rechecking my F/D

[gabshere]

ok guys i'm out checking my F/D and adjusting my feedhorn

its a BSC621
its mounted on a unimesh 7 1/2 ft dish

90"
to the strings is 14 1/2 inches
to the scaler is 35 1/2 inches

http://www.geo-orbit.org/ says D squared =8100 devided by 16 X 14.5 = 232 which all equals to 34.91

is my math good ?

i don't know exactly where the scaler should be at i know now its currently at 35.5and the F/D listed above says i should adjust my lnbf down to the 34.91
i can't remember if this is all right... there are no marking like the chap has on the feedhorn.

I will check back and look for answers I do have signal and its pretty good
it was even off on two sides of the scaler close to 36 i think this is due to my bent support arm which i straightened out.

so i will align everything up and get a few numbers and come back in to check comments
thanks

 

[Lak7]

When I installed the BSC621, I matched it up to the existing LNBF, and adjusted it for the best Ku signal.

 

[linuxman]

Use this site to calculate it for you.

You'll have to convert inches to cm using this site, and use the same site to convert it back.

I use it all the time.

 

[satcom1]

Lak7,

Good idea but what did you then do with the scaller ring?

 

[gabshere]

ok great fred i will check my figures and bookmark that site

FD = 0.39 which i have no markings to go by wonder if i can take a measurment from the chap

oK and the lnb distance to dish is 34.9 so that part was close

another problem i'm having is getting the scaler level / square so i will have to work on that

 

[Lak7]

Lak7,

Good idea but what did you then do with the scaller ring?

I left the existing Scalar Ring in place.

 

[gabshere]

ok i adjusted and leveled the scaler its right at 35 1/2 on all sides
I will have to work on it to get it close to 35" to 34.9 " like the calculator says
i got it level by twisting the scaler and it leveled right up ( by eye ) i will have to check on one of those digital angle meters cause it looks like it would help in this area.

I adjusted the feedhorn to where i thought .39 should be ... i measured a chap and a cal amp and they both measured out to 3/4 for a F/D of 0.39

have good to great c-band signals on the east arc good in the center and poor in the west
only have ku on one or two sats in the east at 74 & 72

I stopped adjusting cause my pole is moving ( weve had 7 inches of rain in the past week) so i will have to shore it up with a bit more concrete in a few days and re level the pole.

switching to the 10 ft dish which is on the pole that the 7 1/2 fter used to be on.

hoping i can get it tuned cause i'm missing c-band

so more measurments comming up

 

[Hermitman]

Here's a Chaparral web page with information concerning feedhorns and scalar rings. About halfway down is a small chart showing the amount of feedhorn extending forward of the ring at a specific f/d ratio. Once you set your f/d ratio, set your focal distance for the strongest signal. If its close to specs, good. If not, also good. Good luck.

Welcome To Chaparral Communications

 

[gabshere]

well with the 7 1/2 fter couldn't make the 34.9 inches but when i reset the pole i will just try to peak it right where it is.


now on the 10 fter it call for 42.9 inches and a .36 F/d
well theres no way i can get the current support arms to adjust out that far 42 3/8 is the max. plus to gain the signal i had to adjust the feedhorn in (and i'm only hitting the center of the arc so far didn't try anything east of 95) but i get 95-107 with average signals ( no ku tested yet )

so i still have a lot of adjusting left to do and also readjusting so i hit the arc .

thanks for eveyones comments .. this project looks like it will take a few days as i'm working nights ..... but i have a few weeks until football season kicks in

thanks Hermitman I bookmarked it and read through it

 

[linuxman]

Yes Thanks Hermitman,

I read it and bookmarked it too. I may have to try those measurements on the CK-1 I have.

 

[Anole]

confused

Yes Thanks Hermitman,

I read it and bookmarked it too. I may have to try those measurements on the CK-1 I have.

Thanks from me, too.

But, people are always saying, "measure to 1/4" inside the feedhorn", or something like that.
How deep inside the throat of the Chaparral feed horn are the goodies, and should we check how deep they are in the CK-1 ???
The probes are pretty darned far back inside that bandstacked LNB Sadoun sells!

 

[gabshere]

well i will have trouble getting the correct distance between the lnb & dish won't get there with these support arms. so that why i figured i would just go ahead and try to gain the best signal.

for the 10 fter the F/D is 42.9 scaler is at 42.375 but the feed is already adjusted 1.25 inches toward the dish so i suspect the BSC621 is figured differently than the older type chaps & cal amps with the F/D ratio. so like hermitman said I feel like i'm to the point of tuning to the signal and trying to get the best signal .... i'm sure the ck1 would be simular , its not marked on the side with f/d ratio is it ?

 

[Anole]

... the ck1 ..., its not marked on the side with f/d ratio is it ?

Sadlly no, not on the CK-1, and not on the B1satC.

 

[Mauiguy]

well i will have trouble getting the correct distance between the lnb & dish won't get there with these support arms. so that why i figured i would just go ahead and try to gain the best signal.

for the 10 fter the F/D is 42.9 scaler is at 42.375 but the feed is already adjusted 1.25 inches toward the dish so i suspect the BSC621 is figured differently than the older type chaps & cal amps with the F/D ratio. so like hermitman said I feel like i'm to the point of tuning to the signal and trying to get the best signal .... i'm sure the ck1 would be simular , its not marked on the side with f/d ratio is it ?

Keep in mind that the measurement method is only a starting point. On my paraclypse 12 foot dish all lof the numbers worked out perfectly.

However when I rebuilt my fourteen foot dish the numbers told me to go to a specific distance for focal distance. I got nothing there. So I moved the focal point until I got maximum reception.

If you are on a given satellite and you can then adjust for your best reception then I would say that is the one for you.

Lastly if you are getting great reception on a few birds then some that are not so great it is most likely not the focal distance or the F/D ratio. It is amore likely a combination of true south pointing and elevation.

 

[gabshere]

thanks for the comments Mauiguy

It is amore likely a combination of true south pointing and elevation.

i suspect most is is a combination of several factors but i will have to check each one once i gain the best signal, i will retune for TS and elevation my biggest problem is all the rain and the dish being up so high ( its on a 9 ft 4 inch pole and its a 10 ft dish) makes it a hassle to work on

first i have to get one of those digital angle levels at sears to help me out