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  • #16
    Originally posted by MidwestCamper View Post
    I used a Tektronix Spectrum Analyzer when I was at Chrysler but its been so long I can no longer remember the model. Used AstroMed strip chart recorders back then too. Things have advanced but that old equipment was accurate then and now.

    What do you do for a living Gene?
    JIm,

    I was a technician, used to work on electronics comm gear in the Navy, then same at Shell, later electrical and instrumentation with them.
    Easy to refresh my leaky memory with some internet searching now days.
    Gene and Kim
    2015 Grand Design Reflection 317RST
    2017 RAM 3500 CC, LB, 4x2, 6.7L CTD

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    • #17
      Very cool Gene,

      This equipment also takes me back. We hope to get some measurements this coming week where I will post what we are measuring at the booster.

      Jim
      2017 Imagine 2600RB
      2015 GMC Sierra 4x4

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      • #18
        Originally posted by MidwestCamper View Post
        Looks like he has the background for sure. The TV issue from the fans is a big problem. Curious if folks have the same issue with the king antennas?
        Coincidentally, I noticed just 20 minutes ago that the bathroom fan disrupts signal from our replacement antenna, the Winegard Air 360 that GD is using on at least some of its trailers now.

        I had previously noticed that the same fan wiped out - didn't just disrupt, wiped out - most channels when we had the King Jack antenna on the roof.

        Looking forward to gbkims recommended final solution to this problem that he doesn't even have (and how come he doesn't?). (Thanks Gene!)
        Mark - 2018 Solitude 310GK - Ford F-350 SRW diesel short box - Pullrite Superglide hitch

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        • #19
          Pulled the booster out this evening where it has four wires connected. All white. Pulling fuses from the fuse panel shows the kitchen roof fan and range hood fan are on the same feed. The bathroom fan is on another. The booster is not connected to the same feed as the fans though would be connected to the input side of the power distribution panel. Planning to have the analyzer here this Wednesday.

          With all three fans on the TV is not viewable at all.

          Jim
          Attached Files
          Last edited by MidwestCamper; 10-05-2019, 11:40 AM.
          2017 Imagine 2600RB
          2015 GMC Sierra 4x4

          Comment


          • #20
            Gene,

            We looked at the signal coming from the battery charger and also when each fan was running. We took the measurement from the power distribution panel which also feeds the antenna booster. We then disconnected the AC power from the rig and measured only the fans. We also took measurements with the furnace running. Based on what we found so far, the noise from the 12V sources are at 100 kHz and below on my RV. Well below the frequencies the TV operates in. We fired up my friends old CRT system analyzer next where we were thinking the noise may be coming in from the RF side induced by the motor brushes which may be operating as a pseudo oscillator according to my friend. Unfortunately the old analyzer failed and we did not get the measurement. He is picking up his other HP analyzer from out of state where we hope to resume next week. Getting equipment from our employer is not easy so fortunately my co-worker has his own tools. Attached is what we had seen from the scope.
            Pic on the left is the battery charger. Pic on the right is AC power dropped and what we measured from the fans.

            Jim
            Attached Files
            Last edited by MidwestCamper; 10-05-2019, 11:42 AM.
            2017 Imagine 2600RB
            2015 GMC Sierra 4x4

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            • #21
              I ran some measurements at home with fan motors hooked up to a spare progressive converter.
              Used another o-scope 40 MHz bandwidth with FFT(1st time I've used) and did a bit of experimenting with a toroid ferrite core and a snap on ferrite core that I had in parts box.
              Both ferrite cores had an effect on the noise. Snap on is more compact and can snap on existing wire if there's a bit of slack.
              The noise signals are a bit hard to get a lock on.

              I suppose some of the noise signals from the motors are interfering with the television's RF front end and or tuner/mixer.

              Couple of things could try:
              Ferrite cores. +12V motor wires wrap 2 or 3 loops through the core.
              Coax connectors. Snap-n-seal. I had replaced some with snap-n-seal type when working in the underbelly & passthru basement.
              Last, a high pass filter at the television could be tried. 54 MHz high pass ones fit on the end of the coax.

              DC Brushless Motor without Ferrite core.




              DC Brushless Motor + LED light w/o Ferrite Core:


              DC Brushless Motor with snap on Ferrite core.



              Gene and Kim
              2015 Grand Design Reflection 317RST
              2017 RAM 3500 CC, LB, 4x2, 6.7L CTD

              Comment


              • #22
                Very nice Gene!

                The ferrite cores are interesting. I've used them on combustion system sensor cables which were transmitting static charges in pC. but I would not know what's involved in designing them. We were looking only at the antenna toward the end of our testing to find the center frequency with the fans on when the old Wavetek analyzer quit on us. HP analyzer should be here this week. I see your showing 25Mhz which still is low for TV RF but there may be higher frequencies on the AC component.
                Man this has been fun!

                Jim
                2017 Imagine 2600RB
                2015 GMC Sierra 4x4

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                • #23
                  The ferrite core I used was like these: Clip-on Ferrite Core Ring Bead
                  The above picts had the scope set to FFT, 25 MHz per division, and was trying to capture the fast rising noise, the scope was measuring about 100 MHz.
                  Since I don't have a signal generator to vet my o-scope against, I didn't want to push it up to 125 MHz / Div.
                  My Scopemeter 125 did show the same signal.

