50 channels for GPS /WAAS?

[dingbat]

What the heck?
Saw an ad where a Fishfinder/Chartplotter combo was advertised as having 50-channel GPS/ WAAS.

I didn't think there was even that many birds in the sky?

 

[John_S]

Re: 50 channels for GPS /WAAS?

The new HB 700 and higher models comes with that. I can't say I have ever filled all of 16 in the older models. Supposidly, the new 50 gets a position lock much quicker and can be more accurate than the 16. HB also has an upgrade from the 50, which supposidly has 1 meter accuracy. It is a $200 receiver.

The new receivers are not compatible with older 700 series. They draw more power than the aux can supply.

 

[Moody Blue]

Re: 50 channels for GPS /WAAS?

More of a sales gimmick than anything else I think.

From what I remember, there are only 27 satellites in orbit, and only 24 are operational at any given moment. The other three are spares incase one of the 24 stops functioning.

From what I have read, the best positional accuracy possible is <3m if able to lock onto one of the two WAAS satelites.

 

[John_S]

Re: 50 channels for GPS /WAAS?

I don't really know. I do know that getting my boat ready for possible weekend fishing, the 16 channel showed 10 birds and a 10' position error. Thats in the garage. Below is some user feedback on the new GPS.

http://www.postimage.org/gx22wYt9.jpg
I Just received my new 798c and .... And I was truly amazed at the accuracy of the 50 channel receiver. The snapshot clearly shows it. And that's with the antenna setting on the coffee table and aquiring the satellites through two rooves.
P.S. I do get a little better with the GRHA but not much.



FWIW, here is the HB Press release: http://www.humminbird.com/uploadedF...ess_Releases/Humminbird/High_Accuracy_GPS.pdf

I do know that both the 50 channel and High Accuracy can not be used on older units, because they draw too much power from accesory bus!

 

[jhebert]

Re: 50 channels for GPS /WAAS?

My interpretation of these newer receiver chips which feature 50-channel processing is that they are able to acquire more satellites and track them faster than older chips. The receivers are also ready for tracking signals from other systems besides the NAVSTAR GPS, such as the European system under development. At some time in the future there may be many more satellites in orbit than now. It is unusual to have more than 12 satellites in view at any one time.

The GPS receiver chips are not made by manufacturers like HUMMINBIRD; they're made by highly specialized firms. The 50-channel line of receiver chips is the latest generation. You will see these on more marine GPS receivers. I believe that STANDARD HORIZON has a new GPS receiver with a 50-channel chip, as well.

 

[Wee Hooker]

Re: 50 channels for GPS /WAAS?

Imported John S, do you know where the cut-off is on "older 700 series"? The press release sais they are compatable with the 700s but no other details. I've got a 767 (bought this winter. ) Just wondering if this is ever an option for my unit.

 

[dingbat]

Re: 50 channels for GPS /WAAS?

Did a bit more reading up on it. As already noted its nothing more than a GPS chip set that is capable of processing 50 channels of data. Doesn't mean the antenna can pick up 50 channels to process.

GPS-106E is designed by u-blox, and sets a new standard for GPS and GALILEO receiver modules. Featuring the high performance 50-channel u-blox 5 technology, these modules provide excellent performance and flexibility at an economical price.

I find it interesting that HB insinuates improved performance, i.e. accuracy, yet the chip manufacturer makes no such claim.

 

[Boatist]

Re: 50 channels for GPS /WAAS?

I agree with everyone else there are only 24 active gps birds and about a max of 5 WAAS birds that can be seen from the US and Canada.

My best GPS unit has 16 channels and I have seen as many as 12 locked on but 2 of those were WAAS Units. The other channel will be set up looking for the next satellites to rise above the horzion.

 

[John_S]

Re: 50 channels for GPS /WAAS?

Imported John S, do you know where the cut-off is on "older 700 series"? The press release sais they are compatable with the 700s but no other details. I've got a 767 (bought this winter. ) Just wondering if this is ever an option for my unit.

If its not one of these: http://www.humminbird.com/uploadedFiles/Global_Content/Press_Releases/Humminbird/700_Series.pdf then the answer is no. Officially, my 797 is not supported, either. I have been told it is because the new receivers require more power. I think it is a rather simple mod to make to the pig-tail, powering the receiver from a switch (like how GPS is linked to PC's) with its own fuse, and "clipping" the +12 coming from unit side.

I plan to get a 798 and a GRHA recceiver. My 797 will move to the bow. I already have an AS LINK, so only want one GPS receiver in the boat. Not sure when I will do this, but will let people know if the receiver pig-tail mod works.

BTW, I have suggested to HB to make an "official" cable to support the older units.

 

[dchris]

Re: 50 channels for GPS /WAAS?

This receiver can't be fully functional yet. There are 27 active GPS sats and WAAS has a few. Some of the additional channels are to be used for new L2 freq CA Sats that are not in orbit yet. Currently there are only one or L2 CA sats, most are still broadcasting Y code only. Having a dual freq receiver corrects for ionosphere errors what are only estimations now. The other possibility of the extra channels are to be used with the Galileo system in Europe. Taking reading from multiple systems should yield more accurate results. There are multiple GPS systems other than GPS in orbit. When the new L2 CA comes on line you can expect and accuracy increase of 5 meters or greater and we all get to buy new receivers.

 

[jhebert]

Re: 50 channels for GPS /WAAS?

There are no "channels" on a GPS receiver as one would think of a receiver having different frequency channels. All the signals are transmitted on the same frequency, the L1 carrier frequency of 1575.42-MHz. Signals are differentiated by their spread-spectrum modulation psuedo-random number (PRN) sequence, which are numbered for identication 1 through 32.

There are only two WAAS signals-in-space for the NAVSTAR GPS. They are sent from geo-stationary satellites. Their position in the sky does not change. They are always either in view or not in view, depending on where you are located. The currently active WAAS signal-in-space sources are GALAXY 15 at 133?W and ANIK F1R at 107.3?W. You can discover your look angle to those satellites using a calculator such as the one at

http://satcalculator.freehostia.com/

For the eastern United States, generally the look angle is better to ANIK F1R, so most GPS receivers should prefer that WAAS signal (which is PRN 138). Users in the western United States may find GALAXY 15 is better (which is PRN 135).

 

[dchris]

Re: 50 channels for GPS /WAAS?

L1 frequency is currently used for military and civilian signals. L2 is 1222 Mhz and transmits military only at this time. New space vehicles are being deployed that offer a civilian signal at the L2 frequency. There is also a L5 frequency in the works. Separate channels would be required to use L2 frequencies. L2 CA code is not on line yet.