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RE: [stationpro] Hum problem on StationPro II

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  • Jim Garland
    Hi Andre, Sorry to hear of your hum pickup problem. It s hard to say explicitly where the hum is coming from, inasmuch as the StationPro and all your Icom gear
    Message 1 of 8 , Mar 21, 2013
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      Hi Andre,

      Sorry to hear of your hum pickup problem. It's hard to say explicitly where the hum is coming from, inasmuch as the StationPro and all your Icom gear run on DC only. Obviously you've got a ground loop somewhere, most likely a result of a grounding problem. Let me suggest you study the writeup on understanding and eliminating ground loops and hum with the StationPro at http://www.w8zr.net/stationpro/images/download%20files/Microphone%20Hum.pdf   That should give you a good idea of where to start looking. Fortunately, since you're hearing the hum on your headphoenes, as well as on the microphone line, it's likel to be coming from something pretty basic and not a subtle problem.

       

      If you haven't done so already, a couple of things to check:

      1. Try running your StationPro from the same 12V power supply that powers your Icom transceiver(s) and station accessories. Be suspicious of any Wall Warts in  your station, since they often have lots of ripple and, more significantly, have ungrounded (floating) outputs.

      2.  See if your main 12V power supply is grounded to its chassis at the negative output. If it is (Astrons usually are), then try to make that the only common ground for your station.

      3. Make sure you're not powering your station from different 120VAC lines, since you can get hum currents crossing between the different lines.

      4. Make sure the hum goes away when you plug a microphone or headphone directly into your transceiver. If it does, then the problem is definitely coming from something connected to the StationPro. Try unplugging cables from the back of the SP controller one at a time, to see if the hum goes away.

      5.Double-check the pod wiring (especially the mic wiring) for your transceivers. Icoms are a bit tricky, as I recall, because they usually supply +V (roughly 5V) on the MIC+ line. Be careful where you ground the MIc- line, if you don't keep it floating.

       

      Let us know how you fare with your experimenting.

      73,

      Jim W8ZR

       

      From: stationpro@yahoogroups.com [mailto:stationpro@yahoogroups.com] On Behalf Of dxer_dad
      Sent: Thursday, March 21, 2013 6:16 PM
      To: stationpro@yahoogroups.com
      Subject: [stationpro] Hum problem on StationPro II

       

       

      I recently completed installing my stationPro II and today for the first time had some time to play with it on SSB and I am experiencing a bad hum. It is first noticeable when plugging my headphones into the unit, and it is going through into my transmit audio too. I am using modern Icom equipment and a Heil headset with a Heil PR-781 on the second port of the Station Pro. I did some initial investigation:
      I tried a different DC power supply. Same problem. The hum does become louder when I move the DC power cable plugged into the StationPro but not much. Everything is grounded to a single ground bar and all DC equipment is connected to 2 Rig runners into a single power supply.

      Any suggestions / hints would be very much appreciated.

      73
      NJ0F

    • Andre VanWyk
      Hi Jim, Thanks for the response, and I did read your paper on the hum. I will follow your advice and start by unplugging one cable at a time from the Station
      Message 2 of 8 , Mar 21, 2013
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        Hi Jim,
         
        Thanks for the response, and I did read your paper on the hum. I will follow your advice and start by unplugging one cable at a time from the Station Pro to see where it comes from. All my equipment uses one single DC power supply.
        My 7700 runs from the same AC supply as the power supply power equipment.
         
        I will do some digging and post my findings.
         
        As a backup (yes I am paranoid at times)  I ordered one of these http://www.ebtechaudio.com/hedes.html in the event I cannot find the source as I plan to use my station Pro in the CQ WPX SSB contest and I have little time in between to find the source.
         
        73
        Andre NJ0F
         
         
         

        Sent: Thursday, March 21, 2013 8:45 PM
        Subject: RE: [stationpro] Hum problem on StationPro II

         

        Hi Andre,

        Sorry to hear of your hum pickup problem. It's hard to say explicitly where the hum is coming from, inasmuch as the StationPro and all your Icom gear run on DC only. Obviously you've got a ground loop somewhere, most likely a result of a grounding problem. Let me suggest you study the writeup on understanding and eliminating ground loops and hum with the StationPro at http://www.w8zr.net/stationpro/images/download%20files/Microphone%20Hum.pdf   That should give you a good idea of where to start looking. Fortunately, since you're hearing the hum on your headphoenes, as well as on the microphone line, it's likel to be coming from something pretty basic and not a subtle problem.

