External antenna for hiking GPSr

[Mohamed Ellozy]

I often lose the signal while hiking with my Garmin GPSmap 76CS, which is annoying as I try to record tracks of all my hikes. Also, looking at the tracks, there are points that are obviously off course, presumably due to a weak satellite reception. What kind of performance improvement can I expect with an external antenna? And which antenna is best for a hiking GPSr? Most seem to come with hardware more suitable for mounting on a car or boat than on a human!

Thanks!

 

[bobandgeri]

The GPS that we use (earlier version of the GPS V) has an external attenna and does a great job of reception in trees and poor weather. Most hikes we never loose a signal. We attach it to the outside of the pack, high up in a weather proof case.

We also have one or the more exspensive eTrex series that we only use for kayaking as it has much poorer reception. When we go sailing we use an external antenna as we keep the gps below decks with the laptop.

I would think that an externa antenna mounted to the top of your pack would provide a great improvement in reception - attached to a pole to get above your body would do even more.

This place has them for $49.95:
http://www.gilsson.com/garmin_gps/antennas/mcx.htm

 

[Papa Bear]

I have an external antenna whuch plugs into my Garmin 60CS. It comes with a 10 foot cable.

What I have done is to "mount" the thing on a cardboard square, about 5" square (using duct tape). This serves as a stiff platform for the antenna. I then stick this in the top pocket of my pack so that the antenna is facing up at the top most point of my pack. The cardboard square was fashioned to just exactly fit in the pocket. It takes up very little space, so other normal items (bug net, etc.) still fit in the pocket. I suppose you could also mount it on your hat.

Anyway, I thread the cable (a very thin co-ax) down so it doesn't get caught in my arms or any strap, etc. and plug it into my GPS which is either in my pocket or on my belt. A little trial and error will allow you to get the cable out of the way and you will soon not notice it.

Warning: dont take of your pack and fling it to the ground without taking care of your GPS. At the end of the hike, or during a rest break, I usually leave the thing plugged in and just lay it on the pack on the ground or where ever it is.

Does it help? Can't proove it since I did no test under the same conditions, but I generally get good reception.

Hopefully Doug Paul will chime in here. He's the expert.

 

[DougPaul]

An external antenna will probably help. Its primary advantage is that it allows one to put the antenna in a good spot (ie above everything else) and still be able to look at and operate the GPS.

I have:
http://www.pc-mobile.net/gpsant.htm. GAST3X (mcx connector). $27.90. Works well, smaller than most. Magnetic base--works on car or in/on pack. (Just keep it away from your compass when taking bearings.) It will work with a 76CS.

Best mounting places, top of hat, on a pole mounted on your pack. Next best is in/on the top of your pack as described by Papa Bear.

Two threads with a bunch of info on external antennas:
Question on GPS use under heavy canopy: Garmin vs Magellan
http://www.vftt.org/forums/showthread.php?t=7393
Help with GPS
http://www.vftt.org/forums/showthread.php?t=6583

A search on "external antenna" will bring up a bunch more.

Doug

 

[maineguide5]

I have a Garmin Etrex Vista, and found the same problem. I got a Garmin see thru GPS case that I clip onto the top edge of my pack and it "backtracks" very well for me, without the use of an external antenna. The Garmin case is made for the Vista and has the proper openings to allow the signal to be captured. Pete B

 

[Kevin Rooney]

I have a Garmin Etrex Vista, and found the same problem. I got a Garmin see thru GPS case that I clip onto the top edge of my pack and it "backtracks" very well for me, without the use of an external antenna. The Garmin case is made for the Vista and has the proper openings to allow the signal to be captured. Pete B

I also have the Vista, and got the Garmin case to protect the LCD face as it was getting pretty scratched. I clip it to the top of my pack and rarely lose signal lock -has to be very dense overstory or almost a slot canyon before that happens.

 

[DougPaul]

I have a Garmin Etrex Vista, and found the same problem. I got a Garmin see thru GPS case that I clip onto the top edge of my pack and it "backtracks" very well for me, without the use of an external antenna. The Garmin case is made for the Vista and has the proper openings to allow the signal to be captured. Pete B

In general, the signals go right through the cases (typ fabric, plastic, and/or neopreme) unless they are wet. Large wet objects such as foliage, tree trunks, tree leaves, and flesh block the signal. Rock, soil, and metal also block the signal. (Airborne precipitation has essentially no effect--the drops/snowflakes are too small.)

