LNB alignment on 1.8m C-band (small FTA dish)

[climy]

I installed a 1.8m Channel master offset dish to improve my FTA viewing on C Band--I liked the idea of the mini-bud. I removed the Ku bracket and fabricated new (from others, as seen on this site) that attached the flat scalar with emt box clamps. The flat scalar holds the BSC-621-2d. I used the conical scalar with some improvement. Can some in the small C band dish community help me with LNB alignment? I have made progress; I can view the Virgin Island mux on 99W, get DVB-S2 mpeg-4 EScapes and one time barely, KRBK with the installation shown.

I assume LNB is located in the focal point since I get signals. Now I wanted to be sure I have the LNB "axis" aligned and pointed correctly. "axis" is that the technical term? I figured the "axis angle" was correct because the Ku LNB points at the dish in this direction. What about a C-band LNBF? Is it the same angle as the Ku LNB? Assume I use the lnb arms as a guide, I noticed some mini buds shown the LNB pitched upward--don't know if that's because of the dish size or the lnb arms are shorter. My setup is pointed in line with LNB arms.

I'm trying to get KRBK. Thank you. Please don't warn me that I can't get any better with a 6 foot dish--I've already invested and read a lot before getting this far. Thank you for your help.
Climy

 

[gardenman2002]

climy,
gardenman2002 here.

glad to see you have signal. if you have a satellite meter i would loosen up the lnbf and move it slowly inward and or outward to peak signal.

i usually use a 19 dollar analog meter to get first peak, when moving dish up, down, left right. do this slowly. i personally have received c band on a 90 cm dish and i used duck tape to hold the lnbf down untill i could order the correct mount. i use the same c\ku band lnbf. you can use c band or ku but to use both you have to use a switch. Getting back to your pics, looks good. the focal point stays the same whether you use a cband lnbf, ku lnbf, or brackets to mount multiple lnbfs.You may try rotating the c band lnbf which is called skewing, either left or right. this website has a link to a sat calculator to figure azimuth and elevation. Since you have a signal, i would 1 try grabbing dish and gently pull downward and then gently push upward, and see which gives a peak on signal. then left, and then right gentle pushes on dish to see if signal peaks. if that doesnt work, bring a tv out to the dish, with a receiver and peak for max quality. thats how i did mine and since i am using a c band lnbf, on a ku dish, i had to move lnbf slowly in toward dish, while watching tv,same for moving it outward. i tuned my 36" offset dish in about 20 minutes using this technique. i receive 99w, 103w, some channels on the 87w sat, and receive network channels on 118 w?
thats where hot tv and about 6 or 7 tv channels are. not bad for a 36" offset dish. you will find that the c \ku band lnbf you have is specially designed for small dishes. i didnt know that when i ordered mine. found out that the diameter is smaller than regular lnbfs for c band.
it makes it easier to match up a mount,but that my opinion. anyway congrats on the 1.8. once you peak all the way around, you should be able to motorize it and hit other satelites like i did my dish.go to the link here on this website for the "list" follow the other links at top of page for sat calculator. it will layout the skew(position of lnbf off zero either left or right),elevation,and azimuth.

hopes this helps and hope i dont come across trying to say this or that, i found that this site has alot of good people who will help when needed ,and not alot of fta people have ried to receive cband on a small dish. By the way, i found on some channels , without the scalor ring, i could peak the signal more, but that is with my dish. anyway congrats!!!!!!!!!!!!.

 

[joshrr]

Dont give up. I have a 180cm prime focus cband setup and get krbk loud and clear in upper michigan at 75% qual even in bad weather. Dmx741 lnbf and openbox s9 receiver. I agree with adjusting the focal depth as the previous poster sAid. That makes all the difference for me.

 

[climy]

Skew and focal depth Adjustments

climy,
gardenman2002 here.

.. try grabbing dish and gently pull downward and then gently push upward, and see which gives a peak on signal. then left, and then right gentle pushes on dish to see if signal peaks.

The 1.8m fiber glass dish is not that flexable. It's set in concrete with a 4-1/2 inch pipe. I use the adjusment screws on the mount for Az and El. One problem with the Andrews mount is re-tightening the lock bolts--it moves the dish up slightly becase it stiffens the frame--not the best for constant adjustments. I try to under compensate elevation a bit which usually works to bring the siganl back up.

Not the dish but the LNBF focal depth and skew adjustment set screw is a pain. It's one screw and seems the BSC 621 feed tube is *slightly* tapered. The screw works into the tube to scratch up the coating. After a while, the thread boss cracked. I found a new scalar and put cut pieces of foam tape on the inner raised pads to reduce the play when the screw is backed off. That helped with making consistant and gradual adjustments.

. anyway congrats on the 1.8. once you peak all the way around, you should be able to Motorize it and hit other satelites like i did my dish.

I would like to motorize with an actuator arm. Who has this? It might have to be all custom or expensive channel master/Andrews part. I'd like to move in the arc 87 to 121W. That would get a lot of viewing.

. anyway congrats!!!!!!!!!!!!.

Thank you. It's been a fun ongoing project.

 

[PrvtN00b]

I installed a 1.8m Channel master offset dish to improve my FTA viewing on C Band--I liked the idea of the mini-bud. I removed the Ku bracket and fabricated new (from others, as seen on this site) that attached the flat scalar with emt box clamps. The flat scalar holds the BSC-621-2d. I used the conical scalar with some improvement. Can some in the small C band dish community help me with LNB alignment? I have made progress; I can view the Virgin Island mux on 99W, get DVB-S2 mpeg-4 EScapes and one time barely, KRBK with the installation shown.

