# What is a scalar ring and what exactly does it do?

Status

#### Pepper

Supporting Founder
I asked the entire question in the thread title.

Once there's an answer to this maybe it should be in the FAQ.

#### qwert1515

##### SatelliteGuys TheList
A scalar ring is the ring you see around C-Band LNBs, because the focal distance (Size of dish vs. the LNBs distance away from the dish) for dishes is different the scaler ring is used to adjust how much of the dish the LNB will see. If the LNB sees more area than the dish it will pick up additional noise, if it sees less area than the dish it is like having a smaller dish.

#### Pepper

Supporting Founder
I don't really understand that at all. In all the pictures I've seen the scalar ring is outside of the "tube" and at or behind the opening, so how could it possibly affect signal bouncing from the dish face into the tube?

Pictures or diagrams illustrating the effect would be nice.

#### trinidex

##### SatelliteGuys Pro
I was about to say that was a very succint explanation, I have never heard it put that way before...but then I read Pepper's post.

#### Pepper

Supporting Founder
Not only that, I just noticed I used "affect" and "effect" correctly! But still have no idea what the thing actually does.

#### Lak7

##### SatelliteGuys Master
Pub Member / Supporter
It's like Blinders on a Horse.

#### Mauiguy

##### SatelliteGuys Pro
I don't really understand that at all. In all the pictures I've seen the scalar ring is outside of the "tube" and at or behind the opening, so how could it possibly affect signal bouncing from the dish face into the tube?

Pictures or diagrams illustrating the effect would be nice.

Footprints by Dish Size - Adjusting the Polar Mount for Prime Focus Antenna - C/Ku-Band Satellite Systems - Tuning, Tracking, Azimuth, Elevation, Declination Angles, F/D Ratio, Focal Distance, Inclinometer, LNB/Feedhorn Assembly, Actuator Assembly, C

If you go to : F/D Setting/Scalar Adjustment

on that site, you will find diagrams, and some explatations.

#### satcom1

##### SatelliteGuys Pro
Interesting,according to that link they are noise interference rings. They look like they are in the realm of waveguide and microwave cavity magic. I take it that they function as unwanted radiation QRM eliminators.

#### tvropro

##### On Vacation
In all feedhorns the scaler rings reject thermal noise (kelvin), TI, etc from beyond the edges of the dish. Also normal feedhorns such as (Chaparral) the scaler rings act as a choke plate to cut off noise and out of focus energy being picked up by the feedhorn throat. In a dual mode hybrid feed (ADL) the moding chambers take this out of focus energy, puts it back in phase to be used as good signal. This is why a properly set up ADL (dual mode hybrid feed) such as a RP1-C will out perform a Chaparral.

#### satcom1

##### SatelliteGuys Pro
Last week I was on I-55 going through West Memphis and I saw a large Commercial C-Band TVRO in a horizon to horizon sweep and vertically truncated design. It also has a matching "waveguide" slotted aperature for the LNB. Anyone have information about this design?

#### sideswiper

##### SatelliteGuys Family
very good read thanx guyz