The antenna in a Vista is under the globe symbol above the display. The front should be pointing upward (same as if you lay it flat on a table) for best performance.

If you mount an Etrex Vista valt on top of your hat, it should do essentially as well as an external antenna. Flat on top of a pack is almost as good--your head will block part of the sky (unless you have a rather tall pack...).

I have clipped my Vista into the adjusting strap at the back of a baseball cap. The orientation is close to vertical instead of horizontal and my head interferes with the forward view, but it still works pretty well. (Since I am usually looking down at the trail, the GPS is turned somewhat upward.) Normally I just carry my Vista in a small pouch attached to the upper front of a pack shoulder strap--convenient and usually good enough.

If you need an external antenna for a GPS without an antenna jack (such as the eTrex Vista), you can use a reradiating antenna. See my link to pc-mobile for some commercial examples.

Doug

 

[zman]

I also have an external antenna which plugs into my Garmin 60CS. It comes with a 10 foot cable. I have put Velcro patches on the tops of my pack lids and tops of the shoulder straps of my packs w/o lids and have a patch on the back of the antenna. I am then able to clip the GPS to my hipbelt-

great reception, easily accessible. Iin winter I keep the unit in a small pouch on my hipbelt with a handwarmer if temps are really cold-haven't tried the antenna on my hat or pole!!

 

[DougPaul]

haven't tried the antenna on my hat or pole!!

One technique is to sew a steel washer (or bit of thin sheet steel) into your hat. Most external antennas have magnets which will stick to the steel.

Doug

 

[CaptCaper]

I've used a Gilsson antenna with 3 ft, cable for my 76S's and never lost a signal through out the Whites.

Go to Ebay were gpsgeek.com has a store and you can buy it cheaper than there main store is.

I've bought about 7 of em so far and they haven't failed even sitting on front of my truck while plowing in storms for 3 years.

I'd give you a direct link to there store but I'm in Maui and have to leave for a hike. I don't have the favorite pages here at the station in my resort.

Maybe someone can link you to them. They have the best MCX connector that can be had. Just make sure you get the right angle connector so it lays flat coming out from the gps.

Capt.

 

[Mohamed Ellozy]

An external antenna will probably help. Its primary advantage is that it allows one to put the antenna in a good spot (ie above everything else) and still be able to look at and operate the GPS.

Best mounting places, top of hat, on a pole mounted on your pack. Next best is in/on the top of your pack as described by Papa Bear.

The pole obviously seems the best solution, as it will get the antenna clear above all of my body. Has anyone actually done it? Fixing the antenna to the pole looks like an "interesting" project (duct tape, perhaps???).

 

[MichaelJ]

The pole obviously seems the best solution, as it will get the antenna clear above all of my body.

Until you snag it on an overhanging limb. I'd stick with the top of the pack to be safe.

 

[DougPaul]

The pole obviously seems the best solution, as it will get the antenna clear above all of my body. Has anyone actually done it? Fixing the antenna to the pole looks like an "interesting" project (duct tape, perhaps???).

Never used a pole myself. I have carried skis attached to my pack--clearance issues should be similar. In general, you should get most of the advantage if it is a bit above head height--8 or so inches should be enough. (The primary purpose is so that signals clear your head.)

One method for mounting the antenna is to put a steel washer at the top of the mount and use the magnet in the antenna. If you use tape, I would use electrical tape rather than duct tape. (Less sensitive to moisture and the adhesive isn't as gummy.)

I have attached the antenna to a flat plate (to stabilize it) and put it in the top pocket of my pack. I then threaded the cable along my pack strap to the GPS in a small pocket on the pack strap.

If you have a Tilly hat, there is a pocket in the crown which should work pretty well. (As long as the hat stays dry...)

It is most convienient if you attach everything to your body or to your pack. If part of it is attached to your body and part attached to your pack, you have to be careful when you take your pack off...

Doug

 

[CaptCaper]

I've had mine on top of my packs for years all over the Whites and then some and never lost a signal. My son wears his on his shoulder strap at the shoulder so it faces up. He's gotten good reception that way. I prefer the top of the pack.
Pole hiking sounds like a challange I'll join in.

