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Isolation transformer

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  • Mike
    So i think i floated the question a few months ago and i dont see a response .... So ill ask again .... any one know of a stereo isolation transformer? or SMD
    Message 1 of 30 , Jun 26 10:25 PM
      So i think i floated the question a few months ago and i dont see a
      response ....
      So ill ask again ....

      any one know of a stereo isolation transformer? or SMD ?

      Mike KC7NOA

      --
      Mike KC7NOA
    • warrenallgyer
      Mike An eBay search turns up a number of discrete units of unknown quality and a pretty healthy price. For what it is worth, I used some broadcast quality
      Message 2 of 30 , Jun 27 2:27 AM
        Mike

        An eBay search turns up a number of discrete units of unknown quality and a pretty healthy price.

        For what it is worth, I used some broadcast quality 600:600 ohm transformers in my quest to eliminate ground loops and hum with only limited success. In the end I decided the benefit was not worth either the cost or the mess. Others may disagree.

        Warren Allgyer
        9V1TD
      • Alan
        Original Message ----- Subject: [softrock40] Re: Isolation transformer ... Mike, I agree with Warren. I think they need to be high quality to match phase and
        Message 3 of 30 , Jun 27 3:51 AM
          Original Message -----
          Subject: [softrock40] Re: Isolation transformer


          > > Warren said
          > An eBay search turns up a number of discrete units of unknown quality and a pretty healthy price.
          > For what it is worth, I used some broadcast quality 600:600 ohm transformers in my quest to eliminate ground loops and hum with
          > only limited success. In the end I decided the benefit was not worth either the cost or the mess. Others may disagree.
          >

          Mike,

          I agree with Warren.
          I think they need to be high quality to match phase and amplitude.
          I tried several pairs including ones similar to what Warren describes. I used DRM audio to test. In all cases decoding deteriorated
          when transformers were used.
          Also the hole in the middle was, in my opinion no better than the small amount of remaining noise after careful attention to ground
          paths.
          I guess for a RXTX two pairs would be required.

          73 Alan G4ZFQ
        • Zack Widup
          There s the one in this article, shown and mentioned starting on page 11: http://www.rfsystem.it/shop/download/SB_Creative_XFi_Pro_USB.pdf He gives a little
          Message 4 of 30 , Jun 27 7:08 AM
            There's the one in this article, shown and mentioned starting on page 11:

            http://www.rfsystem.it/shop/download/SB_Creative_XFi_Pro_USB.pdf

            He gives a little more detail on this page:

            http://www.rfsystem.it/shop/product_info.php?manufacturers_id=10&products_id=43

            The isolation transformer, a Triad SP-70, is sold by Digi-Key:

            http://www.digikey.com/product-search/en/transformers/audio-transformers/786564?k=sp-70

            So I rolled my own. Took me half an hour on some perf board. Note, you need two of them, one for each channel.

            73, Zack W9SZ


            On Fri, Jun 27, 2014 at 12:25 AM, Mike Patriot121@... [softrock40] <softrock40@yahoogroups.com> wrote:
             

            So i think i floated the question a few months ago and i dont see a
            response ....
            So ill ask again ....

            any one know of a stereo isolation transformer? or SMD ?

            Mike KC7NOA

            --
            Mike KC7NOA


          • Sid Boyce
            For detailed analysis of different isolation transformers http://www.cliftonlaboratories.com/softrock_lite_6_2.htm 73 ... Sid. ... -- Sid Boyce ... Hamradio
            Message 5 of 30 , Jun 27 8:01 AM
              For detailed analysis of different isolation transformers
              http://www.cliftonlaboratories.com/softrock_lite_6_2.htm
              73 ... Sid.

              On 27/06/14 10:27, allgyer@... [softrock40] wrote:
               

              Mike

              An eBay search turns up a number of discrete units of unknown quality and a pretty healthy price.

              For what it is worth, I used some broadcast quality 600:600 ohm transformers in my quest to eliminate ground loops and hum with only limited success. In the end I decided the benefit was not worth either the cost or the mess. Others may disagree.

              Warren Allgyer
              9V1TD



              -- 
              Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
              Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
              Senior Staff Specialist, Cricket Coach
              Microsoft Windows Free Zone - Linux used for all Computing Tasks
              
            • ve7vv
              Mike, the stereophile guys like Lundahl transformers for having great specs and supposedly great performance, but they are pricey, see K & K Audio - Lundahl
              Message 6 of 30 , Jun 27 4:52 PM
                Mike, the stereophile guys like Lundahl transformers for having great specs and supposedly great performance, but they are pricey, see
                K & K Audio - Lundahl Transformers for Tube audio: output, input, interstage, preamp, microphone and general purpose transformers. Some with Amorphous core or mu-metal cores.
                Some of these have spec sheets showing freq response to 100 kHz, which might mean they have relatively little phase change to 48 kHz.

