Proper length of P* 84e feed support arm

[K'bick]

Hello to all,

I've been a member for over a year but have never posted so first hello and thanks to all who contribute to making this a great site.

I'm in the process of replacing my rooftop-mounted Fortec Star 1M dish with something more rigid that doesn't lose it's parabolic shape in light/moderate windy conditions. So I recently obtained a new in box Channel Master 84e and a used P* dish (74e I think).

The 84e dish came complete but had a strange looking rectangular feed arm with a dual feed holder and one eagle aspen LNB off to one side (I'll try to attach some pictures). All the P* dishes I have seen have the traditional rounded triangular rib on the top side of the arm.

What I was wanting to do was to put a traditional P* type arm on the 84e to bring the feed back to the center. I have only one TV so one feed centered seems like a better choice than a feed off to one side of a dual feed holder (please correct me if I'm wrong).

In my quest I got what was described as an 84e feed arm from a P* dish but when comparing it to the arm on the 74e dish it is identical. When comparing those P* arms to the strange rectangular arm that came with the 84e the two P* arms bring the feed about 3/8-1/2 inch closer to the dish than the rectangular arm.

I'm pretty confused as to what I've got and I'm hoping someone can help me sort this out. Are the 74e and 84e arms identical or did I just end up with 2 74e arms? What is the actual length of the arm for a P* 84e? If I switch to a P* arm to bring the feed to the center of the dish can I still use that brand new feed from the rectangular arm or should I use the "Dove bar" feed on the P* 74e arm?

 

[Mr Tony]

pics are always good

the 84e dish is 40x30 whereas the 75e is 37x27

I just measured the arm and from the front of the dish to the right angle bend up to the LNB holder is 18 1/2" (see attached pic)....I dont have my 75e dish nearby to measure that

But yes you want to the LNB to be in the middle and really not off to the side...I wonder if the 84e has a KU/DBS LNB setup? Is there any other markings on the dish?

 

[osu1991]

The arms are not the same. Some Primestar dishes had dual feeds, do a search for Linuxman and you will see photos of them. I had the same problem, I had an 84e dish but a 75e arm.

http://www.satelliteguys.us/free-ai...ally-some-success-my-makeshift-primestar.html

Here is a thread I started with some measurements. I dont remember if i ever got a final measurement. I found and ordered a new arm from Impakt Products and my 84e worked great until I dismantled everything for my move last month.

 

[K'bick]

Here are the pictures...

- The dish-ends of the support arms when the feed ends are lined up.
- Feed ends of the arms lined up.
- Full side-by-side view of arms.
- The 84e and 74e dishes.
- The roof mounted Fortec Star (during installation).

 

[Mr Tony]

osu
in your thread I got the same measurement if I went to the back of the arm of the dish (where it bolts)

the arm for the 84e is 22 1/2 inches from bottom end to top end ( where lnb mounts)

 

[Mr Tony]

ok...first off nice pics

The offset LNB one looks like when Primestar was attempting to do 2 LNB setup...they never got to that point but there are some of them around. I forget what the gap is between them (4 degrees? 6 degrees?) so you could possibly do a 2 LNB setup with that one

The 1st pic the far right arm is most definitely for a 75e dish. My Starchoice (Channelmaster) dish uses the same type of arm

both of those dishes look the same size just from looking at the pic

 

[K'bick]

Thanks for the super fast responses - even before I could get the pictures uploaded!!

One more question. Would it make a difference what feed I use? (please see pics). The "Dove bar's" feed is considerably larger. How about putting the new Eagle Aspen LNB on the larger feed?

 

[K'bick]

ok...first off nice pics

both of those dishes look the same size just from looking at the pic

I think that was a cameraman error when you "stack" one inside the other its easier to see...

 

[Mr Tony]

Thanks for the super fast responses - even before I could get the pictures uploaded!!

One more question. Would it make a difference what feed I use? (please see pics). The "Dove bar's" feed is considerably larger. How about putting the new Eagle Aspen LNB on the larger feed?

either LNB will work. I would use the sturdier feed bracket...Less flex in the wind
The one drawback of the Primestar LNB (the left one) is the dual output is one side H and one side V so you need to use a multiswitch to combine the two polarities

 

[Mr Tony]

I think that was a cameraman error when you "stack" one inside the other its easier to see...

or the fact its midnite and my eyesite isnt the best

Yeah they are different. The back one must be 40x30 and the front one 37x27 then

 

[K'bick]

either LNB will work. I would use the sturdier feed bracket...Less flex in the wind
The one drawback of the Primestar LNB (the left one) is the dual output is one side H and one side V so you need to use a multiswitch to combine the two polarities

Would it make a difference to transfer the larger feed horn from the Dove bar setup to the newer LNB (with H and V integrated)?

 

[Mr Tony]

If that Eagle Aspen LNB can be skewed, then yes I would (unless you need multiple receivers)

just take the 4 screws off the LNB where skew is and put the new LNB on that bigger feedhorn

 

[K'bick]

If that Eagle Aspen LNB can be skewed, then yes I would (unless you need multiple receivers)

just take the 4 screws off the LNB where skew is and put the new LNB on that bigger feedhorn

Thanks a lot IceBerg. I appreciate all of your help.

