Omni vs Directional

Lunyfringe · EVDO Fledgling Joined: 17 Jan 2006 Posts: 20

I purchased the omni trucker antenna, and got about 2 bars...
wet summer, much more greenery in the valley I live in- went back to 1 bar
all this time the initiation of a connection is slow, sometimes taking 3-5 times to successfully connect- and I can't let it go dormant, or it will do it over again (30sec-5minutes to restart connection)

I got an CA-819 amp hoping to resolve that issue- went to 3 bars, but no change in the symptoms... so I start to wonder "is my valley just noisy" like anyone using a regular TV antenna in the mountains has seen, there's ghost images caused by signal reflection off the mountains..

so I try using the little window antenna with suction cups- stuck it on the LNB of an old satellite dish, and started pointing it around... SE, no good- same symptoms- right at the cell tower (no, my carrier VZ is not on that tower..) no good.. point it NW, and the connection is only -108 without the amp, but it connects up in less than 2 seconds!.. disconnects fast, re-connects fast... I think I need to get a Yagi (I realize my makeshift directional is hokey, it was a test)

moral of the story, it looks like there MAY be situations where a directional makes sense even if you DON'T have line of site to the tower... the same reason why people in the mountains put directional TV antennas up- to reduce the ghosts...

n6gn · Posted: Fri Sep 22, 2006 5:50 pm Post subject: Re: Omni vs Directional

Scott · Posted: Fri Sep 22, 2006 6:20 pm Post subject:

While a parabolic (even if its home-made) is directional, its in a different class than a yagi. Parabolics can reflect a LOT of energy, focusing on a dipole or in your case what sounds like a Booster Antenna. That doesn't mean it will work well, that there won't be issues with multipath, etc.

That's not to say a yagi may not help you, just that in many instances the focused gain is no better than a good 'trucker' antenna when there is foliage or hillsides or multiple structures blocking the signal path.

Keep in mind that antennas sold in the U.S. for dual-band cellular/PCS licensed frequencies must comply with FCC limitations for allowable gain. That is, there are limits. You could build a more powerful directional antenna which would easily rival omni directional dual-band antennas sold by reputable dealers.

We have done hours and hours of testing with many of the dual-band omnis and single or multi-band yagis sold for PCS/Cellular networks and in many instances where there was a major obstruction, the yagis provided no more gain that omnis.

For many EVDO enthusiasts it is just less headache to get a good omni and put it in the RIGHT place than to spend time learning how to set up a yagi. Its NOT that hard, just a hassle for some people that want the 'easy button'. Many using EVDO don't even know how to monitor signal as decibels or RSSI, something that may not always be needed but can be quite helpful for tuning a yagi (or omni, for that matter).

Note that not all 'truckers' are the same either. We've spent some time with back-to-back comparison tests to be certain that the Omni External 'trucker' we carry provides the gain advertised and is worth the money.

We've even taken the competition's antennas APART (such as cutting open radomes or environmental housings, etc). You'd be surprised by the differences in materials and cosmetic tricks used to make an antenna look like a good one.

Your antenna is the first thing that the signal "sees" and the last thing that is leaves. Its worth getting a good one AND mounting it somewhere where it will make a difference.

Signal doesn't MAGICALLY appear when using a signal amplifier. That amp is just increasing the signal the antenna provided.

Lunyfringe · EVDO Fledgling Joined: 17 Jan 2006 Posts: 20

"Keep in mind You should have good line of site with a directional antenna otherwise you are just as well served trying to get the omni as high up as possible ."

I'll have to take issue with this statement- I had the omni on my roof, with the top of it higher than any point on the roof- connections would sometimes take 4-8 MINUTES to establish... today I took the SAME anetnna, and put it on the railing of my deck, but with the parabolic sitting about 14 inches behind it (after playing with it, this seemed optimal)

now it consistently connects within 4 seconds, speeds are up to consistent 131kbps with OR without the amp... (I was getting inconsistent 40-80 kbps before without the amp)

the amp is DEFINATELY improving the signal levels... -104 without, -90 with
but the performance is roughly the same...

I think in my case, the omni just picks up way too much noise from all directions... I could take a short video showing the valley I'm in- alot of mesas at varying distances- so there's vertical cliffs that would reflect well in almost all directions.. so even if the one cell tower wasn't here, just reflections of my own signal could be ugly..