                Not being in that $$ league, I used much less expensive Neutrik microphone transformers to transform balanced lines to unbalanced pre-amp inputs in my stereo system, with good results to my ears. 

                These are likely limited to 20 kHz freq response, and may have significant phase change at that freq.

                How they would work in SDR I/Q lines I would not know, but it would not cost a lot to try.

                http://www.neutrik.com/en/accessories/accessories/transformers/


                I am not sure what application you had in mind actually.


                For my digital transmit setup (non SDR) I have the PC soundcard output isolated from the transmitter mike input using a small (1 amp?) 12 volt filament transformer, PC to the 120 V side, transmitter to the 12 V side, as a step down and isolation transformer. For the 2.4 kHz bandwidth needed, this worked fine for me even though it is not an audio transformer.


              • cc_photo
                Wouldn t using optical isolation work for this? Would be much cheaper, and should be flat way out. Just 2 optical Tx chips, and 2 optical Rx chips. Roland, KB
                Message 7 of 30 , Jun 28 7:49 AM
                  Wouldn't using optical isolation work for this? Would be much cheaper, and should be flat way out. Just 2 optical Tx chips, and 2 optical Rx chips.

                  Roland, KB 8XI
                • Jean-Paul Louis
                  Roland, Isolation transformer is for analog signal while optical isolator is for digital signal. I/Q signals are analog, so you cannot use those here. Just my
                  Message 8 of 30 , Jun 28 8:25 AM
                    Roland,
                    Isolation transformer is for analog signal while optical isolator is for digital signal.
                    I/Q signals are analog, so you cannot use those here.

                    Just my $0.02,
                    Jean-Paul
                    AC9GH

                    On Jun 28, 2014, at 10:49 AM, kb8xi@... [softrock40] <softrock40@yahoogroups.com> wrote:

                    > Wouldn't using optical isolation work for this? Would be much cheaper, and should be flat way out. Just 2 optical Tx chips, and 2 optical Rx chips.
                    >
                    > Roland, KB 8XI
                    >
                    >
                  • yl2qn_andy
                    Hi, Absolutely agree with Warren. All my experiments with different transformers have no success. The results was from the same as without transformers to
                    Message 9 of 30 , Jun 28 3:42 PM
                      Hi,

                      Absolutely agree with Warren. All my experiments with different transformers have no success. The results was from "the same as without transformers" to "without transformers much better". 

                      Finally, I'm remove any transformers, remove USB sound card from box, mount it near Softrock PCB and connect audio by short good quality wires without any jacks (solder). No more any problems with ground loops, RX images and central peak on display.

                      Regards.
                      Andy - YL2QN
                    • warrenallgyer
                      Thanks Andy. I know many disagree but I consider expensive audio cards, expensive audio transformers, and high power PCs to be the monster cable of the
                      Message 10 of 30 , Jun 29 3:22 AM
                        Thanks Andy. I know many disagree but I consider expensive audio cards, expensive audio transformers, and high power PCs to be the "monster cable" of the Softrocks world. As I have said on a number of occasions, the best return for investment for Softrocks is antennas (because they are what really makes it work), whiskey (to savor the results of the Softrocks and the antennas) and flowers (to apologize to the wife for having so much fun with the Softrocks, antennas, and whiskey).

                        Warren Allgyer
                        9V1TD
                      • cc_photo
                        From Wiki .... A common type of opto-isolator consists of an LED and a phototransistor in the same opaque package. Other types of source-sensor combinations
                        Message 11 of 30 , Jun 29 7:05 AM
                          From Wiki ....

                          A common type of opto-isolator consists of an LED and a phototransistor in the same opaque package. Other types of source-sensor combinations include LED-photodiode, LED-LASCR, and lamp-photoresistor pairs. Usually opto-isolators transfer digital (on-off) signals, but some techniques allow them to be used with analog signals.

                          Photodiode opto-isolators can be used for interfacing analog signals, although their non-linearity invariably distorts the signal. A special class of analog opto-isolators introduced by Burr-Brown uses two photodiodes and an input-side operational amplifier to compensate for diode non-linearity. One of two identical diodes is wired into the feedback loop of the amplifier, which maintains overall current transfer ratio at a constant level regardless of the non-linearity in the second (output) diode.[38]

                          A novel idea of a particular optical analog signal isolator was submitted on 3, June 2011. The proposed configuration consist of two different parts. One of them transfers the signal, and the other establishes a negative feedback to ensure that the output signal has the same features as the input signal. This proposed analog isolator is linear over a wide range of input voltage and frequency.[39]

                          Roland
                        • Gordon JC Pearce
                          ... Wouldn t it be simpler just to convert the incoming analogue signal to a PWM signal, and then integrate it on the other side of the optoisolator? Why
                          Message 12 of 30 , Jun 29 7:14 AM
                            On Sun, Jun 29, 2014 at 07:05:31AM -0700, kb8xi@... [softrock40] wrote:
                            > From Wiki ....
                            >
                            > A novel idea of a particular optical analog signal isolator was submitted on 3, June 2011. The proposed configuration consist of two different parts. One of them transfers the signal, and the other establishes a negative feedback to ensure that the output signal has the same features as the input signal. This proposed analog isolator is linear over a wide range of input voltage and frequency.[39]

                            Wouldn't it be simpler just to convert the incoming analogue signal to a PWM signal, and then integrate it on the other side of the optoisolator?

