Best of the ISP-Lists

C and Ku Satellite Bands

Members of the ISP-Satellites list discuss the relative advantages of cheap Ku band service and expensive C band service.

[November 28, 2001]

On the ISP-Satellites list in November, JW asked,

"I remember reading that C band was best used for broadcast mode and that Ku band was better for interactive Internet browsing. What's really the difference between the two?"

A number of respondents noted that rain fade is the biggest difference:

[MP offered] "C band is virtually unfazed by rain, whereas Ku band is severely affected. A while ago, I was contemplating building a transportable Ku uplink, so when ESPN was covering a nearby golf tournament, I talked to the fellow who had the C band uplink. He told me the only reason he had got the job was that his predecessor had thought it was safe to use a Ku band rig to cover a game in Arizona, but had lost the signal when some clouds blew through, and he missed a million-dollar putt by Arnold Palmer."

[PM suggested] "Think of it in terms of availability. If you need 99.95 percent availability in an area with high rainfall, it's difficult to get that at Ku band without a very large antenna. But if you only need the service to work 95 percent of the time, it's not a problem. The tradeoff between the cheap (mostly consumer-grade) equipment and small antennas at Ku band and the relatively expensive (professional grade) equipment and larger antennas at C band is really all about how critical your needs are on availability."

[JM added] "Apart from Ku's susceptibility to rain fade, there is no other difference between the characteristics of Ku and C band that would make one better or worse for any IP application than the other."

Others warned that C band can cause severe licensing headaches:

[DS advised] "The FCC requires frequency coordination and licensing of C band, plus a lengthy and expensive approval process for each C band uplink. Our first C band project was for fifteen schools in rural Wyoming, and it took the FCC almost nine months to approve each school. The very powerful lobby known as the Fixed Wireless Communications Coalition (FWCC) was formed to protect the C band from satellite providers, and will object to many applications for C band service."

[TG agreed] "C band licensing is tedious. Every site must get a separate interference analysis and license, while Ku band can be done with a single blanket license good for thousands of similar sites."

PM observed that when you're working globally, licensing issues aren't confined to C band:

"There are regulatory issues in most countries which define what the bands should be used for. Some parts of each spectrum are shared with other uses and users, such as terrestrial microwave, military radar, etc. This can make it difficult or impossible to get a license for an uplink antenna, impose minimum size restrictions on it, or render it susceptible to interference from other sources. Make sure you read the small print."

—End