Does anyone understand antenna db gain?

rwbradley wrote:

n7bsn wrote:
Antenna gain is also directional, even an "omni" antenna is "directional". That it concentrates it's "listening" to a plane horizontal to the antenna. If the desired direction is above (or below) that plane, the antenna doesn't yield the published gain.

Not to correct you, but for the benefit of the OP, think of the signal from an Omni directional antenna like the Wilson ones you referenced as somewhat donut shaped

To be more specifc, N7BSN is correct when talking about vertical beamwidth, and the more published GAIN, the narrower the VERTICAL beamwidth. Thats where the gain comes from.

These days with tens of thousands of cell sites sitting at ~100' it may not be a big deal. But in the olden' days when cell sites were placed on 2-3000' towers or mtn top sites, it was often a problem to have high gain, narrow vertical beamwidth antennas whose pattern totally missed the cell site, even though you could see it. Too narrow.

Not for cellular but for Wifi, a 24 db yagi set me back a whole lotta money. It really works but without using CAIG DeOxit D100 on the connections half of the gain would have been lost.

In simple laymen's terms - antenna gain is a measurement of increased signal strength compared to a reference antenna that transmits equally in all directions (a sphere) at a specified distance. Total transmission power is never changed, only the pattern in which it is distributed. A gain of 0 (zero) would mean that at the same distance from either antenna, the received signal strength is the same. A 3 db gain means the signal strength at the receiving end is twice as strong as from the reference antenna. A 6 db gain is 4 times (3db + 3db = double x double; it's a logarithmic thing). A negative number means the signal strength at the receiver end is less than a reference antenna.

Now, the gain in reception comes at a price, and the price is you are limiting your transmission footprint. In most cases this is not an issue as the transmission usually becomes a flattened sphere, so you aren't transmitting up in the sky or down to the earth as much but out to the sides. A directional antenna gets far more gain, but then it will only transmit or receive from specific directions.

n7bsn wrote:
Antenna gain is also directional, even an "omni" antenna is "directional". That it concentrates it's "listening" to a plane horizontal to the antenna. If the desired direction is above (or below) that plane, the antenna doesn't yield the published gain.

Not to correct you, but for the benefit of the OP, think of the signal from an Omni directional antenna like the Wilson ones you referenced as somewhat donut shaped

I believe the band that you see the signal loss (as opposed to gain) on antenna2 is used by Tmobile 4G. So if you are on Tmob, don't upgrade the antenna, it won't help you, it will make your signal worse.

One thing to consider is that most of the Cell amps provide about 25db of gain with the stock antenna installed. The antenna upgrade really does not provide a significant amount of improvement (a few extra db). Yes every little bit helps when you are really on the fringe, but I personally would not pay the $50 to get a couple extra db of gain unless I was really sure I needed it with my provider and the locations I am regularly at. Especially when just using the Wilson with the stock antenna is a huge improvement by itself.

Antenna gain is also directional, even an "omni" antenna is "directional". That it concentrates it's "listening" to a plane horizontal to the antenna. If the desired direction is above (or below) that plane, the antenna doesn't yield the published gain.

Thanks all

it means a signal LOSS, instead of a gain

all numbers except one represent a gain on the test device
except for the -4 which represents a decrease in signal sensitivity for that Frequency

One way to look at it is an increase of 3.0DB is double the gain...

In regards to the cellphone however reading the gain indicated by the number of bars is not a exact reading. Yes the more bars you have is great but probably no way one can come up with how many DB's this is to make changes...

I use the older WILSON CRADLE for my VERIZON MIFI unit with a 3GB dataplan and it really helps keeping enough signal inside our Truck,RV or in and around the RV to keep the WIFI going to all of WIFI Enabled devices. My Antenna is the taller one with a coil in it.... I think my bigger savings grace is being on the VERIZON TOWERS. This setup works very well everywhere we go. Hard to find an area where the VERIZON doesn't work for us.


I normally keep either the cellphone or the MIFI unit sitting in the WILSON CRADLE when driving. The WILSON CRADLE only provides a PASSIVE connection to the CELLPHONE or MIFI unit and I think the specs says they have to be with a couple of inches to work properly. When I have the VERIZON MIFI sitting in the cradle my DROID CELLPHONE is sitting in its holder just a few inches to the side of the cradle. It never drops any signals sitting there when going don the road so I suspect it is being fed by the cradle as well...

Ive been thinking about upgrading my MIFI unit to VERIZON JET PACK that would support a little better downstreaming. My current MIFI is grandfathered and the low $27 a month cost per is hard to give up haha... The WIFI footprint generated is based only on a 56K signal which being used with my tablets to downstream some TV Programs falls into the problem of not having enough throughput to keep the buffer full to keep the downstream video always going. Alot of starts and stops as you watch the generated video.

My older DROID X does have MOBILE WIFI capability but every time I try to use whenever I down the TV PROGRAMS it is diverts to VERIZON and says I don't have the right plan to support it. I do have unlimited DATAPLAN however so who knows what that means... Someone told I needed to ROOT my DROID X but that is illegal I guess... Too old to do any of that stuff... I can always watch DVDs when we in travel mode.

Roy Ken

Gain figures are how well the antenna performs as compared to a reference antenna. The higher the gain the better it performs.

Negative gain means the antenna is not going to perform well at all ON THAT FREQUENCY Band

now.. Cellular phones and data use a number of different frequency bands.. Alas, Differentr providers may use different bands and I do NOT know what the current usage is.

Call your Service provider 6-1-1 for most of them and ask for Technical support.. Ask what frequency bands your phone/devices use.. IF they do not use that band then Ant-2 is the better one.. if they do go with Antenna 1