                            Why bother, though? If you've earthed things correctly, it should never be an issue.

                            --
                            Gordonjcp MM0YEQ
                          • Mike
                            I agree .... but like some, im stuck with the antenna i have ... a MFJ1798 in a residential neighbourhood with a AM BC station less than a mile from me (line
                            Message 13 of 30 , Jun 29 7:31 AM
                              I agree .... but like some, im stuck with the antenna i have ... a MFJ1798 in a residential neighbourhood with a AM BC station less than a mile from me (line of sight too) ... im planning on building a mag loop of sorts to try out too. ( you can google earth me and see the AM BC too )

                              Iv given up on trying to Rf ground every thing ... any 1' wire is a friken antenna and my cheap soundcard picks up BC ... i want to see if isolation of the soundcard from the Rf front end helps with that issue --

                              Mike KC7NOA


                              On 06/29/2014 03:22 AM, allgyer@... [softrock40] wrote:
                               

                              Thanks Andy. I know many disagree but I consider expensive audio cards, expensive audio transformers, and high power PCs to be the "monster cable" of the Softrocks world. As I have said on a number of occasions, the best return for investment for Softrocks is antennas (because they are what really makes it work), whiskey (to savor the results of the Softrocks and the antennas) and flowers (to apologize to the wife for having so much fun with the Softrocks, antennas, and whiskey).

                              Warren Allgyer
                              9V1TD


                              -- 
                              Mike KC7NOA
                            • Alan
                              Original Message ----- Subject: Re: [softrock40] Re: Isolation transformer ... friken antenna and my cheap soundcard picks up BC ... i want to see if isolation
                              Message 14 of 30 , Jun 29 7:50 AM
                                Original Message -----
                                Subject: Re: [softrock40] Re: Isolation transformer


                                >Iv given up on trying to Rf ground every thing ... any 1' wire is a
                                friken antenna and my cheap soundcard picks up BC ... i want to see if
                                isolation of the soundcard from the Rf front end helps with that issue --

                                Mike,

                                I'm not sure that audio transformers will be much good at RF isolation. Powerline frequencies, yes.
                                All screening well bonded, chokes and capacitors are more likely to succeed.
                                But I don't envy you:)

                                73 Alan G4ZFQ
                              • warrenallgyer
                                I understand your issue now Mike and it makes sense to try almost anything. In this case you are simply looking for isolation. I picked up a pair of 600:600
                                Message 15 of 30 , Jun 29 7:56 AM
                                  I understand your issue now Mike and it makes sense to try almost anything.

                                  In this case you are simply looking for isolation. I picked up a pair of 600:600 ohm transformers on eBay for 5 dollars and they work just fine for this. I would not be too concerned about audiophile performance that costs the big bucks. We align phase and gain at a single point on the 48, 96, or 192 KHz bandpass anyway. Compensating for the transformer at a single point should add no further complication.

                                  The cheap transformers may not have the frequency response that the big boys have so your spectrum display may tail off a bit at the edges. But at the normal 10 KHz operating frequency almost any generic audio transformer would work just fine.

                                  I would go to Radio Shack and paw through the parts drawers to see what they have.

                                  I feel your pain. When I lived in Beijing I had a high power short wave transmitter within a mile of my apartment and I was getting about 2 milliwatts at 7.295 MHz coming in on my 40 meter dipole. Not fun!

                                  Warren Allgyer
                                  9V1TD
                                • Sid Boyce
                                  Hi Mike, It should be easy to knock up a magnetic loop even to test it out on RX. For TX you would need either a high voltage vacuum capacitor (preferred) or a
                                  Message 16 of 30 , Jun 29 8:24 AM
                                    Hi Mike,
                                    It should be easy to knock up a magnetic loop even to test it out on RX.

                                    For TX you would need either a high voltage vacuum capacitor (preferred) or a wide spaced split stator or butterfly capacitor due to the high voltages.

                                    I have been looking at my 13' diameter (hexagonal loop) for 160/80m today trying to figure out the best way of keeping it up as last time 60 MPH+ winds brought it down and smashed the vac. The replacement vac is much larger and heavier so I am contemplating mounting at the bottom of the loop this time.

