cross-posted from: https://lemmy.zip/post/33672853
So I live in a small city of around 50,000 people and we have a router that’s 200 feet up on a tower with a 5.8 DBI antenna.
There’s a guy 17.5 miles away who wants to get into the mesh and his node is on a 30-foot flagpole and also has a 5.8 DBI antenna.
There is no major elevation change between the two nodes and according to a distance calculator, the line of sight between both antennas should be about 24 miles, which would cover the distance with no problem.
With that said, the nodes are not connecting together. And I’m wondering if that’s because of the 5.8 DBI antenna gain on both sides, or if there’s something else I might be missing.
Edit: On a side note, I live 3.7 miles from the router, and it has trouble hearing me, but I do not have trouble hearing it with my T1000E. And I’m also wondering if that’s because of the antenna gain on the router side.
Have you considered a yagi since youre dealing with 2 fixed points?
Not yet. was hoping an omni would work so that anybody around them could also get into the local mesh. With an omni, anybody within 8 miles of them should be able to get in with a yagi though. That would be much more limited in any other direction besides the front lobe.
They could get a really long yagi, and connect to your omni. That sounds like the most reasonable solution. Do you know what power and sensitivity is used?
Have you considered the Fresnel zone? You know, the ellipse between sender and receiver where most of the signal power is located? If you are 200+30 feet up, at 17.5 miles, my back of the napkin map says you are barely having a line of sight, so much of the Fresnel zone is probably obscured by the earth.
Some random online calculator says that at 433 MHz, you have a Fresnel zone radius of 230 ft, (145 MHz has 395 ft, 866 MHz has 161 ft). So half of the signal path is blocked at 433 MHz, and apparently the rule of thumb is it should be at least 60% free. I am too lazy to do actual math right now, but that might be a reason.
If it has trouble hearing you then it’s likely there’s something near by producing lots of noise. Maybe cellular antenna. Look up cavity filters and maybe install one on it.
I found out they were using a 3 foot jumper of RG-316 cable and I’m betting on 900 megahertz that the antenna is not really getting any other power and that the cable is acting as the antenna.
Likely… What a waste for a node that someone went through the trouble of putting high up.
Well, that’s just what it came with. Once I found that out and mentioned it, they are ordering a low-loss cable so that should no longer occur.
I had a similar experience with RG58 and UHF. I guess the good old tech support wisdom is true: when in doubt, check the cable…
According to something I saw on the internet, RG-316 has 47 dB worth of loss at 3 GHz. So even if it’s a third of that at 1 GHz, that’s still 15.6 dB per foot, which considering the transmission is only 30 dB or 1 watt, that means that the entire power would be lost after 2 feet of cable.
Late reply, and forgive me if I am over-explaining. I found some random datasheets that say RG-316 has 26-29 dB per 100 ft at 1 GHz. So in the worst case, 3 ft would be 0.87 dB. Doesn’t sound like much, but 30 dBm - 0.87 dB = 29.13 dBm = 818 mW, so he is losing 182 mW to the cable. Not great, not terrible.
It definitely should not make that much of an impact. Maybe look into antenna tuning / SWR? Or broken connectors / pinched cables? If my past IT jobs have taught me anything that that it’s always the cable, unless it’s the plug :)
