I've seen this before on an MSR-2000 or two... or twenty... It might be related to the added interconnection cables. What kind of wire are you using from the receiver to what- ever external devices (repeater controller) you have connected?
The black multi conductor round wire found and used on older Motorola Desk Mics and remotes is pretty much the only wire I use on any critical analog communications project. The brown wire within the cable is very specially shielded for low level audio applications and it makes a BIG Difference in many applications. I found out the hard way when wiring many different types of external tone and trunking controllers onto the MSR-2000 repeater back plane. I could actually see induced noise when using other high quality cables... so I went back to using only the Motorola black mic cable and have never had an external device hum problem. Motorola used to sell it separate to the mics as available wire and of course they no longer do. You could steal the wire off a used Motorola Desk Mic. I've compared the wire to other shielded wires and for some magic reason it works better for the application not to mention the color codes match the Motorola function codes I standardized on. If you trouble shoot the problem to the applied wire and are not able to locate the mentioned black mic wire... you're welcome to contact me direct about it. After mucho searching I found the mfgr and became a Dealer. If you have a short run... I might have some around to ship you for the cost of the postage. Otherwise it does cost between $1 & $2 a foot.. but it does work very well. Might be something else... but the external repeater controller wiring is something I've had to take an evil eye look at more than once. Something in your original setup might have changed/moved to start-up the hum problem. Sometimes what ever caused the hum to start up is not an easy "figure out". One quick generic test to source tired power supply caps (ESR)... at the repeater site remove the exciter connection from the RF Power Amplifier and terminate it into a proper load. Key the repeater with the terminated exciter and listen for the hum with the PA not drawing much current (being used). If the hum goes away... you might have tired filter caps or induced RF causing the hum introduction. cheers, skipp skipp025 at yahoo.com www.radiowrench.com/sonic > "Bill" <[EMAIL PROTECTED]> wrote: > > Howdy group. > I have a Motorola MSR2000 repeater on the ham bands that I maintain. > VHF 147.32 in Austin (Oak Hill)Texas. > It has developed a hum on the receive signal. I know it's the receiver > as there is no hum when the machine ID's with no input from the > receiver. The hum has been getting worse and now I need to take a look. > I have schematics and instruments. I'm asking to see if anyone has seen > this kind of issue before. I run a 114.8 PL but it sounds more like > 60Hz not 114 hz I'll have to look at the audio and measure. > The machine is on IRLP if anyone wants to take a listen the node is > 3364. Any input would be helpful. Jim K5VPW monitors the machine and > runs the IRLP node so he may be listening and is willing to assist. > Bill N5ZTW >
