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Re: [softrock40] Mini-Circuits

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  • Leon Heller
    ... I buy what I need direct from MCL UK. On one or two occasions I ve bought 50 pieces, and sold the excess to fellow hams, to get the cost down. I didn t
    Message 1 of 19 , Oct 12, 2012
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      On 12/10/2012 04:14, electricham@... wrote:
      > All,
      >
      > I hope this is not too off topic, but I was hoping to get an idea on
      > where you guys get your Minicircuits parts? Sometimes they offer the
      > part I need but only in larger quantities. Clearly, this is a problem!
      > :-) I have seen many kits out there with these parts, so I know I'm not
      > the only one off Guy out there.

      I buy what I need direct from MCL UK. On one or two occasions I've
      bought 50 pieces, and sold the excess to fellow hams, to get the cost
      down. I didn't have any problems getting rid of them.

      73, Leon
      --
      Leon Heller
      G1HSM
    • electricham@rocketmail.com
      Leon, Thanks loads for the feedback! I was wondering about a bulk order and then selling what I didn t need. Do you have a recommendation on where to try to
      Message 2 of 19 , Oct 12, 2012
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        Leon,

        Thanks loads for the feedback! I was wondering about a bulk order and then selling what I didn't need. Do you have a recommendation on where to try to get interest in a batch order from other HAM's or do you just talk to the HAM's you know personally?

        Thanks!
        73


        --- In softrock40@yahoogroups.com, Leon Heller <leon355@...> wrote:
        >
        > On 12/10/2012 04:14, electricham@... wrote:
        > > All,
        > >
        > > I hope this is not too off topic, but I was hoping to get an idea on
        > > where you guys get your Minicircuits parts? Sometimes they offer the
        > > part I need but only in larger quantities. Clearly, this is a problem!
        > > :-) I have seen many kits out there with these parts, so I know I'm not
        > > the only one off Guy out there.
        >
        > I buy what I need direct from MCL UK. On one or two occasions I've
        > bought 50 pieces, and sold the excess to fellow hams, to get the cost
        > down. I didn't have any problems getting rid of them.
        >
        > 73, Leon
        > --
        > Leon Heller
        > G1HSM
        >
      • Zack Widup
        Mini-Circuits will sell small quantities of parts. I have bought 3 or 4 mixers at a time from them. I do believe they give you a price break on larger
        Message 3 of 19 , Oct 12, 2012
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          Mini-Circuits will sell small quantities of parts. I have bought 3 or
          4 mixers at a time from them. I do believe they give you a price break
          on larger quantities. In fact, I think 10 of one of the ADE series
          mixer that I bought turned out to be cheaper than buying only four!

          73, Zack W9SZ

          On 10/11/12, electricham@... <chr1s.wynk00p@...> wrote:
          > All,
          >
          > I hope this is not too off topic, but I was hoping to get an idea on where
          > you guys get your Minicircuits parts? Sometimes they offer the part I need
          > but only in larger quantities. Clearly, this is a problem! :-) I have
          > seen many kits out there with these parts, so I know I'm not the only one
          > off Guy out there.
          >
          > Thanks!
          >
          > 73
          >
          >
          >
          >
        • Leon Heller
          ... I think I mentioned the offer on the QRP-L and GQRP lists, and got rid of most of them that way. I sold the remainder on Ebay. 73, Leon -- Leon Heller
          Message 4 of 19 , Oct 12, 2012
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            On 12/10/2012 13:55, electricham@... wrote:
            > Leon,
            >
            > Thanks loads for the feedback! I was wondering about a bulk order and
            > then selling what I didn't need. Do you have a recommendation on where
            > to try to get interest in a batch order from other HAM's or do you just
            > talk to the HAM's you know personally?

            I think I mentioned the offer on the QRP-L and GQRP lists, and got rid
            of most of them that way. I sold the remainder on Ebay.

