Need DC filter for CDM1250 - Suggestions

[Vercomm]

Hey Guys,

Here's the problem. I just did an install of a CDM1250 into a Cat 163H grader. I've done quite a few over the past 2 weeks and this is the first problem. It is a brand new grader and the beacon on top is 24volt .

When the beacon is off the radio works 100%, but with the beacon on the receive of the radio goes to hell and theirs a ton of noise. When I Tx other users can hear the noise of the beacons in the backround. I've moved the antenna all over but have determined that the beacons must be feeding some AC noise backinto the 24volt system, which the 24 > 12 volt converter is picking up.

The radio is powered directly from the output of the factory installed 24 > 12 volt converter.

I need some info on a good DC filter to isolate the AC noise that the beacons are creating. I don't want a cheap 5 dollar filter, I need something that is going to work very well.

What have you guys used in the past for such issues?

Thanks,

Jamie






Ok, I was a little lazy before I posted. I just did a search and found that motorola makes a decent in line filter, TLN5277E. Any thoughts on that, good or bad?

Thanks,

Jamie

[Jim202]

What noise are you trying to work around? If your talking
about a solid state strobe light, it's the switching power
supply noise from the strobe power pack. Yup, your going
to need a good in line filter for the radio feed.

Moving the antenna won't do you a bit of good. You could try
installing some bypass caps right at the strobe power feed
entry to the light. Ground the other side of the caps. Try
a value of .01 or .001 for a start. Kind of depends on the
radio and how bad the noise problem is.

Jim

Hey Guys,

Here's the problem. I just did an install of a CDM1250 into a Cat 163H grader. I've done quite a few over the past 2 weeks and this is the first problem. It is a brand new grader and the beacon on top is 24volt .

When the beacon is off the radio works 100%, but with the beacon on the receive of the radio goes to hell and theirs a ton of noise. When I Tx other users can hear the noise of the beacons in the backround. I've moved the antenna all over but have determined that the beacons must be feeding some AC noise backinto the 24volt system, which the 24 > 12 volt converter is picking up.

The radio is powered directly from the output of the factory installed 24 > 12 volt converter.

I need some info on a good DC filter to isolate the AC noise that the beacons are creating. I don't want a cheap 5 dollar filter, I need something that is going to work very well.

What have you guys used in the past for such issues?

Thanks,

Jamie






Ok, I was a little lazy before I posted. I just did a search and found that motorola makes a decent in line filter, TLN5277E. Any thoughts on that, good or bad?

Thanks,

Jamie

[n5tbu]

I have a lowband customer whose beacons created rf hash,try taking the ant coax off the radio.If it goes away it is RF,if it doesn't then maybe a filter will help.
mod

[jackhackett]

Since the noise is being transmitted too it's probably getting in on the power leads.

Your best bet would probably be to eliminate it at the source if possible. If they're self contained strobes capacitors on the power leads might help as Jim said. You could try one of those clip on ferrites as well.

You could try caps on the input and output of the 24-12 converter too. And then there are the inline filters, which are usually an inductor and capacitor, you just have to make sure the one you get will handle the current the radio draws. I haven't tried the Moto one, I've used some from Tessco though, probably about the same thing. Sometimes they help, sometimes they don't.

[ve3nsv]

If the light is a revolving style light with the dual sealed beams manufactured by Star warning systems they have RF filters available for them. We had a local PUC on VHF with the same problem and a quick call to the manufacturer cleared things up.

Of course they make you buy them though.

Even if it isn't made by Star I would give the manufacturer a call.

[Vercomm]

The lights are the revolving style made by grote. The other graders which run 12volt revolving beacons are ok, but this new one has 24volt beacons and it's a pain in the ass. I'm going to get a filter from Moto and see what happens. I'll post next week when the filter shows up and let you know what happens.

Jamie

[jackhackett]

Just remember, if you're going to put a filter on the 24 volt side make sure that it's rated for that voltage.