Sirius causing static on CB?

Discussion in 'CB Radio Forum' started by nj diesel, Jan 15, 2013.

  1. nj diesel

    nj diesel Bobtail Member

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    Apr 22, 2012
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    For over a year now my co-workers have been telling me they hear static underneath when I'm talking on my CB. I'm running a Uniden 78 with a fiberglass antenna, just put brand new coax in place, cleaned all connections and still have a SWR of 1.3-1.6. Receive sensitivity is good, grounds are solid and power output is good. I'm also running a Sirius Starmate 5 in a vehicle docking station station. I just noticed that when I have the CB on with the squelch low and I turn on the Sirius radio I get what I call "hash" on the CB and have to raise the squelch slighly to stop it. So, I'm thinking the FM transmitter for the Sirius is generating an RF field into the CB, which may be coming across the mic as low level static. My mic gain is down to about a 3 out of 10 here. I just ordered an Astatic 636L noise cancelling mic to try also. Any thoughts or similar experiences?
     
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  3. EZ Money

    EZ Money Road Train Member

    I have the Starmate 5 and have never noticed a change in the CB.
    The FM transmitter on mine is turned off though because i use the direct input with the mini plug on the face of the stereo.

    Is the Sirius run off the same power connection as the CB? That could affect it.
     
  4. mike5511

    mike5511 Road Train Member

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    I've noticed the noise level change (go up) when I plug my old XM radio in, even before I power it up! I figured it was just bad grounds in the electric system. I've never had time to chase the problem.
     
  5. nj diesel

    nj diesel Bobtail Member

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    Apr 22, 2012
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    No it's a Mack tri-axle so I use the two barrel connectors on the dash for the CB and the cigarette lighter plug for the Sirius. I thought about the direct antenna plug for the Sirius as I use these in my POV's but don't want to go through all this for a company truck.

     
  6. EZ Money

    EZ Money Road Train Member

    Interesting. I wonder if a 12 volt noise filter on the CB power cord would help?
    You would not think the low power FM signal from the Starmate would be picked up by the CB.....Strange!

    I will turn the FM transmitter to on and see if mine does it too.
     
  7. windsmith

    windsmith Road Train Member

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    All modern electronic devices create RF 'noise' when they're operating. Most often the culprit is the power adapter, but sometimes the device itself creates some interference as well. Most 12V power adapters use what's called 'switching' technology to convert 12V to a voltage that's required by the device - usually 5V. The shape of this switching waveform is perfect for creating high frequency harmonics that are radiated from the adapter case and cable and received by the CB IF circuits. Most are shielded, but some RF will still leak through. Most of this interference is picked up by the internal IF circuits of the CB, not through the antenna. You should find that physically moving the adapters and cables away from the CB will greatly reduce the amount of hash that you're hearing. You could also try bonding the metal chassis and case of the CB to ground to see if that helps any.
     
    EZ Money Thanks this.
  8. BossOutlaw88

    BossOutlaw88 Road Train Member

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    I had that same problem until I got the "stuffing" out of my co-axial wire of my CB. That simply means that if you have your antenna co-axial wire neatly tied together with a zip tie, you're "stuffing" your signal. Just put the excess wire in the passenger area or anywhere out of your way. Problem solved.

    Sent from waterproof phone using Tapatalk 2 Blue
     
  9. MsJamie

    MsJamie Road Train Member

    I bought one of those FM transmitter units for my old iPhone, so I could listen to music on a cross-country trip. It worked well, but you HAD to unplug it (couldn't even charge the phone) if you wanted to listen to AM.
     
  10. cadillacdude1975

    cadillacdude1975 Road Train Member

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    welcome to the world of EMI (electro-magnetic interference)
     
  11. Gambi80

    Gambi80 Medium Load Member

    I had that problem in my old truck (Mack CH) when I had the CB on the dash and XM mounted above to the windshield..........then I moved it down below on the dash, below the CB and the noise quit. Not sure how or why that affected it, but it was no longer a problem.
     
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