skipp025 wrote: > Hopefully you are using decent balanced wire or fairly standard > telephone lines from the remotes to the base station equipment. > The two remote locations are on conditioned radio circuits ordered from the local telco. The first one is all cable going from the firehouse (RB location) to the town hall via an interconnection at the central office. This one is made up of about 6 miles of cable. The second is a combination of a cable pair from the firehouse to the central office, then a SLC-96 system to the town garage. This has about 2 miles of actual copper cable plus the SLC (subscriber line carrier) system. They pass tests, including ground influence test.
> All remotes should bridge (high impedance - CPI says their units > bridge about 5,000 ohms each remote) the telephone line to the > base station equipment with the exception of one "terminated > remote", which is the one placed the furthest on the line(s) > physical distance from the radio. > I am using the terminate mode at two remote locations and the 5k option at the remote located at the firehouse location on the recommendation of a two-way shop here in Connecticut. This terminates the far end of the cable systems and the remote at the the firehouse (15 feet of local cable) does not need it. > Multiple remote setups in different location buildings invite > serious hum problems. You'll be fighting the wires and then > the ground loops at the equipment end. A hint is to actually > try and observe the hum frequency... Is it 60Hz, 120Hz or > something else. > > My thoughts are to put 600:600 ohm isolation transformers on all the remotes. This should eliminate the possibility of ground loops between the remotes. My question is how to tie the 3 transformers together at the radio side of the circuit. I also have lightning hit damage at times, so I'm hoping that the transformers might help a little bit in this area. > The CPI remotes I just installed were preset for -10dB, which > is not the value I use. Check your levels once you get everything > sorted out. > > Mine work OK with the preset levels, enough headroom with the volume control. > There's a trick to finding ground loop problems at the radio > equipment end... If you need help/ideas... email me direct > for more leads. > > I'm interested in your tricks, 73, Joe, K1ike