                                    All my Stateside contacts on 80m were made with that loop and 100W.

                                    You may be able to null out or reduce the BC station quite a bit with a loop.

                                    The first loop I made was with 1m diameter 3/8" copper and a not so wide spaced single gang capacitor. With >7W it would arc over but with 7W I worked all over Europe on 40m with it indoors on the landing upstairs. I was also able to null out completely the power line noise from the pylons ~100 yards away.
                                    73 ... Sid.

                                    On 29/06/14 15:31, Mike Patriot121@... [softrock40] wrote:
                                     

                                    I agree .... but like some, im stuck with the antenna i have ... a MFJ1798 in a residential neighbourhood with a AM BC station less than a mile from me (line of sight too) ... im planning on building a mag loop of sorts to try out too. ( you can google earth me and see the AM BC too )

                                    Iv given up on trying to Rf ground every thing ... any 1' wire is a friken antenna and my cheap soundcard picks up BC ... i want to see if isolation of the soundcard from the Rf front end helps with that issue --

                                    Mike KC7NOA


                                    On 06/29/2014 03:22 AM, allgyer@... [softrock40] wrote:
                                     

                                    Thanks Andy. I know many disagree but I consider expensive audio cards, expensive audio transformers, and high power PCs to be the "monster cable" of the Softrocks world. As I have said on a number of occasions, the best return for investment for Softrocks is antennas (because they are what really makes it work), whiskey (to savor the results of the Softrocks and the antennas) and flowers (to apologize to the wife for having so much fun with the Softrocks, antennas, and whiskey).

                                    Warren Allgyer
                                    9V1TD


                                    -- 
                                    Mike KC7NOA


                                    -- 
                                    Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                    Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                    Senior Staff Specialist, Cricket Coach
                                    Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                    
                                  • Mike
                                    These guys have a yahoo group ... http://www.hlmagneticloopantennas.com/ and iv been talking with them about a 2 element 160M(up to hope 40M) that i might
                                    Message 17 of 30 , Jun 29 8:41 AM
                                      These guys have a yahoo group ...

                                      http://www.hlmagneticloopantennas.com/

                                      and iv been talking with them about a 2 element 160M(up to "hope" 40M) that i might try to build .... its more like a Bi-Quad in design with a cap in the bowtie spot.

                                      Iv got a Vac Cap that iv had for almost 20 years now and its never been hooked up ... im not evern sure how to hook up the limit switch its been so long.

                                      Mike KC7NOA


                                      On 06/29/2014 08:24 AM, Sid Boyce sboyce@... [softrock40] wrote:
                                       

                                      Hi Mike,
                                      It should be easy to knock up a magnetic loop even to test it out on RX.

                                      For TX you would need either a high voltage vacuum capacitor (preferred) or a wide spaced split stator or butterfly capacitor due to the high voltages.

                                      I have been looking at my 13' diameter (hexagonal loop) for 160/80m today trying to figure out the best way of keeping it up as last time 60 MPH+ winds brought it down and smashed the vac. The replacement vac is much larger and heavier so I am contemplating mounting at the bottom of the loop this time.

                                      All my Stateside contacts on 80m were made with that loop and 100W.

                                      You may be able to null out or reduce the BC station quite a bit with a loop.

                                      The first loop I made was with 1m diameter 3/8" copper and a not so wide spaced single gang capacitor. With >7W it would arc over but with 7W I worked all over Europe on 40m with it indoors on the landing upstairs. I was also able to null out completely the power line noise from the pylons ~100 yards away.
                                      73 ... Sid.

                                      On 29/06/14 15:31, Mike Patriot121@... [softrock40] wrote:
                                       

                                      I agree .... but like some, im stuck with the antenna i have ... a MFJ1798 in a residential neighbourhood with a AM BC station less than a mile from me (line of sight too) ... im planning on building a mag loop of sorts to try out too. ( you can google earth me and see the AM BC too )

                                      Iv given up on trying to Rf ground every thing ... any 1' wire is a friken antenna and my cheap soundcard picks up BC ... i want to see if isolation of the soundcard from the Rf front end helps with that issue --

                                      Mike KC7NOA


                                      On 06/29/2014 03:22 AM, allgyer@... [softrock40] wrote:
                                       

                                      Thanks Andy. I know many disagree but I consider expensive audio cards, expensive audio transformers, and high power PCs to be the "monster cable" of the Softrocks world. As I have said on a number of occasions, the best return for investment for Softrocks is antennas (because they are what really makes it work), whiskey (to savor the results of the Softrocks and the antennas) and flowers (to apologize to the wife for having so much fun with the Softrocks, antennas, and whiskey).

