PA Horn/Speaker & ICOM 422 Noise Filter

[Jaredell]

Installing a SH horn on outside of console and wiring to a ICOM 422. There are two wires out of 422, one labeled (in manual) for external speaker, the other labeled for PA horn. Each of these wires has a center copper line and outside of this wire's insulation, each wire has multi-wire braid of steel wire.

Before installing I tested set up with the inner wire of the PA Horn line connected to one of the horn's connects....and the center wire of the 422's other "external spkr" wire connected to the other PA Horn lines. Neither 422's outside steel braids were connected to anything. 422's PA worked great....422's external speaker function (through the Horn) worked great.

Am I correct in this wiring? ::) Do the external steel "braid" on each of the two 422 output speaker/PA wires have to be wired to anything or am I okay the way I've tested it??? Any help would be appreciated. 006

ALSO - after the install of an ICOM 422 radio into my new DLV 218 /115 Suzi...which worked great...I found that when the engine was running...there was a pretty pronounced high pitched hum coming through the radio speaker. Talking with the ICOM service folks - who were very helpful - they suggested a few different diagnostics. If sound persisted when disconnecting antenna - it was probably associated with engine operation (this was the case). They suggested a 10 amp Newmar noise filter (about $60). I've installed in in the power line to the 422 and, sure enough, NO MORE hum with engine running. yay ;D

Just a comment too... rather than attach the noise filter directly to XL console...I've installed a 18" x 18" piece of PT 3/4" plywood- attaching it to the inside of the console - using four of the six console front seat backrest bolts. If I ever get the energy, time and advice from you all there's plenty of room to attach breaker buses for the malaise of electronic wiring currently under console. We'll see how it works.

Bill Korn
Brooksville, FL
2008 DLV 218 w/ 115 Suzi

[mbfishing]

Great info you have posted, very helpful. thumbsup

[Shakespeare]

Typically an outside shield wire (braid) is only grounded on one end... the "field" end floats or in other words is not connected to anything. This is most critical in long lengths of instrumentation wiring where it's possible for the cable to pick up some induced "noise". Grounding on one end gives that noise a path to go to. If grounded on both ends you just created a ground loop and in some cases an "antenna".

If your cable run is fairly short then you probably won't be able to discern any difference between bonding it to ground or not. For things like speaker wire, communication cabling, etc. it's best to not allow it to be in close proximity to something highly inductive like pump motor wiring.

Mike C.

Edited for syntax correction.

[Jaredell]

Thanks Mike... I just won't worry about the outside "braid" then... just cut it off at end.

Appreciate it!!

[hogtown_usa]

??? The PA speaker output and the external speaker output are two different things. The radio is designed so that two separate speakers can be attached, one for external receive audio and one for PA function. Generally the center conductor of the cable would connect to one terminal of the speaker and the outer shield (braid) would connect to the other terminal. What is probably happening is one output (either the PA or ext. speaker) is at ground potential when that function is not enabled, so the other output's return path is through the former output center conductor instead of through latter output's cable shield. The way you have it wired is sort of unconventional, but if it sounds okay and hasn't blown up anything then I guess it's fine. ;D

Icom was right on with the noise filter. That's noise being generated by the charging circuit in the motor.

Hope this makes sense.

Philip

[Shakespeare]

Looking at this a little closer I believe hogtown's explanation makes the most sense. I looked at the documentation for the radio and now see that there are two separate wires; yellow for external speaker and blue for public address. For some reason I was thinking that all this was coming out of the same cable with paired speaker wires, overall shield and so forth... thus my generic reply to your question.

I need to be sent to the corner for that one. I'm not sure how your speakers are working without the shield connection but if they work, then they work. 006

Thanks to hogtown for clearing that up.

Mike C.

[hogtown_usa]

Mike, I cheated. 005 I read the manual BEFORE I posted a reply. nutkick

Philip ;D