        If you haven't done so already, a couple of things to check:

        1. Try running your StationPro from the same 12V power supply that powers your Icom transceiver(s) and station accessories. Be suspicious of any Wall Warts in  your station, since they often have lots of ripple and, more significantly, have ungrounded (floating) outputs.

        2.  See if your main 12V power supply is grounded to its chassis at the negative output. If it is (Astrons usually are), then try to make that the only common ground for your station.

        3. Make sure you're not powering your station from different 120VAC lines, since you can get hum currents crossing between the different lines.

        4. Make sure the hum goes away when you plug a microphone or headphone directly into your transceiver. If it does, then the problem is definitely coming from something connected to the StationPro. Try unplugging cables from the back of the SP controller one at a time, to see if the hum goes away.

        5.Double-check the pod wiring (especially the mic wiring) for your transceivers. Icoms are a bit tricky, as I recall, because they usually supply +V (roughly 5V) on the MIC+ line. Be careful where you ground the MIc- line, if you don't keep it floating.

        Let us know how you fare with your experimenting.

        73,

        Jim W8ZR

        From: stationpro@yahoogroups.com [mailto:stationpro@yahoogroups.com] On Behalf Of dxer_dad
        Sent: Thursday, March 21, 2013 6:16 PM
        To: stationpro@yahoogroups.com
        Subject: [stationpro] Hum problem on StationPro II

         

        I recently completed installing my stationPro II and today for the first time had some time to play with it on SSB and I am experiencing a bad hum. It is first noticeable when plugging my headphones into the unit, and it is going through into my transmit audio too. I am using modern Icom equipment and a Heil headset with a Heil PR-781 on the second port of the Station Pro. I did some initial investigation:
        I tried a different DC power supply. Same problem. The hum does become louder when I move the DC power cable plugged into the StationPro but not much. Everything is grounded to a single ground bar and all DC equipment is connected to 2 Rig runners into a single power supply.

        Any suggestions / hints would be very much appreciated.

        73
        NJ0F

      • Paul Christensen
        ... Here s one potential solution. It s often used in cases of last resort when interconnecting unbalanced equipment. At the destination end of the cabIe, a
        Message 3 of 8 , Mar 22, 2013
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          > 5.Double-check the pod wiring (especially the mic wiring) for your
          transceivers. Icoms are a bit tricky, as I recall, because they usually supply +V (roughly 5V) on the MIC+ line. Be careful where you ground the MIc- line, if you don't keep it floating.
           
          Here's one potential solution.  It's often used in cases of last resort when interconnecting unbalanced equipment.  At the destination end of the cabIe, a coupling cap (typically 0.1 uf) is used from the audio shield to the ground connection or Mic (-) line.  You can try it both ways with the (-) floating or connected to the equipment ground point.  The idea is to break-up the ground loop caused by the simultaneous connection between the two shield ends of the audio cable and any other secondary ground pathway between equipment. 
           
          Again, this is a solution of last resort.   Well, maybe second to last (see below).  Probably the best solution is to seek out the root cause and try to manage it.  Don't be too concerned at first about the size of the coupling cap.  If you find that it reduces or eliminates hum/buzz, then you can optimize its value.  I can provide you with a simple formula that allows for a -3dB roll-off at say...100 Hz.  Increasing the cap size beyond the desired -3dB point only serves to increase the potential for low frequency hum.  For a mic circuit, there's no need to go below a 100Hz turnover point.
           
          I think someone mentioned a commercial audio isolation transformer.  That's the easy but expensive way to the solution.  However, adding an audio isolation transformer at the transceiver mic input does have the advantage that any RFI is almost sure to never become a problem.  The better audio transformers have extremely high common mode rejection ratios (CMRR).   But, if you have multiple rigs, adding a transformer for each can become very costly.  So, one can experiment by moving the transformer back to the SPII.  It's not ideal as the effect of transformer's CMRR is best realized near the input to the mic amp.  
           
