6' Panel Dish with Feedhorn?

[cream123]

I am putting together a Sadoun 6' panel dish with a GeoSat Pro LNBF.
In following recent threads I was wondering does a Chaparral C-Band dual feedhorn with 2 LNB's and a modified multiswitch with 18V provide better reception or is this not necessary on this type of dish?
Thanks,

 

[Mr Tony]

That might be overkill

I am putting together a Sadoun 6' panel dish with a GeoSat Pro LNBF.

thats the same setup I have and it works great

 

[cream123]

Thanks Ice for responding!

 

[crackt]

an ortho on a 6 foot dish would be analogous to a governed big block in a chevy vega. save your money for something else.

crackt out,.

 

[cream123]

Thanks crackt for responding!

 

[jduffin]

I've been thinking about adding an ortho feedhorn with some good lnbs for my 6' dish as well. I've been pretty happy with my Geosat C2 LNB with this dish, but I'm thinking that the ortho setup would give me an edge with some high FEC and/or S2 signals that I currently can't get or am having a hard time locking.

Can someone with a 6' ortho setup comment??

 

[pendragon]

I've sat on my tongue so far because I have a dual ortho with some excellent LNBs on my 6'. I always enjoy a chuckle when others insist one needs at least a 10' to get the high FEC S2 signals, because my 6' ortho pretty much gets them all. A single ortho would work even a little better.

 

[jduffin]

pendragon -- you've peaked my interest. Tell me about your ortho set up. What LNBs, feedhorn, and switch are you using? What 6' dish do you have?

 

[pendragon]

For C-band I have 6', 7.5', 10' and 10.5' prime-focus reflectors with four single orthomode feeds (three linear and one circular) and one dual ortho. All the C-band LNBs are Norsat 8115s and originally I had Norsat 2707A LNBs on the dual. I have since converted the dual to use a C120-flanged Invacom QTH-031 quatro universal LNB.

I've played around with different configurations, but I decided to keep the single orthos on my biggest dishes because they deliver slightly better CNRs on C-band than does the dual ortho. The dual got relegated to my 6' Fortec because that dish is a solid petal and has the highest f/D of all my prime-focus reflectors. Dual orthos do ok on Ku-band, but they are a compromise design at best. I have some ideas on improving the dual ortho Ku performance, but frankly it would be of no use to me.

I would highly recommend a single ortho with a 6' dish if you want to squeeze out every last dB. The costs will add up, but the combination of a low-loss feed and low phase noise LNBs should beat just about anything for high-FEC, high-SR S2 signals. With something like Norsat 8515 LNBs and a Chap single ortho feed, one can get away with spending about $150 new. I'm happy with my dual ortho, but I am reluctant to recommend it because the C-band performance is a little less than with a single ortho, Ku performance can be problematic and the cost is considerable.

 

[cream123]

Pendragon, you have all of our attention!
Please explain the difference between single and dual orthos and their applications.
Thanks,

 

[Anole]

Here's some reading material: .
Thinking about orthomode feedhorns

edit: Some people confuse the terminology.
C-band only takes two LNBs. Dual band (C & Ku) takes four LNBs.
So, is "dual" a dual LNB or a dual band?
If you make the answer clear, then everyone will understand.

Oh, and single band orthos are much cheaper than dual band units.

 

[pendragon]

An orthomode feed by definition is capable of receiving two polarities simultaneously. Thus it will generally require two LNBs in the most basic version. The FTA vernacular for this is 'single ortho' which normally indicates it is capable of C-band reception only. A 'dual ortho' is capable of simultaneous C and Ku-band reception for two polarities, which means there are generally four LNBs mounted - two for C and two for Ku.

Single ortho feeds can be had for around $60 plus of course two C-band LNBs. A new dual ortho is hard to find for less than $200, to which one needs to add four LNBs. A single ortho is a very low loss feed and is hard to beat.

A dual ortho generally employs two coaxial feeds - the large one has a typical C-band style scalar, while the smaller Ku feed is scalar-less. This tends to reduce Ku gain and causes a poor beam pattern. The waveguide for Ku-band is longer than ideal, causing further losses. On top of this the C-band side will likely perform a bit better if the focal point is located slightly inside the feed, but that will cause a corresponding loss for Ku. The presence of the Ku feed does reduce the performance of the C-band side. I suspect a dual ortho would work best on a high f/D reflector, perhaps 0.42 or larger. But a single ortho will invariably beat it.

If you want the best possible C-band reception, save your money and get a single ortho. If want both C and Ku, get the single ortho and use the money you're saving over a dual ortho to buy a 1.2m offset for Ku. Anyone looking at any type of ortho feed should read the thread Anole posted as there are several other considerations that might not be immediately obvious, including powering the LNBs and switching the beast.

 

[cream123]

Issue with LNB's

I saved and was finally able to purchase a Chaparral single ortho (11-1329-1) and two Norsat 8515 LNBs and am having an issue I cannot solve. (All testing is at the dish)
I am pointed at Anik F3 at 118.7 and am able to view the horizontal stations when only the horizontal lnb is attached to the multiswitch.
Once I attach the vertical lnb coax to the switch I lose all signal, remove the vertical lnb coax from the multiswitch and the picture appears.
I have tested with 2 different WNC SWA-48 switches each with the 18V mod, a Zinwell SAM-3402 switch, and different coax cables.
Could a bad lnb be causing the issue, does anyone have any ideas or testing procedures for me to follow?
The Chaparral feedhorn has been attached to the dish with the inside plastic probe in the vertical position, does this plastic covering need to be removed?
Is there something I am overlooking in this installation?
Find attached two pics, one of the plastic part, the other of the way I have it installed at the dish
Thanks again for all of your help!

 

[Chewie]

Hello Cream
Did you try swapping the lnb's?
Regards.
Chewie

 

[cream123]

While testing I had a viewsat at the dish and decided to run all wires straight thru to the living rooom where the AZBox is.
Everything is working fine now.

 

[Anole]

Okay, I assume the problem was something embarrassing.
Go ahead... tell us... we've all done silly things before. :up

 

[cream123]

Nothing embarrassing at all, while outside at the dish with a tv, multiswitch and an old Viewsat STB I could not get a picture when both the vertical and horizontal LNB's were attached to the multiswitch at the same time. I took down the temporary setup at the dish and decided to run both coax cables straight thru to the AZbox in the house. The multiswitch in the house is the same as the one that was used outside, a mod WNC SWA-48 for 18v. Everthing then worked!

I believe the problem was the order of the coax cables connected to the multiswitch and which one went to the 18v port and which one went to the mod 18v port.
When I reverse the coax cables at the mutliswitch nothing works, put them back then it works.
Also, both 18v ports on the multiswitch need to have both LNB's attached.
If I remove either the v or h coax from the multiswitch one at at time, I lose both v and h signal.

Any comments or suggestions are welcomed!

Thanks

 

[brentb636]

Is there a link available to the multiswitch mod for the orthomode lnb application : Found 2 links to seperate mods. That's a bonus.

 

[mjac]

Here is a link to a thread that contains one of the mods.

http://www.satelliteguys.us/fta-shack/174802-naughty-mods-ii-4x8-switch-all.html

I believe there was another thread that involved another brand switch mod but I can't find it.

 

[mjac]

I found the the other mod.

http://www.satelliteguys.us/free-air-fta-discussion/190889-naughty-mods-iii-6x8-switch-power.html