Installation of 788CI

1100, 900, 800 and 700 series Units without Side Imaging
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karlep
Posts: 8
Joined: Thu Dec 30, 2010 5:58 pm
Location: Eden Prairie, MN

Installation of 788CI

Post by karlep » Thu Dec 30, 2010 7:04 pm

I own a 788C (w/ external GPS antenna) that I have mounted at the rear of my 18 foot tiller and I have been EXTREMELY HAPPY with this unit. My lovely wife tried to purchase a second unit as a Christmas gift to replace an old Lowrance I have in the bow, only to discover the 788C has been discountinued and only the 788CI (internal GPS antenna) is available. My issue is the unit I am replacing is mounted on the floor at the front of the bow kind of tucked up against the gunnal - I can not mount the unit on the top of the bow (the triangle part) as my trolling motors covers most of that area and the motor cables swipe across the are not cirectly covered by the motor itself. My question is - how much of the horizon must a unit with 50 channel internal antenna see? If it can see 1/2 of the horizon, will it work o.k.? If not, I have to spend another $150 for an external antenna.

Thank You in advance !

SilmarilS
Posts: 188
Joined: Wed Oct 14, 2009 12:19 pm
Location: Canada, QC

Post by SilmarilS » Fri Dec 31, 2010 4:43 am

It doesn't matter that much.. since you are on water, you have a clean view of the sky and the GPS receiver will get a good signal.

Just try it, and you will be happy... I don't think that 150$ will be a good investment in that case..

Humminbird_Greg
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Joined: Tue Apr 17, 2007 6:26 pm
Location: Eufaula, AL.
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Post by Humminbird_Greg » Fri Dec 31, 2010 10:39 am

You can certainly try testing the installation location before making anything permanent. I am assuming that you have an aluminum boat hull and if you do the hull itself should block some of the satellite signals from be received directly. I say “directly” as these signals could be received but they will be what is called “multi-path” and would add to the inaccuracy of your GPS positioning. Try testing the new internal unit positioned where the other bow unit is (transducer does not have to be in the water for the test – it will not hurt the unit or transducer) and compare the EPE number versus what the external 788 unit is showing. If you are happy with the difference than go for it. If not, I would look at a mount that would clamp or bolt to the gunwale of your boat or maybe you could get creative and mount it off the trolling motor itself.

Oh, suggested installation is for a clearance of 5 degrees up from the horizon.
Greg Walters at Humminbird
gwalters@johnsonoutdoors.com
I help because I can

SilmarilS
Posts: 188
Joined: Wed Oct 14, 2009 12:19 pm
Location: Canada, QC

Post by SilmarilS » Sat Jan 01, 2011 2:18 am

Can you interlink the two units to share the GPS position?

Would it be better than a second external antenna??

karlep
Posts: 8
Joined: Thu Dec 30, 2010 5:58 pm
Location: Eden Prairie, MN

Post by karlep » Sat Jan 01, 2011 11:17 am

Could interlink the two units but that's another $150. Think I'll try Greg's suggestion. Easy enough to temporarily mount it in the perferred location and see how it performs compared to the other unit with the exernal antenna. If performance difference is dramatic, I will have to buy an external antenna for the unit. Far easier to add an external antenna than to interlink them together (wiring issues from front to rear of boat).

Thanks for you input.

Humminbird_Greg
Posts: 4482
Joined: Tue Apr 17, 2007 6:26 pm
Location: Eufaula, AL.
Contact:

Post by Humminbird_Greg » Mon Jan 03, 2011 10:53 am

Karlep,
Is your original 788c with the external GPS Receiver actually mounted on the transom of the boat? If so, maybe the thing to do is to swap the units around and place the 788c with the external GPS Receiver at the bow (so the external GPS Receiver can be mounted on the gunwale or wherever it will work) and the internal GPS 788ci gets mounted on the rear transom.
Greg Walters at Humminbird
gwalters@johnsonoutdoors.com
I help because I can

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