Re: Converting a US 300MHz RMS18/MS12A motion sensor to transmit at 433.92 MHz

[nobody@xxxxxxxxxxxx (Dave Houston)]

Actually, the changes you make *reduce* the power. It's the added antenna
that gives you extra range.

Here, soldering the antenna lead will detune the transmitter. But range can
be increased substantially by just placing a wavelength/2 wire *near* the
device but with no direct connection.

nobody@xxxxxxxxxxxx (Dave Houston) wrote:

>I should have read your article before commenting. ;)
>
>I now see you are changing the components that control the output power.
>
>Since you're installing a SAW resonator you won't see tuning problems but
>it's easy to detune the US models just by adding a little solder.
>
>"Stefan van der Horst" <stefan@xxxxxxxxxx> wrote:
>
>>Hi Dave
>>
>>Thx for the 310 notice. I changed the article.
>>
>>The RF transmitter I build is 100% the same as the RF transmitter installed
>>in the european MS13E motion detectors. The current and voltage provided to
>>the RF module are the same as the european models. I don't have the
>>equipement to test the power but I was able to span app 30 meters in open
>>field and 20 meters in house through brick walls.
>>
>>I'll add your link to the article as well.
>>
>>For my purpose the rf power is high enough.
>>
>>"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message
>>news:43c6cc5b.105778578@xxxxxxxxxxxxxxxx
>>> One correction: The US frequency is 310MHz.
>>>
>>> You also should be aware that the FCC severely restricts the power that
>>> can
>>> be used by these devices. CE power limits are much higher. So while you
>>> might save a bit (assuming your time has no value) this way you'll end up
>>> with much less range than with the European versions. See...
>>>
>>>     http://www.radiometrix.co.uk/apps/apnt102.htm
>>>
>>> A simpler approach might be to merely disable the 310MHz circuitry and add
>>> a
>>> 433.92MHz RF transmitter module. There's a small 4-pin transmitter widely
>>> available (Velleman, CrownHill, etc.) that will work quite well and has a
>>> higher power output than the US X-10 devices.
>>>
>>> I've done the reverse, adding a small 310MHz transmitter to the DigiMax
>>> 210
>>> RF thermostat sold by X-10 Europe.
>>>
>>> "Stefan van der Horst" <stefan@xxxxxxxxxx> wrote:
>>>
>>>>Forgot to mention this is an X10 device
>>>>
>>>>"Stefan van der Horst" <stefan@xxxxxxxxxx> wrote in message
>>>>news:dq6f7k$i30$1@xxxxxxxxxxxxxxxxxxxxxxxxxx
>>>>> For those who are interested in modifying a US RMS18/MS12A to transmit
>>>>> at
>>>>> 433.92 MHz into I have written an tech doc for the modification. It is
>>>>> located at:
>>>>>
>>>>> http://project.actopus.nl/X10/rms18toms13/Index.html
>>>>>
>>>>> regards
>>>>> Stefan
>>>>>
>>>>
>>>
>>