The Small Radio Telescope (SRT) is contained here.

• A System overview of the SRT
• The Software suite that makes  up the antenna and receiver control
• The various Hardware components for the SRT

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Problem of the Day

2008-08-21 First Light + 2

Finally achieved a decent peak on the sun.  This is the run down:

Used my SRT data collection tool running at 500 mSec and the attenuator in line. Control of the antenna was from my Paraclipse control program version 2.2

This is the procedure:

1. Created a sun position chart from the U.S. Naval Observatory http://aa.usno.navy.mil/data/docs/AltAz.php - This gives sun position in Az/El in 10 minute increments
2. Home the dish
3. Move the antenna to the first sun position and find the peak
4. Record the data.  Distance is from the center plate of the dish to the lip of the C-Band feed
5. Slide the horn in an inch or as close to that as possible.
6. Go to step 1.

It looks like reading number 6 was close to the peak so I set the horn a little bit longer (53 1/4 inch) and locked it down.  Why the peak so 53.5 and not 60.5 as calculated - I haven't a clue.

I will re-run the chart this afternoon when the sun comes down into my elevation range (about 3 pm).

2008-08-20 First Light + 1

No light/No joy yesterday so now what.

Last night with the horn & receiver back on my bench I was able to see the noise source as expected.  I found that you have to hold the noise source about six inches from the horn and orient the dipole to be parallel with the 1420 MHz probe but it does seem to work.

The two pictures below are of a software test module collecting data from the receiver and of the noise source oriented about 6 inches from the probe.  The probe is difficult to see but its at 11 o' clock inside the center ring of the horn.

With 6 mA running into the noise source I get about 2400 on the meter.  With the noise source shut off I get about 1600 on the meter.  With the probe rotated 90 degrees I get about 2400 on the meter with or without power to the noise source. Rodolfo Montez U. of Texas measured 108 K in his paper on the Noise Calibrator so this un-calibrated change of 800 seems to be in the ball park.

Back To Basics

So the receiver does seem to be working.  That leaves the possibility that I did not have it mounted at the focal point of the antenna.

The focal length F is given by:

    F= D²/16z

D is the diameter of the dish and z is the depth of the dish.

Next is to measure the diameter and depth of the dish to make sure I know what they are.  I'll use a piece of wire stretched across the dish for the measurement.  This is actually not an easy measurement to make because my dish is mounted and is 12' across.  Reaching in to make the depth measurement will be a challenge.

By pulling a wire as tight as I could make it from one spreader to an opposite spreader I measured 146" in diameter.  By pushing a tape measure through the hole in the center of the back of the dish and up to the same wire I measure 22" of depth.

This makes F = 146²/16*22 or 60.5"  I don't think this is where the horn was yesterday.

2008-08-18 First Light

Enough of the system works so that today is the day to try to gather our first set of photons.  I have decided to mount the receiver on a spare button hook for my Paraclipse antenna and use my antenna positioning software to move the antenna and the SRT application to collect data from the receiver.  It aught to be exciting...

Well - No Joy.  Something is amiss.  I cannot see any difference in power reading when I sweep the sun.  I am getting data back from the receiver.

Work'n it boss.

2008-08-17 Software testing

After thrashing myself half to death on Java I finally got a working system.  This is what I had to do:

• Recruit a Java expert - Jon Petrescu, also a member of SDAA stepped up to the plate
• Install NetBeans - NB is a clean development environment for Java applications and is a lot like Delphi so, with Jon's help, I was able to get it started.  Jon and I use the Microsoft Windows Live Messenger to communicate with each other during the day.
• Download H180 - We were using the wrong version of this software for a while but after we downloaded the correct Java files from MIT's web site we were able to start communicating.  The H180 designator is the type of antenna mount we have.
• Switch to RxTx -The serial interface module used in the original Java code is woefully out of date.  Jon suggested we switch to the RxTx package and after a bit of tweaking it came on line.
• Learn the SRT User Interface - This is a 'painful' piece of software.  I was written about eight years ago in Java and shows its age.  Its alright to use to get the thing under control but *must* be replaced to be usable.
• Delphi test application - While I was learning Java I needed to keep my sanity with a small Delphi module that connects to the receiver and displays the resulting data.

There are still many things going on in the Java interface but its starting to work.

2008-07-23 Software startup - I have the Receiver and the Computer Interface in my lab for testing.  What I don't have is the dish and the positioning rotors.  For the test I have to open the software and disable the rotor commands and to do this I have to bring myself up to speed in Java.

I have downloaded the Java development environment from SUN Microsystems and have it installed on my computer.  Now I have to learn Java.  Luckily Java and Delphi (my native langue) are similar so it won't be like starting from scratch but it will be a challenge.  I'm running some 'Java for Boys and Girls' programs now.

As they say - Stay Tuned...

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