                                      Warren Allgyer
                                      9V1TD


                                      -- 
                                      Mike KC7NOA


                                      -- 
                                      Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                      Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                      Senior Staff Specialist, Cricket Coach
                                      Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                      

                                      -- 
                                      Mike KC7NOA
                                  • Mike
                                    Oh .. much better pic ... http://www.hlmagneticloopantennas.com/2elementloop/ Mike KC7NOA ... -- Mike KC7NOA Oh .. much better pic ...
                                    Message 18 of 30 , Jun 29 11:11 AM
                                      Oh .. much better pic ...

                                      http://www.hlmagneticloopantennas.com/2elementloop/

                                      Mike KC7NOA
                                      On 06/29/2014 08:41 AM, Mike Patriot121@... [softrock40] wrote:
                                       

                                      These guys have a yahoo group ...

                                      http://www.hlmagneticloopantennas.com/

                                      and iv been talking with them about a 2 element 160M(up to "hope" 40M) that i might try to build .... its more like a Bi-Quad in design with a cap in the bowtie spot.

                                      Iv got a Vac Cap that iv had for almost 20 years now and its never been hooked up ... im not evern sure how to hook up the limit switch its been so long.

                                      Mike KC7NOA


                                      On 06/29/2014 08:24 AM, Sid Boyce sboyce@... [softrock40] wrote:
                                       

                                      Hi Mike,
                                      It should be easy to knock up a magnetic loop even to test it out on RX.

                                      For TX you would need either a high voltage vacuum capacitor (preferred) or a wide spaced split stator or butterfly capacitor due to the high voltages.

                                      I have been looking at my 13' diameter (hexagonal loop) for 160/80m today trying to figure out the best way of keeping it up as last time 60 MPH+ winds brought it down and smashed the vac. The replacement vac is much larger and heavier so I am contemplating mounting at the bottom of the loop this time.

                                      All my Stateside contacts on 80m were made with that loop and 100W.

                                      You may be able to null out or reduce the BC station quite a bit with a loop.

                                      The first loop I made was with 1m diameter 3/8" copper and a not so wide spaced single gang capacitor. With >7W it would arc over but with 7W I worked all over Europe on 40m with it indoors on the landing upstairs. I was also able to null out completely the power line noise from the pylons ~100 yards away.
                                      73 ... Sid.

                                      On 29/06/14 15:31, Mike Patriot121@... [softrock40] wrote:
                                       

                                      I agree .... but like some, im stuck with the antenna i have ... a MFJ1798 in a residential neighbourhood with a AM BC station less than a mile from me (line of sight too) ... im planning on building a mag loop of sorts to try out too. ( you can google earth me and see the AM BC too )

                                      Iv given up on trying to Rf ground every thing ... any 1' wire is a friken antenna and my cheap soundcard picks up BC ... i want to see if isolation of the soundcard from the Rf front end helps with that issue --

                                      Mike KC7NOA


                                      On 06/29/2014 03:22 AM, allgyer@... [softrock40] wrote:
                                       

                                      Thanks Andy. I know many disagree but I consider expensive audio cards, expensive audio transformers, and high power PCs to be the "monster cable" of the Softrocks world. As I have said on a number of occasions, the best return for investment for Softrocks is antennas (because they are what really makes it work), whiskey (to savor the results of the Softrocks and the antennas) and flowers (to apologize to the wife for having so much fun with the Softrocks, antennas, and whiskey).

                                      Warren Allgyer
                                      9V1TD


                                      -- 
                                      Mike KC7NOA


                                      -- 
                                      Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                      Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                      Senior Staff Specialist, Cricket Coach
                                      Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                      

                                      -- 
                                      Mike KC7NOA

                                      -- 
                                      Mike KC7NOA
                                    • Gary Steinhour
                                      Not necessarily correct. Optical isolators can be used for analog signals and are a good choice for audio. See this link:
                                      Message 19 of 30 , Jun 29 11:23 AM
                                        Not necessarily correct. Optical isolators can be used for analog signals and are a good choice for audio.

                                        See this link:


                                        73,
                                        Gary KF6U


                                      • Sid Boyce
                                        Certainly way lighter than my 30mm hard copper though much higher inductance but in my book if it works, it works. I have seen some made of aluminium curtain
                                        Message 20 of 30 , Jun 29 12:45 PM
                                          Certainly way lighter than my 30mm hard copper though much higher inductance but in my book if it works, it works.

                                          I have seen some made of aluminium curtain track and of aluminium tubing.
                                          73 ... Sid.

                                          On 29/06/14 19:11, Mike Patriot121@... [softrock40] wrote:
                                           

                                          Oh .. much better pic ...

                                          http://www.hlmagneticloopantennas.com/2elementloop/

                                          Mike KC7NOA

                                          On 06/29/2014 08:41 AM, Mike Patriot121@... [softrock40] wrote:
                                           

                                          These guys have a yahoo group ...

                                          http://www.hlmagneticloopantennas.com/

                                          and iv been talking with them about a 2 element 160M(up to "hope" 40M) that i might try to build .... its more like a Bi-Quad in design with a cap in the bowtie spot.

