Higher Gain Antenna Options for a Fixed Location With Poor Reception


#1

Unfortunately, not every place I want to put a sensor has great cell coverage. I am interested in testing (and, yes, perhaps having to certify) an external antenna and I thought a directional antenna would make sense. In looking at the options, it seems there are some requirements I need to understand. They are (with my assumptions - please correct if needed):

  • Passive Antenna
  • Need to cover the 3G and LTE frequencies - 700-2700 MHz
  • Some connector that can be converted to u.FL with a cable (SMA or N Male)
  • Impedance - 50 or 75 ohms? Which does the Electron require?
  • Gain - Claim to be +10 dB - is this reasonable?

I found a reasonably priced external antenna here:
Wilson Electronics Outdoor Directional Antenna

Am I on the right track? Are there other considerations?

Thanks,

Chip


#2

We also work in very remote areas and often have poor cellular coverage.

We tried several antennas with our electrons, including some directional models. The directional antennas had a downside in that folks doing the install had to have quite a bit of expertise to get them aimed properly. Also, we had some deflected post-install by wind, inadvertent bumps by technicians, etc.

We ended up going with this omni directional antenna (Taoglas TLS.01.305111) plus a 12 inch square ground plane - mounted about 6-8 ft above the ground. These have been working really well for us at some very remote sites for over 2 years. .
[https://www.digikey.com/product-detail/en/taoglas-limited/TLS.01.305111/931-1437-ND/5962683]


#3

@micromet,

Wow, very nice. Thank you for the recommendation, I will give this a try.

I want to experiment with the directional antenna as well and will share my results. I can certainly see how the installation and post-install issues could be a problem.

Thanks, Chip


#4

I have used the wilson directional for several years and it has worked well. However, I find that it may well not perform better than an outdoor omni because of SNR. Yes, the signals are stringer, but so is the noise. My home is on a mountain looking down at town where the cell towers are (~12 miles away) and I’m totally noise limited as far as I can tell.


#5

@tve,

I am wondering if the new signal strength feature would help me understand this effect. It is touted as a Boron feature but it works for the electron as well. As you can see from the screenshot below, I can now see the connection technology, quality and signal strength.

So, as I test this antenna against others, I think I need to look at both the strength and quality metrics. This information could be of interest to you as well. Happy to share the code for this if needed.

Thanks, Chip


#6

Our experiences with directional antennas have been mixed.

Keep in mind, If you are in an area with multiple towers (but all have poor reception), you may be worse off with directional antennas. e.g. If one tower goes down and it was the tower you had your single directional antenna pointed towards.

We’ve also seen examples where the towers are modified/optimised and they’ll re-point antennas requiring a complete change in direction of antenna to reach a different tower with ease.

We are working in high volume products, so found it easier to go omni-directional and do pay attention to if the antenna manufacturer recommends a ground plane. They make a difference.


#7

@Cameron,

Thank you, I had not thought about the issue of the towers themselves changing. Based on your and @micromet’s advice, I am going to test both directional and Omni with ground plane antennas locally before driving off to the mountains.

I appreciate all the advice and will share what I learn.

Chip


#8

So I tested my new directional antenna today and here are the results:

Antenna that ships with Electron - Taoglas - PC.104.07.0165C - UMTS 31% Signal Strength, 88% Quality
Higher Gain Omni Antenna - Taoglas - TG.30.8113 - UMTS 33% Strength and 88% Quality
Directional Antenna - Wilson - Model 314411 - UMTS 40% Strength and 88% Quality

I was a bit underwhelmed by this as it seems that going from 31% to 40% is not a very big gain for the extra cost, effort and re-certification that a non-stock directional antenna brings.

Am I thinking about this right? Should I use a different metric?

Thanks, Chip


#9

Did you do any more research on these antennas you can share? What solution did you end up utilizing? I’m also facing a similar issue with poor signal strength and looking for a solution. I have the device publishing the strength and quality as part of it’s normal data publish every minute and find the values to be quite variable. I can’t test directly in the field so didn’t want to buy the Taoglas TLS.01.305111 just yet.

A note on the % values you received. The actual values for strength are -121db to -25db and quality -24.5db to 0db. The reference document online doesn’t show the math of how this is mapped to 0 to 100% exactly. I haven’t checked the coding in the github repo though. With decibles being a log scale, even 2% may be a big difference (depending on that mapping). Personally, I’ll likely switch over the code to see the db just so I can get the raw measurement for comparison. Something you may want to look at too.


#10

@jonpasc,

As I noted above, the difference in the % numbers given for the higher gain antennae did not look that impressive. However, The two field installations I have done (one with the omni and one with the uni directional antennas above) have both performed very well. I have been able to push deviceOS and firmware updates that they are connecting reliably. Based on this, I plan on using the omni-directional antenna (Taoglas TLS.01.305111) going forward as it is an easier install, can connect to multiple cell towers and you don’t have find / and maintain precise alignment with a tower.

I think the install effort is the real difference here:

!

As you can see, I was able to mount the omni directional antenna 10’ above the ground on a wooden light pole.

As for your question on the mapping of the logarithmic dB scale to %, I am also now very curious. Let’s see if we can get an answer on this thread otherwise, I might change my code as you suggest to just look at the raw dB numbers. Thank you!

Chip