winter zephyr
I'm trying to get a connection with an ESPCam in the washroom to watch the power meter.
My first attempt is a cantenna. It got me about 3x the original range but it still wasn't enough.
I somewhat worry I'm only getting a better reception because this is so much bigger than the board's built-in antenna, but at the same time it showed the expected directional properties of a cantenna, so I do think it's working.
hazy cove
Do you have any kind of equipment to tune/measure the cantenna? It might be useful to visit a lab/makerspace/friend with a network analyzer. A nanoVNA is sufficient from what I have gathered.
winter zephyr
Sadly I don't have any kind of access to that stuff, but I did do a bunch of math and I actually figured out that this can has a diameter wider than the ideal, and the antenna inside the can is much longer than it should be. The issues with the can size actually make a lot of sense (now that I understand the math better) but I don't have an intuitive understanding of why the internal antenna length matters.
hazy cove
You have a radiator inside the can, do you?
For basic measurements you can try to scan for hotspots and compare RSSI with the cantenna and with whatever it's replacing
winter zephyr
Yeah, that's what I've been doing.
It gets about 3x the range the stock antenna gave me. It also works a lot better when I point it at the hotspot.
naive shoal
Sadly I don't have any kind of access to that stuff, but I did do a bunch of mat...
For the intuition, I think you can safely say that the antenna inside the can is an actual antenna — needs to be tuned to a certain factor of the wavelength — while the can is basically just a reflector that points the output in a particular direction.
That is, aiui, not entirely true, but I think it’s true enough.
winter zephyr
As I've read more into it, that's what I've found too.
I actually found an amazing webpage on wayback machine.
From which I wrote a python script that calculates the ideal cantenna.
Which outputs:
Nominal Wavelength: 122.44897959183673 mm
Cutoff Wavelength: 127.6595744680851 mm
Guide Wavelength: 433.0127018922204 mm
Antenna Length: 30.612244897959183 mm
Tube Diameter: 74.82976229078845 mm
Minimum Tube Length: 324.7595264191653 mm
Antenna Position: 108.2531754730551 mm
I'm working on a design for a printable version of this cantenna.
Since I can't find an ideal can.
hazy cove
What about etching a 2.4GHz yagi onto a PCB? It has a similar directional characteristic
vagrant oak
hazy cove
https://www.ebay.com/itm/363659278617?chn=ps&_trkparms=ispr%3D1&amdata=enc%3A1WH...
These are very nice, but I don't think the esp is kilometers away from the base station... Also, I don't think it's possible to reduce the transmit power on the ESP enough so that you don't exceed the legal limit on the maximum output power with that antenna...
winter zephyr
It's also wildly massive for the task. This is in a community laundry room, so I want to be at least somewhat descrete.
winter zephyr
What about etching a 2.4GHz yagi onto a PCB? It has a similar directional charac...
I had no idea you could just etch one of those into a PCB, but it makes perfect sense that you could. (I should also note that I've never had a PCB made)
I think I should explore this idea more. Do you have any resources on the subject?
vagrant oak
Sorry, I should have said, I meant it as a joke 🙂 so sorry!
I really do love your cantenna!
winter zephyr
Thank you! This is much more informative than what Google was giving me!
hazy cove
Sorry, I couldn't find anything better that doesn't require a deep dive into electromagnetic fields... (Not that I'm that I know much of the subject, only as much as needed for a CEPT license)