What Is The Best EVDO Antenna?

Scott · Posted: Mon Aug 21, 2006 1:17 pm Post subject: What Is The Best EVDO Antenna?

What Is The Best EVDO Antenna?

We are often asked, "what is the best outdoor antenna?"

We always try to reply, "for what application?"

That's what it comes down to: what are you going to use it for? What do you expect it to do? And how much do you want to spend?

Frankly, I would use bailing wire stuck on a rusty nail if I could. I can be THAT cheap. But luckily I've had the wisdom of some RF engineers and old ham radio ops to ponder.

Not everyone needs an external antenna for their EVDO device, especially if the use location provides good signal levels and good speeds without an added antenna. Don't waste your money. On the other end of the spectrum, antennas won't make signal 'magically appear' where non exists. But they can increase signal.

Often its more about location: put the antenna where there is more signal, and hey, lookit THAT... you have MORE signal. ;] Just like how a mobile phone can work in some parts of a building and not in others, where you locate your EVDO modem w/built-in antenna or where you locate the antenna matters.

Much ado about antenna things

The purpose of an external EVDO antenna in our case is to increase the radio signal that carries EVDO packets between your data device and back to the provider's cell tower and connected network. The reason for increasing signal is that upload and download speeds are typically better when you have greater signal levels. More 'bars' usually means faster, but not always. Speed increases with signal only up to a point.

These antennas are non-powered lengths of metal that are tuned by their shape, size and length, mass, and conductive composition. Sometimes they have a plastic cover or housing called a radome, sometimes not (radomes protect the antenna element and should have no effect on the incoming/outgoing signal).

Now the trick (and what makes a good antenna) is to only pick up the radio signal we want, and to likewise transmit the signal we want back to the provider's tower, all while ignoring other radio signals or what is referred to as 'noise'.

Murmurs are fine, but don't turn them into SCREAMS

Think of it as the desire to only hear one individual's voice from across a crowded room with other voices chattering away, and then for you to talk and have that one individual hear your voice clearly back on their side of the room, all while NOT raising your two voices.

In this case, your voices are the 'signal' and all the other voices are the 'noise'.

Good antennas help to increase just the voices we want, while reducing the voices we DON'T want. Or to put it another way, we want to increase the amount of signal and NOT increase the noise so our EVDO cards can provide the highest speeds possible.

You may have heard the term 'signal-to-noise ratio' which simply means 'signal compared to noise'. Keep the signal high and the noise low, and your EVDO modem radio can transmit faster. That ratio is an important thing. Bigger signal isn't always better signal.

Back to our voice analogy: if you and the other individual you're talking with across the room RAISE your voices amongst all the other chattering and ALL the other voices are then raised yet even MORE, you're going to have a harder time hearing each other even though you've raised your voices.

That's one of the main concerns when increasing signal with an antenna (or an amplifier). Its not only about increasing signal level. It also about keeping the signal-to-noise ratio at least as good as when you started, or if even possible, to make the ratio better: more signal and LESS noise.

So, getting your 'bars' to jump from 1 to 4 or signal level to increase from -105 dBm to -68 dBm is only good if the NOISE didn't jump up HIGHER than the signal.

So, why all the tests?

Because that's how we find out which antennas and signal amplifiers really increase USABLE signal and don't increase the noise level too much. Have to fly 'em up the flag, um, antenna pole. ;]

Remember, the connection software we all use only shows signal level, NOT signal and noise level, so by comparing the upload and download speeds and latency of lots of antennas in real-world situations we can see which ones really work and which ones don't. Over time we get a picture of which antennas and amplifiers really are helping bandwidth and thus are probably raising signal level while keeping signal-to-noise ratios somewhat constant.

Now onto our main course: antennas

Omnidirectional antennas work for structures, boats and cars/trucks/RVs. Directional antennas, such as the yagis we tested, are generally only used for static mounting on structures, though some die-hard RV'ers don't mind the setup and enjoy the benefits where they have good line-of-sight.

Omni Antennas

The best external omni dual-band Cellular(800MHz)/PCS(1900 MHz) antenna tested so far is the 32" Omni External that we sell. We wouldn't carry it otherwise.

Our 18" RV/shorty and 21" Spring-Base versions works just as well (the antenna element is identical on all three).

While our tests indicate that this is the best performing antenna, we also take into account cost, manufacturing consistency, and manufacturer's warranty and SUPPORT. You can find cheaper, buy you won't find better.

In all but one case the 32" Omni External Antenna, the 18" Shorty RV Through-Roof Mount Antenna and the 21" Spring-Base surpassed the performance of all other small to medium sized outdoor omni antennas by a notable margin (some of the other antennas could not connect to the nearby EVDO network even with an EVDO-locked card, and when in 1xRTT-only mode had much lower signal levels and higher latency).

Marine Antennas

Runner up to the Omni External was an 18" dual-band Marine Omni we first tested months ago. We are now officially selling this antenna. After repeated tests the Marine Omni came in second place because of lower upload rates (with and without a signal amplifier). Different antenna lead lengths (tuning) will effect transmit power and thus latency and upload speed.

