I believe this is the correct formula - sounds familiar. haven't used it in quite a few years - close to a decade. But it does sound familiar. the focal point is the point at which all reflections from the entire dish focus to the center of the feed - so it would have to be the distance to the center of the dish to work correctly. This only works on parabolic dishes however. And CBand dishes are parabolic. Also only works on center feed dishes - also cband qualifies. So you should be good to go.
Steve ----- Original Message ----- From: "ocsrc1" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, January 02, 2008 1:09 PM Subject: [TVRO] Re: Need help with measurement on 5 foot dish support arms >I used > ( D*D ) / 16/d = f > > d=depth of dish > D=diameter of dish > f=focal distance > > f/D = focal depth for feedhorn > > I have to plug the numbers into the triangle formula and see what > they come out to. Now that I know that the focal distance is from > the bottom of the dish to the feedhorn I should be able to temp. > mount the feedhorn and take some measurements to be sure. > > Building the mounts is the next tough step. > > Bill > > > > > --- In [email protected], "Stephen Smith" <[EMAIL PROTECTED]> wrote: >> >> Focal Point is usually from the center of the dish to the front end > of the >> scalar rings. The end towards the dish. If this is a shallow > dish, it will >> be farther away, obviously. I would double check the dish depth > just to >> make sure. What formula did you use for FP? >> >> Steve >> >> ----- Original Message ----- >> From: "ocsrc1" <[EMAIL PROTECTED]> >> To: <[email protected]> >> Sent: Wednesday, January 02, 2008 12:14 AM >> Subject: [TVRO] Re: Need help with measurement on 5 foot dish > support arms >> >> >> > If my math is correct the Focal Distance is between 21 and 22" >> > >> > But I'm not sure if this from the dead center of the dish or even >> > with the outer edge. >> > >> > If it was dead center then the feedhorn would only be 11" above > the >> > dish edge. >> > >> > If it is from equal with the edge of the dish, then it would be > 31" >> > from the bottom of the center of the dish. >> > >> > Does anyone know which of these is true? >> > >> > Once I have the correct location for the feedhorn, then it form a >> > triange with a 90 degree right angle and I should be able to find > the >> > length of the long side since I would know the 2 other sides. >> > >> > I know there is a formula to do this, but it's been a long time > since >> > I was school. >> > >> > AutoCAD would be able to plug these numbers in and find the > answer in >> > a second. >> > >> > If you have AutoCAD and can make a sketch, or JPG, SWF , or other >> > type of file, please send it to my primary address >> > [EMAIL PROTECTED] >> > >> > Thanks again >> > >> > Bill >> > >> > >> > >> > >> > >> > --- In [email protected], "ocsrc1" <radical.bill@> wrote: >> >> >> >> The dish is 59" wide and 10" deep. >> >> >> >> Hope this helps >> >> >> >> Bill >> >> >> >> >> >> >> >> --- In [email protected], "Geraldo Paiva" <loures@> wrote: >> >> > >> >> > Considering the attachments is being stripped away by Yahoo, >> >> please see the two dimensions I need: dia of dish and depth of >> > dish. >> >> > >> >> > >> >> > !------------------ dia of dish ------------------! >> >> > ...................................................... ---- >> >> > .......................!..................... >> >> > ..................!.............. HOW DEEP >> > IS >> >> DISH >> >> > ............!......... >> >> > ....!.... ----- >> >> > >> >> > >> >> > ----- Original Message ----- >> >> > From: Richard A. Keirstead >> >> > To: [email protected] >> >> > Sent: Tuesday, January 01, 2008 4:36 PM >> >> > Subject: Re: [TVRO] Re: Need help with measurement on 5 foot >> > dish >> >> support arms >> >> > >> >> > >> >> > Yahoo Groups strips away all attachments. You will need to > send >> >> the >> >> > sketches direct to the other person instead of via Groups. >> >> > RAK >> >> > >> >> > Geraldo Paiva wrote: >> >> > >> >> > > I tryed three times to send the sketch. Certainly, >> > Yahoogroups >> >> is >> >> > > blocking the attached sketch, I see. >> >> > > >> >> > > You have already furnished the distanCe between holes of >> >> feedhorn ring >> >> > > (5.3/4"). Ring deep 1'. OK. tHe opening of the feedhorn >> > extends >> >> down >> >> > > 3/4" from the bottom of the ring. OK. >> >> > > >> >> > > Are missing >> >> > > >> >> > > DIAM >> >> > > <------------------------------------------------------> -- > --- >> > -- >> >> > > . . ! >> >> > > . . ! >> >> > > . . ! DEPTH >> >> > > . . ! >> >> > > . . ! >> >> > > . ------- >> >> > > >> >> > > Loures >> >> > > >> >> > > >> >> > > >> >> > > >> >> > > >> >> > > >> >> > > >> >> > >> >> > >> >> > >> >> > >> >> > [Non-text portions of this message have been removed] >> >> > >> >> >> > >> > >> > >> > >> > >> > Yahoo! Groups Links >> > >> > >> > >> > >> > >> > -- >> > No virus found in this incoming message. >> > Checked by AVG Free Edition. >> > Version: 7.5.503 / Virus Database: 269.17.12/1202 - Release Date: >> > 12/29/2007 1:27 PM >> > >> > >> > > > > > > Yahoo! Groups Links > > > > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.503 / Virus Database: 269.17.12/1202 - Release Date: > 12/29/2007 1:27 PM > >
