Increase range of 433MHz remote sensor [closed]

My question is similar to this one but with some differences. I have wireless weather station with 3 remote 433MHz sensors so I cannot change the protocol and program the controllers. Also I'm new to radio but have some basic understanding how it all works.

I'm trying to modify the stock product to increase its capabilities, a sort of DIY project for home.

The sensors and station base are mounted on concrete walls of my home, where maximum distance between base and sensor is about 15 meters (and crosses 3 walls). The Base is able to receive signals from all sensors except one that is the most distant.

Link to the weather station on amazon. Transmitters run on 2 AAA batteries, 3V.

What is the easiest way to allow it receive the signal? Attach better antenna to the transmitter? Or completely replace the transmitter module?

I understand that I didn't provide much information about the circuits because I'm not sure if it matters in my case. I can post images of the inside later if needed.

UPDATE

Here is a receiver module of the station Base.

The Sensor box is harder to open because it looks like sealed. I'll try to open it later and now hope the receiver can give some ideas.

• These are bought-in modules that are already packaged up therefore you don't have the circuit so, my advice to you is contact the supplier and ask them why they are not transmitting at least 100 foot (specified). This is not a valid question for this site because they are bought-in items without any schematics or design information. – Andy aka Jan 19 '16 at 10:37
• Yep, it looks so, but I'm trying to modify it somehow, kind of DIY project where I don't know the easiest way to begin with. – neleus Jan 19 '16 at 12:34

"I didn't provide much information about the circuits because I'm not sure if it matters in my case"

Oh yes that matters ! There are several 433MHz receiver modules you can buy on ebay etc. I have a simple one:

And a more complex one:

Mine is similar shape but with a metal shield covering the components. I have never seen the simple model (first picture) with a shield.

If you have the simple module, then that is the reason why you experience poor range. The more complex module has a better receiver with AGC (Automatic Gain Control) this helps a lot.

For maximum range you want to use an antenna of the proper length of 1/4 * lambda, at 433 MHz this comes to 17 centimeters. It is best to stretch out the antenna to its maximum length but it will also work when coiled up a bit.

• I guess mine has sort of simplest module. Is it easy to replace it without any modifications to other components and power voltage 3V? – neleus Jan 19 '16 at 12:39
• In principle yes but it totally depends on what is in there at the moment. I would have to see the thing in person to be able to say yes or no. – Bimpelrekkie Jan 19 '16 at 12:45
• I've added a photo to my post, the receiver module. I'm having some troubles opening the Sensor box, please let me know if you need it also. – neleus Jan 19 '16 at 12:57
• No the receiver is the part we're interested in. To me it looks very similar to the simple receiver from my answer. It also appears to have only 3 connections to the main board, which is good ! These will be, gound, data and 3 V supply. Just like on the receiver modules I suggested. I would get a receiver module with an AGC and replace it. Just make sure you connect ground to ground, data to data and Vcc to Vcc. You can just re-use the same antenna. What a shame that they used such a basic receiver module, the better version is also quite cheap (only a few Euros). – Bimpelrekkie Jan 19 '16 at 13:35
• Great, your comment is exactly what I'm looking for! I've found some receiver that seems what I need, dx.com/p/… What do you think? And one small correction: the Base station has 4XAAA so 6 volts. Is it Ok for the spec of 5.5V? – neleus Jan 19 '16 at 14:37

I am quite unsure what you are trying to achieve. As these are packaged product and there is not much detail provided about antenna. The way radio transmission works is by transmitting power which is absorbed/reflected/spread in medium and receiver only receives a part of it. Device specification clearly states that it is good for 100ft line of sight without interference. If you want to increase range either you have to increase transmitted power or, receiver sensitivity. Both requires lots of circuit debugging and not worth the cost if direct probe is not available. If there is probe for antenna then probably you could set up a high power antenna to increase some range. But increased interference might be a problem if it is not set properly.

• "The way radio transmission works is by transmitting power which is absorbed in medium" - no this is not how radios work. The medium (free space or air) doesn't absorb the power - it is a medium for the power and there is no appreciable attenuation of that power. – Andy aka Jan 19 '16 at 12:37
• you could set up a high power antenna Can you please give a link? – neleus Jan 19 '16 at 12:44
• You're not allowed to transmit more power, you would violate regulations. Only the people that do not really understand radio will shout: "use more power". To a deaf man you can shout as loud as you like, he will not hear you. – Bimpelrekkie Jan 19 '16 at 12:48
• ok, my understanding that it could be still low-power antenna but with higher signal quality or perhaps directed to the receiver. I believe that I dont have to increase the power itself. – neleus Jan 19 '16 at 13:00
• Obviously you have to look for regulations, I only pointed out that part(increase output power) because there was no information regarding transmitter/receiver in the product detail. Yes making it directional and improved signal quality will surely help. – Purnendu Kumar Jan 20 '16 at 13:44