I did some testing by driving around with the magnetic base omni that came with the amp... lots of different areas it was working very well- UNTIL I got into this valley, once it went dormant it took MINUTES to re-establish.. so I there's alot of reflections here that create noise- and an amp will amplify noise just as well clean signal- it can't tell the difference.

I'm leaning towards keeping the amp, since a -104 with my parabolic is still weak, and could fade to nothing with a little snow... -90 gives me a much more comfortable buffer- and Vz is now showing my area as a "future EVDO", and I think -104 would result it lousy EVDO performance..

but the question is, stick with my parabolic mounted permanently, or get a yagi... and I'm sure nobody can answer that with certainty...

Thanks for the replies, it's especially interesting to hear a parabolic COULD perform better than a yagi..

Gary

Lunyfringe · EVDO Fledgling Joined: 17 Jan 2006 Posts: 20

"I am going by the description of the terrain he is dealing with . That is why the height is suggested . Every situation is different But this one does not seem condusive to a Yagi / Directional antenna"

I agree with this- without a site survey, you couldn't know that to get LOS to the Verizon tower, I'd probably need a 500' tower here... maybe only 300-400' would help, but 100' is definately too low..

so using height in my case is out of the question...
I know rooftop TV antennas reduce ghosts in my area. so I'm going on an assumption that while a yagi may NOT improve signal Db, they will improve the S/N ratio

if you'd like me to email a short video taken with my digital camera with a panoramic view, I can do that...

Thanks,

Gary

jschurawlow · Posted: Sat Sep 23, 2006 9:29 pm Post subject:

Nolos · EVDO Newbie Joined: 25 Sep 2006 Posts: 10

I am in a similar situation with terrain and tower proximity. I have tried a Trucker and a Yagi, and the Yagi helped in my situation (both using a Wilson amp). I definately do not have LOS, and the YAGI is aimed right at a hillside about 500 ft away, but it definately made a difference in connect times. With a signal of -98db, I still have a very slow upload speed, but I get a pretty stable download of ~200kbps which is better than my dial-up alternative.

Lunyfringe · EVDO Fledgling Joined: 17 Jan 2006 Posts: 20

I'm now getting EVDO when in Colorado Springs- and I think that's where I'm getting my signal from...

but when I try at home, I "see" a EVDO signal (never could before)... but when I attempt to connect, it drops back to 1xRTT... I think the noise in my valley is striking again...

I'm tempted to get a Yagi, and since I'm in an 800Mhz area, one of the newer 7watt amplifiers.. to see if I can pull in the broadband signal...

only thing holding me back is that someone in the area is working on WiMAX on the tower that I can see from my house (the permit has been applied for)

horsessmellfunny · Posted: Tue Nov 21, 2006 2:17 pm Post subject:

Ah, where are you located that you think you are getting your EVDO from the springs?

n6gn · Posted: Tue Nov 21, 2006 2:27 pm Post subject: Re: UPDTATE: EVDO now on tower

Semi75 · EVDO Junkie Joined: 25 Feb 2006 Posts: 230

This is just an observed guess (note I didn't say educated) but you may be seeing the EVDO signal as a signal bounce but cannot connect to it because your card can't talk to the tower.

I experienced a similiar situation at my house that is cleary not within los of the nearest EVDO tower, in fact I am about 7 miles away from the nearest evdo tower with hills in the way. Using an antenna I would see an EVDO signal but could never connect. With a Yagi and an amp pointed about 45 degrees from where I knew the closest EVDO tower to be I could lower my signal reading to the -80s easily. I could never connect becauase my card could not cummunicate with the tower even though the signal could be seen. I discussed this here and with radio savvy people I know and it appears it had to come from the signal from the EVDO tower bouncing around but not being usable.

Lunyfringe · EVDO Fledgling Joined: 17 Jan 2006 Posts: 20

JT · EVDO Fledgling Joined: 23 Apr 2006 Posts: 24

n6gn · Posted: Wed Nov 22, 2006 11:18 am Post subject: Re: UPDTATE: EVDO now on tower

slug · EVDO User Joined: 25 May 2005 Posts: 46

where can i get a good omni directional antenna for sprints service, outdoor mounted?