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Esp8266 modules with ceramic antenna

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dr pepper

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I have a couple of projects comming where I want to operate a wifi device at longer range.
So instead of bodging an aerial onto a esp module that has a pcb one I was thinking of getting a couple of esp modules that have the ufl aerial connector onbaord.
I also see these modules have a 'ceramic' aerial, what are these?, id there a diplexer onboard or is the 'ceramic' doo dah a device that tunes the input or something.
I'm still going to bodge an aerial though, maybe a 3 or 5 element yagi.
 

JimB

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A ceramic antenna is just that, a block of ceramic material with a metal surface deposited on it. The metal surface is the conducting part of the antenna, just as a metal rod would be in a simple dipole.

The ceramic has a high permittivity and so increases the capacitance of the metal surface and makes the small antenna appear to be resonant at a much lower frequency than I would be without the ceramic.

JimB
 

Nigel Goodwin

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I also see these modules have a 'ceramic' aerial, what are these?, id there a diplexer onboard or is the 'ceramic' doo dah a device that tunes the input or something.
From what I can gather these modules come configured to use the ceramic aerial, if you want to use an external one you have to physically move a VERY small surface mount link.
 

be80be

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Les Jones

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I think you just remove a zero ohm resistor to use the external antenna connector.

1705141451052878062.jpg1705141455223134340.jpg

It looks like the antenna connection goes directly to the socket and is linked to the ceramic antenna via a zero ohm resistor. It measures zero ohms with my multimeter. (But it could be some value below 0.1 ohms. It could also be an inductor. I hafe inclued a picture showing the edge of the "resistor". It looks like ceramic with a metalic coating on the top surface.

Les.
 

dr pepper

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Ok then.
I see you can get these modules without the ceramic doo dah, if I can get those that'd be best methinks.
The smd probably was a choke, the schem shows a lpf with 2 chokes with the ceramic antenna.
I wondered if the ceramic doofer worked as a tuned filter part of the input, and yes I see permitivity and other stuff in coax affects the speed of signal travel, ie slows it down, so it makes sense to do that with an ant to reduce size.
The data sheet depicts the chip has a 50 ohm input inpedance at wifi freq's, so its a good candidate for a home bodged yagi or co-phaser.
I'm not sure how low in sig strength esp8266 01's go, but I've just been doing some tests and got a long way off through metal structures & walls, and the device was still working at -88dB, not bad for a pcb ant.
 
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dr pepper

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Well that makes it easier to bash into something else then.
 
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