 

[Mohamed Ellozy]

Well, my PC-Mobile antenna arrived, and I did some testing at home, both indoors and outdoors. Clearly location matters immensely; the receiver without antenna gave as good a fix on my porch (great visibility in three directions) as it did with the help of the antenna indoors (lousy visibilty). Some preliminary screen shots are here; I hope to do a few more experiments (at trailheads, where I can bring my laptop) in a few days.

Right now I am busy sewing a steel washer to the top of my pack, the location is at approximately shoulder height, and a few inches behind my body. Not as good as on my head, but I do not wear a hat except in winter, which is fast going away.

 

[arghman]

Well, my PC-Mobile antenna arrived, and I did some testing at home, both indoors and outdoors.

sweet! I gotta get one of those.

Edit:

If part of it is attached to your body and part attached to your pack, you have to be careful when you take your pack off...

I vote to attach it via a snap or velcro or something that can give before the cable/connector does.

 

[DougPaul]

Well, my PC-Mobile antenna arrived, and I did some testing at home, both indoors and outdoors. Clearly location matters immensely; the receiver without antenna gave as good a fix on my porch (great visibility in three directions) as it did with the help of the antenna indoors (lousy visibilty). Some preliminary screen shots are here; I hope to do a few more experiments (at trailheads, where I can bring my laptop) in a few days.

Certainly looks better with the external antenna.

Was the external antenna in the same place as the GPS when taking the measurements? And was your body out of the way? Also, was the GPS oriented properly (vertically for the 76CS)?

Looks like you made the measurements in close (time) succession so that the satellite constellation did not change much.

Doug

 

[DougPaul]

I vote to attach it via a snap or velcro or something that can give before the cable/connector does.

The antenna cable connects with a right-angle connecter which would put a nasty strain on the connecters if one pulls too hard. The MCX connector is rather small...

A caution: the plastic where the belt clip attaches is not very strong. People have broken their cases by stressing the clip. IIRC, people have also dropped the GPS because the clip didn't hold very well either. I have removed my clip and carry the GPS in a case: the Gilsson R60N was the best I could find (for my 60CS, I haven't looked at cases for the 76 line).

Doug

 

[DougPaul]

Well, my PC-Mobile antenna arrived, and I did some testing at home, both indoors and outdoors. Clearly location matters immensely; the receiver without antenna gave as good a fix on my porch (great visibility in three directions) as it did with the help of the antenna indoors (lousy visibilty). Some preliminary screen shots are here; I hope to do a few more experiments (at trailheads, where I can bring my laptop) in a few days.

I did a quicky comparison of internal vs external antennas out in my back yard, a location with a pretty good skyview. The GPS was a 60CS with a quadrifilar helix, and both it and the external antenna (a PC-Mobile GAST3X with an amplified patch antenna) were placed in the same location (top of a fence post) when receiving the signals. I was able to keep my body and head down below and generally out of the way. The location is far enough away from reflecting objects that standing waves (multipath) are not likely to be a problem. (Standing waves--ie delayed copies of the same signal bounced around so that they are coming from multiple directions--make the GPS very sensitive to the antenna location. Anybody who has played with an indoor Rabbit Ears TV antenna has seen them in action...) Signal strengths were good and I was receiving 10 or 11 satellites, many at or above the highest signal strength line on the display. I switched back and forth between the internal and external antennas several times and compared the signal strength (actually S/N, IIRC) indicators or the satellite display page. There were minor differences--a particular satellite might be a bit better on one antenna or the other--but overall, neither antenna was obviously better than the other.

This result is consistent with my earlier statements that the primary advantage of an external antenna is that it allows one to place the antenna in a better location than the display unit.

This is just a single simple qualitative comparison. A rigorous comparison would compare actual numbers averaged over a day or so. This comparison was also made under good signal conditions where either antenna was quite adequate. The conclusion might be different under poor signal conditions.

Doug

 

[CaptCaper]

I don't agree with that. All the information I've read about these antennas is that they have amplified and have more gain and will pick up birds lower on the horizon than OEM built in antennas. Also I know you have to leave the gps on for quite awhile to get a good data pattern so to say.
Did you try turning it around in a carousel type movement? In a perfect world you'd be stationary and have a clear view of the sky. But when things start changing I believe you would see different results.
Under trees wit leaves,especially wet ones,etc. a antenna with more gain would have an advantage.
Also different GPS's have different antennas. So using the just a 60CS would not mean much.
I find the stock antennas too sensitive to movement and the Gilssons more forgiving.