                  My o-scope is set to use Channel 2 which is Blue. FFT is Green in dB. Channel 1 not used, it shows in Red.
                  Measurements were for: Frequency, Peak-Peak Voltage (Rise Time and Period added today.)

                  Found how to put the screen cursors on the FFT dB level and saw a drop in the FFT signal from -29.80dB to -44.0dB when added the ferrite core.
                  Measurement Cursors X1 moved to lie at the 100 MHz mark and X2 moved to the next mark (25 MHz) to 125 MHz mark.

                  Ferrite Core:


                  Scope FFT readings for 100 MHz noise signal, with Measurement and FFT Menu
                  Without Ferrite Core:


                  With Ferrite Core



                  Yeah this has been fun for me. Got me to learn a bit more.
                  Gene and Kim
                  2015 Grand Design Reflection 317RST
                  2017 RAM 3500 CC, LB, 4x2, 6.7L CTD

                  Comment


                  • #24
                    Found how to put the screen cursors on the FFT dB level and saw a drop in the FFT signal from -29.80dB to -44.0dB when added the ferrite core.
                    Measurement Cursors X1 moved to lie at the 100 MHz mark and X2 moved to the next mark (25 MHz) to 125 MHz mark.

                    Gene,
                    This is a significant reduction. My friend is having an issue with the second unit where I am trying to source one from work. Man when it rains it pours. Can you unplug the coax from the TV and proble it there with the fans running and without the fans? Looking for the frequency generated by the fans at the TV.
                    Jim
                    2017 Imagine 2600RB
                    2015 GMC Sierra 4x4

                    Comment


                    • #25
                      Originally posted by MidwestCamper View Post

                      Gene,
                      This is a significant reduction. My friend is having an issue with the second unit where I am trying to source one from work. Man when it rains it pours. Can you unplug the coax from the TV and proble it there with the fans running and without the fans? Looking for the frequency generated by the fans at the TV.
                      Jim
                      Jim,
                      I can take a look and see what mine looks like. Probably I'll be at the rig later this week.
                      Gene and Kim
                      2015 Grand Design Reflection 317RST
                      2017 RAM 3500 CC, LB, 4x2, 6.7L CTD

                      Comment


                      • #26
                        I suspect a poor connection on the shield side of the coax somewhere. Giving signal DC level shifts rather than noise coupled into the signal.
                        Second guess is a booster problem, either power coupled noise or a shielding issue allowing noise to couple.

                        Receivers are usually pretty good at ignoring noise unless it messes with their AGC or gets amplified.

                        My troubleshooting process would start with getting another antenna and hooking the coax directly to the TV. Then move the feed point to the input of the booster. If the booster seems involved, I’d consider trying to see if you can power the booster independently from the RV as a test.

                        I spent a career chasing gremlins like that. I always started by trying to figure out what things aren’t causing the problem so I could focus on the things that might be causing it.

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                        • #27
                          Thanks Jkwilson,

                          We have been working to find the frequency that is making its way to the TV which we think is on the RF side. So we need to be looking at frequencies in the 54MHz and up to around 400+ MHz. Our signal analyzer is not functioning where a friend is looking into repairing it. We looked at the AC component on the DC side which was showing no higher than 100kHz on my rig where this would not mess with the TV.
                          Gene has also spent a good amount of time measuring the fans directly. The cheap TV in our rigs most likely do not have very good filtering.
                          Jim
                          2017 Imagine 2600RB
                          2015 GMC Sierra 4x4

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                          • #28
                            Originally posted by MidwestCamper View Post
                            Can you unplug the coax from the TV and probe it there with the fans running and without the fans? Looking for the frequency generated by the fans at the TV.
                            Jim
                            Jim,

                            I checked yesterday the coax cable center conductor where they feed into the television with my scopemeter.
                            Measured with the coax connected and unconnected to the televisions with all the fans(bathroom, hallway, living room, stove, frig brushless) On and Off.
                            The scopementer didn't see any measurable noise or frequency on the coax at the televisions from my rig's fans..
                            The television picture is not affected by my rig's fans. Clipping the scopementer's 10X probe onto the center conductor to a television would freeze the picture.

                            I could still see some small noise at a couple different frequency ranges at the fuse panel with the fans on. It's smaller amplitude than what I was measuring at home.


                            Gene and Kim
                            2015 Grand Design Reflection 317RST
                            2017 RAM 3500 CC, LB, 4x2, 6.7L CTD

                            Comment


                            • #29
                              Gene,

                              Good info and its interesting that your TV is not affected. My TV is destroyed when all three fans are on. Lol. My co-worker friend is working to fix his signal analyzer where I'm not sure how long this will take but right now we are at a stand still. I tried to borrow a unit from work where it is capable of up to 25gHz where its worth over 200K. Major overkill for what we need but none the less, that unit was not going to leave the building. Our goal on my rig is to identify the frequency response that may be on the RF side (we know the DC supply side is no issue on my rig) and to see what filtering would be most effective at the source....the three DC motors. Your measurements on the DC side of the panel may be similar to ours which was at 100kHz and lower.

                              I hope that we will be back in business soon and will share what we find.

                              Jim
                              Last edited by MidwestCamper; 10-14-2019, 03:25 PM.
                              2017 Imagine 2600RB
                              2015 GMC Sierra 4x4

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