Is there any way I can change out the antenna or make any modifications to boost the range of the receiver?

Another antenna is officially not allowed on the RFXtrx433 transceiver because this product is certified with the supplied antenna but for the RFXrec433 receiver it should not be a problem.

To increase the receiving range you can connect for example a www.conrad.com order nr 190073 433MHz ground plane antenna with BNC coax cable,
Or a http://www.radioshack.com/product/index ... PerPage=60 scanner antenna. This antenna needs a coax cable with PL-259 and SMA or BNC connector.

This adapter can be used for SMA- to BNC http://www.ebay.com/itm/BNC-female-SMA- ... 2a03ea8391

The location of the sensor and the RFXCOM is also important if the RF signal has to pass through walls. See chapter 2.4 in the RFXtrx User Guide
http://www.rfxcom.com/documents/RFXtrx% ... 0Guide.pdf

It is expected that RF interference is happening if sensor signals disappear for several hours. RF interference will occur if sensors of the same type are configured to the same channel.
Here is the list of Oregon sensor types TEMP1, TEMP2... http://www.rfxcom.com/oregon.htm#Oregon

If sensors disappear for a longer period the source can be another transmitter that is transmitting continuously or with short intervals. If X10 MS13 sensors are in use check the battery in this sensor. When the battery becomes almost empty the MS13 starts transmitting a weak continuous RF signal but just enough to disturb the sensitive RFXCOM receiving.

I’ve been using the conrad 190073 as above with my rfx device for the last few weeks… made a massive difference to the signal strength and i’ve not had any issues with “shadows” as other people have reported. I’ve got mine mounted in the loft with about 10m of 50ohm coax cabling.

Wow... I went to Conrad.com to see what they would charge me and they have no choice for the US. Obviously I am biased living here... but how is this possible?

Well.. they do ship to the Democratic People’s Republic of Korea (North Korea)… have you considered moving there?

Alternatively do you know anyone in one of the countries that they do ship that could forward it onto you?

I may explore alternatives... I've only got one sensor that I'm having troubles with. Maybe just try to get a USB extension and get it more central in the house.

This worked very well for me...

RadioShit Outdoor VHF-Hi/UHF Scanner Antenna
Model: 20-176
Catalog #: 20-176
29.99

I now pick up an Oregon Scientific transmitter from 60 yards away, from my greenhouse which is through 2 concrete block garage walls and through an attic wall where I placed the antenna. The antenna is connected with an 50 ft SO239 cable and an adaptor to the RFXCOM receiver. The RFXCOM receiver is plugged into a powered USB hub with a 5' USB cable.

Now if someone could only help me eliminate the errors I am getting in my logs:
Error device state key humidityStatus not defined (ignoring update request)
Error device state key type not defined (ignoring update request)
Error device state key batteryLevel not defined (ignoring update request)
Error device state key signalStrength not defined (ignoring update request)
Error device state key humidityStatus not defined (ignoring update request)
Error device state key type not defined (ignoring update request)
Error device state key batteryLevel not defined (ignoring update request)
Error device state key signalStrength not defined (ignoring update request)

Can you send me a part of the logfile where you see the data from the RFXTRX ?