Focal Point

[NightTripper]

I have heard several different versions about focal points. More to the point, where the focal point is.

I got a 3.8 meter dish donated by Mediacam Cable when they scrapped their dish farms near me. But it had an older analog setup. The plan is to setup an NOAAport system. The a Boy Scout wants to do a Eagle project on distributing the data. He wants to send data to the local school, village, and nursing home.

I ordered these items before I was told that my dish would not work as is.

1329 FEED, DUAL, ORTHOMODE, 4GHZ
3220FB LNB,C BAND PLL +/10KHZ, 20 DEG​

But I was thinking why can't I bore the mounting plate for the old feed horn out to where the new feed horn fits.​

But where does the feed horn have to be to the focal point?​

I put pictures on my website. I used a php script to resize the images. If you D/L the pictures you can see them better.

http://www.burgus.org/wxsat.php​

Mark​

 

[NightTripper]

Is the focal point where at the start of the feed horn. And I was told I would have to get new struts, and mounting plate. I thought I could bore out picture #11 so it had the same hole as picture #9. But again I was told that this would not work?

Mark

 

[NightTripper]

Thank You

Mark

 

[jayn_j]

I will defer to the FTA folks, except to say that you might get a better response over in the Free to Air section of the site. Those are the folks who like to experiment with using dishes in ways not originally intended.

Basically, that is an eliptical dish. That means that any distant signal coming in parallel to the axis will get reflected to a single point. That's the focal point, and that is where you want the front of the feed horn. Do what it takes to get it there. You likely need a new mounting plate to fit the new feed, and will need to adjust the length of the rods so that the horn is at the focal point.

How far away are the school, village and nursing home? Also, are they close to each other. when you transmit with a dish, it will take a signal from the focal point and send all the energy out in a single direction. If the targets are more that a degree or so apart, as seen from the dish, he may find that he can only hit one at a time.

Good luck to your son(?) on his Eagle project. It sounds like a fun one. My son built and deployed birdhouses. Lots and lots of birdhouses.

 

[NightTripper]

Thank you for the reply. I thought that since a moderator had moved my post to here that it was the best section.
After the dish is setup. The Scout will send a wifi signal to the three distant points. The nursing home is right across the street from me. The school is just up the street from me, with a couple of trees in the way. But he can use my tower to overcome that. And the plan is to send the last wifi signal from my tower to the village water tower.
I use several battery backups in my shop. And the NOAAport computer will be on one them. I use a 5500 watt portable generator as my backup power. I take it out to the shed and "plug it in" to the transfer switch. This makes for a 99% up time of the NOAAport system. The other three also have backup power. This is important in this area. All the wind has to do is blow at a power line and we lose power. The idea of his project is to make weather information, including radar data, to groups that need it.
And why do I need a NOAAport system. I don't, but it sounded like a good way to learn a little bit about satellites and computer servers.