                                          Iv got a Vac Cap that iv had for almost 20 years now and its never been hooked up ... im not evern sure how to hook up the limit switch its been so long.

                                          Mike KC7NOA


                                          On 06/29/2014 08:24 AM, Sid Boyce sboyce@... [softrock40] wrote:
                                           

                                          Hi Mike,
                                          It should be easy to knock up a magnetic loop even to test it out on RX.

                                          For TX you would need either a high voltage vacuum capacitor (preferred) or a wide spaced split stator or butterfly capacitor due to the high voltages.

                                          I have been looking at my 13' diameter (hexagonal loop) for 160/80m today trying to figure out the best way of keeping it up as last time 60 MPH+ winds brought it down and smashed the vac. The replacement vac is much larger and heavier so I am contemplating mounting at the bottom of the loop this time.

                                          All my Stateside contacts on 80m were made with that loop and 100W.

                                          You may be able to null out or reduce the BC station quite a bit with a loop.

                                          The first loop I made was with 1m diameter 3/8" copper and a not so wide spaced single gang capacitor. With >7W it would arc over but with 7W I worked all over Europe on 40m with it indoors on the landing upstairs. I was also able to null out completely the power line noise from the pylons ~100 yards away.
                                          73 ... Sid.

                                          On 29/06/14 15:31, Mike Patriot121@... [softrock40] wrote:
                                           

                                          I agree .... but like some, im stuck with the antenna i have ... a MFJ1798 in a residential neighbourhood with a AM BC station less than a mile from me (line of sight too) ... im planning on building a mag loop of sorts to try out too. ( you can google earth me and see the AM BC too )

                                          Iv given up on trying to Rf ground every thing ... any 1' wire is a friken antenna and my cheap soundcard picks up BC ... i want to see if isolation of the soundcard from the Rf front end helps with that issue --

                                          Mike KC7NOA


                                          On 06/29/2014 03:22 AM, allgyer@... [softrock40] wrote:
                                           

                                          Thanks Andy. I know many disagree but I consider expensive audio cards, expensive audio transformers, and high power PCs to be the "monster cable" of the Softrocks world. As I have said on a number of occasions, the best return for investment for Softrocks is antennas (because they are what really makes it work), whiskey (to savor the results of the Softrocks and the antennas) and flowers (to apologize to the wife for having so much fun with the Softrocks, antennas, and whiskey).

                                          Warren Allgyer
                                          9V1TD


                                          -- 
                                          Mike KC7NOA


                                          -- 
                                          Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                          Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                          Senior Staff Specialist, Cricket Coach
                                          Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                          

                                          -- 
                                          Mike KC7NOA

                                          -- 
                                          Mike KC7NOA


                                          -- 
                                          Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                          Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                          Senior Staff Specialist, Cricket Coach
                                          Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                          
                                        • MICHAEL TALLENT
                                          I just looked through this audio application and while it is interesting and similar to some things I have designed for video applications, none of the apps
                                          Message 21 of 30 , Jun 30 10:03 AM
                                            I just looked through this audio application and while it is interesting and similar to some things I have designed for video applications, none of the apps use the isolators for ground isolation which is what the original question was concerning.  I am not sure how you would put the opto-isolator in the audio signal path to isolate the grounds and still have the low noise- high dynamic range needed for a SDR receiver.
                                             
                                            Mike  W6MXV
                                             
                                            Sent: Sunday, June 29, 2014 2:23 PM
                                            Subject: [softrock40] Re: Isolation transformer
                                             


                                            Not necessarily correct. Optical isolators can be used for analog signals and are a good choice for audio.
                                             
                                            See this link:
                                             
                                             
                                            73,
                                            Gary KF6U
                                             
                                             
                                          • Gordon JC Pearce
                                            ... Earth loops are nature s way of saying FIX YOUR SHITTY WIRING! -- Gordonjcp MM0YEQ
                                            Message 22 of 30 , Jun 30 10:14 AM
                                              On Mon, Jun 30, 2014 at 01:03:00PM -0400, 'MICHAEL TALLENT' mwtallent@... [softrock40] wrote:
                                              > I just looked through this audio application and while it is interesting and similar to some things I have designed for video applications, none of the apps use the isolators for ground isolation which is what the original question was concerning. I am not sure how you would put the opto-isolator in the audio signal path to isolate the grounds and still have the low noise- high dynamic range needed for a SDR receiver.
                                              >
                                              > Mike W6MXV

                                              Earth loops are nature's way of saying "FIX YOUR SHITTY WIRING!"

                                              --
                                              Gordonjcp MM0YEQ
                                            • Mike
                                              Sure ... https://www.youtube.com/watch?feature=player_detailpage&v=r5K1VU8AAoM ... -- Mike KC7NOA
                                              Message 23 of 30 , Jun 30 10:19 AM
                                                Sure ...

