Polk XRt12 XM Reference Tuner - Antenna

BlueMDPicker

At the urging of forum member ardvark1, I recently purchased Polk's XM Reference tuner and I've been very pleasantly surprised by the overall sound quality.

There were a couple of reasons I hesitated from getting involved with XM. First of all, I seldom listen to radio due to all the hype that comes with "free" music. But, more importantly as it applies to satellite delivered transmission, I was certain there was a very limited area of my home in which the unit could be placed -- due to the need for a south-facing sky antenna placement. And, I really didn't want to run an extension cable for the antenna.

When I first installed the tuner, I placed it downstairs (walkout basement) approx. 10 feet from a south-facing, glass door. I ran the supplied antenna lead along the baseboard and sat it on the back of a sofa for testing. Full signal bars, cool, I'll build a bracket to attach it to the door casing. Later that evening, and out of curiosity, I moved the antenna to on top of the TV, 10 feet from the window, angled toward the southeast to "look" out the glass door. Full signal bars, cool, I don't need to build a bracket to attach it to the door casing.

Last night I decided to try the tuner upstairs on my SE OTL rig, fully expecting it to NOT work since the rack location is well over 30 feet from a south-facing window. I sat the antenna on top of the rack and thought to myself "this is going to be a short-lived experiment." Full signal bars, cool, placement "near" a south-facing window is really more of an expanded distance than I ever would have imagined. So, I thought I'd share my experence with those who may have had the same reservations about getting the tuner.

disneyjoe7

I'm happy with my XM Tuner also, my stereo is actually near a window, which is facing east. My antenna is facing southwest through the ceiling / roof with full signal level bars.

BlueMDPicker

That's even better news, Steve!

steveinaz

I was surprised when I sat my Xrt antenna on top of the rack and got full signal. Shooting thru the house and all.

bknauss

XM isn't completely "satellite" radio. They have terrestrial hoppers to help out when you can't aim directly at the satellite. I don't know why XM doesn't make that information more public since I would think some people would be scared off with bad satellite TV experiences.

BlueMDPicker

I did a lot of reading on XM's site before deciding to buy. They do talk about the land-based repeaters. My surprise with antenna placement is that I'm getting full signal, direct/satellite so far from a window. I'm glad a didn't buy the $30 piece of coax (which I considered) knowing what I know now.

Another surprise, after several years of SAT TV, is that I never lost reception during a heavy overcast and thunderstorm last Friday night. My DirecTV looses signal fairly regularly in the same weather scenario. The dish for it is 30' above ground level, aimed to perfection, with no obstructing trees or topography. More complex signal, weaker signal? Go figure?

stevemol

The XM satellite signal is approximately 30x's more powerful than DBS (Satellite TV) - and they're not carrying video, so the datastream is much more tolerant of problems.

As a commercial XM installer, I was surprised one time years ago when I set up an XM radio in a telephone closet, getting ready to drill holes in the building roof for the antenna just to find full satellite bars in a closed, windowless, equipment room!

I've found that the signal is blocked by steel and concrete, but wood and drywall don't bother it - much. Those materials do, in fact, reduce signal. Apparently the bars are misleading. Full bars doesn't indicate full signal, only that the full recommended signal strength has been acheived. (The probably do this to keep consumers from complaining they can NEVER get full bars. Check the signal strength of your DBS TV reception on a clear day - you'll never get 100%.)

It's best to place the antenna outside (not even through glass) where it gets an unobstructed view of the southern sky. Remember, Rock, Roll, and Rythm are located at different points in the sky - that's why you can't use a parabolic antenna. You actually receive different channels from different satellites, so if you aim at one exclusively, you've excluded yourself from channels not carried on that bird.

Even if you get full bars in the rack under the magazine rack, you'll just experience static more quickly than if you mount the antenna outside.

When installing DBS (TV), we (yes, I am a DBS and Internet installer, too), we have to do the aiming on a perfectly clear day because the signal can be "bent" by refraction of clouds.

On XM, I recommend the opposite approach: Since you're not really "aiming" at any one bird, and since the signal strength meter is essentially limited to a low, recommended signal strength, find your best mounting location and position on the most miserable, rainy, cloudy day you dare to be out in. That way, if you find a "full bars" position, you'll always have full bars.

If you permanantly mount your antenna on a beautiful day, you may find dreary days less exciting. And aren't those the days you'll be inside listening to your XM?

