The Stanford University Dish some 46m or 150′ in diameter was erected in 1961 and became one of world’s largest dish antennas, even today. The Dish was commissioned by the Stanford Research Institute that later became SRI International. This fact made complete sense when one was standing at the control position and proudly posted on the console was the amateur radio call-sign of W6SRI. The dish is primarily used to support spacecraft operation as it is located in an electrically noisy area limiting radio astronomy work.
Care and Feeding of a Large Dish
While inside the fence around the dish one immediately notices the various feed antennas set about the grounds in an organized manner. The feed installed while we were onsite favoured the 70cm band. The dish in only operable to about 2GHz at the extreme high end of its capabilities and really works best below 1650MHz. In fact, one of its main tasks is helping to keep tabs on the NAVSTAR GPS constellation.
Two log periodic antennas were observed at the base of the dish. Based on there size they appeared to be for the high HF region well into the VHF.
Over near the south fence what appeared to be a no longer loved feed was found with some other debris.
Looking up at the dish showed some detail of the feed presently installed.
The dish is fit on top of a large track to allow it to rotate in azimuth.
Running off down the hill was a track of L-band wave-guide heading to a large building we didn’t get access to. We where told this contained a L-band transmitter.
A Journey Inside the Dish
The control room for the Dish is located in a building a bit bigger than a mobile home on the dish itself. It rides along in azimuth and as our guide noted can be rather disorientating ending a shift and coming out in the middle of the night to find your car.
Once inside the control center it is divided into four main areas. Work room, operations room, 70cm transmitter, and wave-guide room.
Lying on one of the work room benches was another feed. At this point it became clear how elegant the feed design was. The feeds are designed to fit inside each other. So you leave the big bit in the antenna all the time and simply remove the smaller easy to handle parts when needed.
The dish has a staging area on the tarmac where the long periodic feeds are stowed. The dish itself can be lowered to allow access to the feed point from the ground here allowing for the ease of changing feeds or service on the feed.
Into the Operating Den!
Just when you think you have seen all the feeds this dish could possibly need. in the operating room on a table is a ‘special’ feed designed for GPS constellation work. And as an added bonus the feed control box was open beside it!
The control room has a simple layout. No classified equipment just what you need to control the antenna system and collect raw data.
Our host was kind enough to take us for a ride around in a circle while the dish lowered and raised elevation. And of course, we got to sit in the control seat !!
Wave Guide Closet
At the center of the dish control building is located the wave-guide/coax closet.
The Bulletin Board
A few dated yet cool posts on the station’s bulletin board.
The 70cm Klystron Transmitter
A crowd gathered around some equipment racks to wonder what this mysterious beast was from the distant past. A 70cm Klystron transmitter of course!
The transmitter consisted of multiple racks and was still in service. They planned on using the following day to perform a test with the Van Allen Probe…
Here’s the business end!
Final driver here.
With Thoughts of Earth-Moon-Earth in my Head!
We stepped outside to be greeted by a wonderful Moon rise. Reminding us that part of the Dish’s first usage was to listen for Soviet radars unintentionally bouncing off the moon in the early 1960s. The Moon was the first SIGINT satellite. This fact alone made it clear why the Dish was built.
With our visit here concluded we headed to the Wilcox Solar Observatory (WSO). I’ll post details of out visit there soon. My thanks to our host from SRI International for the wonderful tour!