                                                https://www.youtube.com/watch?feature=player_detailpage&v=r5K1VU8AAoM


                                                On 06/30/2014 10:14 AM, Gordon JC Pearce gordon@... [softrock40] wrote:
                                                 

                                                On Mon, Jun 30, 2014 at 01:03:00PM -0400, 'MICHAEL TALLENT' mwtallent@... [softrock40] wrote:
                                                > I just looked through this audio application and while it is interesting and similar to some things I have designed for video applications, none of the apps use the isolators for ground isolation which is what the original question was concerning. I am not sure how you would put the opto-isolator in the audio signal path to isolate the grounds and still have the low noise- high dynamic range needed for a SDR receiver.
                                                >
                                                > Mike W6MXV

                                                Earth loops are nature's way of saying "FIX YOUR SHITTY WIRING!"

                                                --
                                                Gordonjcp MM0YEQ


                                                -- 
                                                Mike KC7NOA
                                              • Jean-Paul Louis
                                                That is exactly why I do not use a commercial sound card in my SDR, the ADC is part of the radio front end, so what goes to the PC is just digital I/Q signal,
                                                Message 24 of 30 , Jun 30 10:25 AM
                                                  That is exactly why I do not use a commercial sound card in my SDR, the ADC is part of the radio front end, so what goes to the PC is just digital I/Q signal, much less prone to noise.
                                                  As I use an AK5394A for high dynamic range, I have 24it resolution and 192 kHz bandwidth. What goes to the PC is a much lower rate as I pre process the signal (frequency offset, filtering and decimation) in an FPGA.

                                                  my $0.02,

                                                  Jean-Paul
                                                  AC9GH



                                                  On Jun 30, 2014, at 1:14 PM, Gordon JC Pearce gordon@... [softrock40] <softrock40@yahoogroups.com> wrote:

                                                  > On Mon, Jun 30, 2014 at 01:03:00PM -0400, 'MICHAEL TALLENT' mwtallent@... [softrock40] wrote:
                                                  > > I just looked through this audio application and while it is interesting and similar to some things I have designed for video applications, none of the apps use the isolators for ground isolation which is what the original question was concerning. I am not sure how you would put the opto-isolator in the audio signal path to isolate the grounds and still have the low noise- high dynamic range needed for a SDR receiver.
                                                  > >
                                                  > > Mike W6MXV
                                                  >
                                                  > Earth loops are nature's way of saying "FIX YOUR SHITTY WIRING!"
                                                  >
                                                  > --
                                                  > Gordonjcp MM0YEQ
                                                  >
                                                  >
                                                  >
                                                • Gordon JC Pearce
                                                  ... Not sure how that relates to an earth loop. It certainly looks like shitty earthing, though. -- Gordonjcp MM0YEQ
                                                  Message 25 of 30 , Jun 30 10:32 AM
                                                    On Mon, Jun 30, 2014 at 10:19:19AM -0700, Mike Patriot121@... [softrock40] wrote:
                                                    > Sure ...
                                                    >
                                                    > https://www.youtube.com/watch?feature=player_detailpage&v=r5K1VU8AAoM

                                                    Not sure how that relates to an earth loop. It certainly looks like shitty earthing, though.

                                                    --
                                                    Gordonjcp MM0YEQ
                                                  • Paul Playford
                                                    During my working life I installed a closed circuit television security system at a nuclear power plant. The guard shack was about 100 feet (30 meters) from
                                                    Message 26 of 30 , Jun 30 10:57 AM
                                                      During my working life I installed a closed circuit television security system at a nuclear power plant.  The guard shack was about 100 feet (30 meters) from the generating building and the two were connected together with an 8” (20 cm) copper ground bar.
                                                       
                                                      We connected the outer shields of 26 Belden triax cables to ground at both ends, the inner shield to ground at the generator end, and we measured 8 vrms on a Simpson 260 volt ohm meter between the inner shield and ground on the guard shack end.
                                                       
                                                      This was not due to shitty earthing – ground loops are a fact of life and you have got to learn how to work with them.
                                                       
                                                      Paul, W8AEF
                                                       
                                                      Sent: Monday, June 30, 2014 10:32 AM
                                                      Subject: Re: [softrock40] Re: Isolation transformer
                                                       
                                                       

                                                      On Mon, Jun 30, 2014 at 10:19:19AM -0700, Mike Patriot121@... [softrock40] wrote:

                                                      > Sure ...
                                                      >
                                                      >
                                                      https://www.youtube.com/watch?feature=player_detailpage&v=r5K1VU8AAoM

                                                      Not sure how that relates to an earth loop. It certainly looks like shitty earthing, though.