            73, Leon
            --
            Leon Heller
            G1HSM
          • Dave
            Leon: You could try this group or other Yahoo groups such as UHFSDR, ARRLHBC. Dave -WB6DHW
            Message 5 of 19 , Oct 12, 2012
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              Leon:
                You could try this group or other Yahoo groups such as UHFSDR, ARRLHBC.

              Dave -WB6DHW
              <http://wb6dhw.com>

              On 10/12/2012 5:55 AM, electricham@... wrote:
               

              Leon,

              Thanks loads for the feedback! I was wondering about a bulk order and then selling what I didn't need. Do you have a recommendation on where to try to get interest in a batch order from other HAM's or do you just talk to the HAM's you know personally?

              Thanks!
              73

              --- In softrock40@yahoogroups.com, Leon Heller <leon355@...> wrote:
              >
              > On 12/10/2012 04:14, electricham@... wrote:
              > > All,
              > >
              > > I hope this is not too off topic, but I was hoping to get an idea on
              > > where you guys get your Minicircuits parts? Sometimes they offer the
              > > part I need but only in larger quantities. Clearly, this is a problem!
              > > :-) I have seen many kits out there with these parts, so I know I'm not
              > > the only one off Guy out there.
              >
              > I buy what I need direct from MCL UK. On one or two occasions I've
              > bought 50 pieces, and sold the excess to fellow hams, to get the cost
              > down. I didn't have any problems getting rid of them.
              >
              > 73, Leon
              > --
              > Leon Heller
              > G1HSM
              >


            • John
              I was reading one of DG8SAQ s pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance to the RX mixer. On the same
              Message 6 of 19 , Oct 14, 2012
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                I was reading one of DG8SAQ's pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance to the RX mixer.
                On the same page he mentions replacing the two 10 Ohm resistors on the mixer inputs with shorting links.
                 
                I have just tried this with the folowing result:
                 
                With the two 10 Ohm resistors:
                 
                Frequency 1.977 MHz
                With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -110 dB 
                 
                 
                Without the two 10 Ohm resisors:
                 
                Frequency 1.977 MHz
                With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -104 dB
                 
                This appears to have improved signal + noise / noise ratio by 6 dB
                 
                Has anyone else tried this?
                 
                John G3UGY
              • David Turnbull
                Hi John, Don t forget that changing these resistor values will alter the filter response. 73 David AE9RB http://AE9RB.com/
                Message 7 of 19 , Oct 14, 2012
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                  Hi John,

                  Don't forget that changing these resistor values will alter the filter response.

                  73 David AE9RB
                  http://AE9RB.com/

                  On Sun, Oct 14, 2012 at 10:01 AM, John <v321uk@...> wrote:
                  I was reading one of DG8SAQ's pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance to the RX mixer.
                  On the same page he mentions replacing the two 10 Ohm resistors on the mixer inputs with shorting links.

                • Alan
                  ... Subject: [softrock40] RXTX v6.3 improved signal to noise John, I m no expert but what is the noise you see on HDSDR? I suspect it is op-amp noise.
                  Message 8 of 19 , Oct 14, 2012
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                    ----- Original Message -----
                    Subject: [softrock40] RXTX v6.3 improved signal to noise

                    John,

                    I'm no expert but what is the noise you see on HDSDR?
                    I suspect it is op-amp noise.
                    Certainly on lower frequencies antenna noise overcomes this.
                    Removing the 10Rs will increase the front end gain without altering the op-amp noise.
                    Seems to me that you are measuring the wrong SNR?

                    73 Alan G4ZFQ




                    >I was reading one of DG8SAQ's pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance
                    >to the RX mixer.
                    On the same page he mentions replacing the two 10 Ohm resistors on the mixer inputs with shorting links.

