Diddy1
join:2003-07-19
Sidney, NE
| Flat Panel vs. Grid
I've asked this question in the past and got good answers but thought I'd throw it out again just for knowledge purposes. I've encountered several situations where a 12db flat panel will by far out perform a 15dbi grid antenna. Now this could be due to manufactuerer quality but there really is'nt much inside a passive antenna from what I've seen. One instance tonight was clear LOS except a single power line about 50' off across the road and the panel did much better. I've seen examples of the radiation pattern but wanted to hear more details why in general, a flat panel out performs? I should also mentione that this is off an sector AP antenna. I figured you people would be the best to ask!
Aaron |
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milbrath
join:2006-03-27
Dresden, TN | My guess is wider beamwidth. A panel would be more forgiving than a grid.
BM |
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Diddy1
join:2003-07-19
Sidney, NE
| I considered this, but we spent some extra time at our most distant client today just toying with it. I informed her prior that we'd like to try some things and she was just as curious as we were if it would work etc. We had the 15dbi grid and the 12dbi panel and tweaked each ones settings ever so meticulously and the panel just blew the grid away on both RX and TX. I forgot to mention that with the panel, we set the power to be right at 36db and did not change this once we put the higher gain grid up and the panel still produced a stronger RX at the AP.
Aaron |
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SipSizzurp
Fo' Shizzle
Premium
join:2005-12-28
Hilo, HI
 ·RoadRunner Cable
| reply to Diddy1
To add some spice to your findings, it would be interesting to know the specific manufacturer/models of the antennas you tested, and whether or not the feed lines and pigtails were the same for each antenna.
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LLigetfa
join:2006-05-15
Fort Frances, ON
1 edit | reply to Diddy1
You didn't mention polarity. My guess is the panel is more polarity agnostic while the grid needs to be more precise. I heard that a few degrees off on rotation can really drop off on a grid.
When a sector is down-tilted, the further out from centre you go, the greater the polarity rotational skew.
Also, the panel can make more of multipath signals than can a grid. Keep also in mind that the Rx levels reported are just raw signal strength not reflective of signal quality, so multipath signal that does not help the link will still be seen in the Rx strength.
I think a better head-to-head shootout would be to compare grid to grid and panel to panel between two towers where they are straight shots with little multi-path. |
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SipSizzurp
Fo' Shizzle
Premium
join:2005-12-28
Hilo, HI | reply to Diddy1
LLigetfa, I swear I was about to edit my post with the polarity purity idea. You put it very well.
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Mi ultima pinche Carta Blanca. Que triste ! |
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superdog
I Need A Drink
Premium,MVM
join:2001-07-13
Lebanon, PA
| reply to LLigetfa
said by LLigetfa  :Also, the panel can make more of multipath signals than can a grid. Agreed. Whenever I am installing a customer that has limited LOS, I will always use a panel over a grid. They pick up more of the multipath because of the antenna pattern. See the pictures. The picture on the left is a grid, and the right side is the panel.
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John Galt
What...me panic??
Premium
join:2004-09-30
Happy Camp
| said by superdog :They pick up more of the multipath because of the antenna pattern. Bear in mind that they will also pick up more interference (if any is present in your area) for the same reason.
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A is A |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to SipSizzurp
said by SipSizzurp :To add some spice to your findings, it would be interesting to know the specific manufacturer/models of the antennas you tested, and whether or not the feed lines and pigtails were the same for each antenna. These antennas were both Pacwireless antennas. The pigtails were all stock with the Deliberant 2300s. |
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Diddy1
join:2003-07-19
Sidney, NE
1 edit | reply to LLigetfa
Your right, I didnt' include RSSI levels, but I will say that they were all low and no properly corresponding to RX/TX levels. Didn't make sens but again, I was reading of the CPE itself and it's own interpretations.
