Re: CPI Tone-Remote system configuration > > skipp025 wrote: > > Hopefully you are using decent balanced wire or fairly standard > > telephone lines from the remotes to the base station equipment.
> Joe <k1ike_m...@...> wrote: > 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. Who reported they passed tests? The phone company promise the moon report... or did someone other than the phone company actually check them at least for loss and hf roll-off? You can bet the actually line impedance is probably not close to 600 ohms unless you verify/test it. Rare do I believe what I'm told without minimal verification done someone on my side of the job. > > 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. How are you dealing with the two terminated remotes across one line? > > 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. Look at the diagram for the remote... if it's an "electronic type" of circuit it might not have a transformer in the output line driver section. If it's a more traditional remote with an actual transformer in the circuit... would you expect the double transformers (one in the remote, one external) to help or hinder? > This should eliminate the possibility of ground loops between > the remotes. Not really in all cases... do you know the frequency of the/any hum you're hearing? It's a clue as to the source of a problem. Are you hearing hum/buzz from one particular line? or the combination of the local and distant 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. You could wire transformers in a number of schemes... just paralleled, as a hybrid or using different secondary values... into a custom interface. I just pulled the manual for the CPI TR Series Tone Remote and it has true physical transformers in place... so you should be able to interface all the remotes without a problem without a bunch of extra stuff. I know it's a pain, but you should probably find and deal with external to the equipment problem generators. > > 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. If you don't have a telco metering setup (line-man, transmission line tester "tims") the levels across the phone line can be read with any decent AC volt meter. I would suspect even a double terminated dual end remote(s) setup should work fairly well if you properly modify the levels. > > 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 First, find where any/the problem is getting introduced to your package. Pull/remove sections of the system to find where things are sneaking into the mix. s.