BTW, the terrestrial repeaters are predominantly in large metropolitan areas where tall buildings and bridges interfere with automotive reception. They also tend to be taken down occassionally for maintenenace. So, don't count on terrestrial reception for a stationary antenna unless there is no other choice.

Happy listening...

BTW, "IT" is on the air this week. If you haven't experienced IT, you're in for a treat. XM plays every hit song in chronological order. Every song, from 1930 to 1999. We're already into 1952 right now, so IT is on 50's on 5. When we get to 1960, IT will jump to 60's on 6, etc.

They do this a couple of times per year - and it's alot of fun...

madmax

Obviously you don't want it to fade out on bad days but if it doesn't actually "fade out" is there any loss of quality with a less than great signal?
madmax

stevemol

Yes, bad weather does affect the signal.

I don't have access to the protocols, so much of what I am going to say is speculation based on experience with installing these radios in varying locations with varying conditions (most not cars).

I believe the XM protocol has a "core" signal that has a high level of error correction so that it gets through - if at all possible. This signal is flat, at times even mono. If you have poor signal, even if your signal is not "faded out" momentarily by a passing cloud (assuming you had minimal signal to start with), you may not have a service interruption, but you will loose quality. And, if you're using an XRt-12, you paid for higher quality.

I think the higher quality sounds experience with more "bars" is achieved by receiving additional (L-R/L+R?) data that, when combined with the "core" signal yields a better 3D experience.

Going way out on a limb, I wonder if the signal strength bars are really just a function of bad packets? (Less bars = more bad packets) These bars may not really be a true RF reception meter at all - just an indication of the integrity of the data stream...

But, what happens if the "core" data is corrupted? You'll hear white noise for that moment. If the corruption continues beyond about 1 second, they'll mute the white noise.

Again speculating here, I don't think the white noise is actually decoded - I think it's added during data interruptions, because white noise is less intrusive than total silence. Some of these white noise "gap fillers" may be so short that you don't notice them - where you would notice a total loss of audio.

In any case, I have found it best to aim and mount the antenna where I get the best signal under the worst conditions, where mounting DBS (TV) it is best to aim and mount the antenna for the best signal under the best conditions.

disneyjoe7

My XM antenna is looking at my ceiling then thur my roof, and never had a bad storm stop my XM tuna.

stevemol

Maybe no storm as "stopped" your tuner -- yet -- but my experience shows that your quality of signal - and your quality of audio - is affected by the weather. Maybe you haven't heard the problem. Heck, maybe you haven't had any problems. Maybe you'll never get any problems.

But, reading some of these posts where you guys are trying to get every last bit of quality, placing the antenna anywhere but your best possible location simply doesn't make sense.

I follow my procedures so that I don't get support requests and complaints from the installations I provide. I'm just sharing my field experience. It's up to you if you want to use it...

If you're happy with your signal quality, great. Just remember that "full bars" doesn't necessarily mean "full signal."

SCompRacer

stevemol wrote:

I follow my procedures so that I don't get support requests and complaints from the installations I provide. I'm just sharing my field experience.

I like that approach. Thanks for sharing.

disneyjoe7

SteveMol,

Just wondering are you a DirecTV or Dish installer? You stated that XM was 30x stronger than video, but do you know DirecTV / Dish SLD (Small Lilly Dish BUD "Big Ugly Dish" Joke) is stronger then C-band? I'm thinking something like 6x stronger.

So XM is 180x stronger than C-Band :eek:

dorokusai

I think he's under the impression that none of us are the "Communications" business

However, it's certainly good information, and he touches on some points that are often overlooked and should be common sense. It's nice to see an installer give a shite and that alone speaks volumes.

brettw22

Thanks for the information steve.......I only had one comment about this:

stevemol wrote:

.........If you have poor signal, even if your signal is not "faded out" momentarily by a passing cloud (assuming you had minimal signal to start with), you may not have a service interruption, but you will loose quality. And, if you're using an XRt-12, you paid for higher quality.

People using an XRT-12 didn't pay for higher quality signal, they paid for a higher quality component to process what it receives. It goes (almost) without mention that the XRT can't improve, or lessen the strength of a signal.

disneyjoe7

dorokusai wrote:

I think he's under the impression that none of us are the "Communications" business

However, it's certainly good information, and he touches on some points that are often overlooked and should be common sense. It's nice to see an installer give a shite and that alone speaks volumes.

