Another question, this time about a clicking PA speaker.

[-Spazmatic-]

Sorry to keep bugging you guys, but I have yet another question.

When my truck is idling, if I listen closely (my truck is pretty loud, so it's not really noticable unless you've got good ears or you're listening for it) I can hear the PA speaker make a clicking noise (like when you push the mic to talk into it, the PA makes that "click" on noise) every so often when the truck switches idle speeds (like when you kick on the ac/heater, the vehicle's engine will usually speed up to keep up). Is this common? Why is it doing that? I'm a bit worried because it's only connected to the CB, so is something not right with my CB?


Note, this happens when the CB is off and while it is on.

 

[Moleculo]

It sounds to me like it might be fuel pump noise. That and ignition noise getting into the speaker / radio are pretty common problems. If it's not that loud, I wouldn't worry about it. If it's loud enough that it bothers you, there are a few things you can try and do to get rid of it. You mention that you get the noise even with the radio off. I would start with wrapping the speaker wire around a toroid choke a whole bunch of times. That might be all you need. If that doesn't work we can go from there...

 

[Hardhead]

Sounds like you need a DC line filter.

 

[-Spazmatic-]

I'm not talking of an external speaker or the internal speaker on the unit, I'm talking about a Public Address speaker, the ones you put under your hood and talk to innocent bystanders with.

If that's what you're talking about, then I need to know one thing...what's a toroid choke?

 

[Hardhead]

I forgotten what radio we are talking about, but.. if you have a talkback put in a certain way it will feed into the pa speaker as well.

 

[Moleculo]

That's from Radio Shack. Is the PA speaker under the hood? If it is, the noise probably isn't the fuel pump. But it definately is something mechanical. It's probably coming in through both the speaker wire AND mostly the power leads. You can use a DC line filter on the power leads (radio shack or auto parts stores have them) ,or you can wind a toroid like the picture and also put a .01 capacitor across the power leads at the PA speaker. The DC line filter is easiest, but you'll still probably have to put a toroid on the speaker leads.

 

[-Spazmatic-]

It doesn't bother me, it's just a small click, but I was just wondering if it would damage my CB or PA speaker. (Yes, it's under the hood, mounted on the firewall right next to the brake booster.

 

[bandaid kid]

Nah, it won't harm your radio or speaker. And since it doesn't bother your, don't worry about it.

73

 

[-Spazmatic-]

Thanks.

Just an off-topic question, what's "73" for?

 

[bandaid kid]

Thanks.

Just an off-topic question, what's "73" for?

It is "best regards." Used by both amateur radio operators and CBers. It's original with hams and CBers picked it up.

73

 

[bushwacker]

That's from Radio Shack. Is the PA speaker under the hood? If it is, the noise probably isn't the fuel pump. But it definately is something mechanical. It's probably coming in through both the speaker wire AND mostly the power leads.

I agree-- that little "snap choke" will do the trick (or helps)
In my neck of the woods Rat Shack doesn't sell them anymore-- but I picked up the last few they had-- great things to have around-- using a snap choke and maybey a cap or 2 across the incoming power line helps alot
Very nice picture you added in there above-- gives someone a real good idea of how to choke off the incoming power line

Sometimes the tick of a bad plug, spark plug wire, distributor or whatever is a pain-- can use a rf sniffer to find where the crap is coming from
I've heard of some real extreme measures to get rid of interfernce-- from running the power line from the battery through conduit to the radio--- to actually building a metal box around the distrubuter to sheild it
Your case isn't that extreme--I had the same problem-- snap choke helped-- Magnium makes a good filter too
Choke off all wires running through the engine compartment-- especially that PA speaker since that might be mounted under the hood-- choke it off close to the speaker
Torriods and snap chokes are cheap so I choke off everything running under the hood-- it might help you, it might not-- depends where the crap is coming from