I assume LNB is located in the focal point since I get signals. Now I wanted to be sure I have the LNB "axis" aligned and pointed correctly. "axis" is that the technical term? I figured the "axis angle" was correct because the Ku LNB points at the dish in this direction. What about a C-band LNBF? Is it the same angle as the Ku LNB? Assume I use the lnb arms as a guide, I noticed some mini buds shown the LNB pitched upward--don't know if that's because of the dish size or the lnb arms are shorter. My setup is pointed in line with LNB arms.

I'm trying to get KRBK. Thank you. Please don't warn me that I can't get any better with a 6 foot dish--I've already invested and read a lot before getting this far. Thank you for your help.
Climy

I have the same dish, one 1.8 Raven and also I have the same problem, is this the best solution available?

sorry team, for bringing back an old topic

 

[RimaNTSS]

This is one of my favorite topics! To install C-band LNB on the offset dish you have to have LNB-holder properly adopted. On this picture I combined all needed dimensions for 1.2m and 1.8m Channel Master dishes (yellow digits for 1.2m and blue digits for 1.8m). Some time ago I've designed universal holder which fits to any CM offset dish (0.9m, 1m, 1.2m, 1.8m and 2.4m) and can be used for Ku and C band LNBs, only the clamp has to be changed from 40mm to 63.5mm . C-band LNB on the offset dish should have conical feedhorn.

 

[Cham]

I have a 240cm offset and found it is really helpful to have the feedhorn and scaler to be adjustable independently, like Rima's mounting system above. First I maxed out the most TPs without the (conical) scaler installed by moving the feed horn in and out and adjusting polarity, using the original Ku feed horn opening position as a starting point. Once maxed out, I added the scaler to the mix. The scaler works like a filter and it's position affects frequency bandwidth by controlling signal-to-noise ratios. Start with the position that lines up with the focal ratio of your dish, then adjust (very minutely) in or out to maximize the TPs of interest without changing the position of the feed horn. Lock it down to the feed horn, then adjust the feedhorn/scaler assembly to maximize signals again... maybe a 1/10 of an inch forward or backward can bring up signals again by a dB or so. Go back and fourth on these adjustments, it is a rather delicate operation, but yielded results for my situation.
Main thing is to take your time. Also a good satellite meter that displays S/N in dBs or a receiver that does so remotely (smart phone etc app) is almost a necessity. A receiver out at the dish is fine too, you need to see results of adjustments in real time.
Most importantly...have fun!

 

[iBoston]

I have a question. When i am adjusting an LNBF, your blocking the signal. Especially on the smaller dishes. I find it best to fine tune off the weakest signals, but then you block the dish messing with the lnbf and you loose the signal. Arrggh.

Also, you talk about all these fine adjustments, but when ever i try and loosen the lnbf from the scaler ring, it wants to then offset up or down and is very difficult to make fine adjustments with those conditions. Is there a trick that i have missed out on?

 

[RimaNTSS]

When i am adjusting an LNBF, your blocking the signal.

On PFA, yes, while adjusting LNB signal is blocking by body (bigger body, heavier the obstruction). When it is offset dish then no problem with blocking, just need to stay low enough.

 

[PrvtN00b]

RimaNTSS so you build it your self, are you welling to sell them?? or at least share a blue print so I can have someone build one for me here in Panama?

Thanks.

 

[RimaNTSS]

Pop quiz:
1- Who knows how by using of digital protractor and measuring-tape is possible to check whether LNB is located in antenna's focus (LNB's Phase center is co-located with antenna's focal point)?
2- If you know the answer to question #1: Did you do it in real life and what was the result?

 

[Corrado]

I have 3 Prodelin 6' dishes here converted to C band. I just matched the locations of the original feeds and tweaked them until I had the desired TPs with the best quality.

Now out of curiosity, I want to measure them for comparison to the specs RimaNTSS posted.

 

[RimaNTSS]

I want to measure them for comparison to the specs

I was posting numbers for Channel Master dishes. Prodelins will have them little bit different. If you wish I can make similar picture for Prodelin.

 

[Trust]

I have a question. When i am adjusting an LNBF, your blocking the signal. Especially on the smaller dishes. I find it best to fine tune off the weakest signals, but then you block the dish messing with the lnbf and you loose the signal. Arrggh.

Also, you talk about all these fine adjustments, but when ever i try and loosen the lnbf from the scaler ring, it wants to then offset up or down and is very difficult to make fine adjustments with those conditions. Is there a trick that i have missed out on?

Some time ago I made this coincident moving device to test the optimum position for the distance scalaring / dish and lnb / scalaring .
Once the best position was found , I used the distance data and changed to the standard scalaring .
Picture is made testing a 1.2 m Echostar Offset dish .

 

[iBoston]

WOW, Impressive... Nice gadget...

 

[Olalekan]

Wao! Its Inspiring.

 

[espaun206]

This is one of my favorite topics! To install C-band LNB on the offset dish you have to have LNB-holder properly adopted. On this picture d all needed dimensions for 1.2m and 1.8m Channel Master dishes (yellow digits for 1.2m and blue digits for 1.8m). Some time ago I've designed universal holder which fits to any CM offset dish (0.9m, 1m, 1.2m, 1.8m and 2.4m) and can be used for Ku and C band LNBs, only the clamp has to be changed from 40mm to 63.5mC-m band LNB on the offset dish should have conical feedhorn.

you sell or where I can buy
I have one Channel Master 1.8m

 

[Olalekan]

How does cornical feedhorn look like.

 

[beavs2112]

How does cornical feedhorn look like.

 

[Titanium]

This one is purtier'... LOL!!!

We all this that way about our own kin folks... don't we?