How to improve SNR/RSRQ

Hi to all,

I currently have an HD4 with the following setup:

Cellular 1: T-Mobile. 2x Laird LAI-TRA6927M3PW-0. These are up the mast connected by LMR600, 25-30 Meters.

Cellular 2: T-Mobile. Poynting Mimo-402 5 meters of cable LMR200

Cellurar 3: T-Mobile. Poynting Mimo-402 5 meters of cable LMR200

Cellular 4: AT&T Interior Mimo antenna. 2 meters of cable.

As you can see, the SNR and the RSRQ are very low.

I do not know the cause and I yet don’t exactly understand how to troubleshoot SNR and RSRQ signal levels.

The maximum speed I get in Miami with 4 SIM’s is 40mbps down and 55mbps up with Speedfusion.
I currently have Vodafone UK cards in the USA and they have told me that the speeds could be throttled.

I think these signal levels are not good and I would like to know where I should be looking.

The yacht is steel, would this affect on the antennas?

Thank you all for your help

Vodafone UK SIms in Miami will under perform compared to local in country SIMs. Often when roaming like this your internet traffic will get routed via the home country for accounting purposes, and if it does then you’ll take a bandwidth hit due to increased latency.

Looking at your numbers above I’d be interested to see the physical install of the Poynting antennas. Cellular 3’s high SINR suggests that it is in an area with a higher level of background RF noise.

Cellular 1 with its antennas up high away from the rest of the vessel has much better SINR on those same frequencies (Band 2).

Look at the B12 on Cellular 2 sitting there with SINR @ 13dB and a RSRQ @ -13dB thats interesting.

And the cellular 4 - is that antenna inside or just a lower gain antenna element I expect. Either way, the reduced reception of signal is working well on that module as less noise is being received so the SINR looks better.

I think you’re in an area with a high density of user equipment (smart phones / routers etc) likely a marina. The antenna at the top of the mast is more distant from those devices working at sea level and so is getting a cleaner signal. Cell 4 is either having its signal attenuated by the vessel itself (which is blocking a chunk of the crap noisy signal), or it just has lower gain antennas connected so less noise is being picked up.

I’d be tempted to force the other cellular modules to use B12 too and see what happens.

Do check what your public IP is on the VF UK SIms and then geoip lookup to confirm where that IP breaks out.

Also speedtest across all cellular modules individually and let us no the results for comparison, I suspect that you’ll find you get the best results using the mast head antennas and the internal Mimo because of the level of RF noise in your vicinity.

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Hey Martin,

Thank you for your detailed explanation.
I understand the consequences of having a Roaming card, I have fusionhub running in the UK and the latency is of about 157ms.

The location of the antennas is just above the bridge. I thought it would be a good installation point as they are very close and there isn’t anything around them. They are separated by more than 3m. We are currently in dry dock so all navigation equipment is off and there should be no EMI or background noise that I can think of.

This is the speed of 4 Cellular working together:

Cellular 1 speed:

Cellular 2 speed:

Cellular 3 speed:

Cellular 4 speed:

The cellular 4 antenna is this one:
image

This antenna has a peak gain of 4dbi while the Poynting 402 have 6.2dbi
It isn’t a great deal of difference and there are placed at the same area. T

My rotational partner made the installation and bought LMR400 (good copy of Times Microwave) and N-type connectors from Amazon. He also made all the crimps without the proper tools. Hence the thought that it might be wiring.

I have ordered 4 Times Microwave SMA female to SMA male LMR240 from here:
https://fieldcomponents.com/SMAF-LMR240-SMAM-Length.html

Any feedback would be very helpful.

Thank you!
J

I agree - this feels like a likely possible issue. Take that little panorama antenna and try in on the other three cellular modules and see what the difference in throughput (and SINR) is using a factory terminated antenna.

So I think that one of three things is going on, either the cable termination is causing lower SINR or the cable route taken by those cables through the vessel is compromised (passing next to a source of RF interference like generators, other RF equipment etc), or you’re just in an environment where there is a load of noisy RF that’s being captured by the very successful poynting antennas.

Trying the panorama antenna on each cellular module will give you an another data set to compare against showing how much throughput is available when you’re not using your installed antennas.

If the result is better with that and also better with the replacement cable you have ordered then you’ll know to replace (or more likely properly re-terminate) the installed coax cable.

If however you use the panorama antenna on the other modules and bandwidth for each is similar to that with the poynting then you know its a local environmental issue.

The anomaly in all of this is that B12 on Cellular 2 was being received so well on the Poynting 402’s. If you do replace the coax run and throughput doesn’t improve, I would force the use of B12 on the pair of poynting 402 attached modules and see what throughput you get then.

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May I add a brief comment to @MartinLangmaid’s excellent answer?

We’ve installed literally thousands of connectors on everything from tiny coax cables to 1 5/8" “hard line.” The only time we do that any more is when we are unable to acquire factory pre-assembled and tested cables. Period. To us, “testing” always includes “sweeping” (e.g., with a TDR) and often includes hi-pot testing as well.

In our experience, the “right tools” are an absolute requirement for attaching connectors, as is a way to test the results. (A test with an Ohm meter is a good starting point but is insufficient.) And, if you find a bad cable the great likelihood is that it will get worse over time – particularly in your environment. What we’d do: If a bad cable is identified we’d pull it out, measure it, and order a pre-made, tested, “connectorized” cable.

