Amateur Radio

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antenna question (lemmy.zip)

submitted 1 week ago by [email protected] to c/[email protected]

13 comments fedilink hide all child comments

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.

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[–] [email protected] 1 points 1 week ago (1 children)

Likely.. What a waste for a node that someone went through the trouble of putting high up.

[–] [email protected] 1 points 1 week ago (1 children)

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.

[–] [email protected] 1 points 1 week ago (1 children)

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..

[–] [email protected] 1 points 1 week ago (1 children)

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.

[–] [email protected] 1 points 6 days ago* (last edited 6 days ago) (1 children)

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 :)

[–] [email protected] 1 points 6 days ago

No prob. Thanks for that info