I've noticed most of the LTE modems have two anntena/ports for external antennas.
How does the second antenna work? Is each anternna for a specific range of frequencies?
What happens if I use a 2 > 1 SMA reverse splitter going out a single antenna?
Re: LTE: Why two antennas?
Space diversity.I've noticed most of the LTE modems have two anntena/ports for external antennas.
Read about Space Diversity here: https://en.wikipedia.org/wiki/Antenna_diversityHow does the second antenna work? Is each anternna for a specific range of frequencies?
At best, it won't work as well. May very well damage the radios.What happens if I use a 2 > 1 SMA reverse splitter going out a single antenna?
Don't do that!
Re: LTE: Why two antennas?
Thanks for the input. The police cars in town have computer-aided dispatch, so I'm assuming an LTE modem in the car (or maybe on the laptop, itself?). I've noticed that they have a small antenna on the trunk that looks like a hockey puck. I'd assume that's the LTE antenna. Is it likely that that single antenna has two connectors? Or is it that their modem probably only supports a single antenna?Space diversity.I've noticed most of the LTE modems have two anntena/ports for external antennas.
Read about Space Diversity here: https://en.wikipedia.org/wiki/Antenna_diversityHow does the second antenna work? Is each anternna for a specific range of frequencies?
At best, it won't work as well. May very well damage the radios.What happens if I use a 2 > 1 SMA reverse splitter going out a single antenna?
Don't do that!
Re: LTE: Why two antennas?
The puck could very likely be for GPS.
Re: LTE: Why two antennas?
Or both. I work in city Radio Shop. We have hockey puck style antennas that have as many as 5 antennas for some combination of WiFi, cellular (often more than one band), and GPS.
Re: LTE: Why two antennas?
Thanks for the input. Looking around on Amazon, they have "pucks" that support LTE + GPS with 3 different SMA connectors.Or both. I work in city Radio Shop. We have hockey puck style antennas that have as many as 5 antennas for some combination of WiFi, cellular (often more than one band), and GPS.
Compared to a cellphone's internal antenna (or the antennas inside something like the LtAP), how well would you expect a "puck" to perform?
Is there a better antenna setup for rural areas where signal strength can be a problem?
Re: LTE: Why two antennas?
Yes, almost any outside antenna will work far better if you have anything except great coverage. Let's face it, if you have a cell site across the street, it's not gonna make a damn bit of difference. Most of us don't have a cell site across the street. Going back to my Radio Shop experience, take a police command post car that has the radio equipment inside a steel box that is inside the vehicle body. Performance SUCKS! Hook up external antennas to the various radios (WiFi, cellular, GPS, etc.) and it works FAR better.
Let me give you another real world experience. In my data cabinet at home, I have a NTP server device that uses GPS. It came with a little sqarish hockey puck antenna a little over an inch (3 cm) across with a 10 foot (3 meter) cable. I put the antenna on top of the data cabinet inside my garage. There is nothing inside between the antenna and the underside of the roof - wood construction with composition "shingles". From an RF standpoint, not bad at all - EXCEPT I have solar panels covering the garage roof - not so good. It works, but not as well as it would with the antenna in the clear. Bought a 16 foot (5 meter) extension cable and moved the antenna outside the garage with a clear view of the sky. Signals and number of satellites received improved quite a bit...
Let me give you another real world experience. In my data cabinet at home, I have a NTP server device that uses GPS. It came with a little sqarish hockey puck antenna a little over an inch (3 cm) across with a 10 foot (3 meter) cable. I put the antenna on top of the data cabinet inside my garage. There is nothing inside between the antenna and the underside of the roof - wood construction with composition "shingles". From an RF standpoint, not bad at all - EXCEPT I have solar panels covering the garage roof - not so good. It works, but not as well as it would with the antenna in the clear. Bought a 16 foot (5 meter) extension cable and moved the antenna outside the garage with a clear view of the sky. Signals and number of satellites received improved quite a bit...
Re: LTE: Why two antennas?
So are most of the improvements with a small "puck" antenna going to be from the fact that the antenna is outside versus inside? Or is the antenna that much better, itself?Yes, almost any outside antenna will work far better if you have anything except great coverage. Let's face it, if you have a cell site across the street, it's not gonna make a damn bit of difference. Most of us don't have a cell site across the street. Going back to my Radio Shop experience, take a police command post car that has the radio equipment inside a steel box that is inside the vehicle body. Performance SUCKS! Hook up external antennas to the various radios (WiFi, cellular, GPS, etc.) and it works FAR better.
Let me give you another real world experience. In my data cabinet at home, I have a NTP server device that uses GPS. It came with a little sqarish hockey puck antenna a little over an inch (3 cm) across with a 10 foot (3 meter) cable. I put the antenna on top of the data cabinet inside my garage. There is nothing inside between the antenna and the underside of the roof - wood construction with composition "shingles". From an RF standpoint, not bad at all - EXCEPT I have solar panels covering the garage roof - not so good. It works, but not as well as it would with the antenna in the clear. Bought a 16 foot (5 meter) extension cable and moved the antenna outside the garage with a clear view of the sky. Signals and number of satellites received improved quite a bit...
Is there an "On The Road" antenna you would recommend that performs even better? I'd like to find an effective antenna that works well, but can stil be used when the vehicle is being driven (< 30" long for clearance purposes, and low wind load).
Re: LTE: Why two antennas?
Even best antennae hardly exceed gain of 10dBi ... and those tend to be directional antennae requiring turning it mechanically in optimal direction. Most omnidirectional antennae reach up to around 5dBi gain. OTOH thin antenna cable can have loss of 1dB per few metres (e.g. 10ft), taking away some (or all) of antenna gain.
Losses induced by walls, metallized windows or metallic body of a car OTOH easily exceed 15 dB or more, 30 dB loss is not unheard of.
So yes, most effect of using puck (or any other external) antenna comes from placing antenna outside of Faraday cage created by building walls or car body.
Losses induced by walls, metallized windows or metallic body of a car OTOH easily exceed 15 dB or more, 30 dB loss is not unheard of.
So yes, most effect of using puck (or any other external) antenna comes from placing antenna outside of Faraday cage created by building walls or car body.
Re: LTE: Why two antennas?
mkx's last line completely nailed it perfectly. Get the antenna out of the steel box.
Re: LTE: Why two antennas?
Whether I'm going to mount an external antenna was never up for debate. The real question is what type of omnidirectional antenna would be best for on-the-road use. The puck antennas are low-profile and seem affordable, but I do see some larger LTE antennas advertised as being higher gain (whether that's actually the case or not, I have no idea).mkx's last line completely nailed it perfectly. Get the antenna out of the steel box.
Re: LTE: Why two antennas?
As I mentioned: larger antennae with high gain require manual turning. That's fine for stationary use (e.g. when staying in a camping place or similar), but far from usable for mobile use.
Another note: always check gain figures of antennae for different frequency bands. Most "high gain" antennae have decent gain at higher frequencies (i.e. at 2GHz and higher) while many have mediocre or bad figures for lower frequencies (900MHz and lower). And if staying far from beaten path, it's usually the lower frequencies that provide the service.
Another note: always check gain figures of antennae for different frequency bands. Most "high gain" antennae have decent gain at higher frequencies (i.e. at 2GHz and higher) while many have mediocre or bad figures for lower frequencies (900MHz and lower). And if staying far from beaten path, it's usually the lower frequencies that provide the service.
Re: LTE: Why two antennas?
This has been a great thread so far. I’ve learned some very good things from the discourse. Thanks for sharing!