Still, for marine environments the dual-band Marine Omni would be a better choice than our Omni External, due to the sealed radome which eliminates antenna element corrosion and resulting loss of power. Exposed antenna elements will pit and corrode eventually, lowering power and necessitating replacement.

We suggest that you mount the Marine Omni at the top of a sailboat's mast, or at the top of a radio/radar bridge. Elevation matters at sea. I believe the FCC spec is 12 inches of separation between different types of antennas (cellular/PCS, VHF, 2.4GHz, AM/FM, AIS, etc). Discuss mounting options with your radio outfitter if you use a pro. We do carry alternate cables and mounts.

Yagi Antennas

Our favorite yagi antennas tested so far are the Wilson Cellular yagis tuned for 'cellular'/800MHz or Sprint's 'PCS'/1900MHz. Runner up were the Digital Antenna yagis, also tuned to 800MHz or 1900MHz. Third place was the Digital Antenna multi-band (at nearly double the cost).

We don't sell a dual-band yagi antenna because we have yet to find ONE antenna that can do it all at a fair price. The best and most cost-effective yagis so far, are those that are tuned to one band, yet EVDO carriers use one of two bands, 800MHz and 1900MHz, bands that are far enough apart to limit efficiency when an antenna is tuned to BOTH.

The good multi-band yagis that we have tested cost twice that of other yagi antennas and our omni, while not providing that much greater gain (and they also require more attention to correct setup). The bad yagis we have tested have LOWER gain than our omni, so we ask, "what's the point?"

When we find a dual-band yagi that has more true power than our omni, that works for both 800MHz and 1900MHz and that has a retail price that fairly matches its performance, THEN we'll be selling a dual-band yagi.

Antennas... are we DONE?

Hardly.

We constantly test and compare antennas. When we find something better/cheaper/faster, you can bet we'll carry it. If you're a manufacturer, contact us and we'll be happy to check out your antenna(s).

Keep in mind we're not focusing on "boutique" cost-is-no-object antennas. In our case, we have to keep FFC limits in mind, along with how the antennas work with other antennas and devices around them (what kind of RF "citizen" they are). While it may be possible to build or purchase a highly powerful antenna, its not helping anyone if it makes your nearby mobile phone unusable or cooks your kid's pet gerbil. ;]

My amplifier goes to ELEVEN.

All the antennas were tested with and without signal amplifiers (three different brands/models). We even tested short and long cables with the different signal amplifiers to determine how they would react (and to determine whether amplifiers magically account for longer cables).

Our findings? The shorter and thicker the cable the better, regardless of what signal amplifier you choose to go with. Long coax length degrades signal level and can pick up noise. The idea here is to preserve as much signal level and keep out noise. In many instances where there are long cables used to connect to the antenna, signal amplifiers are employed to deal with signal loss, not really to boost signal overall.

Just keep in mind that bringing the computer (or ROUTER!) nearer to the antenna can really pay off too and can be a LOT cheaper. Relocating a router nearer to the antenna allows for shorter coax and then gets your signal onto ethernet for the long run down to where you need it. Plug in a Wi-Fi access point at the far end of the ethernet run and you're mobile again. Check out power over ethernet if you need to remotely power a router.

One last thing to touch on regarding signal amplifiers is that they have the potential to greatly increase noise. So while the signal level numbers go up, so does the noise (sometimes more than the signal). Going back to the first part of this post: you have to have SOME useful signal to increase in the first place.

A Quick Note On Cable.

I had some fellow laugh at me the other day during a pre-sales phone call. He said, "I used to sell coax... don't tell ME that there is a difference between some expensive stuff you sell and something I can get for a quarter of the cost, har har har."

I wish I could have showed him the physical size/quality/shielding difference between what we consider good cable and the cheapo stuff and then shared the actual antenna output numbers between the so-called "low-loss" coax and something decent, and then some test results where the cheapo cables with poorly terminated connectors resulted in poor or NO connectivity. Oh well, his loss (literally)...

Lastly, a note about 'SPECS'.

While antenna specifications are supposed to reflect some reasonable measurement of the true gain or power of an antenna, we have found that both manufacturer's sites and resale sites tend to 'hype the numbers'. I'm being polite here, and I won't 'OUT' any site or manufacturer.

We've spent WAAAYY too much time doing side-by-side tests with antennas and amplifiers sold by vendors that state lots of impressive SPECS but in reality DON'T DELIVER. "Why you could be 60... no, 70... no, a HUNERT miles out to sea and connect at EVDO speeds!!!"

You get the idea.

For example, when you take an antenna marketed as 6.12 dBi for 1900MHz, it had better BEAT our little Booster Antenna that is rated at 3dBi for the same frequency.

When it doesn't, and to be fair, we go back and buy another supposed "6.12 dBi" antenna and test it, and it again delivers no more power than the Booster Antenna, we're prone to think someone is fibbing about SPECS.

HI... while we LOVE to discuss antennas of all types, we unfortunately cannot provide free advice and support for products we didn't or don't sell. If you need technical guidance for a product 3gstore.com doesn't carry, contact the manufacturer or the outlet that sold you the product. If you have general questions, the forum is a great place to post them... everybody benefits.