Elevation Angle and High Schhol Trig

[jerryyyyy]

I have had a problem with signal strength off the 61.5 sat and moved to 148 with noticeable improvement and it now runs 87-88 and have less pixelation. I do not think I am having a receiver problem since when I look at the 119 sat, which is over my head, no pixelation and signal is 94-95.

I have a hill in the direction of the 148 but when I do the trig and eyeball it the top of the hill is at most at 14 degrees (distance 1000 feet and elevation gain at most 250) and the pointer says the sat should be at 39. The little degree indicator on the dish says 39 or so but the dish looks like it is pointing very low.

Should I go back to High School and relearn trig, or am I missing something.

Should I ground the dish?

This thing was professionally pointed at a noticeable cost.

[Nick]

What is your location?

No trig necessary. The el angle is higher than the 'apparent' angle of the dish because the LNB is below center and the look angle is actually higher than it appears. When the el and az angles are correct, you will achieve max SS.

[TomCat]

It's an "offset" dish, which the dead giveaway for is that the focal point is not directly centered. "Eyeball" the angle between the LNBF and the center of the dish, and guestimate the reflective angle, and you will quickly see that the dish is designed to work this way, not perpendicular to the plane of the dish. It's also not a true parabolic dish, but parabolic in one plane and spherical in the other, which allows for multiple focal points for multiple sats.

[jerryyyyy]

Thanks. I am at Stanford, just souith of San Francisco. So, if line of sight to the edge of the hill to the southwest is say 15 Deg., and elevation is 39 Deg to the Sat, I should be at the maximum available signal. There are no other obstructions.

What do LNB and LNBF stand for?

Very helpful. The thing has been behaving better with 148 than 61.5 whose elevation at my place is down at 11 Deg I recall.

[AppliedAggression]

hmm, i've been thinking about trying 148. Is it possible to get 148 in the northeast. I thought i looked it up sometime and it didn't point right.

[TomCat]

...What do LNB and LNBF stand for?....

They are essentially interchangeable. Old C-band sats had an LNA or low noise amplifier. Since at that time the signal from a sat 23,000 miles away was on the order of -200 dBi (which for those who have no frame of reference is a very, very weak signal) it was necessary to capture the signal at the focal point and immediately amplify it for transmission to the receiver. The amplifier had to have a particularly low noise figure in order to not induce noise into the signal.

An LNB, or low noise block converter went one step further and converted the 4GHz signal to L-band (typically 950 to 1450 MHz) making transmission to the receiver easier. We still use L-band today in DBS, although the transmission signal is in the Ku band or even higher.

Modern LNBF's add electronic polarization control to the basic LNB so that a polarotor or other means is not needed to receive both poles from a single LNB. An LNBF switches polarity dependent upon the different voltages sent back to it from the receiver.

About how weak those signals are: I once heard someone (probably a scientist geek) say that the energy received by all of the dishes ever erected combined was less than the force of a single snowflake hitting the ground. Now that's a tiny signal!