                    I have just tried this with the folowing result:

                    With the two 10 Ohm resistors:

                    Frequency 1.977 MHz
                    With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                    With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -110 dB


                    Without the two 10 Ohm resisors:

                    Frequency 1.977 MHz
                    With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                    With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -104 dB

                    This appears to have improved signal + noise / noise ratio by 6 dB
                  • John
                    Alan, Those 10 ohm resistors before the mixer are dropping precious nanovolts of wanted signal. Worsening signal to noise ratio. John G3UGY From: Alan Sent:
                    Message 9 of 19 , Oct 15, 2012
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                      Alan,
                       
                      Those 10 ohm resistors before the mixer are dropping precious nanovolts of wanted signal. Worsening signal to noise ratio.
                       
                      John G3UGY
                       

                      From: Alan
                      Sent: Sunday, October 14, 2012 7:23 PM
                      Subject: Re: [softrock40] RXTX v6.3 improved signal to noise

                       


                      ----- Original Message -----
                      Subject: [softrock40] RXTX v6.3 improved signal to noise

                      John,

                      I'm no expert but what is the noise you see on HDSDR?
                      I suspect it is op-amp noise.
                      Certainly on lower frequencies antenna noise overcomes this.
                      Removing the 10Rs will increase the front end gain without altering the op-amp noise.
                      Seems to me that you are measuring the wrong SNR?

                      73 Alan G4ZFQ

                      >I was reading one of DG8SAQ's pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance
                      >to the RX mixer.
                      On the same page he mentions replacing the two 10 Ohm resistors on the mixer inputs with shorting links.

                      I have just tried this with the folowing result:

                      With the two 10 Ohm resistors:

                      Frequency 1.977 MHz
                      With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                      With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -110 dB

                      Without the two 10 Ohm resisors:

                      Frequency 1.977 MHz
                      With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                      With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -104 dB

                      This appears to have improved signal + noise / noise ratio by 6 dB

                    • John
                      Hi David, The stock band pass filters are broad. The response on the spectrum analyzer and tracking generator looks the same shape as with the
                      Message 10 of 19 , Oct 15, 2012
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                        Hi David,
                         
                        The stock band pass filters are <extremely> broad.
                        The response on the spectrum analyzer and tracking generator looks the same shape as with the resistors.
                         
                        John G3UGY
                         

                        Sent: Sunday, October 14, 2012 7:12 PM
                        Subject: Re: [softrock40] RXTX v6.3 improved signal to noise

                         

                        Hi John,


                        Don't forget that changing these resistor values will alter the filter response.

                        73 David AE9RB
                        http://AE9RB.com/

                        On Sun, Oct 14, 2012 at 10:01 AM, John <v321uk@...> wrote:
                        I was reading one of DG8SAQ's pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance to the RX mixer.
                        On the same page he mentions replacing the two 10 Ohm resistors on the mixer inputs with shorting links.

                      • Alan
                        ... Subject: Re: [softrock40] RXTX v6.3 improved signal to noise ... John, It does not seem that simple to me. My initial thought was After many years of
                        Message 11 of 19 , Oct 15, 2012
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                          ----- Original Message -----
                          Subject: Re: [softrock40] RXTX v6.3 improved signal to noise


                          >Those 10 ohm resistors before the mixer are dropping precious nanovolts of wanted signal. Worsening signal to noise ratio.

                          John,

                          It does not seem that simple to me.
                          My initial thought was "After many years of Softrocks how could this be?"
                          6dB is a big difference.
                          From a practical point of view with a Softrock connected to a good antenna what difference will it make?
                          On a sufficiently sensitive low noise receiver SNR is established at the antenna input. Signal/atmospheric etc. noise. Provided the
                          receiver adds no noise the SNR is fixed. Indeed with the lower frequencies an attenuator can be used with no effect on SNR. Tony
                          uses attenuators in the Ensemble RX.

                          Now, maybe on the higher frequencies a Softrock might need to be a little more sensitive. I understand this is sometimes done by
                          using a low noise card and reducing op-amp gain. So why, apart from Tom, has nobody suggested removing the resistors?
                          What are they doing? Is there something else that is degraded if they are removed? Are they an integral part of the mixer?

