14 Channels Vs. 12 Channels ?

[+Ticklegrass]

The newer Magellan eXplorist series of GPSs are boasting 14 parallel channels instead of the 12 channels found on most units. My question is: does it matter?

 

I understand the concept of more-is-better; but would I notice a difference with only 15% more channels? The unit specifications still only claim a three-meter accuracy, the same as 12 channel models. Will it get a 15% faster lock? Drain the battery 15% faster? Or, am I missing the point of the two extra channels all-together?

 

Just wondering

[Neo_Geo]

My question is: does it matter?

Right now, no. My 12 channel receiver usually only picks up 10 sats at any given time. Sometimes I just can't pick up the other two, and sometimes there are just 10 sats that can be received. I don't think I've EVER seen all 12 on the radar scope. And with just 8 sats received, I can get 2-meter accuracy.

 

They're always launching new sats into orbit. Eventually the skies will become crowded with GPS birds. OK, "crowded" is a relative term here. Anyway, maybe in a few years, you might have the opportunity to lock onto 13 or even 14 birds. That might result in a slightly faster lock on your postion, and better chance of locking onto 4 birds down in a valley somewhere, which in turn would give better accuracy under such conditions.

[tossedsalad]

I'm not certain about this, but I think the number of channels helps the receiver pick out satellites rather than making a difference in how many are used in a location calculation.

 

It might be like this, each sattelite transmits on its own channel. So to try to find a sattelite, it must "tune" to that channel and listen. The more receiver channels, the more satellites you can try to pick up at one time. Even if you only receive four, it is still listening for the others that might be visible in the sky. If your receiver didn't have enough channels to try to listen to them all at once, the receiver might be missing one that is actually visible, since it doesn't have a spare channel to listen with.

 

I'm not certain that this is how it works, but I expect it is. I also don't know if the "channels" the satellites transmit on are multiplexed in frequency or if they are CDMA multiplexed or use some other multiplexing. But given that there are a variable number of satellites in orbit at any given time and they keep launching more, the CDMA method is what I expect and that would fit my description above. Frequency multiplexing would also fit the above description, but would require all channels to be allocated from the get-go. This is unlikely if they keep adding new birds. TDMA would not work well with satellites moving in separate orbits. CDMA seems to fit the facts best and explains why more channels are better.

[+The Jester]

I've noticed when I turn on WAAS that I have only 10 GPS slots and then two for the WAAS. I thought that Magellen was adding two extra for the WAAS, while still leaving 12 for the GPS sat's.

[+EraSeek]

Jester is correct. The 2 additional channels are dedicated to WAAS sats, and it no longer requires giving up 2 normal GPS channels to get WAAS.

 

Basically now you have a better oportunity to get a better position fix via availible sat geometry and the WAAS corrections at the same time.

[+EraSeek]

A couple of things.

 

I have had 12 normal GPS sats up before.

 

Your GPS knows which sats are availible in the sky above it via the transmited almanac. You GPS dedicates channels to those sats according to that almanac. The common maximum is 12 sats, but there can on occasion be more (or less) in sight as I understand it. Dropping 2 to use WAAS limits what may be available for use when others become blocked or unusable.

 

Say you are walking in the woods where there is tree cover. Your GPS will use the best solution that it can see, but that keeps changing as some are blocked and others come in to sight. The 2 extra channel give you more options, a better chance a getting a lock and a better position.

[stevesisti]

The newer Magellan eXplorist series of GPSs are boasting 14 parallel channels instead of the 12 channels found on most units. My question is: does it matter?

 

I understand the concept of more-is-better; but would I notice a difference with only 15% more channels? The unit specifications still only claim a three-meter accuracy, the same as 12 channel models. Will it get a 15% faster lock? Drain the battery 15% faster? Or, am I missing the point of the two extra channels all-together?

 

Just wondering

Sounds like a sales gimmick to me.....if there were more sats available in orbit, well then maybe, but as it is, under tree cover, I usually average 5 or 6 sats...adding the ability to scan for two more sats that aren't going to be there is a waste of processor time. For the most part, under tree cover, I'm pretty much only picking out the sats that are at the 45 or above, which are the 4 or 5 sats I'm getting now. So right now I have an extra 5 slots that receive nothing....having an extra seven slots to look for nothing is the same situation as having 5 look for nothing.

 

Out in the open, I get lock on 6-10 sats with very good accuracy readings... having the ability to lock on 2 more isn't going to effect already good reception and accuracy.

[+briansnat]

I used the Lowrance GO2 unit and it has a 16 channel receiver. I didn't see any noticeable difference in performance. In fact I was consistently getting better accuracy the 12 channel units I was using alongside it.

[vagabond]

My 500 constantly locks on to 2 or 3 more birds then my gold. it is constantly closer to caches then the gold by anywhere from a couple of feet to 15 feet. Its even locked on to both waas sats a couple of times, I've never seen this in my gold So whether its the sats or just newer technoglogy who's so say?

[+dino_hunters]

I will say something I find impressive about my new Explorist 500. With my old Garmin Vista, I have never recevied a WAAS lock. I live in Utah, so its probably not the best place for it. Well, First time out with the new Explorst 500, I get a WAAS lock with 7 foot accuracy. WOW!!!. Now, with the exploist I get a waas lock almost all the time, except in bad conditions, like a deep canyon. Not sure if its the 14 channels, newer processors or what, but I like it. It also seems to hold onto a lock better in bad conditions than the vista.

[+Trail Buzzards]

I get a WAAS lock every time on my eXplorist 600... it just takes a few minutes more than the regular birds. I hardly ever get more than one WAAS sat. on my STP. So.... I think there is something to the 12 channels.

[+EScout]

My eX500 has an excellent receiver, about equal to my Meridian. I have tested both in difficult locations and at super-accurate benchmarks and they are about the same. I often get both WAAS signals and occasionally have seen 14 sats on the eX500. What is important is the sensitivity of the receiver, and the ability of the processor to quickly process signal information, eliminate bad/reflected/corrupted information.

[vagabond]

Sure glad to see some more happy owners making their selves heard