete.
10. Giant Leap Backwards 2/27/99 - After completing the rotor mount and some of the controlling software I ran into a problem with the rotor hardware. The elevation encoder failed. No A/B pulses were coming out of the thing. Since the encoder is buried inside the case of the rotor I cannot get to it without removing the rotor itself from the pole. This means that the antenna must come down again and the whole mechanism returned to my lab for work. This will put the project back a couple of weeks at least. Task Complete.
9. 'Scope Repair AS Of 1/25/99 - I got side tracked when I fired up my Tektronix 475 oscilloscope and found that it wasn't working right. This has to be fixed before I go any further. check out the progress on the Test Equipment page. I will also have to work some of the bugs out of my Spectrum Analyzer - but that can be put off for now. Task Complete.
8. Weak Signal Source AS Of 1/28/99 - During the first search I found that to tune up a receiver you absolutely have to have a low signal source so that the receiver front end doesn't swamp out. Last time I used a VCO from Mini-Circuits and a chain of about 100 db of attenuators. This was very cumbersome. This time I have ordered the weak signal source from DownEast and expected arrival soon. It will be in kit form and will be the next thing I put together.
I received the kit on Friday and had it put together by Saturday afternoon but it doesn't seem to work. The final stage seems to get hot and I don't see any signal from the oscillator itself. I disconnected all the MAR amplifiers and am now looking over the soldering job on the oscillator section.
I thought I had it running after working on my lab 'scope and spectrum analyzer but now I am no longer sure. Still in work.
Weak signal source is now up and running. Pictures of it are available under OtherData and then TestEquipment. Task Complete.
7. FFT AS Of 1/15/99 - I would like to use a 'pre-wired' FFT, rather than code one myself, and one of the best seems to be the from Mike Cooke. Mike tells me that the FFT was coded in Pascal (my favorite language) and that it has been converted to Delphi (better yet). I have downloaded an evaluation package and will start 'evaluating' right away.
I found that the source for FFTDSP wasn't available so I am now looking at an FFT from Lohninger software developers in Vienna, Austria. This appears to be a better choice since it is already a Delphi component and comes with source. They also have several other components, like a report generator that I will make part of the application. I was able to download the software and build a simple test application in a few hours.
6. Feed Horn and LNA AS Of 1/25/98 - Ordered the feed horn and choke assembly from Radio Astronomy supplies located in Plantation, FL. This business is run by an old friend of mine Jeffrey M. Lichtman, who is the founder of the Society of Amateur Radio Astronomers (SARA). The Low Nose Amplifier (LNA) is a 1420 GHZ, 28 dB gain @ .35 - .37 NF design from WD5AGO. Jeff tells me that it will be several weeks before I can expect delivery.
True to his word the horn, choke ring and LNA were waiting for me when I came home from work today. Thanks Jeff. I'm going to be taking pictures of the assembly process and welcome suggestions as I go along.
5. Antenna Monitor AS Of 1/29/99 - Made a visit to the Ham swap meet this morning and came back with a nice color video camera. This is now installed to monitor the antenna movement from the lab. Also shaved off an inch from one of the roof tiles to allow the antenna to move past. I found that there is still clearance problems in certain Az/El combinations. Since I can't remove anymore of the roof overhang I'll have to make software lockouts.
I am considering making the video feed from this camera available over the Internet by adding a CuSeeMe server on my home computer and a link to it from this web page. When I get the receiver running I'll be able to pipe the screen to the server as well and possibly give the control of the camera to who ever is surfing the site at the time.
Added a video switcher to the system so that I can now monitor the antenna and two other cameras in the lab. Everything seems to work. The next step will be to add a CuSeeme server too the video feed
4. Antenna in place and working 1/22/98 - The antenna in on the rotor and the control box is mounted under it. The 1" PVC pipe is routed to the control box and the cables pulled through it. J. R. Kerr was right about the reversal of the motor drive polarity. I found a way to correct that without disturbing the orientation of the manual position switches on the control box. The test software now seems to operate correctly. Next tasks are to shave off about 1 inch from one of the shingles on my roof that is interfering with the Az movement and to install a video camera so that I can watch the antenna from my lab. I can also start laying out the user interface of the control software.
I have shaved the shingle and it seems to clear the roof now.
We had a rain storm this week (seldom occurrence in San Diego) and water got into the control box. The electronics still seem to work, after being dried out, but the box needs better sealing. After sealing and another rain storm the box still works.
3. Ready Antenna and Control Box 12/29/98 - Moved the antenna in position ready to hoist it up onto the rotor. Created the back plate for the control box and made ready to mount it on the pole after the antenna is in place. Task Complete.
2. Move Rotor to the Pole 12/28/98 - Today I decided that I had to move the rotor out of my workshop and on to the pole one way or another and so I disconnected the rotor control cable from the control box and, with the help of my brother in-law planted the rotor back on the pole. Not more than an hour later I got e-mail back from J. R. Kerr in response to my question about this problem. They suggested that I had the motor power signals reversed which is quite possible. I will have to wait until I get the remainder of the system moved outside and connected together to test the theory.
Its typical San Diego weather (mid 60's) today and a good time to be working outside. I have enlisted that help of my son-in-law to horse the antenna up the pole in the next couple of days (thank goodness for in-laws). Task Complete.
1. Rotor Servo Problem 12/26/98 - I have been having a problem with the rotor servo system while it was on my work bench. The servo filter equations would run away after the motors would run for about 2 seconds and the system would shut down with "position error". Using the PWM mode works fine and I can see the phase A and phase B signals from the encoders coming back from the rotor. I sent an e-mail to J.R. Kerr asking for there opinion on the problem.