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[softrock40] Softrock sensitivity

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  • marc olanié
    Lots of people have commented that the softrock is very sensitive, but I m finding it is slightly less sensitive than the Icom. [ ] ...did the very same remark
    Message 1 of 16 , Nov 2, 2008
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      Lots of people have commented that the softrock is very sensitive, but
      I'm finding it is slightly less sensitive than the Icom.
      [>]
      ...did the very same remark some time ago. I changed the op amp of the 6.2
      (with a Maxim equivalent.. You should dig the mailing list to find the exact
      reference) and the feed-back circuit of the op amp. My 6.2 is now far more
      better than my Japanese commercial gears. The quality of the audio cart
      itself plays also an important role in the noise/signal ratio you can
      receive.

      I used to use a TS50S in mobile and field operation. The difference with the
      SR could not be described... I long for the new all bands TX-RX ;-)

      Marc f6itu
    • Alan
      ... From: Christos Nikolaou Re: Softrock sensitivity ... Yes, after I had fitted those I did not feel I needed a preamp on the lower frequencies. ... This
      Message 2 of 16 , Nov 2, 2008
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        ----- Original Message -----
        From: "Christos Nikolaou" Re: Softrock sensitivity
        >
        > A crucial part of sensitivity is the opamp used after the QSD. LT6231
        > has an excellent performance.

        Yes, after I had fitted those I did not feel I needed a preamp on the lower
        frequencies.

        > Of course the ADC of the sound card is the heart of the transceiver
        > and your Softrock will be so good as to what your sound card is.
        > A 96/192KHz, 24Bit with -110dB noise floor is what you need as a sound
        > card if you'll gona compare the softrock to commercial receivers.
        >

        This depends on what comparison you wish to make. I am comparing my less
        than perfect Softrock setup with my less than perfect commercial receivers.
        I assume that most Softrock users do not have a perfect setup (If that
        exists!)
        I should have remarked that a better antenna and soundcard could make a
        difference but if one wishes to improve sensitivity with the setup one has
        then a preamp will work. Obviously we must consider the harmful effects of
        6-8db amplification.


        > In the setup here at least by comparing IC-R75 to my modified
        > Softrock, the performance of SR in 10m is better and can hear stations
        > that the R75 cannot.

        If you are talking about listening to the audio I agree. The Softrock
        produces better, more intelligble audio than my commercial receivers.

        >I use a Terratec Producer Phase24 192KHz/24bit.

        That sounds expensive!
        I now use Delta 44s. With these I do not feel that a preamplifier is needed
        to see the weakest signals, I cannot comment on the high frequencies, I
        rarely go above 7MHz!

        73 Alan G4ZFQ
      • Christos Nikolaou
        ... Allan, I mean directly speaking signal did existed on softrock whereas not existed on R75, not just a pleasant audio. The MDS with a good ADC has proven to
        Message 3 of 16 , Nov 2, 2008
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          >
          > > In the setup here at least by comparing IC-R75 to my modified
          > > Softrock, the performance of SR in 10m is better and can hear stations
          > > that the R75 cannot.
          >
          > If you are talking about listening to the audio I agree. The Softrock
          > produces better, more intelligble audio than my commercial receivers.
          >

          Allan,
          I mean directly speaking signal did existed on softrock whereas not
          existed on R75, not just a pleasant audio. The MDS with a good ADC has
          proven to me that it is better on softrock than on the radios I have
          on 10m.

          > >I use a Terratec Producer Phase24 192KHz/24bit.
          >
          > That sounds expensive!

          Depends on what you mean expensive.
          It cost 200Euro.
          Either way even Flex on its SDR-1000 proposes these specifications and
          that is why the Edirol FA-66 is the DeFacto standard.

          But I insist on the lower frequencies, even with the previous opamp,
          the sensitivity was the same, the only difference was on the level of
          the signals because LT6231 has much higher gain. As a matter of fact,
          I still have my first softrock with the 2462 opamp in Rx and making
          comparisons. The higher gain of the new opamp did not mean better MDS
          there, only lower level on the signals of bands <40m. At least this is
          what I observed.


