Notes on Phone Line RFI

14 Sept 2003  

Added a J toroid to the MODEM line running to Computer at Station # 1. Also put three split bead ferrites on the line to the phone in the bedroom.

Listened for interference -- hear it on the AT&T Princess phone on low and high power on 80, both when that phone is in the bedroom and out here. Do NOT hear it on the bedroom phone (the desk phone). It is severe with the linear running. 80 is worst, about 1/3 as bad on 40, nothing on other bands, even 160.  

Listened with the susceptible Princess phone at the line in puts to the computers. Both are COMPLETELY clean. When I plug that same phone into the wall duct by Computer #3, the interference is severe.  

Conclusion: the crud is on the phone line in the house in the duct and the ceiling, but the ferrites are removing it prior to getting to the computer modems.  

One thing to try: remove the AT&T phone from the system and try operating. Maybe it is the antenna. If not, thenb the signals are being picked up on the phone line running through the house. If this is true, mini-coax will be the solution – put it in the duct and ceiling instead of the zip wire. If it is being picked up outside by Telco lines, there may be no solution. PacketCluster would be the next thing to try.  

Test: Logged onto Telnet at 2017Z. No transmitting. After about 10 minutes of solid reliable connection, I transmitted at full power on 80 on the inv vee over the house with the Princess phone unplugged, with no problem. Plugged it in in the bedroom – no problem. Moved it to the couch table and plugged it in, still no problem. All seems OK, even with the bad phone plugged in in the shack room. Only other thing to try is to transmit with the Europe loop.

All seems OK now, but not sure exactly why. One more test: try transmitting SSB. Did that at full power on 80 and all seems OK. Will test further while doing some K8ND QSOs tonight late.