                          73 Alan G4ZFQ
                        • John
                          Alan, If I get a chance I will put the resistors back in and measure the minimum detectable signal and compare. DG8SAQ also mentions that the impedance looking
                          Message 12 of 19 , Oct 15, 2012
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                            Alan,
                             
                            If I get a chance I will put the resistors back in and measure the minimum detectable signal and compare.
                             
                            DG8SAQ also mentions that the impedance looking into the mixer is closer to 50 Ohms without the resistors than with them as measured on his vector network analyzer. 
                             
                            John
                          • Milt Cram
                            ... Hi All, Shouldn t impedance matching be done with reactive components (transformers, capacitors and inductors)? If the 10 ohm resistors are being used for
                            Message 13 of 19 , Oct 15, 2012
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                              On 10/14/2012 12:01 PM, John wrote:
                              I was reading one of DG8SAQ's pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance to the RX mixer.
                              On the same page he mentions replacing the two 10 Ohm resistors on the mixer inputs with shorting links.
                               
                              I have just tried this with the folowing result:
                               
                              With the two 10 Ohm resistors:
                               
                              Frequency 1.977 MHz
                              With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                              With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -110 dB 
                               
                               
                              Without the two 10 Ohm resisors:
                               
                              Frequency 1.977 MHz
                              With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                              With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -104 dB
                               
                              This appears to have improved signal + noise / noise ratio by 6 dB
                               
                              Has anyone else tried this?
                               
                              John G3UGY

                              Hi All,

                              Shouldn't impedance matching be done with reactive components (transformers, capacitors and inductors)?  If the 10 ohm resistors are being used for impedance matching, they will both attenuate the signal, and contribute noise power.  This will reduce the S/N.  Removing them should improve S/N....?  If necessary, adjust the turns ratio of the input transformer to provide the impedance match.

                              73, Milt
                              W8NUE
                            • John
                              Agreed... John G3UGY Hi All, Shouldn t impedance matching be done with reactive components (transformers, capacitors and inductors)? If the 10 ohm resistors
                              Message 14 of 19 , Oct 15, 2012
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                                Agreed... John G3UGY
                                 
                                 
                                Hi All,

                                Shouldn't impedance matching be done with reactive components (transformers, capacitors and inductors)?  If the 10 ohm resistors are being used for impedance matching, they will both attenuate the signal, and contribute noise power.  This will reduce the S/N.  Removing them should improve S/N....?  If necessary, adjust the turns ratio of the input transformer to provide the impedance match.

                                73, Milt
                                W8NUE
                              • Milt Cram
                                ... Additional comments regarding the 10 ohm resistors-- I m guessing that the 10 ohm resistors are also used to swamp the variations in the on-resistance of
                                Message 15 of 19 , Oct 15, 2012
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                                  On 10/14/2012 12:01 PM, John wrote:
                                  I was reading one of DG8SAQ's pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance to the RX mixer.
                                  On the same page he mentions replacing the two 10 Ohm resistors on the mixer inputs with shorting links.
                                   
                                  I have just tried this with the folowing result:
                                   
                                  With the two 10 Ohm resistors:
                                   
                                  Frequency 1.977 MHz
                                  With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                                  With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -110 dB 
                                   
                                   
                                  Without the two 10 Ohm resisors:
                                   
                                  Frequency 1.977 MHz
                                  With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                                  With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -104 dB
                                   
                                  This appears to have improved signal + noise / noise ratio by 6 dB
                                   
                                  Has anyone else tried this?
                                   
                                  John G3UGY

                                  Additional comments regarding the 10 ohm resistors--

                                  I'm guessing that the 10 ohm resistors are also used to swamp the variations in the "on-resistance" of the switches.  At low HF frequencies, external noise probably dominates the S/N and the resistors "stabilize" the input impedance.  At higher frequencies, it would seem desirable to eliminate, as much as possible, resistors in the input circuitry.