                                                      --
                                                      Gordonjcp MM0YEQ

                                                    • Mike
                                                      I did that same test with a NLS-1(nonLinear systems portable scope) and the Atlas180 ... on a 12V Battery (both were on same battery ) ... same result. My
                                                      Message 27 of 30 , Jun 30 11:02 AM
                                                        I did that same test with a NLS-1(nonLinear systems portable scope) and the Atlas180 ... on a 12V Battery (both were on same battery ) ... same result.

                                                        My antenna has a 12' copper pipe as a ground rod ... it was sunk into the earth with water pressure -- you know, hook a water hose on one end and let it flow at full tilt ... bob the pipe up and down as it goes into the ground .... easy/peasy grounding.....

                                                        Only ground loop is in the air and the ground between me and the radio station ...

                                                        I think ill take a roof top pic of the AM BCS for show an tell this summer ..

                                                        Mike KC7NOA


                                                        On 06/30/2014 10:32 AM, Gordon JC Pearce gordon@... [softrock40] wrote:
                                                         

                                                        On Mon, Jun 30, 2014 at 10:19:19AM -0700, Mike Patriot121@... [softrock40] wrote:
                                                        > Sure ...
                                                        >
                                                        > https://www.youtube.com/watch?feature=player_detailpage&v=r5K1VU8AAoM

                                                        Not sure how that relates to an earth loop. It certainly looks like shitty earthing, though.

                                                        --
                                                        Gordonjcp MM0YEQ


                                                        -- 
                                                        Mike KC7NOA
                                                      • MICHAEL TALLENT
                                                        I don t have any ground loop problems! I was responding to answers given to someone else who asked how to solve ground loop problems. Someone suggested using
                                                        Message 28 of 30 , Jun 30 11:34 AM
                                                          I don't have any ground loop problems! I was responding to answers given to
                                                          someone else who asked how to solve ground loop problems. Someone suggested
                                                          using an opto-isolator instead of transformers.

                                                          I think there could be some real uses of a low noise wide dynamic range
                                                          analog audio "opto-isolator" so I was reading through all the replies that
                                                          stated that such a device existed but when reviewing the given answers I
                                                          have not found one yet, and from your helpful answer I guess you don't have
                                                          any answers either.

                                                          Mike W6MXV

                                                          -----Original Message-----
                                                          From: Gordon JC Pearce gordon@... [softrock40]
                                                          Sent: Monday, June 30, 2014 1:14 PM
                                                          To: 'MICHAEL TALLENT' mwtallent@... [softrock40]
                                                          Subject: Re: [softrock40] Re: Isolation transformer

                                                          On Mon, Jun 30, 2014 at 01:03:00PM -0400, 'MICHAEL TALLENT'
                                                          mwtallent@... [softrock40] wrote:
                                                          > I just looked through this audio application and while it is interesting
                                                          > and similar to some things I have designed for video applications, none of
                                                          > the apps use the isolators for ground isolation which is what the original
                                                          > question was concerning. I am not sure how you would put the
                                                          > opto-isolator in the audio signal path to isolate the grounds and still
                                                          > have the low noise- high dynamic range needed for a SDR receiver.
                                                          >
                                                          > Mike W6MXV

                                                          Earth loops are nature's way of saying "FIX YOUR SHITTY WIRING!"

                                                          --
                                                          Gordonjcp MM0YEQ



                                                          ------------------------------------
                                                          Posted by: Gordon JC Pearce <gordonjcp@...>
                                                          ------------------------------------


                                                          ------------------------------------

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                                                        • Gordon JC Pearce
                                                          ... I have *never* - in the shack or in the studio - encountered an earth loop. I have in vehicles, but they re a bit weird and special. -- Gordonjcp MM0YEQ
                                                          Message 29 of 30 , Jun 30 1:50 PM
                                                            On Mon, Jun 30, 2014 at 10:57:25AM -0700, 'Paul Playford' w8aef@... [softrock40] wrote:
                                                            >
                                                            > This was not due to shitty earthing – ground loops are a fact of life and you have got to learn how to work with them.
                                                            >

                                                            I have *never* - in the shack or in the studio - encountered an earth loop. I have in vehicles, but they're a bit weird and special.

                                                            --
                                                            Gordonjcp MM0YEQ
                                                          • vbifyz
                                                            Gordon, you are so lucky. I do electronic design for a living, and ground loops bit me many, many times. When signals are in microvolt range, ground loops are
                                                            Message 30 of 30 , Jul 1, 2014
                                                              Gordon, you are so lucky.
                                                              I do electronic design for a living, and ground loops bit me many, many times. When signals are in microvolt range, ground loops are very visible.

                                                              The guidelines for avoiding ground loops are fairly simple. The main one is to connect all grounds of the system parts to a single point. If this is not possible, then you have to resort to isolation. Then come actively driven shields, magnetic iron boxes and other exotic measures.

                                                              73, Mike
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