XM Satellite Weather Woes

[Ironflight]

Originally Posted by garrys

Why is it that different pilots report such widely varying experiences with XM? That absolutely shouldn't be the case. Something screwy is going on, and I don't think ANY of us know the whole story.
As far at the XM communication being "one way", I don't think so. If I haven't paid my monthly subscription, they turn me off, which means they send out a discreet signal to each and every unique subscribere ID. Same thing when they "refresh" the service......they send out a refresh signal to my Unique ID.

Well.....this IS the internet, and the fact is, on the 'net, you primarily hear about the problems that people have - you don't get the 95% of the people that have never had a problem logging on to say "I didn't have a problem today!" So you have to keep that in perspective. If it makes you feel better, I have only had my XM drop out once or twice in over four years of CONSTANT flying and use.

As for the one-way, this was described a few posts back. It takes just a slight amount of cleverness to design a radio that needs to get "pinged" every once in awhile in order to work. I don't believe it has any kind of transmitter - it's just a receiver that needs to get a code to get activated, and can also receiver a code to be de-activated (it's still receiving all the time, it just refuses to give you any data. It can be built with a "watchdog timer" that forces it to deactivate itself if it doesn't hear an appropriate code every so often. I'm not saying that I know specifically how it works, I am just saying that the logic to design it this way is not that hard to engineer.

Paul

[Brantel]

It is still "one way"... From them to your receiver...

Originally Posted by garrys

As far at the XM communication being "one way", I don't think so. If I haven't paid my monthly subscription, they turn me off, which means they send out a discreet signal to each and every unique subscribere ID. Same thing when they "refresh" the service......they send out a refresh signal to my Unique ID.

[Steve A]

I had an intermitten problem with my 396 Garmin receiver. I moingved the antenna, thought I had a conflict with my other GPS, finally I turned off my I Phone. It seems to be the solution to the problem. My IPhone has a gps receiver and so it makes sense that the two my conflict. I will continue to monitor the situation but I would try it.

STeve Anderson
RV 7A Flying
Lafayette, La.
130 hoiurs

[cguarino]

Originally Posted by Steve A

I had an intermitten problem with my 396 Garmin receiver. I moingved the antenna, thought I had a conflict with my other GPS, finally I turned off my I Phone. It seems to be the solution to the problem. My IPhone has a gps receiver and so it makes sense that the two my conflict. I will continue to monitor the situation but I would try it.

STeve Anderson
RV 7A Flying
Lafayette, La.
130 hoiurs

I asked XM tech support if a GPS receiver would interfere with the XM and I was told that I could put the antennas and receivers as close to one another as I wanted to. There is a lot of talk about XM/GPS interference on the net but XM tech support doesn't seem to agree. BTW, my GPS reciever/antenna and xm antenna are side by side (almost touching) and seem to work fine. I just do the refresh thing as a precaution. If I flew everyday I don't think it would be required.

[chrispratt]

Originally Posted by garrys

Several of my pilot friends have been noticing degraded performance from their XM Satellite Weather systems...
Garry Stout, Tampa FL RV7A

What I've noticed is how the yearly fee keeps degrading too . I got my renewal notice a few weeks ago and the Aviator Lite subscription has gone from $360/yr to $420. Considering how seldom I use it, I've got to believe I can get the info cheaper off a cell phone. This is likely to be my last year using XM weather.

Despite my infrequent use, I have never noticed any interruption in service. For $420/yr why would they risk cutting someone off from a prepaid subscription? That's marketing suicide.

Correction 6/26/10: With taxes it came to $454.56 for the Aviator Lite annual subscription.

Chris

[chinch]

Originally Posted by Ironflight

I don't believe it has any kind of transmitter - it's just a receiver that needs to get a code to get activated, and can also receiver a code to be de-activated (it's still receiving all the time, it just refuses to give you any data.

There's an analogy here with satellite based subscription television. The dish receives every channel, the receiver can decode every channel, but I can't watch every channel. But I can call up the provider and subscribe to a new channel, even with the landline modem built into the receiver unplugged - in other words, the "activation" is delivered via satellite. There is a portion of bandwidth explicitly set aside for this purpose.

A while back, we investigated the possibility of using XM to multicast tracking data *back* to aircraft in a secure and selective manner based on the same principles. As I recall from those discussions, Paul, you are exactly correct.