 

[WTguy]

The holder for the two lnbs is supposedly for 6 degree separation (at least I have read it in a couple of places, but nothing official). I have had an 84e with one of these arms and holders with the two "coke can" lnb's for awhile but have only recently started working on setting it up (it came off a farm and had basically become a condo for bugs, spiders, etc., plus the holder was broken and some of the plastic was torn off the cover of the lnb's).

I have another 84e which I have used for over 6 years and it has the triangle arm for the one "coke can" lnb. THe only thing I would say about replacing the lnb is during my research to start refurbishing the twin lnb 84e, one comment I read was the small feedhorn on these lnb's are designed for these dishes and help improve the performance. I had replaced the original lnb on the older 84e and during the testing to see if the two lnb's on the newer one still worked, I did find there was a little improvement, for a weak signal it could make a difference between watching a feed or not. So I plan to use the original lnb's with the refurbished dish. They will be set up for 105w and 99w.

Good luck with your project.

 

[K'bick]

The holder for the two lnbs is supposedly for 6 degree separation (at least I have read it in a couple of places, but nothing official). I have had an 84e with one of these arms and holders with the two "coke can" lnb's for awhile but have only recently started working on setting it up (it came off a farm and had basically become a condo for bugs, spiders, etc., plus the holder was broken and some of the plastic was torn off the cover of the lnb's).

I have another 84e which I have used for over 6 years and it has the triangle arm for the one "coke can" lnb. THe only thing I would say about replacing the lnb is during my research to start refurbishing the twin lnb 84e, one comment I read was the small feedhorn on these lnb's are designed for these dishes and help improve the performance. I had replaced the original lnb on the older 84e and during the testing to see if the two lnb's on the newer one still worked, I did find there was a little improvement, for a weak signal it could make a difference between watching a feed or not. So I plan to use the original lnb's with the refurbished dish. They will be set up for 105w and 99w.

Good luck with your project.

Thanks! Yes, I think its worth it to change to the newer "coke can" LNB.. If nothing else it eliminates my need for a switch to combine the V and H polarities. If I can get a bit more gain off the newer LNB then that would be icing on the cake.

The two feedhorns I have both have the same shape - round with a triangular surface facing the dish so it seems like they both match the shape of the dish. The only difference is the size. After looking at the two I'm starting to think that the dual feed arm came with the smaller feedhorn because two of the larger feedhorns would not fit next to each other in the dual holder.

I'm going to try the larger feedhorn on the newer LNB - I may have this wrong, but it seems a larger feedhorn (that still has a profile matching the dish) makes a larger "sweet spot" that might be more forgiving of my aiming blunders and any small tolerances in how I attach the arm and feed.

 

[Wescopc]

Your 84e dual LNB is for 6 deg spacing. I have one that has each LNB with a horizontal and vertical output.
Bob

 

[ziggy1222]

Measuring the bottom of the feedhorn arm an 84e is 21" long and a 75e arm is 19 1/2" long. A 84e elliptical feedhorn measures 3 1/2" top to bottom and a 75e feedhorn measures 2 5/8". If you look on the back of your dish there should be a mold number stamped on it as 84e or 75e.

I also have one of those dual mounts from a WSnet dish and will reconfirm that it is for 6 degree spacing...I have the owners manual. They used two 75e feedhorns on an 84e dish because as you say...so they wouldn't physically bump into each other.

I would also agree to use the larger elliptical feedhorn(84e) however if you have the shorter 75e arm you will still be under illuminating the dish because its not stepping out as much away from the dish and getting a total view of the dish. In this instance the 75e or 84e feedhorn would give the same result(I think !!). At any rate you want to use an elliptical feedhorn(as opposed to a round feedhorn) on an elliptical dish.

 

[WTguy]

Sorry for the confusion, but the "coke can" refers to the lnb's with the separate v and h will require a switch. (I saw that phrase used by someone else and thought it fit pretty well.)

 

[phlatwound]

Sorry for the confusion, but the "coke can" refers to the lnb's with the separate v and h will require a switch. (I saw that phrase used by someone else and thought it fit pretty well.)

WT, I've been told they were relatively uncommon, but some of the (later model?) P* "coke can" LNBFs had a single (voltage-controlled H & V) output, no switch required.

Also, if any one has a pic of the dual-LNBF Primestar, please post in this thread or PM me for email addy info, I'd like to see one of those.

 

[K'bick]

Measuring the bottom of the feedhorn arm an 84e is 21" long and a 75e arm is 19 1/2" long. A 84e elliptical feedhorn measures 3 1/2" top to bottom and a 75e feedhorn measures 2 5/8". If you look on the back of your dish there should be a mold number stamped on it as 84e or 75e.

I also have one of those dual mounts from a WSnet dish and will reconfirm that it is for 6 degree spacing...I have the owners manual. They used two 75e feedhorns on an 84e dish because as you say...so they wouldn't physically bump into each other.

I would also agree to use the larger elliptical feedhorn(84e) however if you have the shorter 75e arm you will still be under illuminating the dish because its not stepping out as much away from the dish and getting a total view of the dish. In this instance the 75e or 84e feedhorn would give the same result(I think !!). At any rate you want to use an elliptical feedhorn(as opposed to a round feedhorn) on an elliptical dish.

I found out (thanks to all of you sharing your measurements) that I had only 84e arms all along. Even my 75e came with an 84e arm - fine for what I want to do with the 84e dish (bring it back to a "stock" P* feed setup) and bad for when I find a use for the 75e.. I'll need to locate a 75e arm somewhere down the road.