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Slate roof — 4G signal attenuation

GrumpyPatzer

Regular Member
I currently have an XPOL-A0002 directional antenna mounted just over 3m up on the back of our garage (with a Huawei B315, shortly to be replaced by a Mikrotik Chateau LTE12). I may try making a parabolic dish antenna, along the lines described by @dazmatic , so am giving some thought to how best to mount it. We nearly — but don’t quite — have line of sight to the mast, which is just over 6.5 miles away. The best speeds are achieved using band 3 (1.8GHz).

There are three main options:

1. A stronger pole attached to the back of the garage (timber frame), at a similar height.
2. A 2-3m pole attached to a suitably robust post in the ground, within a 20-30m radius of the garage (possibly with slightly better, but not perfect, line of sight to the mast).
3. Mounting the dish (ultimately two of them, if it works) in the garage roof space.

With option (1), I am somewhat concerned that, given our rather exposed location in the Highlands, two dishes could be vulnerable to high winds (the worst case would be ripping off part of the garage fascia or back wall). So, at least as an initial experiment, I would be interested to try option (3): positioning the dish(es) in the garage roof space.

The obvious question then is: would the attenuation of the signal caused by the pitched slate roof negate the advantage that dishes would hopefully have?

So I would be interested to hear of any relevant experience that any of you might have.

For what it’s worth, I did come across one study that has some relevant measurements:


See diagram (c) on page 3. On the face of it, this looks quite encouraging, no more than around 2dB loss at 1.8GHz. Of course, I have no idea how closely their slate test case matches the construction of our roof, which is slate, waterproof membrane and what appears to by plywood board (no insulation in the roof space and hopefully nothing metallic in the membrane!).

Thanks in advance for any thoughts.
Andrew
 
The obvious question then is: would the attenuation of the signal caused by the pitched slate roof negate the advantage that dishes would hopefully have?
To date I have found that it doesn't cause that much signal degradation as long as it is only wooden beams and slate roof. There are some attics I've seen that foil backed insulation/membrane installed that do affect the signal and in very strange/surprising ways!

There is a slight performance drop when it rains, but I see that with my outdoor antennae as well, wet trees especially.

I prefer them in the attic actually as they can become a liability in the harsh winter weather. Plus equipment will last longer in the dry and out of sunlight. One small issue is that if you have a very hot summer, an attic can get VERY hot, so try and locate it with good ventilation to prevent over heating and performance issues related to that.
 
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Oddly enough, my speeds increase when it rains. No line of sight though and the mast is the other side of a large hill (mountain by Welsh standards).
Noticed that as well, I guess wet surfaces are more reflective.
 
I mentioned it to the the bloke I bought my big dish from who was a retired telecoms engineer and he said it was a well known phenomenon probably caused by the water in the atmosphere refracting the radio waves down.
 
What about this polar vortex weather bomb the media are speculating about with 3 inches of snow?!
 
Oddly enough, my speeds increase when it rains. No line of sight though and the mast is the other side of a large hill (mountain by Welsh standards).
Are you using a dish / directional antenna?
 
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So there is obviously some loss beneath roof tiles - there's also a lot of reflection also, imagine the roof angle reflecting some of the received RF upwards.

There's also a case for noise also, when transmitting within the loft, it's essentially a house of mirrors with some of the RF being reflected inside.

A high gain dish will help to punch through the tiles no doubt.

As always, height and clear line of sight are your friends here.
Just 0.5m of extra height netted me 2-3dBm of RSRP.

My aim was to keep the dishes low, below the peak of the roof to minimise exposure to the elements and to minimise exposure to the wind. It was always going to be a trade-off.
 
To date I have found that it doesn't cause that much signal degradation as long as it is only wooden beams and slate roof. There are some attics I've seen that foil backed insulation/membrane installed that do affect the signal and in very strange/surprising ways!

There is a slight performance drop when it rains, but I see that with my outdoor antennae as well, wet trees especially.

I prefer them in the attic actually as they can become a liability in the harsh winter weather. Plus equipment will last longer in the dry and out of sunlight. One small issue is that if you have a very hot summer, an attic can get VERY hot, so try and locate it with good ventilation to prevent over heating and performance issues related to that.

Excellent! That’s exactly the sort of thing I was hoping to hear. Thanks, @clivejo . Of course, there is bound to be some degradation or attenuation; the key thing for me is that it be materially less than the gain (no pun intended) that parabolic dishes would hopefully give me vs. the XPOL-A002.

I’m sure you’re right, any sort of foil-backed insulation would change the equation entirely. Fortunately, our garage roof space is not insulated. As for heat, well, we’re in the NW Highlands, not far south west of Inverness (as the eagle flies), so it’s not perhaps as much of a concern as it would be in, say, a Victorian house with an insulated dark slate roof in Hampshire.

Thanks again …. Andrew
 
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Oddly enough, my speeds increase when it rains. No line of sight though and the mast is the other side of a large hill (mountain by Welsh standards).
That would be great. We had roughly 2m of rain in 2022 …. 😱☔🌧️

Fortunately, the mast we connect to is to the east. There are mountains north, west and south. 😀
 
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So there is obviously some loss beneath roof tiles - there's also a lot of reflection also, imagine the roof angle reflecting some of the received RF upwards.

There's also a case for noise also, when transmitting within the loft, it's essentially a house of mirrors with some of the RF being reflected inside.

A high gain dish will help to punch through the tiles no doubt.

As always, height and clear line of sight are your friends here.
Just 0.5m of extra height netted me 2-3dBm of RSRP.

My aim was to keep the dishes low, below the peak of the roof to minimise exposure to the elements and to minimise exposure to the wind. It was always going to be a trade-off.
I’m sure you’re right about reflections, @dazmatic .

Actually, I found that I got a better signal with the XPOL-2 by moving it slightly lower but closer to the roof (it’s on a short pole attached to the fascia on the back gable end of the garage). There’s presumably at least a chance that that is due to some sort of effect with reflections.

As for noise and reflections within the garage roof space, well, I think it’s a case of try it and see. Medium term, the better option is quite probably (2) in my original post, above; having checked map contours a little more carefully (and revisited the Solwise elevation tool), I’m fairly sure that there is a materially better line of sight 50m or so south west of the house (and I could quite easily dig a trench and use armoured power and Ethernet cables to place the router in an enclosure with the antennas). But I’ll try it in the garage roof space first.

Cheers …. Andrew
 
I had my dish mounted on the wall with brackets just under the guttering, got the best signal with the dish just over the slate. If I put the dish higher then instead of the signal increasing as expected it instead dropped. Guessing that the dish close to the slate was gaining from reflections off the slate. Only sarking boards under the slate.
 
Isn’t the Chateau POE?

Ignore that. It isn’t.
It can be, with the right equipment! Just like the B535! :sneaky:

Can you guess what's in the box?

MikroTik_Mast.webp
 
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It can be, with the right equipment! Just like the B535! :sneaky:

Can you guess what's in the box?

View attachment 5102
Just to revisit your question:

Is the first sentence a clue? Is it a PoE splitter (i.e. the reverse of a PoE injector), to both power a router and give it an Ethernet connection?

Alternatively, perhaps it’s simply a Huawei B535 with a regular power supply …. 😮

(Actually, given the amount of time — and money — my B535 has caused me to spend, I half think that what it now deserves is a nice, direct connection to the 33kV line from which our supply is taken. 😬⚡️)
 
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