External Antenna While Backpacking?

[jcn37203]

Have any of you guys tried using an external antenna with your receiver for backpacking?

 

My GPSr (60CS) loses connection pretty easily under tree cover. I'd say it is certainly worth the cost of a good antenna if it makes a big difference in reception under tree cover. I really like keeping tracks so I can share topo maps with friends and have the trail reflected on the map. But it's hard under heavy cover. In fact, basically impossible.

 

I was thinking I could put the antenna on top of the pack, maybe even attach it to the top of the frame, and run the cable down the shoulder strap or something. I'd hate to waste the time and money rigging this up if it doesn't make a big difference though.

 

I see some +28 dB antennas, and some +55 dB antennas. Is there a big difference? I know with coax amplifiers it's is very easy to over-amplify the signal, is that an issue with a GPSr?

[+Olar]

Have any of you guys tried using an external antenna with your receiver for backpacking?

 

I was thinking I could put the antenna on top of the pack, maybe even attach it to the top of the frame, and run the cable down the shoulder strap or something. I'd hate to waste the time and money rigging this up if it doesn't make a big difference though.

That's exactly what I do (did) with my 76C when I go caching/hiking with my backpack. It certainly made enough of a difference that I rarely lost complete sat. lock and don't have to carry the unit out in front of me looking like the statute of liberty.

 

I say "did" because that need has gone out the window since upgrading to a 60 CX. That baby can maintain a strong lock just about anywhere within reason.

 

Cheers, Olar

[+GPS Guy]

I have done this with good results. My external Titan III has 28dB gain. I have mounted it to a pole attached to my pack, or to my hat. I use a 4" diameter steel plate as a ground plane for improved performance. The antenna mounts to the plate with it's magnet.

The key to getting a decent signal under the trees is to give the antenna it's best chance to see the sky. That means getting your body and head out of the way. Mount the antenna on or above your head. On your hat is better if you do any bushwhacking.

Carefully evaluate the specifications of your GPSr and any candidate externals. Watch the voltage if you use NiMh batteries, lower current draw will help prolong battery life. Too much gain, as you mention could overload the input of your receiver.

[jcn37203]

Thanks for the replies!

 

I like the steel plate idea, but I'm not too hot on the elevated pole idea, unless it's a flexi-pole of some sort. My external-frame pack already catches on low rock formations and tree branches. I'd hate to see how it would handles another 13 inches of height.

 

But I guess some sort of spring-pole might work.

 

Thanks for the help, I'll look in to this.

[+Klatch]

Thanks for the replies!

 

I like the steel plate idea, but I'm not too hot on the elevated pole idea, unless it's a flexi-pole of some sort. My external-frame pack already catches on low rock formations and tree branches. I'd hate to see how it would handles another 13 inches of height.

 

But I guess some sort of spring-pole might work.

 

Thanks for the help, I'll look in to this.

 

Be careful where you store that magnetic mount antenna, you can trash a magnetic compass with it. (Not to mention really getting bizarre reading when using a magnetic compass.)

[nhfours]

... or to my hat. I use a 4" diameter steel plate as a ground plane for improved performance. The antenna mounts to the plate with it's magnet.

It is even easier to sew a 1" steel washer to the hat, magnet is strong enough to hold on to it. I thread the antenna cable down my back under my t-shirt to keep it out of the way, and carry the GPSr in a "belly pack" (fanny pack worn in front) for convenient storage/access.

 

There is no doubt that the antenna helps a lot, but my older GPSr (76cs) still occasionally loses signal under heavy tree cover. I am reluctantly thinking of upgrading to the x series ... big bucks

[Grasscatcher]

Forget the ground plane and extra weight....put velcro on the bottom of the antenna and the other half on your cap, or pack frame orcar dash, or whatever. It has worked perfectly for me for years.

[GeoidPS]

Actually, Gilsson recommends a 2" square ground plate, and it actually says so on the bottom of the antenna. So I figured I'd get the windshield mount and it straps to the top of my shoulder strap. Hope my fat head doesn't block the signals.

[+GPS Guy]

Actually, Gilsson recommends a 2" square ground plate, and it actually says so on the bottom of the antenna. So I figured I'd get the windshield mount and it straps to the top of my shoulder strap. Hope my fat head doesn't block the signals.

 

That is the point of mounting on or above your head. Consider that under heavy tree cover you are getting poor coverage. Then stick your head in the way, and it is suddenly blocking 30-40% of the sky in addition to the tree cover. That makes it hard to keep a lock and a continuous track log.

[+Red 07Z]

Actually, Gilsson recommends a 2" square ground plate, and it actually says so on the bottom of the antenna. So I figured I'd get the windshield mount and it straps to the top of my shoulder strap. Hope my fat head doesn't block the signals.

 

That is the point of mounting on or above your head. Consider that under heavy tree cover you are getting poor coverage. Then stick your head in the way, and it is suddenly blocking 30-40% of the sky in addition to the tree cover. That makes it hard to keep a lock and a continuous track log.

 

i should design and produce the GPS hat starting at $60 bucks you'll get a funky hat with a lump on the top

[Centerfield]

Those pesky brain eating cellular phone microwaves will get you even if you are hiding in a concrete block basement - why didn't they design the gps with signals that could go through leaves? After all - what's more important - knowing where I am when treaking in the wilderness or being able to order a pizza without having to get up from the couch while watching the football game?