Earlier this week, I wrote a message asking how to increase the range of my Oregon Scientific wireless temperature sensing remote transmitters that come with the BAR-888A atomic clock. Thanks to a user here that wrote me off list...the problem is solved. For a long range transmitter, use a wireless amp module such as the Phillips BGY687B. It is a simple amplifier that can be used without input and output tuning if spectral purity is not an issue. This amp operates with milliwatt input power levels such as these low power 433 Mhz transmitters produce and can produce a 1 watt output transmitter or more. The device is a CATV broadband amplifier module, it's easy to use and already has 50 ohm input and output impedances. This is a simple fix for a significant boost in range. You will exceed the (ISM) FCC limits for power output by doing this, so do so at your own risk...or, get an amateur radio license and run as much output power as you want....these devices operate in amateur radio spectrum where amateur's have the primary spectrum allocation. So, it's all quite legal provided the amateur service rules and regulations are complied with. You can also get another 10 db of effective radiated power by simply adding a small quarter wave dipole transmitting antenna, the stock PCB loop antennas are not good::> This also violates FCC rules unless one has an amateur radio license. This should give you a 1 mile range, or more...depending on the terrain. ----------------------------------------------------------------------------- In the process of my research, I found these devices use SAW devices to set the operating frequency. Saw devices have poor stability and are very sensitive to temperature changes. As a result of the saw use, the transmitted frequency can vary by 200 KHz (or more). This means that receivers have to be very broadbanded, so they admit a lot of noise, which reduces the transmitting range. So, converting to quartz crystal receivers and transmitters on both ends of the link can easily add another 15 db of sensitivity (or more). ---------------------------------------------------------------------------- For the ultimate in range, use the remote temperature unit in it's stock configuration and buy a simplex repeater (Wireless Signal Repeater, model RT918) sold by Oregon Scientific. This is a simple receiver and re-transmitter that listens on 433 Mhz until it hears a digital signal from the remote temperature transmitter. When the signal is heard, it stores the signal, then re-transmits it (on the same frequency) a few milliseconds later. By converting one of these repeaters to high power as explained above, the entire repeater assembly can be placed at the feedpoint of a hygain yagi antenna antenna for extremely long range transmissions. 20 or 30 miles (or longer) range should be easily obtainable depending on the terrain and how high/big the outdoor antenna is. Enjoy::> Art Disclaimer:These 433 Mhz license free devices are regulated by the FCC (in the US) and cannot be modified legally in any way unless they are operated under an amateur radio license or a part 5 experimental license. If you choose to modify one of these units, you must comply with all applicable rules and regulations. This is your responsibility, not mine. -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.407 / Virus Database: 268.12.9/458 - Release Date: 9/27/2006 -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist