Author Topic: Any tips for mounting an antenna on a house roof?  (Read 125 times)

amadeuspzs

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Any tips for mounting an antenna on a house roof?
« on: March 26, 2021, 09:59:32 AM »
Hello,

I'm using an RFM69HW at 433MHz and would like the antenna to be mounted on my house roof, probably tied to a chimney stack, as I have a number of sensors out in the fields, and the house is situated well at a high point.

I'm using an SMA connector, so have tried both a "rubber needle" and magnetic base whip antenna attached directly to the PCB.

Despite the different rating (3dbi vs 6dbi) I have detected negligible difference in transmission power. Maybe this is to be expected.

My question is around best practice for mounting at a decent distance from the power supply (mains):

1. Do you keep your power supply and pcb as close as possible to the antenna e.g. build a weatherproof enclosure and stick the antenna straight out of the PCB or
2. How far can you run a coax from your pcb to your antenna before you run into issues (e.g. use a 15m sma extension cable)
3. Or do you do a bit of both - I can get power quite far as it's DC, and I could use an e.g. 5m antenna extension cable for convenience.

I'm just moving into the "physical installation" stage of electronics so any tips or general rules of thumb appreciated.

Cheers,

Amadeus




Felix

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Re: Any tips for mounting an antenna on a house roof?
« Reply #1 on: March 26, 2021, 10:10:42 AM »
Typically in such a scenario you'd want the electronics inside (like your TV), and run a cable to the antenna where you get best signal IO. You have some cable loss but hopefully the elevation gains will far outweigh that disadvantage. And if you go through that effort I'd use a dipole if I were you (or at least compare to the others, my gut feeling is you will get even better signal reception and propagation).

Kilo95

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Re: Any tips for mounting an antenna on a house roof?
« Reply #2 on: April 12, 2021, 12:46:53 PM »
Since the moteinos are low power, I'm concern with power loss due to the coax length. smaller coax is worse. UHF (433mhz) is worse than VHF. I'd probably get one of the gray electrical boxes that's weather tight, drill holes for your power to the unit, and fill that with silicone to make it weather tight. I've got a WeatherShield I put in the top of my kids' playset 150' from the house in one of those boxes. I put vents in the sides with the louvres turned down to shed the rain. Drilled a couple of 1/8" holes in the very bottom so any moisture could drain. (I did the louvres and holes in the bottom because I didn't want it to sweat. I'm using a ~6"long SMA pigtail to one of the PCB dipoles that someone on here was selling. It's been out there 2-3 years and works fine. I've opened it up a couple of times. No moisture inside