Antenna Height vs. Cable Distance?

New to the community here, and looking for advice on building a new system for a 52ft catamaran. It will be for a world cruiser, so need to be able to work with global frequencies. My main goal is to get decent internet further offshore or in a remote anchorage. Secondary goal would be to get fast speeds, but I don’t really have a need for redundancy like with the dual modems. I can manually switch sims if one network isn’t very good.

From my googling and reading of posts, it seems like there are two products that would work well for me: the Max Transit (Cat-18 or new 5G) or the Max HD Dome 1. I like the price, 5g capability, and simplicity of the Max Transit, but worried about the length of the antenna cable run to get it to a place where I can easily access the SIMs to switch them when I get to a new country. The Max HD Dome 1 seems like a good alternative with no signal loss over the run up the mast, but is more expensive and seems more complicated with a SIM injector and no built-in wifi capabilities.

I guess my question boils down to this - how important is the height of the antenna, and at what point does the signal loss in the cable runs negate the benefit of having an antenna mounted high up.

To put some concrete numbers out there, our options are either to put it on the spreaders (1m out on spreader + 10m to mast step + 3-4 for routing to modem = 15m run) Would it affect our distance much to put it lower on the mast somewhere, or even on the coach roof (~3-4m off the height of the water) On a related note, if we did the HD Dome 1, would putting it on the masthead improve range, or would that be chasing after diminishing returns? (mast height is 24m)

Hello @hoeken,
Welcome to the Peplink Community Forum.
Peplink Partners have access to extensive guides (including an Antenna Selection guide with details covering the marine industry).

If you want the ease of switching SIMs, look at using solutions to support the SIM Injector. The SIM Injector can work with the HD1 Dome & HD2 Dome, the MBX HD2 & HD4 models, and others.

Here are some specific articles to get you started

Where in the world are you based? We are in Australia, though you may have a locally based Peplink Partner who is a Marine expert.

Happy to Help,
Marcus :slight_smile:

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look at some antenna specs, then specs on cabling, and see the loss you can expect per m. it should be able to be calculated…

I really don’t have much experience with this, but I’m familiar with the concepts. Can you check my work here? Looking at the Poynting Omni-402 which seems to be popular: https://poynting.tech/wp-content/uploads/downloads/product_documents/technical_specifications/omni_series/Technical-Specification-A-OMNI-0402.pdf

So, I looked up to see the the gain in dBi, and it also lists the cable loss later on in that pdf. So for example at 2600mhz it lists a 6.2dBi gain, and 0.666 dBi/m loss. So for a 15m cable run, that would be a loss of (0.666 * 15) = 9.99 dBi. Is this correct? Does that mean the signal would actually be worse with that long of a cable run?

Hello @hoeken,

Here are the typical cables used for installation. Our antennas come with CFD-200, which is basically same as LMR-200.

In your case for 15m installation using CFD-200 cables you would get:

  • ~8dB attenuation for mid bands (2.5GHz)
  • ~5dB attenuation for low bands (800MHz)

This is quite a lot and you literally reduce your signal ~4x times.

You could switch to LMR-400 cables:

  • ~3dB attenuation for mid bands (2.5GHz)
  • ~2dB attenuation for low bands (800MHz)

This is much better as you reduce your signal ~2x times, but the cable is quite thick and it comes in 10mm diameter. For CAT-18 or 5G you will need 4 such cables.

I would choose HD Dome with a SIM injector. In MAX series manual you can also find most common installation SIM Injector scenarios.

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Thanks for the great response. It seems like the HD Dome is a much better solution.

Now, for a follow-up question: how much of a difference does mounting height make? My options are coachroof (~3m above sea level), the spreaders (~13m), and at the mast head (~24m). Is 4G/LTE based on line of sight?

Any cons to putting it at the very top of the mast? Its a catamaran so its pretty stable, but would still be moving around a bit more than if it was on the spreaders or the coachroof.

Just wanted to post this doc I found in another thread, very informative: https://forum.peplink.com/uploads/short-url/uLmQBpScOsg7foBAqLEN8SAMKnF.pdf

Hi Hoeken,
let’s talk about “Ease of Installation”. From my experience every antenna cable length longer than 7 or 8 meter is a useless discussion. Guess you have a QuadCellular Router with cat18 or even 5G and you have to bring up 16 cables to the mast with a length of 18m ? Just take a pen and draw 16 circles with a diameter of 10 or even 15 mm on a paper. The owner or architect of the boat will not allow you to destroy the view of the yacht with this monster of cable… :wink: Most of the time you will not find room enough for the cables in the mast. BTW.: This cable is expensive. With this in mind a couple of domes in the mast, an additional balance under deck and sim injector is really cheap and configured and installed in very short time. All it needs are a few good ethernet cables to power the domes.

Theo

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Thanks Theo. I am definitely sold on the HD Dome… it makes a lot of sense. Now I’m just trying to figure out the simplest/cheapest way to get the ability to do Wifi as WAN for when I’m in the marina and I should be sorted.

I think an BR1 IP67 could do the Job. Keep in mind, 802.11b/g/n Wi-Fi WAN or AP.
You can put it on the first spreader. Very easy installation but would be a little to weak for 10 people watching netflix at the same time…
Second Option: DCS-RUG and external antenna on spreader 1. There may be room for a few cables.
The DCS can work on 2.4 and 5 GHz. There is a 3x3 WiFi antenna available from panorama or Poyntings.
Theo

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