hds ext. ant.

[lipripper4x4]

Hello,wondering if there are any low.gurus here?I have a hard time getting my hds 5 to give constant gps while driving in my car.My lms 527had no prob.The hds only rec. when going to the so.WHAT ANTEENA CAN I USE IF ANY ,EVEN IF I NEED TO MNT. TO ROOF? THANKS,RIP SOME LIPS!!!

[acar555]

You can use an LGC-3000 or LGC-4000 with the HDS models without haveing to use an adaptor cable. The 3000 is the standard antenna and the 4000 has the 4 times per second updating for more accurate tracking.

[Catch'nRelease]

I personally don't understand why in this day and age an external antenna should even be necessary. My 2 year-old $200 Garmin Nuvi works great inside my SUV, even without being right up against the windshield, in close proximity to all of the electronic stuff found in a modern car, maintains its lock in any direction even with a partially obstructed view of the satellites.

On the other hand my 2 year old $1500+ LCX37C required an external antenna, which needed to be mounted at least 3 feet away to avoid any interference from the unit itself or the radio antenna, even with a much broader view of the sky in the middle of a lake?

I just added an HDS-5 for the bow-mounted trolling motor, and hopefully its built-in antenna will keep an accurate lock when I put it to use next spring. In the parking lot it seems fine so far....

[I Fish GS]

I have my HDS 7 mounted in my truck, I have it mounted on a pedestal in front of seat (not in clear view of windshield) It locks on slower than Lowrance XOG on dash, maybe 30 sec but once it lock on it stays locked on.
Check to see if your waas is off. If waas is on it will only lock on when waas is at full strength.

Brian

[lipripper4x4]

Thanks for the replys I think I did have the waas on I will try it with it off, I,m heading to Lake wisco. I'll let you know if it helped & how the fishing is.RIP SOME LIPS!!!

[lipper4x4]

I turned off the waas but didn;t seem to help.I guess i'll get a tom tom or something.Lake Wiso. was slow still caught a few dinks & 1 19in. Sauger. RIP SOME LIPS!!!

[hondo]

Have you updated the software in your HDS-5? There have been a few updates, the last one came out in October. The updates have improved the GPS performance.

[VernH]

I personally don't understand why in this day and age an external antenna should even be necessary. My 2 year-old $200 Garmin Nuvi works great inside my SUV, even without being right up against the windshield, in close proximity to all of the electronic stuff found in a modern car, maintains its lock in any direction even with a partially obstructed view of the satellites.
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I just added an HDS-5 for the bow-mounted trolling motor, and hopefully its built-in antenna will keep an accurate lock when I put it to use next spring. In the parking lot it seems fine so far....

My experience with dashmounted GPS units that are intended for use on roads is that although they appear to be very accurate in the location they show, their DOP (the accuracy.. number if you get into the system screens) is worse than a unit with an external antenna or an unobstructed view. Since they are assuming you are in a vehicle on a road, they keep showing you on the road even though the instantaneous error should be showing you in the ditch, nearby field or nearby building.

You can verify this by finding a parking lot or a field at the end of a street where you don't have to make a left or tight turn to get into it. (The act of turning off a known road lets the GPS algorithmns know a change happened and to stop using the "snap to a road" function. Do a couple of 30-50 ft circles and see how good they show up.

The GPS units in my boat with external antennas and a good WAAS signal will log very, very small circles.

Travelling speed, averaging, GPS constellation geometry, WAAS, etc will all also affect the error.

Vern

[Catch'nRelease]

My experience with dashmounted GPS units that are intended for use on roads is that although they appear to be very accurate in the location they show, their DOP (the accuracy.. number if you get into the system screens) is worse than a unit with an external antenna or an unobstructed view. Since they are assuming you are in a vehicle on a road, they keep showing you on the road even though the instantaneous error should be showing you in the ditch, nearby field or nearby building.

