intellectualist
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Registered: Feb 2008
Location: Near Asheville
Posts: 981 |
Garmin antennas demystified....
There always seems to be a Garmin antenna range question on the forum. Being an advanced class ham radio operator for nearly 20 years and having messed with this stuff for nearly 30, take my knowledge and apply it as you see fit if you find it to even be knowledge at all.
I will try to explain here, in plain talk, what is happening with your Garmin.
Lets assume for a second that you have a magnet mount antenna for your truck. This antenna, if you buy the Garmin brand, is what is known as a quarter wave verticle. It is no better than any other quarter wave magnet mount antenna that is designed to operate on the same frequency as the Garmin magnet mount. Just because it says "Garmin" does not mean it was soaked in some magic potion that will allow your astro to get two more miles farther than the competitions quarter wave magnet mount. Just isnt going to happen.
These quarter wave magnet mounts basically have no gain like a directional, 3 element yagi antenna would that you would use on your telemetry trackers.
The antenna that came with the Garmin is called a "rubber duck".
The rubber duck is basically a "negative gain" antenna and is suited for convenience as well as limited stress on the connector.
Now lets think about this for a second. Not only do I have a rubber duck with a negative gain ratio, but if I am inside the truck trying to track my dogs, the cab of the vehicle is going to cause poor signal reception as well. That is where the quarter wave magnet mount outshines the rubber duck. Not so much because you are going from a negative gain antenna to a no gain antenna, but because you are getting it "outside" of the cab area of the truck. Also, more times than not, you are elevating the magnet mount antenna more than what the rubber duck would be inside the cab.
I can't stress how important elevation is when it comes to receiving a signal from your Garmin collar. That is one reason why that handheld long range antenna does better than the rubber duck is because you can elevate it and it is a quarter wave antenna just like the one on your truck. Well, if it is a quarter wave, then why does it not do as good as my truck antenna? Because quarter waves require a ground plane to be 100 percent efficient and the one stuck to your truck has a great ground plane whereas the one sticking up in the air from your hand doesnt.People with metal plates in their head notwithstanding! There is not five bucks worth of material in that long range handheld antenna and the fact it can be elevated is what makes 80 percent of the difference!
Us hams use repeaters on frequencies very close to what the Garmin collars operate on and the difference in making the repeater or not can easily mean you are either sitting, or standing in your living room while trying to work the repeater with a handheld. The Garmin is absolutely no different. If someone claims they are getting 5-6 miles out of their magnet mount antenna, that may be true, but how many times did they loose communication with the collar while trying to reach that 5-6 mile threshold? People are getting hung up on range when really what they need to be doing is determining whether their new fangled antenna really is working any better than their old one.I literally have places here that I can shock and astound you with the range I can get out of my Garmin with the rubber duck. Those claims would be true but not an accurate representation of what you would get in real world tracking situations. The fact that I can put alot of elevation between the Astro and the collar would be why I could amaze you, not because I have revolutionized the world of antennas or because I know something about the Astro that you don't.
How do I determine if my antenna really is better you may ask. Well, I can tell you that if you leave your collar at the house and start driving with the rubber duck attached to your Astro, you should loose signal soon. Go back to the house and stick your magnet mount on the truck and lets see how far you can go before loosing signal.If your quarter wave magnet mount antenna is working properly, you should expect to double your range and even after you loose connection, there will probably be places (even further from the point where you originally lost connection) that you will reconnect because of your orientation to the collar. Nobody can accurately and systematically say "this antenna gets this range or that range" because in another scenario that same antenna with that same astro and collar may not get half that much range!
Now, if you can say that the collar was stationary and I held my astro a certain way with the rubber duck and was getting no signal at all, then I attached this long range antenna and got a full scale communication with the collar, that would be something worth listening to and the ONLY measure you need to determine if the new fangled antenna you have now is better than the one you were using! Same thing with the magnet mount. Next time you have nothing to do, stick the collar on the porch and drive until the rubber duck looses communication with the collar and after stopping, attach your magnet mount and look at the dog info page. I bet in most instances where you lost communication with the rubber duck, you will fully deflect that signal meter on the communication page!
Naysayers want to always elaborate on the poor reception of the Garmins but they are comparing it in the wrong way. I do not look at my Garmin as getting this range or that, rather, I look at it as a collar out there is moving around transmitting position data and on a VHF frequency and all I need to do is capture one short data burst and I will know exactly where my dog is at that point.It is accurate data in "real time" that will never be achieved with a telemetry unit.
But this thread is not a telemetry versus Garmin thread. It is meant to inspire folks to look at the Garmin for what it is, how it is designed to be used, and how these antennas compare.
Now if you really want to stretch the range of your Garmin, lets discuss multi element beam antennas but that should be for another post.
I do not claim to know everything but if there are any other questions about these antennas, I will try to answer them if I can.
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02-14-2011 02:56 AM
BARRY GREEN 