Yes, Thanks SteveMol for your input on this. Stay around.

stevemol

brettw22 wrote:

People using an XRT-12 didn't pay for higher quality signal, they paid for a higher quality component to process what it receives. It goes (almost) without mention that the XRT can't improve, or lessen the strength of a signal.

I was "playing on words."

My meaning is that you paid for a higher quality audio signal - or output - which means you need a higher quality datastream signal - or input...hence the attention to where your antenna should be.

Thanks for the kind words... I don't assume that none of you are in communications, only that some of you are not. Even those that are installers may learn from my experience...and as long as you're not my competitor...

And, yes, I do give a "shite" - and that's why I'm not the cheapest on the block. It takes me longer to do it "right," so it costs more.

BTW, some of my advice (and techniques) runs contrary to manufacturer's instructions. But don't we want what does work best rather than what the engineers think will work best?

stevemol

disneyjoe7 wrote:

SteveMol,

Just wondering are you a DirecTV or Dish installer? You stated that XM was 30x stronger than video, but do you know DirecTV / Dish SLD (Small Lilly Dish BUD "Big Ugly Dish" Joke) is stronger then C-band? I'm thinking something like 6x stronger.

So XM is 180x stronger than C-Band :eek:

And that using a nonparabolic, 2" square antenna. To quote Stan Freeburg, "That's about the size of it."

jdhdiggs

Steve, thanks for the heads up with the "going through walls" thing. Our entire ground floor has a minimum of 2" of rock on all sides and I couldn't get a signal going through those walls so i tried a shot down the all and out the dining room window. That got 2 bars, read your experience and moved the antanna to the top of the enterantment center and aimed it through the stairway and out a window (through 2 walls) and I managed to get three bars and the antenna is no longer at "dog treat" level. Thanks

disneyjoe7

I get 3 bars the antenna is looking southwest at the ceiling. Is my location Florida giving me a stronger signal? I don't think if this was looking out a window, I would get a much better signal?

What 3 bars to 4 bars?


BTW I think Polk XM tuna has a better tuner for XM then a small XM radio has.

stevemol

Yes, Florida will get a better signal than Minnesota, because the signal does not have to travel through as much atmosphere.

In southern states, the signal is coming through at a much higher angle than northern states. (Look at the angle of the DBS dishes out there - in southern states, they look more like "u" than "(", while in northern states they look more like "(" than "u".)

Of course, with the much stronger signal on XM, that difference is going to be small, but it is still there.

Don't forget - 4 bars may not mean the best signal - I believe it just means you have a small amount of data errors. I really recommend that you find the middle of the best locations you can find with 4 bars on a dreary, rainy, humid, foggy -- generally bad weather day.

disneyjoe7

SteveMol,

The large problem I have is the antenna lead being 50' isn't long enough to move outside facing southwest. My XM receiver is dead East, west end of house is a good 55' ft so I have to extend antenna. With an extended antenna lead I question any signal improvement, as I don't notice any trouble now. Don't you think the Polk Audio XM tuner is a better design then Delphi unit, I do.

madmax

Great info stevemol. Keep the input coming.
Thanks!
madmax

stevemol

jdhdiggs wrote:

...and the antenna is no longer at "dog treat" level. Thanks

We've had dogs like that, too...

stevemol

disneyjoe7 wrote:

SteveMol,

The large problem I have is the antenna lead being 50' isn't long enough to move outside facing southwest. My XM receiver is dead East, west end of house is a good 55' ft so I have to extend antenna. With an extended antenna lead I question any signal improvement, as I don't notice any trouble now. Don't you think the Polk Audio XM tuner is a better design then Delphi unit, I do.

It is possible to use more than one antenna extension cable (I think three is the max). So, 50' is not really the limit... Just don't try to modify the cables. They're specifically matched. You'll also notice that the cable sheilding is thicker than that of the built-in cable on the antenna that comes with your tuner.

There are also splitters and high-gain antennae available, in case you want better signal quality getting to your tuner.

I'm not going to comment on any comparison between the Delphi and Polk tuners as I have not had enough personal experience between them. If I have time next week, I'll do a head-to-head comparsion between the SkyFi2 and the XRt12. However, as a commercial installer, I'm really interested in the Polk because of its RS232 control capabilities. Currently, I'm waiting for my own XRt12, and trying to get Polk and my distributor to start working with each other...

disneyjoe7

Thanks Steve for the info, it's great info for all.

Currently, I'm waiting for my own XRt12, and trying to get Polk and my distributor to start working with each other...

That sounds BIG