          73,
          Christos SV1EIA
        • vk7oo
          Hi everyone Many thanks for the many & execelent replies To answer some questions & comments, I ll condense them all into this one post. Keep in mind I work
          Message 4 of 16 , Nov 3, 2008
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            Hi everyone
            Many thanks for the many & execelent replies
            To answer some questions & comments, I'll condense them all into this
            one post. Keep in mind I work exclyusively on 20m, atround 14.230
            where SSTV is. Also take the dBm measurements I quote with a grain of
            salt, they could be 20 dBm or more out.

            "If you have a quiet location (I imagine VK7 to be one!) then I think
            you will find the Softrock lacks that final bit of sensitivity even
            on the lower frequencies."
            Yes it's quiet here, especially lately. PSDR measures band noise
            typically around -124 to _130 dBm at night, a bit higher when the
            band is open

            "A crucial part of sensitivity is the opamp used after the QSD. LT6231
            has an excellent performance."
            My Softrock came with the LT6231

            "A 96/192KHz, 24Bit with -110dB noise floor is what you need as a
            sound card if you'll gona compare the softrock to commercial
            receivers."
            If I disconnect the Softrock from the soundcard, PowerSDR reads a
            noise floor of -147 dBm. The soundcard is a Behringer FCA202 (capable
            of 96Khz, but I'm using it at 48Khz)

            You might think it all sounds pretty good & I have nothing to
            complain about. With the band as quite as it is, most SSTV
            transmissions are very weak. Often the needle does not move but
            MMSSTV can still decode them (very noisy pictures though). The goal
            I'm trying to achieve is to pull those noisy pictures out of the mud.

            -Steve VK7OO
          • Alan
            ... From: vk7oo ... The crucial thing is the mud! Is it background atmospheric noise or noise introduced by the soundcard or some other means? Does the Icom
            Message 5 of 16 , Nov 3, 2008
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              ----- Original Message -----
              From: "vk7oo">
              > You might think it all sounds pretty good & I have nothing to
              > complain about. With the band as quite as it is, most SSTV
              > transmissions are very weak. Often the needle does not move but
              > MMSSTV can still decode them (very noisy pictures though). The goal
              > I'm trying to achieve is to pull those noisy pictures out of the mud.
              >

              The crucial thing is the mud!
              Is it background atmospheric noise or noise introduced by the soundcard or
              some other means?

              Does the Icom produce any better pictures?
              Does pulling out the antenna reduce the background noise or the noise floor
              on PDSR? (Preferably connect a dummy load to do it properly)
              There is a limit, maybe a better antenna is the only answer.

              73 Alan G4ZFQ
            • cesco12342000
              ... wow. How is immigration policy there ? I do get -110 db at best when it´s quiet here. btw testing my netbook with this post. 73, Cesco
              Message 6 of 16 , Nov 3, 2008
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                > Yes it's quiet here, especially lately. PSDR measures band noise
                > typically around -124 to _130 dBm at night, a bit higher when the
                > band is open


                wow.

                How is immigration policy there ?
                I do get -110 db at best when it´s quiet here.

                btw
                testing my netbook with this post.


                73, Cesco
              • Ray
                I have received SSTV on the 756PRO3 and 746PRO and most of the time the pictures are very noisy. My qth IS CENTRAL MINNESOTA 73, Ray, N0FY
                Message 7 of 16 , Nov 3, 2008
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                  I have received SSTV on the 756PRO3 and 746PRO and most of the time the
                  pictures are very noisy. My qth IS CENTRAL MINNESOTA