          You may be tempted to use one of the blister-packed transformers sold by Radio Shack.  It may be worth trying one just to see if any improvement is possible.  But don't make it permanent.  These transformers are inexpensive but even when the secondary is terminated into its optimum load impedance, the transient response and resulting distortion products are horrible.  I once evaluated the two types of RS transformers with a square-wave generator set to 1 kHz.  The result is anything but a square wave on the output.  Yes, we don't speak in square waves but the square wave test is an excellent way to test the transient performance of an audio transformer.  It can be argued that in a bandwidth-limited system (e.g., 100 Hz - 3kHz), the transient response isn't too important.  I generally avoid those arguments.  By contrast, a Jensen audio transformer, even when improperly terminated will produce a near-perfect square wave.  But that performance comes at a very high cost -- about USD $80 per transformer.  If you get to the point of wanting to try a transformer, I recommend either Jensen and CineMag. These can be purchased with or without enclosures. 
           
          Paul, W9AC   
           
           
           
           
           
           
        • Andre VanWyk
          Paul, Thanks for the info. I sat messing with the unit this afternoon and found the bad apple. As soon as I unscrew my Heil PR-781 from the station pro, the
          Message 4 of 8 , Mar 22, 2013
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            Paul,
             
            Thanks for the info.
             
            I sat messing with the unit this afternoon and found the bad apple. As soon as I unscrew my Heil PR-781 from the station pro, the hum is gone. If I push the metal ring a little away form the unit, while still having the mic plugged in, the hum stays away.
            As soon as the metal part of the 8 pin mic plug touch the unit, the hum is back. I will open the plug tomorrow to investigate.
             
            73's
            Andre NJ0F

            Sent: Friday, March 22, 2013 11:33 AM
            Subject: Re: [stationpro] Hum problem on StationPro II

             

            > 5.Double-check the pod wiring (especially the mic wiring) for your
            transceivers. Icoms are a bit tricky, as I recall, because they usually supply +V (roughly 5V) on the MIC+ line. Be careful where you ground the MIc- line, if you don't keep it floating.
             
            Here's one potential solution.  It's often used in cases of last resort when interconnecting unbalanced equipment.  At the destination end of the cabIe, a coupling cap (typically 0.1 uf) is used from the audio shield to the ground connection or Mic (-) line.  You can try it both ways with the (-) floating or connected to the equipment ground point.  The idea is to break-up the ground loop caused by the simultaneous connection between the two shield ends of the audio cable and any other secondary ground pathway between equipment. 
             
            Again, this is a solution of last resort.   Well, maybe second to last (see below).  Probably the best solution is to seek out the root cause and try to manage it.  Don't be too concerned at first about the size of the coupling cap.  If you find that it reduces or eliminates hum/buzz, then you can optimize its value.  I can provide you with a simple formula that allows for a -3dB roll-off at say...100 Hz.  Increasing the cap size beyond the desired -3dB point only serves to increase the potential for low frequency hum.  For a mic circuit, there's no need to go below a 100Hz turnover point.
             
            I think someone mentioned a commercial audio isolation transformer.  That's the easy but expensive way to the solution.  However, adding an audio isolation transformer at the transceiver mic input does have the advantage that any RFI is almost sure to never become a problem.  The better audio transformers have extremely high common mode rejection ratios (CMRR).   But, if you have multiple rigs, adding a transformer for each can become very costly.  So, one can experiment by moving the transformer back to the SPII.  It's not ideal as the effect of transformer's CMRR is best realized near the input to the mic amp.  
             
            You may be tempted to use one of the blister-packed transformers sold by Radio Shack.  It may be worth trying one just to see if any improvement is possible.  But don't make it permanent.  These transformers are inexpensive but even when the secondary is terminated into its optimum load impedance, the transient response and resulting distortion products are horrible.  I once evaluated the two types of RS transformers with a square-wave generator set to 1 kHz.  The result is anything but a square wave on the output.  Yes, we don't speak in square waves but the square wave test is an excellent way to test the transient performance of an audio transformer.  It can be argued that in a bandwidth-limited system (e.g., 100 Hz - 3kHz), the transient response isn't too important.  I generally avoid those arguments.  By contrast, a Jensen audio transformer, even when improperly terminated will produce a near-perfect square wave.  But that performance comes at a very high cost -- about USD $80 per transformer.  If you get to the point of wanting to try a transformer, I recommend either Jensen and CineMag. These can be purchased with or without enclosures. 
             
