Primestar oval feedhorn on FS 1.2m dish

[Das Hammer]

In short, it works, but is it optimal?

So, I had this old primestar (6262?) lnb/feedhorn from one of my oval dishes just sitting there and thought, gee Wally, I bet I could mount that to the 1.2 meter. So, I did. I used the large lnbf holder that is used for holding a c band or c/ku lnbf. The holder was a little too big in diameter, so I wrapped a piece of RG6 around the primestar lnb and it clamped up nicely.

So, this primestar lnb and feedhorn is working pretty nicely and without getting into too many details, I can say that it seems to be performing very well. I don't appear to be missing any channels.

However, I'm thinking that I'm missing out on some signal for two reasons. First reason being the shape of the feedhorn because it is oval shaped and not round.

Second, the holder is clamped around the LNB itself, which pushes the feedhorn closer to the reflector and I believe the ideal focal depth would involve getting the feedhorn closer to the holder. I've got it as far back as I can get it now.

Missing out on all of the reflected signal could mean not getting some feeds. I want to get an invacom, but only if it would give me some benefit. What do you guys think?

PS: I worry too much.

 

[Anole]

empirical evidence

First , let me say none of these pictures are mine.
I find them inspiring, and keep a small collection.
Good thing, because it make this discussion easier.

Are the first two pictures like the feedhorn of your oval PrimeStar?
I believe they are meant to "see" the signal reflected from that oval dish.

The third picture is supposed to be an Echostar/Dish LNB.
It looks at SuperDish, and although built differently, it seem to "see" an oval surface, too.

Last picture are a pair of similar LNBs, opened to expose their feedhorns.
I kinda think Philips wouldn't make both round and oval feeds if they weren't optimized for different reflectors.

So, I'd have to say, based on the evidence, that your feedhorn wasn't optimal for a round dish.

 

[gabshere]

you could probably use the feedhorn off the round prime* lnb to adjust the fd more

a picture of your setup would help envision what you have going on.

here a pic of the round prime* lnb its almost twice the depth of the oval prime* lnb feedhorn.

1st pic is a oval lnb 2nd and 3rd are the round lnb

 

[Das Hammer]

Yes, gabshere, mine is the first pic in your post. Went ahead and ordered an Invacom today. Thanks for the replies, fellas.

 

[gabshere]

well i think you will love the invacom , its a good lnb

i think there is one that will work with both but you would have to have the feed horn for the oval for offset and the one from invacom for prime focus dish

as for other lnb's i would like to compare my QPH-031 to several others , like the Xtream & Xtream II .... the bsc-321s was a good the QPH scored higher in some areas and about the same in others but the QPH was a bit more versitle as it does circular.

 

[Tron]

A perfect match would be the feedhorn in Gabshere's post (which is made for your 1.2 Channel Master, the same as the one I'm using) mounted to an Invacom QPF-031 (note that the QPF is the same as the QPH, but just an LNB instead of an LNBF).

 

[Anole]

Tron -
I thought about that, but aren't we now just splitting hairs?
Aren't we 99% of the way there, by not using an oval dish feed horn on the Invacom ?

Gabsphere -
You got a better end-on picture of that first feedhorn?
I know Tron was talking about 2 & 3 for use with the flange-mount Invacom.

 

[Das Hammer]

I had contemplated switching out the primestar lnb with the snf-031 (use the same feedhorn) and continue to use the primestar oval dish. I never had a real ku only lnbf for the 1.2meter round so installing the primestar lnb/feedhorn onto the 1.2 meter round was a bit of an experiment. After some tweaking I was getting way better numbers with the larger dish, which I somewhat expected.

I don't know how much I'll gain with the invacom qph-031 mounted to the 1.2 versus the primestar lnb/feedhorn on the 1.2, but at the very least I'll free up the primestar lnb/feedhorn so it can go back onto one of the ovals that I've got. Additionally, I'll be able to get that 3x4 switch out of the signal line since the invacom won't need it.

 

[Tron]

Tron -
I thought about that, but aren't we now just splitting hairs?
Aren't we 99% of the way there, by not using an oval dish feed horn on the Invacom ?

Gabsphere -
You got a better end-on picture of that first feedhorn?
I know Tron was talking about 2 & 3 for use with the flange-mount Invacom.

I don't know how much visible surface area we're talking about, but the feedhorn in Gabshere's post is optimized for the "round" 1 and 1.2 meter dishes, whereas the oval feedhorn is made to see a different surface area. There will be an improvement by using the feedhorn made for the dish, how much, I don't know. Might be a good experiment to try if I can find an oval Primestar feedhorn and mount it on my 1 meter CM

 

[Anole]

Tron -

Maybe my post was unclear.
What I meant, was: "Isn't a stock Invacom LNBF good enough on the round dish, compared to a flange-mount Invacom, and the round PrimeStar feedhorn?"

Or maybe I misunderstood.
But, we're all on the same wavelength, here, and just waiting for the final report from Das Hammer.

 

[Tron]

Oh, I misunderstood. I know (from my experience using a Fortec FSKUv on my CM) that it will work, but I have experienced higher quality numbers once I got the feedhorn for my dish. I'm using a .9 NF Norsat LNB on the feedhorn, but that's misleading since the LNB is a PLL with a very stable L.O.

 

[gabshere]

yes when i ordered the QPH-031 it was to place on a oval but have since placed it on a round primestar dish. I feel ( and i have no way of testing , maybe i can try a few things in warmer weather) that the QPH-031 isn't at optimal focal distance , maybe it needs another 1/4 inch to reach it peak. i have it mounted at its limit right up against the head of the lnb. If i had the QPF-031 i could test with the feedhorn from the orginal primestar lnb.

even though it doesn't have a oval type of feedhorn i think i can peak the QPH-031better on the oval dish. so there is some difference between the two. (this will be a summertime test for me )

Yes Anole i will post a few more photos of the feedhorn

 

[gabshere]

ok here are some more photos of the feed horns 2 are for ovals and are alike but one is larger than the other and 2 are for round and are exactly alike.
the size is for the oval dish:
2 3/4 long X 2 3/4 wide oval tapered ribbed feedhorn (small one)
3 inches long X 3 1/2 wide ( 3 1/2 tall) oval tapered ribbed (larger one)

for the round dish :
4 3/4 inches long X 2 inches wide round feedhorn ( both are the same )