PC 122: lousy noise blanker or need to recap/etc?

[dieseldriver]

Hokai, so.

All my radios' noise blankers manage to blank out engine noise. Except my PC 122. It even picks it up from nearby running reefer units. Switching between ANL and NB+ANL seems to make no difference at all.

Thoughts? Diesel engines, so this isn't ignition noise. Probably coming from the injectors.

Do I just need to recap it and/or check for bad joints? it is 30 some odd years old, after all.

 

[fourstringburn]

I noticed when induced noise from injectors is audible in the radio, you can hear that noise ramp up on acceleration. I hear a low end grumbling sound and it eventually disappears at highway cruising speed. These more sophisticated electronic fuel injection systems have been creating havoc for mobile radio's for years and it seems to be getting worse.

Try this to rule out your ANL circuits.

With your NB and ANL off you typically hear the wiper motor running. Try running your wipers and switch the ANL/NB on and off. If there is no attenuation, then you need the NB circuits looked at.

 

[Robb]

Just recapped a PC-122 last night, it was in my ' to do' pile for awhile. Doubtful recapping that radio would help with your problem.

Some noise is a broad banded freq and is a real transmitted signal, even tho we think of it as noise. If it is strong and close enough; there there is little that can be done about it. Best thing you can do is use a cap/choke just outside of the radio power feed in order to eliminate any noise that might come in thru the 13.8v DC power input.

 

[dieseldriver]

ANL works for sure...

Wiper motor doesn't inject any noise to speak of. Driver's window motor does... NB doesn't attenuate that at all so I can tell.

 

[Robb]

The electrical equipment (wipers, etc) in your rig have been capped with OEM bypass caps to remove self-noise. But if one fails on your rig or the rig closest to you; then that is when you will hear that garbage come thru to your radio.

 

[fourstringburn]

Interference noise just like ground loops can be tricky. Both usually require an elimination process.

Do you have a mobile in your personal vehicle or even try it in another drivers truck? At least it will rule out your radio picking up interference in your truck only.

It very well could be the radio with aging components.

Unless you do it yourself, a recap could cost more than the radio is worth unless it's worth hanging on to you. I would guess a CB shop would charge around $75 and shipping charges if you can't find someone in travels who will do it.

 

[dieseldriver]

Yeah, on stuff I own and don't intend to sell, I couldn't give a rat's patootie about what it is or isn't worth. My hobbies are not businesses and I don't approach them with a business sense. they are for my enjoyment and you can't put a price on that.

Anyway, the last time I used that radio, I was in Green Bay, which has a lot of high voltage transmission lines rubbing thru, presumably 345 or 500 KV. The noise from those may have been overwhelming the NB circuit, out in the rural areas today I could hardly hear any engine noise at all.

 

[sonoma]

I have 2 trc-453 , one trcc-465 and 2 pc122 radios. the only thing I ever had a problem with on all of them is a high power radio with in about 1/2 mile of me would kill my receive from overloading them. other wise they work just fine after a recap. these are all the same radios just different manufactuer.

 

[Onelasttime]

When trying to improve blanker you need to sub out resistors, diodes, caps and in some cases transistors. The problem is as far as I am aware their is no formula to follow for each model you have to just do it with trail and error. Same thing on the receive side if you have the time and parts on hand a sub box is handy you can radically improve the receive with cap and resistors sub's. It is very very individual from one radio to the next. You need a sinad meter, singnal generator and some time.

I have two TRC 453's and I have never had issues with NB and I am driving a 2003 Toyota Camry so all of it's electronics besides spark plugs are OEM orignal and old. So I would think the problem is in your car. You might need a better ground from the engine to chassis or from fuel rail/injector rail to ground. My 1986 4Runner had a tinny 12ga wire that went from the fuel rail or the intake manifold I can not recall which to the fire wall. If it came lose it would arc cause an iradic idle and produce a lot of rf noise. One -two turns of a 10mm wrench and it was good as gold again for another few years.

Find out what part it is under the hood making the noise and run a good ground and see if it helps. Just make sure you do not ground a + !

You can also try a cap and ferrite combo inline with your power wire.

 

[sonoma]

I would at least check the diodes in the L2 and L3 circuits. make sure the switch is actually working. it may slide up and down but may not be making connection. also you could have some bad solder joints in the RX area not letting it switch to anl or nb. those little radios are prone for bad solder joints. I have one I had to touch up about 1/2 of them to get the radio working after setting for 5 years.

here is the adjustments for RX on your radio. it is the same as a trc-453

http://www.cbtricks.com/radios/realistic/trc_453/trc453_rx-align.htm

 

[Tucker442]

I was going to say there is a pot in there just for the NB so get a wiring diagram from CB Tips and Tricks and go from there.