I have had a sirius Sat radio in my F150 for a year now and decided to upgrade my sound system with a DVD, and GPS double Din unit, so at the same time I liked the look of the XM Sky Fi unit as it was silver and matched all the chrome in the truck so I gave my Sirius to my wife and installed the XM in the truck, the signal strength in the city is not bad but still below what I got with Sirius and when we get up to the cottage area I finally just turn it off as I loose signal every 2 second where I had full signal all the time with Sirius and never dropped a bar.

At first I had the installer velcro the antenna right on the front of the dash between the 2 air vents right up by the windshield. When that did not work great I took it right outside the truck and put it on the roof to test and still the same thing.

Anyone else try both and have these issues ?

BM

 

Here is an excerpt about the XM/Sirius satellites...kinda interesting. I had XM when it first came out, and had a lot of dropouts. I have had Sirius for about a year with VERY FEW...seems much better to me. Anyway, you can read this and draw your own conclusions!

Here are two basic ways to cover a given area with satellites. The traditional approach and the one used by most space communications systems is to put up a geostationary satellite over the desired area. Geostationary satellites are put into a circular orbit around the equator about 22,300 miles from earth. In such an orbit, the satellite speed matches the rotation of the earth, so the satellite is always overhead to any observer or station on earth. Sirius' competitor XM Radio uses this system with two satellites providing full U.S. coverage. The equatorial geostationary orbit is unique and currently jammed with satellites side by side only a few degrees apart. As with the frequency spectrum, we're simply running out of space.

Sirius takes the other approach of using elliptical orbits. The company has three elliptical orbits over the U.S. They are geosynchronous, meaning that their rotational period is 24 hours just like a geostationary satellite. The satellite apogee (high point) is 29,200 miles over Canada and the perigee (low point) is 14,900 miles. The orbits function in a way where two satellites are over the U.S. at all times. The satellites are spaced eight hours from one another, and each satellite is over the U.S. for about 16 hours. All three transmit the same data.

The elliptical orbits offer the advantage of a very high angle of coverage. With a conventional geostationary satellite, the line-of-sight path runs at a very low angle of elevation above the equator (about 30°) to the south from the U.S. Because microwave transmissions are direct-line-of-sight, signals from geostationary satellites encounter many more obstacles like trees and buildings. With elliptical orbits, the satellites are more directly overhead (always above 60°) and thereby avoid most earth obstacles. Yet at such distances, the attenuation from satellite to earth is enormous. Typical signal strength in the U.S. is −102 dBi, meaning that a hot receiver is needed.

All communications satellites are space-based repeaters that receive an uplinked signal, which is translated to another frequency and retransmitted back to earth. In the Sirius system, the digitized music and talk is uplinked from studios in New York City and retransmitted back to earth.

Mike Ledford, VP of engineering for Sirius, explains the system. Sirius is assigned 12.5 MHz of spectrum from 2320 to 2332.5 MHz centered on 2.32625 GHz (2326.25 MHz). This spectrum is roughly divided into thirds. One third is assigned to transmitting satellite #1 (TDM1) centered at 2322.3 MHz, one third to the terrestrial repeater network (more on that later) centered on 2326.25 MHz, and one third to transmitting satellite #2 (TDM2) centered on 2330.2 MHz. This gives each satellite roughly 4-MHz bandwidth.

 

I think you may have other issues. I have had XM since it came out and its rare for me to get a drop-out. Learn to use the diagnostics in the SkyFi and see what kind of signal strength you are getting. You should not get drop-outs, especially with the antenna on the roof.

Here is the diagnostic procedure:

Make sure your receiver is off.

Press these keys in order: 2 0 7 XM (button in the middle of the wheel on the SkyFi, or the wheel itself on the Roady)

Press Display 3 times to cycle through the normal displays to the first Diagnostic screen.


The Roady displays one piece of information on each screen, so there are many more screens on the Roady, and the order isn't this exact order, but here's the meaning behind the info on the screens.

SkyFi Screen 1
SAT1: East Satellite at 85 degrees west longitude.

SAT2: West Satellite at 115 degrees west longitude.

TERR: Terrestrial Repeater signal

DEMOD: A check mark means you have demodulator lock. This means the receiver is locked on the signal from that source.

TDM: A check mark means you are synchronized with the Time Division Multiplexed signal from that source.

BER %: Percentage Bit Error Rate. This is the percentage of received data bits in error. For satellite this value should be less than 3% for error free audio. For terrestrial, it should be below 6%.

AGC: Automatic Gain Control Level. This is an indication of the amount of internal gain needed to recover the signal. The more negative, the higher the signal being received.


SkyFi Screen 2
BER: Raw Bit Error Rate. This is the number of received data bits in error. This value divided by the maximum number of errors in a measurement interval is the BER % on Screen 1. Max number for SAT1 and SAT2 is 5440. Max for TERR is 6800.

AGC: Same as on Screen 1.

C/N: Signal to Noise Ratio measured as Carrier Power divided by Noise Power. For SATs, this value needs to be greater than 7. It does not apply for TERR. This is a good satellite antenna pointing indicator.

RSBK and RSBY: Reed Solomon Block and Byte Errors. They should be 0.

 

Thanks for the replys guys I will try that !!