Aaron
Edit: this is in V-pol |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to John Galt
said by John Galt :said by superdog :They pick up more of the multipath because of the antenna pattern. Bear in mind that they will also pick up more interference (if any is present in your area) for the same reason. But this is a moot point in my situation, the panel DID out perform the grid. But, I respect your objection and thankyou for reading and commenting on my post.
Aaron |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to LLigetfa
said by LLigetfa :Also, the panel can make more of multipath signals than can a grid. I also like to add that I learned this little fact here 
The test we did vs. the amount of adjustment was less than a degree. We really did a very thorough test but are results may be skewed due to the fact tha we just used a stock radios own display of RSSI and strength.
Aaron |
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John Galt
What...me panic??
Premium
join:2004-09-30
Happy Camp
| reply to Diddy1
said by Diddy1 :But this is a moot point in my situation, the panel DID out perform the grid. But, I respect your objection and thank you for reading and commenting on my post. Oh, I wasn't objecting...just simply pointing out a fact-of-life in the radio world.
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A is A |
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Keithb
join:2003-09-16
US
| reply to Diddy1
Just to add to this, I had a 24dbi grid until recently we were having issues I thought possibly it was the radio. So I bought it down, replaced the radio with same problems. I then brought it down, hung a 19dbi flat panel and got a better RSSI than with the grid. |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to Diddy1
I also would like to ask what some of you do when adjusting an antenna for a client?
What I do is, find a good signal horizontally, then mark the mast with a sharpie or whatever works. Then, if I'm fortunate enough to have a second person there, aim vertically for good RX at the AP. I keep the U-bolt just loose enough to move the antenna slightly without slipping.
This is for a V-pol setup. The little experiment we did, we took the extra time to move the antenna ever so slightly while checking signal.
Aaron |
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Keithb
join:2003-09-16
US
| reply to Diddy1
On most masts and even DDS arms, we keep the bolts slightly loose. We normally have 2 people at each install, so one will adjust while the other watches the site survey screen. With the auto-refresh, it makes it easy to do so.
We normally have everything plum and square with the world. What we learned in the Directv times, was if you get an increase in one, go re-adjust the other. If you increase via vertical, go back and re-adjust horizontal. |
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Diddy1
join:2003-07-19
Sidney, NE
| reply to LLigetfa
said by LLigetfa : My guess is the panel is more polarity agnostic while the grid needs to be more precise. I heard that a few degrees off on rotation can really drop off on a grid. When a sector is down-tilted, the further out from centre you go, the greater the polarity rotational skew. Can you elaborate on these to thoughts? I'm thinking when I mount a mast or DSS arm for client antenna, I may be off slightly on polarity. I just eye-balled it. Does anyone actually take steps to ensure plumbness?
Aarom
Aaron |
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robbin
Premium,MVM
join:2000-09-21
Leander, TX | I always use a small level to insure that the mount is plumb and level. Then if I want it out of plumb I make the necessary adjustments. |
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Diddy1
join:2003-07-19
Sidney, NE | But, we should always start with a plumb mount, would you agree?
Aaron |
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LLigetfa
join:2006-05-15
Fort Frances, ON
| reply to Diddy1
A dish is very much affected by slight polarity skews. If ever you worked with satellite dishes, you would have come across this. The dish normally has only a single element up in the feedhorn and the signal is literally focused on it.
Panel antennas on the other hand are designed with multiple elements arrayed in such a way as to interact with one another. They are generally also designed to accept signals with skewed polarity as one may expect from multipath.
Downtilt on a sectoral is not uniform along its full beam width. Take as an example an old 33 1/3 LP record player with stacking spindle and put one record up on the stacking part. Now, tilt the record so that the edge touches the platter and you will notice that 90 degrees to either side, there is no down tilt. There is however, polarity skew. Now I realize that this is quite an exaggeration and that in reality, the downtilt on a sectoral would normally be less than 5 degrees, but if one is sloppy in not plumbing the masts on both ends, the errors can compound. The mast should always be plumb and adjustments made to the mount. |
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