Is my grid put together correctly for Evdo?

widgetman101 · EVDO Junkie Joined: 02 Apr 2008 Posts: 153

With all the talk of Grid's I decided to give one a shot to see if it would preform better than my Yagi. I just want to make sure its setup correctly here. I didn't get an instruction manual on configurations.

Sorry the pic's kind of blurry but I just got off work and took a quick shot with my cell. Everything is currently vertical and should be mounted vertical on the poll as well. IE if you turn your head 90 degree's that's how it will look on the poll right?

Also this thing is freaking huge! I never would of guessed it was this big.

n6gn

widgetman101 · EVDO Junkie Joined: 02 Apr 2008 Posts: 153

Great thanks for the info. I removed the horn and put it vertical with the grid. I waited this morning until my Yagi gave me a broadband access Rev-A signal.

I then tried to connect with the Yagi and it failed even though it showed 4 bars at the far fast tower. So I took down my mast and put up the grid. I left the Yagi above it because if the Grid didn't work I wanted it to be accurate with the marks on my mast.

So I got everything hooked up. Since the horn is centered with the Grid rather than slightly off to the side like the Yagi I new I'd have to move slightly to the right. I eyeballed it and walked inside.

I'm greeted to a full Broadband Access Rev-A signal again. So the moment of truth! I click connect and within 6 seconds I'm fully connected. I've tried disconnecting and reconnecting a few times and its always fully connected not just authenticating within 6-7 seconds.

Finally no more going out and rotating the antenna's and screwing around. I wish I would have done this a while ago. Speeds seem directly in comparison with the Yagi. Just the Grid is more focused and doesn't get as much interference and connects without issue Smile

I'm so happy right now. No more games running outside connecting the spinning my Yagi at another tower. As far as signal I'm getting -61dBm with the Grid and I normally got -59dBm with the Yagi after I managed to get it connected.

Might be because the Grid is tuned at 900Mhz instead of 850Mhz area. Wow I'm never recommending a Yagi again. This thing owns Yagi's!!!

widgetman101 · EVDO Junkie Joined: 02 Apr 2008 Posts: 153

Grr no edit button. I did notice one thing so far. Even though the total throughput isn't any faster than the Yagi pages seem to load faster. It seems the grid is getting to max download speeds faster than the Yagi could. And so far on download tests it seems much more stable at maintaining downloads. The Yagi would drop down every once and a while while the Grid is pretty steady almost like cable.

I can't get a good pictures because the sun's right behind it but I did take a quick snapshot. I don't think you can even see the Yagi about 1 foot above the Grid.

Why on earth isn't 3G's store selling Grids???

n6gn · Posted: Fri Oct 10, 2008 2:02 pm Post subject:

SlyFerret · EVDO User Joined: 19 Mar 2007 Posts: 92

That's a nice looking antenna. Got a link?

-SF

widgetman101 · EVDO Junkie Joined: 02 Apr 2008 Posts: 153

n6gn · Posted: Sat Oct 11, 2008 6:54 pm Post subject:

FWIW...
It's interesting to me that there is likely an error in their data sheet. This isn't uncommon for antenna vendors but what surprises me is that this error seems more like an honest one and doesn't particularly serve to exaggerate the product. Here's why I say this-

They claim it to be a 15 dBi antenna at 850 MHz, however, in the data sheet they also claim a 19 by 30 degree beamwidth. This claim is affirmed by the pattern plots they provide. From these numbers, the directivity of this antenna should be approximately:
(360x360)/(19x30) = 227, and 10 log(227) is more than 23.5 dBi gain/directivity if the feed and reflector were perfect.

However, this much gain and a pattern like this isn't possible from an antenna with an aperture (physical size) of .6 x 1=.6 square meters, at 850 MHz.
An isotropic antenna (the reference antenna in a dBi rating) has an aperture of
wavelength squared/(4pi).
At 850 MHz this is about .125/4pi = .01 square meters. This would lead to a theoretical maximum gain of .6/.01 =60 or, 10*log(60) = ~ 18 dBi. Typically simple feeds like this antenna has have on the order of 55% efficiency which would lead to 10*log(60*.55) = 15.2 dBi

So it looks to me like they got the gain about right in the bold print but that they used pattern numbers for that antenna from a measurement at some frequency where the antenna had very different performance.
My summary opinion is that it is still a very good antenna that probably is doing about as well as one can expect for its size. Just don't count on the pattern being what they say.

n6gn