You can verify this by finding a parking lot or a field at the end of a street where you don't have to make a left or tight turn to get into it. (The act of turning off a known road lets the GPS algorithmns know a change happened and to stop using the "snap to a road" function. Do a couple of 30-50 ft circles and see how good they show up.

The GPS units in my boat with external antennas and a good WAAS signal will log very, very small circles.

Travelling speed, averaging, GPS constellation geometry, WAAS, etc will all also affect the error.

Vern

Good information. My first GPS unit was a Garmin GPS-V - tiny black & white screen, flip-up antenna, just 17MB of internal memory so you had to constantly download different maps depending on where you were going. It also would show you being off the main road at times and had a general tendency to get confused. They sold a separate external antenna but I never purchased it as the built in seemed adequate most of the time.

A couple of years ago I upgraded to a Nuvi 760 and of course it's leap years ahead compared to the old one. Besides the color display and its ability to hold maps of the entire U.S. and Canada, it locks on way quicker and always seems to show your correct position. But as you seem to indicate, much of this improvement may be due to improved algorithmns as opposed to a better internal antenna? Probably a combination of the two, but as long as it shows my correct position on the road, updates quickly when making turns and gets you to your destination, I'm OK with it.

But thanks to your explanation, I can see why it's a different situation on the water, with no roads for the algorithmns to lock onto. I can also see why, at least in theory, a dedicated external antenna should improve accuracy compared to a built in. It will be interesting to compare the HDS built in antenna with the LCX-37C/LCG3000 combination when I get back on the water next spring.

[1625rebel]

The estimated position error on my HDS 7 is about the only disappointing thing I've found. I have an H20c also, and it consistently can get down to 14 ft EPE while on the water. At the same time, my HDS 7 was at about 25 feet. It always tracks 10-15 feet higher than my tiny little H2Oc. They both have internal antennas. I was under the impression that the HDS series had a great internal antenna that would pretty much eliminate the need for an external one.

[TravisC]

My last 3 boats had lowrance and the units wouldnt connect sitting in my shop. i switched new boat to garmin units with internal antennas and they power up right away. thought that was interesting.

[Catch'nRelease]

The estimated position error on my HDS 7 is about the only disappointing thing I've found. I have an H20c also, and it consistently can get down to 14 ft EPE while on the water. At the same time, my HDS 7 was at about 25 feet. It always tracks 10-15 feet higher than my tiny little H2Oc. They both have internal antennas. I was under the impression that the HDS series had a great internal antenna that would pretty much eliminate the need for an external one.

Probably a dumb question, but I'll ask it anyway. If these units have the capability of estimating your position error - which implies that they know what your true position really is - why aren't they able to give you a more accurate position in the first place?

[VernH]

Probably a dumb question, but I'll ask it anyway. If these units have the capability of estimating your position error - which implies that they know what your true position really is - why aren't they able to give you a more accurate position in the first place?

They don't really "know" the true position. They know that, based on the signal strength of the various GPS signals, the shape of the earth as described by the info stored the different map datums (it ain't round), the number and position of the currently visible satellites, atmospheric factors and a bunch of other stuff, you are within a certain distance of the absolute true spot. The reading could be dead on or it could be up to the DOP or EPE distance away in any of the 360 degrees of NSWE. That distance is typically a horizontal measurement. Many GPS units will give a 3D fix and try to estimate your altitude.

It's kinda like believing you have 10 gallons of gas in your vehicle and believing that you can go for 300 miles cuz you get believe you get 30 mpg. Terrain, headwinds, cross winds, stop and go traffic, etc. will all play into that final figure.

EPE and DOP are "fudge" factors. (Garmin typically displayed EPE, Estimated Position Error info in its units. Others displayed DOP which means Dulution of precision... In both cases bigger numbers meant more inaccuracy.

Vern

[Catch'nRelease]

Thanks again for the explanation, Vern.

[1625rebel]

If you're familiar with statistics, estimated position error is similar to a confidence interval. More satellites with good fixes will give a tighter estimate and confidence of true position. Just like more samples out a population will give you a tighter estimate of the true population mean.