            Paul, W9AC   
             
             
             
             
             
             

          • Paul Christensen
            Andre, I am interested in the wiring configuration between your PR781 XLR and the 8-pin plug. If you can, please report back with your PR781 wiring
            Message 5 of 8 , Mar 22, 2013
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              Andre,
               
              I am interested in the wiring configuration between your PR781 XLR and the 8-pin plug.  If you can, please report back with your PR781 wiring configuration that describes the number of mic cable conductors and the wiring connections between the XLR and 8-pin connector  -- as well as any common ties between the cable shield and any other conductor(s).  A quick hand-drawn diagram would be even better! 
               
              Paul, W9AC
               
              ----- Original Message -----
              Sent: Friday, March 22, 2013 9:11 PM
              Subject: Re: [stationpro] Hum problem on StationPro II

               

              Paul,
               
              Thanks for the info.
               
              I sat messing with the unit this afternoon and found the bad apple. As soon as I unscrew my Heil PR-781 from the station pro, the hum is gone. If I push the metal ring a little away form the unit, while still having the mic plugged in, the hum stays away.
              As soon as the metal part of the 8 pin mic plug touch the unit, the hum is back. I will open the plug tomorrow to investigate.
               
              73's
              Andre NJ0F

              Sent: Friday, March 22, 2013 11:33 AM
              Subject: Re: [stationpro] Hum problem on StationPro II

               

              > 5.Double-check the pod wiring (especially the mic wiring) for your transceivers. Icoms are a bit tricky, as I recall, because they usually supply +V (roughly 5V) on the MIC+ line. Be careful where you ground the MIc- line, if you don't keep it floating.
               
              Here's one potential solution.  It's often used in cases of last resort when interconnecting unbalanced equipment.  At the destination end of the cabIe, a coupling cap (typically 0.1 uf) is used from the audio shield to the ground connection or Mic (-) line.  You can try it both ways with the (-) floating or connected to the equipment ground point.  The idea is to break-up the ground loop caused by the simultaneous connection between the two shield ends of the audio cable and any other secondary ground pathway between equipment. 
               
              Again, this is a solution of last resort.   Well, maybe second to last (see below).  Probably the best solution is to seek out the root cause and try to manage it.  Don't be too concerned at first about the size of the coupling cap.  If you find that it reduces or eliminates hum/buzz, then you can optimize its value.  I can provide you with a simple formula that allows for a -3dB roll-off at say...100 Hz.  Increasing the cap size beyond the desired -3dB point only serves to increase the potential for low frequency hum.  For a mic circuit, there's no need to go below a 100Hz turnover point.
               
              I think someone mentioned a commercial audio isolation transformer.  That's the easy but expensive way to the solution.  However, adding an audio isolation transformer at the transceiver mic input does have the advantage that any RFI is almost sure to never become a problem.  The better audio transformers have extremely high common mode rejection ratios (CMRR).   But, if you have multiple rigs, adding a transformer for each can become very costly.  So, one can experiment by moving the transformer back to the SPII.  It's not ideal as the effect of transformer's CMRR is best realized near the input to the mic amp.  
               
              You may be tempted to use one of the blister-packed transformers sold by Radio Shack.  It may be worth trying one just to see if any improvement is possible.  But don't make it permanent.  These transformers are inexpensive but even when the secondary is terminated into its optimum load impedance, the transient response and resulting distortion products are horrible.  I once evaluated the two types of RS transformers with a square-wave generator set to 1 kHz.  The result is anything but a square wave on the output.  Yes, we don't speak in square waves but the square wave test is an excellent way to test the transient performance of an audio transformer.  It can be argued that in a bandwidth-limited system (e.g., 100 Hz - 3kHz), the transient response isn't too important.  I generally avoid those arguments.  By contrast, a Jensen audio transformer, even when improperly terminated will produce a near-perfect square wave.  But that performance comes at a very high cost -- about USD $80 per transformer.  If you get to the point of wanting to try a transformer, I recommend either Jensen and CineMag. These can be purchased with or without enclosures. 
               
              Paul, W9AC   
               
               
               
               
               
               

            • Andre VanWyk
              Paul, I will open it up and get back with my findings. The XLR going into the PR781 is a 3 pin so there is bound to be common ties. This is a standard Heil
              Message 6 of 8 , Mar 23, 2013
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                Paul,
                I will open it up and get back with my findings.
                The XLR going into the PR781 is a 3 pin so there is bound to be common ties. This is a standard Heil cable.
                73
                NJ0F

                Sent from my iPhone

                On Mar 22, 2013, at 8:58 PM, "Paul Christensen" <w9ac@...> wrote:

                 

                Andre,
                 
                I am interested in the wiring configuration between your PR781 XLR and the 8-pin plug.  If you can, please report back with your PR781 wiring configuration that describes the number of mic cable conductors and the wiring connections between the XLR and 8-pin connector  -- as well as any common ties between the cable shield and any other conductor(s).  A quick hand-drawn diagram would be even better! 
                 
