Humminbird Side Imaging Forums
General => General Discussion => Topic started by: jazz4627 on January 17, 2011, 03:03:18 PM
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I am looking to upgrade to SI and one of the difference I see between 798 & 797 is the Channel GPS. What would I be missing not having the 50 compared to 16.
Thanks for any advice.
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16 channel capability vs 50 channel capability. the more channels (satelites) the better the accuracy of position. Of course this depends on the number of visible satelites on the horizon.
Something else to consider is that currently there are about 25 satelites orbiting the earth for GPS. So 50 is a future wish list.
I also heard that the 50 aqquires the satelites faster than the 16.
Ther rumor mill has it that the 16 is no longer available new ship. It is replaced by the 50. (unconfirmed)
Chuck
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Here is a 50 channel map from one of the HB pro staff units.
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Wayne...good post I forgot to add that from the diag window. Glad you thought of it.
It shows the possible satelites at the time it was captured. From that you can see that 12 satelites would be conversing with the unit. That should get a good accuracy of position. If using the 5 digit decimal degrees that will give you a reliable 3 foot of error..
Imagine what will happen when we get 50 satelites..... ;D
Chuck
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Here is a link to the GPS comparison chart showing a 24hr period with Gr16, Gr50, GrHA (no longer sold)
The difference between the GR16 and GR50 is quite noticeable. The GR50 certainly has much better position accuaracy but it also acquires a position at boot much faster as well.
Some other differnces in the 797 vs 798 is the screen. Also 798 has faster processor.
Unless the 797 is like half the price of the 798, I would go with the 798 hands down!
Just my two cents. Good Luck,
Robert
(Note: thanks Robert. It was the GrHa that was pulled. ) Chuck
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Awesome info all. The differnce I am seeing is about $150 to $200 in price. Add a Interlink and a new trolling mount transducer for the 787 already have that would go up front, I am already making up that $200 difference. Combine that and looking at 788 DI I am glad the water doesn't thaw for a few months to give me time to decide on which is best. I installed a new transducer last year that I believe was for SI. (need to check on that again when the snow disapears) Again thanks for the great post.
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Just a question out of curiousity:
Are there still models shipped out with the 16 channel receivers???
In thought that most of the units already have the 50 channel receivers.
Regards / Harry
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None are shipped from Humminbird with the 16 ch now, but some dealers may have units in stock with them.
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Thanks for the information Wayne!
Strange that quite a lot of the descriptions on the internet still state "16 channel" for the GPS receivers. I guess most of the dealers just copy and paste their product descriptions from other websites. Therefore it might be good to ask what year the unit was produced.
Regards / Harry
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Not only ask the dealer, but tell them to read the unit description on the box. That will be as close to reality as you can get without actually opening the box and checking the antenna.
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Right Wayne,
Checking the serial number is also an alternative to see what year the unit is made. Year, month, day are the first six digits of the serial number as far as I know. Question then is, since when is Humminbird shipping out the 50 channel receivers.....
Regards / Harry
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Harry,
I think that we slowly switched over from the 16 to 50 channel GPS Receivers based on model – so they did not all switch over on the same date. I am guessing here but some of the boxes that state 16 channel have the 50 in them as we may not have had stickers available on the day that this happened.
Glad Wayne posted that GPS Diagnostic View image. The best that I have been able to get so far I think is 14 satellites at once with the unit using only 13 of them (will have to look for that screen snapshot). I’ll have to look up those coordinates to see where that one was taken from!
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Greg, that was taken in Missouri.. Chuck
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Yes, that GPS diagnostic screen shot was done by Doug Vahrenberg.
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That’s right Wayne. In looking for my best GPS Diagnostic View screen shot I found his as well. Here is mine. Tracking 14 satellites but using only 11 of them. You can see the three WAAS satellites are being tracked, even the rouge SV #48 (PRN 135 Intelsat Galaxy 15). The unit is not using this WAAS satellite, one of the other WAAS satellites (SV #46), and satellite SV #33 to calculate its position. While we may choose to ignore the WAAS satellite for positioning accuracy, we still use the corrections that it provides (unless the GPS system says to ignore all information from it as in the rouge SV #48). This was taken in the parking lot with the GPS Receiver set on top of my van, so the building was blocking SV #33. Not a bad shot for walking outside one day and making a screen snapshot!
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Capability is one thing.
Visibility is another.
And Connectivity is signal strength.
In order for the unit to communicat with the satelite it takes all three.
There must be satelites within visibility on the horizon and not obstructed by an object, be it trees or something on the boat.
The signal strength of the satelite and the unit receiving must be of sufficient level in order to reliably let the unit processor use the data reliably.
Chuck
The GPS 50 is capable of receiving 50 satelites. The question is how many are in view and with the right signal strength.
Satelites on the outer edge of the horizon are less strong than directly overhead...
Water reduces the signal strength so if you are in a leafy area you will not get as good as reception as in the clear.
Chuck
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Chuck,
Your thoughts on how the human body ( mostly water ) affects the signal.
Does it block or let it pass through?
I sit 12 inches in front of the antenna which is at waist level.
I do have the ability to raise it above my head.
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I can tell you this, if I sit or stand right over mine on the stern, it will certainly block the signal!
To get the best readings, it is cretainly best to get an unobstructed view.
Robert
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Just to add to Robert.....yes the human body can be an obstruction. Especially if you hover over the antenna. Even a hand directly over can influence (reduce) the weaker signals.
Best bet is a clear shot. You can make a telascoping antenna bracket if you get creative..
On another note: the GPS antenna needs to be flat and not turned on its side...
Chuck
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Robert & Chuck
Thanks for the info. Gave some thought to this on the original install, but mounted in current location
to keep motion of antenna caused by waves to a minimum. Will raise it up in the spring.
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I have a 797csi interlinked with a 997csi and I am using one GPS puck. I'm wondering if the AS GR50 GPS will work in this setup. The 797 is not listed as an approved unit for the AS GR50 puck on the Humminbird site.