Incidentally, we try to avoid using the LMR400 type cables in some environments due to the likelihood of passive intermod. (No such issues with cables that have a single, solid shield.)

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Hey Martin,
Just to let you know that I have found one of the faults on the installation.
The issue was that the HD4 wasn’t earthed and I believe that the interferences from RF equipment were being induced on the coax cable of the antennas.
After earthing, I found a significant improvement.
However, I still believe that there is a problem with the cables and the signal could be stronger.

I will let you know how it goes.

Now I have the signal, but the speed seems to be the same, as I think I am being throttled by the company. Is there anyway to confirm this?

Thank you for your reply, it was very helpful.

Hi. Well, I know you didn’t address this to me … but … we’ve had a fair amount of experience (hmmm, like 35+ years) with “RF stuff.” Generally, the best solution to avoid “interferences from RF equipment” is to separate the equipment/antennas so as to be able to take advantage of log-normal reductions in power density. And, for antennas, there is nothing like vertical separation. Failing that (and sometimes it’s impossible), the next approach would be to add chokes (of the right “mix”) to the transmission line(s). The latter approach is definitely indicated when induced current is suspected.

It’s also critically important that all such equipment share a common, low impedance ground.

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Hey Rick,

Your answer was as helpful as Martin’s.
Unfortunately installations on yacht are quite tricky and it is very difficult to allocate the antennas on the right place while retro fitting.

I was thinking maybe wrapping the cable with tin foil and ground it haha.

The routers are normally located on the bridges for easy sim card change and on the bridge is where there is more RF equipment.
What do you mean with Chokes?

On steel hull yachts, the ground is all the hull, so it is very easy to ground wherever you like.

We have zero experience with yachts but have worked on hundreds of land vehicles and aircraft.

The point about grounding: The key is not just to “ground” or “earth” but to make it low impedance. This can’t be over-emphasized. Generally this is done by bonding to the same point, the so-called “single point ground.” Bonding to different locations is usually a bad idea as there is likely to be significant impedance between the points which will result in a difference in potential. This is true regardless of the location – vehicles, ships, homes, aircraft. Often one can get away with a “distributed ground” but such an arrangement invites difficulties (and often strange behaviors, particularly in higher power environments.)

Antennas: One of the “general rules” is to separate antennas both vertically and horizontally. This is important, and depending on the design of the antenna, vertical is generally far more effective than horizontal. We’re dealing with very low powered equipment here but the signals received (4G, GPS - whatever) are typically very weak. Many of the TXs are “continuous duty” so when the antenna of a RX is nearby the RX is “densensed.” Solution: Increase the free space “loss” over the path between TX and RX.

OK … “chokes”: https://en.wikipedia.org/wiki/Choke_(electronics)#Radio_frequency_choke. In brief, the purpose of such a component in this context is to remove common mode current from the shield of the transmission line. Transmission lines are shielded but still pick up stray electromagnetic energy – from nearby antennas, poorly shielded electronic equipment, atmospherics, etc. Your comment about tin foil is actually not so far off. :smirk: The chokes of which I speak are placed around transmission lines or, in the case of the torroid type, the line is threaded through the center several times. I could go on and on but this is the “jist” of it.

Our first step would be to deal with the grounding/bonding issue. And that alone is a topic about which many treatises have been written. :smiley:

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Hey Rick,
I will look into the single point grounding. I am guessing that all our GMDSS and VHF equipment will be grounded on the same place, hopefully.

I think the Omni 402 antennas are pretty good. But there is something I still don’t understand.
One of my Omni 402 is on T-Mobile Band 2100/700Mhz. These are the values:
RSSI:-44dBm SINR:-3.2dB RSRP: -84dBm RSRQ: -19dB

How is it possible that RSSI and RSRP have so good values, but RSRQ hasn’t? I am guessing is the SINR low value.
Would you let me know which are the chokes you use for LTE bands? I have seen these: https://www.coilcraft.com/lte_chokes.cfm

Thank you for the reply and sorry for the lateness, very busy at the moment!
J

OK. Before working with chokes I’d do a couple more troubleshooting steps.

  1. What happens when you use one LTE module at a time? Do the signal metrics change? Let’s try to rule out mutual “interference” issues. In particular the RSRQ value is quite low. And, SINR is not too great either. Given the pretty good value of RSRP makes me think there are “issues” in the local vicinity – at least a high high ambient noise floor. (Martin mentioned this, above.)

  2. Have you tried swapping antennas as @MartinLangmaid suggested? I’d like to get a better feel for the performance of each antenna and its transmission line.

  3. Have all the “suspicious” cables and connectors been replaced with “known good” (i.e., “swept” with a TDR or similar instrument) products?

As to chokes: Maybe I should not have suggested this as this is really something that we’d expect engineers to undertake. We do it routinely but it’s not for the faint of heart. But to answer your question: One cannot select a choke until we know the frequencies (ideally fundamentals, not harmonics) we need to suppress. And when exploring unknown “ground” (as in this case), we’d use a spectrum analyzer to try to ID the components of the problem and may well use a network analyzer to evaluate choking impedance. The products we use are from https://www.fair-rite.com/ . Their spec sheets are available on their web site. Having said that, I’d hold off on that approach until all other troubleshooting is complete.

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