[TenTec] False Alarm

Stuart Rohre rohre at arlut.utexas.edu
Fri May 16 22:53:57 EDT 2008


Wayne,
A Hamstick close to a building such as a hotel with many conductors in 
the construction is going to have issues with RFI.
You, not matter the SWR, are going to need some quarter wave 
counterpoise wires, or radials, to tame the ham stick.  You may also 
need to remote the antenna from any fire alarm wiring and circuits.  
These systems are notorius for causing RFI to phone systems, or other RF 
circuits since many fire alarms use a carrier current type of daisy 
chain circuit to poll the various sensors around the building.  Try 
operating with at least quarter wave insulated wire, even stretched 
around the room, or hung out an upper floor window.  Try reducing the 
power, you don't really need 100 watts when the propagation is in. 

Oh, and the good SWR?  Well, a dummy load has an SWR of 1:1, but does 
not contact many other stations.  You may have been loading up the coax 
shield as much as the short antenna.  That would allow outside the 
shield current to come back and cause typically the type of problem you 
had with sensitive electronics.

GL and 73,
Stuart
K5KVH




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