I need more power... boosting signal for weather station

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timmmay

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#160328 2-Jan-2015 18:18

I have an Ambient Weather WS-10 weather station (Xmas pres), with four sensors. One of the sensors is in my greenhouse, but it cuts in and out - it shows the temperature about half the time. It's maybe 10m from the base station but the signal has to go through the thick brick of my shed wall twice and the thin house wall.

Is there any way to boost the signal? Perhaps make some kind of metal dish for the greenhouse unit to focus the signal? Extend the aerial? Anything? I already moved the base station as close as I could to the greenhouse, which helped a fair bit.

richms

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#1207274 2-Jan-2015 18:29

Assuming it is a 433Mhz system like my cheapies, the antenna in them is a loop on the PCB, so you can open them up, cut that track and attach a piece of wire instead.

Internet gives all sorts of "ideal" lengths of wire, but I found that the 17cm that was mentioned worked signifigantly worse than a meter of generic thin hookup wire stapled up. I exited the sensor at the bottom and then went straight up with it.

The one in the greenhouse isnt mounted on a metal structure is it? That will screw the antenna up majorly.

Richard rich.ms

timmmay

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#1207276 2-Jan-2015 18:53

I'll have a look at adding an antenna thanks Rich :) Not mounted on metal, onto plastic which is attached to wood.

Niel

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#1207287 2-Jan-2015 19:45

Every brick wall halves the range. There is a chance the sensor transmitting frequency is not 100% tuned, you can try swapping sensors to find which one gives the best range.

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timmmay

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#1207304 2-Jan-2015 20:31

Niel: Every brick wall halves the range. There is a chance the sensor transmitting frequency is not 100% tuned, you can try swapping sensors to find which one gives the best range.

Yeah I'll do that, I have four so easy enough.

timmmay

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#1219965 22-Jan-2015 12:05

I've replaced the internal antenna (2 inch coiled wire, looks like a spring) with a 1/4 wave antenna. That made it much more reliable, but in the past day or two it's started dropping out again. Is a directional antenna at all practical for something this small and cheap? Or some kind of a dish to try to focus/bounce the signal?

BlueShift

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#1219970 22-Jan-2015 12:12

timmmay: I've replaced the internal antenna (2 inch coiled wire, looks like a spring) with a 1/4 wave antenna. That made it much more reliable, but in the past day or two it's started dropping out again. Is a directional antenna at all practical for something this small and cheap? Or some kind of a dish to try to focus/bounce the signal?

Try something like this: http://www.google.co.nz/&q=coke+can+wifi+boost

timmmay

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#1219987 22-Jan-2015 12:20

Worth a shot, thanks :) Also, this design.

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raytaylor

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#1220045 22-Jan-2015 12:58

I'd look at the wifi surfboard or wok wifi and just make some sort of tinfoil dish.
edit: the concept is the same - your antenna needs to be at the focal point of the dish.

Wifi has a similar concept - with the wok wifi, but at 433mhz you need a much bigger dish to get the same effect as a dish at 2.4ghz. Though 433mhz will go through walls easier than 2.4ghz wifi.

Ray Taylor

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timmmay

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#1220058 22-Jan-2015 13:02

Any idea what size Ray? I could easily do coke can sized as I have the sensor within a little enclosure to prevent sunlight falling on it, but larger would be tricky.

raytaylor

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#1220062 22-Jan-2015 13:08

timmmay: Any idea what size Ray? I could easily do coke can sized as I have the sensor within a little enclosure to prevent sunlight falling on it, but larger would be tricky.

Well a wok size would probably work - they can give a wifi dongle a 10dbi increase, so I imagine it would be around 3dbi at 433mhz.

Or you could find a UHF TV antenna and wire it up to that?

3dbi is double the signal.

The wok I am referring to is here http://www.usbwifi.orconhosting.net.nz/

Ray Taylor

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timmmay

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#1220064 22-Jan-2015 13:13

Haha, funny. I'll try with a coke can first as it's easier, but I'll keep that one in mind, may have to pick up a cheap wok some time.

Niel

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#1221319 24-Jan-2015 12:03

(I'm back from holiday.) With RF you need to use the correct dimensions for an antenna/dish, else it can make it worse. It needs to resonate at the frequency of interest. Maybe a Coke can is about the right size for 2.4GHz. A directional antenna will work even for something like this, but needs to be the correct frequency.

I think either the transmitter frequency is not correctly tuned (or detuned from rain/mounting surfaces), or the circuit is not stable with temperature. If tuned, then the drift is not a big issue as it will likely stay within the band pass filter range of the receiver. Unfortunately you need expensive gear to tune RF circuits.

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timmmay

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#1221473 24-Jan-2015 17:13

Thanks Niel, might just try the coke can to see if it helps, even though it won't be quite right.