LNBF Question

[tvropro]

I recently got from a friend a eliptical dish, I think it's a 80cm. I put it up for G-10, I got it aligned and found the research channel and a few others on horizontal polarity. When I tried to get anything on the vertical such as the Equity channels I couldn't get any quality. I peaked the thing to the max on the Horiz channels and still nothing. I did a blind scan and still no verticals. So I figured I'd try another bird. I locked in T7 and tuned in White Springs Tv. Then I scanned the whole bird H & V and it wouldn't find any verticals there either, which leads me to believe I have a bad LNBF. Is there anyway of checking this for sure? If I need a new LNBF how do I make sure I get the right size to fit in the clamp on my dish? I have a Pansat 2700A receiver. Any input on my problem will be appreciated. Thank's in advance.

 

[Anole]

... which leads me to believe I have a bad LNBF.
Is there anyway of checking this for sure?

Twist it 90º and scan again?
Make sure your satellite has both H and V transponders? (Lyngsat.com)

If I need a new LNBF how do I make sure I get the right size to fit in the clamp on my dish?

There are several common neck sizes.
Measure yours in milimeters (20, 40mm, etc) and post.
Maybe post a picture - it might be something we'll recognize.

Not being able to select both polarities might also be due to a receiver setting (bandstacked LNB) or too-long a cable (or corroded connectors)
If you can check the actual voltage at the LNB in both V and H, that would be useful, but not mandatory.

 

[turbosat]

Check for skew adjustment, sounds like its skewed all the way to one polarity. What kind of dish/lnb is it?

 

[tvropro]

Twist it 90º and scan again?
Make sure your satellite has both H and V transponders? (Lyngsat.com)

I tried that already on G-10, still nothing.

This is on the LNB label:

P1/05 ADTH
11.7-12.2
950-1450
ATLANTA DTH INC

My cable run is about 100 feet. I have an A/B switch in line to swap my C band dish and the Ku FTA Dish, it is a Macom and designed for satellite freq's. Connectors are new and I checked the cable for shorts and continuity.

Does the vertical side use 13-14v and the horiz side use 18vdc?

 

[Anole]

here's a fairly typical data sheet on an Invacom LNB
http://www.invacom.com/products/documents/Single.pdf
note, it's a PDF file.
vert = 12..13 volts
horiz= 18 volts
neck size is a nominal 40 mm

So, if you're only getting H, either the LNB is bad as you suggested, though that's uncommon...
... or you may have your receiver set for bandstacked LNBs, which would supply only a single voltage (18v), no matter what.
The latter is unlikely, too.

edit: I couldn't locate your LNB, but is it so old that it has two outputs?
One for V and one for H ?

Anyone else got any good ideas?

 

[Wescopc]

Try by-passing the switch they can sometimes fail on one port for V or H.
Bob

 

[Mr Tony]

it is possible its only one polarity

 

[Tron]

Some LNB setups, particularly when a dish was used to receive one specific service (for example, a VSAT configuration), only receive one polarity at a time. Do you have a LNBF (combined feedhorn/LNB, similar in construction to a DirecTV LNB), or is it a separate feedhorn/LNB? If you're working with a WR-75 flanged LNB, chances are it is single polarity.

 

[tvropro]

I tried a few things last night. First I bypassed my switch, that made no difference. Then I checked the receiver's LNBF voltage, 14v Vert--- 18V Horiz.

Then a brainstorm hit me: When I rotated the LNBF 90 deg earlier I scanned as Vert which keeps the voltage at 14 v. That don't work... so I went into setup and set the vert transponder as horiz, 18v then went and twisted the sucker 90 deg and got quality, how about that! So then I ghetto moved the dish back to G-10 and aligned it for the best on research tv again. Then I went into setup (advanced scan) on all the Equity muxes, I changed the Vert's to Horiz and scanned. Boom everything came in. I peak and tweaked it on the weak mux (11720) for max quality. Ended up with a 76 quality there.

So a couple thing's could be happening here. Either the switching in the LNBF is defective and not sensing the voltage change or the LNBF is only made for one polarity. Im not sure what this dish was used for and may have been for some single channel service and required only one transponder & polarity.

All in all I got the Equity muxes working so Im happy for the moment
I may pick up another LNBF down the road and mess with it. Right now I was interested in The Equity channels and there working great so that made my day.

One last question?? I wonder what size this dish is? Maybe the math wizards out there can do some calculating and give me an answer. The size is, top to bottom 31.5" side to side 35" It's a steel dish and has a nice rim big rim on it that keep's it parabolic shape well.

Total cost for this job was about $8.00 for coax connectors 10 pack at Home depot and a tube of silicone RTV. Can't beat that with a stick

Thank's for all the quick reply's, this forum is great:up

I now have 4 dishes up and running am I Nut's or what...

 

[Mr Tony]

Cool. Glad it was something simple

I now have 4 dishes up and running am I Nut's or what...

nah. You're just enjoying the fun world of FTA