                Paul, W9AC
                 
                ----- Original Message -----
                Sent: Friday, March 22, 2013 9:11 PM
                Subject: Re: [stationpro] Hum problem on StationPro II

                 

                Paul,
                 
                Thanks for the info.
                 
                I sat messing with the unit this afternoon and found the bad apple. As soon as I unscrew my Heil PR-781 from the station pro, the hum is gone. If I push the metal ring a little away form the unit, while still having the mic plugged in, the hum stays away.
                As soon as the metal part of the 8 pin mic plug touch the unit, the hum is back. I will open the plug tomorrow to investigate.
                 
                73's
                Andre NJ0F

                Sent: Friday, March 22, 2013 11:33 AM
                Subject: Re: [stationpro] Hum problem on StationPro II

                 

                > 5.Double-check the pod wiring (especially the mic wiring) for your transceivers. Icoms are a bit tricky, as I recall, because they usually supply +V (roughly 5V) on the MIC+ line. Be careful where you ground the MIc- line, if you don't keep it floating.
                 
                Here's one potential solution.  It's often used in cases of last resort when interconnecting unbalanced equipment.  At the destination end of the cabIe, a coupling cap (typically 0.1 uf) is used from the audio shield to the ground connection or Mic (-) line.  You can try it both ways with the (-) floating or connected to the equipment ground point.  The idea is to break-up the ground loop caused by the simultaneous connection between the two shield ends of the audio cable and any other secondary ground pathway between equipment. 
                 
                Again, this is a solution of last resort.   Well, maybe second to last (see below).  Probably the best solution is to seek out the root cause and try to manage it.  Don't be too concerned at first about the size of the coupling cap.  If you find that it reduces or eliminates hum/buzz, then you can optimize its value.  I can provide you with a simple formula that allows for a -3dB roll-off at say...100 Hz.  Increasing the cap size beyond the desired -3dB point only serves to increase the potential for low frequency hum.  For a mic circuit, there's no need to go below a 100Hz turnover point.
                 
                I think someone mentioned a commercial audio isolation transformer.  That's the easy but expensive way to the solution.  However, adding an audio isolation transformer at the transceiver mic input does have the advantage that any RFI is almost sure to never become a problem.  The better audio transformers have extremely high common mode rejection ratios (CMRR).   But, if you have multiple rigs, adding a transformer for each can become very costly.  So, one can experiment by moving the transformer back to the SPII.  It's not ideal as the effect of transformer's CMRR is best realized near the input to the mic amp.  
                 
                You may be tempted to use one of the blister-packed transformers sold by Radio Shack.  It may be worth trying one just to see if any improvement is possible.  But don't make it permanent.  These transformers are inexpensive but even when the secondary is terminated into its optimum load impedance, the transient response and resulting distortion products are horrible.  I once evaluated the two types of RS transformers with a square-wave generator set to 1 kHz.  The result is anything but a square wave on the output.  Yes, we don't speak in square waves but the square wave test is an excellent way to test the transient performance of an audio transformer.  It can be argued that in a bandwidth-limited system (e.g., 100 Hz - 3kHz), the transient response isn't too important.  I generally avoid those arguments.  By contrast, a Jensen audio transformer, even when improperly terminated will produce a near-perfect square wave.  But that performance comes at a very high cost -- about USD $80 per transformer.  If you get to the point of wanting to try a transformer, I recommend either Jensen and CineMag. These can be purchased with or without enclosures. 
                 
                Paul, W9AC   
                 
                 
                 
                 
                 
                 

              • jsternmd@att.net
                I am probably way off base here but I wonder if it has something to do with the Heil mics DC blocking cap to remove the IOCM phantom mic power provided on all
                Message 7 of 8 , Mar 23, 2013
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                  I am probably way off base here but I wonder if it has something to do with the Heil mics DC blocking cap to remove the IOCM phantom mic power provided on all modern ICOM radios? I also would be interested knowing how you are wiring the mic to the SPII.

                  73 Jerry
                  K1JOS
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