                                  73, Milt
                                  W8NUE
                                • Kees & Sandy
                                  I agree. Any input impedance matching to the antenna will help and the VNA is a good tool to find out, but I assumed those resistors were in there also to
                                  Message 16 of 19 , Oct 15, 2012
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                                    I agree. Any input impedance matching to the antenna will help and the VNA is a good tool to find out, but I assumed those resistors were in there also to maintain balance between the two inputs. Since you can have some resistance variation between the two FET switches, windings, etc adding 10 ohms will swamp those values. Another approach might be to take a good commercial input RF transformer from someone like Mini-Circuits and use it. You can also parallel FETs to "average" the resistance variation. As Milt suggests, you can adjust the turns ratio and then reduce the 10 ohm resistance so you see 50 ohms with the VNA. Another item that I've found makes a difference is to use bifilar wire for the secondary. Regardless of how much/little you twist the wires, it's not as good as bifilar wire.
                                     
                                    73 Kees K5BCQ


                                    ---------- Original Message ----------
                                    From: Milt Cram <w8nue@...>
                                    To: softrock40@yahoogroups.com
                                    Subject: Re: [softrock40] RXTX v6.3 improved signal to noise
                                    Date: Mon, 15 Oct 2012 09:21:55 -0500

                                     

                                    On 10/14/2012 12:01 PM, John wrote:
                                    I was reading one of DG8SAQ's pages http://www.mydarc.de/dg8saq/switchimpedance/index.shtml where he measures the input impedance to the RX mixer.
                                    On the same page he mentions replacing the two 10 Ohm resistors on the mixer inputs with shorting links.
                                     
                                    I have just tried this with the folowing result:
                                     
                                    With the two 10 Ohm resistors:
                                     
                                    Frequency 1.977 MHz
                                    With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                                    With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -110 dB 
                                     
                                     
                                    Without the two 10 Ohm resisors:
                                     
                                    Frequency 1.977 MHz
                                    With a 50 Ohm resistor connected to the SoftRock antenna input HDSDR noise peaks are about -125dB
                                    With a signal generator set to -93 dBm connected to the SoftRock antenna input the signal peak is about -104 dB
                                     
                                    This appears to have improved signal + noise / noise ratio by 6 dB
                                     
                                    Has anyone else tried this?
                                     
                                    John G3UGY

                                    Additional comments regarding the 10 ohm resistors--

                                    I'm guessing that the 10 ohm resistors are also used to swamp the variations in the "on-resistance" of the switches.  At low HF frequencies, external noise probably dominates the S/N and the resistors "stabilize" the input impedance.  At higher frequencies, it would seem desirable to eliminate, as much as possible, resistors in the input circuitry.

                                    73, Milt
                                    W8NUE

                                     

                                     

                                  • vbifyz
                                    ... I agree with Milt. Shorting these resistors will improve SNR, but may degrade image rejection. There is a tradeoff, which is also frequency dependent. 73,
                                    Message 17 of 19 , Oct 15, 2012
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                                      --- In softrock40@yahoogroups.com, Milt Cram <w8nue@...> wrote:
                                      >

                                      > Additional comments regarding the 10 ohm resistors--
                                      >
                                      > I'm guessing that the 10 ohm resistors are also used to swamp the
                                      > variations in the "on-resistance" of the switches. At low HF
                                      > frequencies, external noise probably dominates the S/N and the resistors
                                      > "stabilize" the input impedance. At higher frequencies, it would seem
                                      > desirable to eliminate, as much as possible, resistors in the input
                                      > circuitry.
                                      >
                                      > 73, Milt
                                      > W8NUE
                                      >

                                      I agree with Milt. Shorting these resistors will improve SNR, but may degrade image rejection. There is a tradeoff, which is also frequency dependent.

                                      73, Mike
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