                  73, Ray, N0FY

                  > -----Original Message-----
                  > From: softrock40@yahoogroups.com
                  > [mailto:softrock40@yahoogroups.com] On Behalf Of vk7oo
                  > Sent: Monday, November 03, 2008 5:44 AM
                  > To: softrock40@yahoogroups.com
                  > Subject: [softrock40] Re: Softrock sensitivity
                  >
                  > Hi everyone
                  > Many thanks for the many & execelent replies To answer some
                  > questions & comments, I'll condense them all into this one
                  > post. Keep in mind I work exclyusively on 20m, atround 14.230
                  > where SSTV is. Also take the dBm measurements I quote with a
                  > grain of salt, they could be 20 dBm or more out.
                  >
                  > "If you have a quiet location (I imagine VK7 to be one!) then
                  > I think you will find the Softrock lacks that final bit of
                  > sensitivity even on the lower frequencies."
                  > Yes it's quiet here, especially lately. PSDR measures band
                  > noise typically around -124 to _130 dBm at night, a bit
                  > higher when the band is open
                  >
                  > "A crucial part of sensitivity is the opamp used after the
                  > QSD. LT6231 has an excellent performance."
                  > My Softrock came with the LT6231
                  >
                  > "A 96/192KHz, 24Bit with -110dB noise floor is what you need
                  > as a sound card if you'll gona compare the softrock to
                  > commercial receivers."
                  > If I disconnect the Softrock from the soundcard, PowerSDR
                  > reads a noise floor of -147 dBm. The soundcard is a Behringer
                  > FCA202 (capable of 96Khz, but I'm using it at 48Khz)
                  >
                  > You might think it all sounds pretty good & I have nothing to
                  > complain about. With the band as quite as it is, most SSTV
                  > transmissions are very weak. Often the needle does not move
                  > but MMSSTV can still decode them (very noisy pictures
                  > though). The goal I'm trying to achieve is to pull those
                  > noisy pictures out of the mud.
                  >
                  > -Steve VK7OO
                  >
                  >
                  >
                  > ------------------------------------
                  >
                  > Yahoo! Groups Links
                  >
                  >
                  >
                • vk7oo
                  Hi Alan I just did another check & got these figures - Soundcard with nothing connected = -149dBm - Softrock with dummyload in place of antenna = -145dBm - 20m
                  Message 8 of 16 , Nov 4, 2008
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                    Hi Alan
                    I just did another check & got these figures

                    - Soundcard with nothing connected = -149dBm
                    - Softrock with dummyload in place of antenna = -145dBm
                    - 20m band is quiet at the moment = -123dBm
                    Remember these numbers are relative as I haven't properly calibtrated
                    PowerSDR
                    I've also discovered that the computers in the shack are often the
                    major source of noise around the band

                    -Steve VK7OO
                    --- In softrock40@yahoogroups.com, "Alan" <g4zfq@...> wrote:
                    >
                    >
                    > ----- Original Message -----
                    > From: "vk7oo">
                    > > You might think it all sounds pretty good & I have nothing to
                    > > complain about. With the band as quite as it is, most SSTV
                    > > transmissions are very weak. Often the needle does not move but
                    > > MMSSTV can still decode them (very noisy pictures though). The
                    goal
                    > > I'm trying to achieve is to pull those noisy pictures out of the
                    mud.
                    > >
                    >
                    > The crucial thing is the mud!
                    > Is it background atmospheric noise or noise introduced by the
                    soundcard or
                    > some other means?
                    >
                    > Does the Icom produce any better pictures?
                    > Does pulling out the antenna reduce the background noise or the
                    noise floor
                    > on PDSR? (Preferably connect a dummy load to do it properly)
                    > There is a limit, maybe a better antenna is the only answer.
                    >
                    > 73 Alan G4ZFQ
                    >
                  • Alan
                    ... From: vk7oo ... Steve, If that -123 does not actually include computer noise it looks like you ve confirmed what Christos said. With a good setup the
                    Message 9 of 16 , Nov 4, 2008
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                      ----- Original Message -----
                      From: "vk7oo"
                      > - Softrock with dummyload in place of antenna = -145dBm
                      > - 20m band is quiet at the moment = -123dBm
                      > Remember these numbers are relative as I haven't properly calibtrated
                      > PowerSDR
                      > I've also discovered that the computers in the shack are often the
                      > major source of noise around the band


                      Steve, If that -123 does not actually include computer noise it looks like
                      you've confirmed what Christos said.
                      With a good setup the Softrock has ample sensitivity.
                      You'd better look out for a decent skyhook!

                      73 Alan G4ZFQ
                    • vk7oo
                      Hi Alan I often get the noise floor around -130dBm, at the moment it s - 126dBm on a noisy part of the panadapter Never the less, on real signals the Softrok
                      Message 10 of 16 , Nov 4, 2008
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                        Hi Alan
                        I often get the noise floor around -130dBm, at the moment it's -
                        126dBm on a noisy part of the panadapter
                        Never the less, on real signals the Softrok is just slightly less
                        sensitive than my Icom 731

                        -Steve

                        --- In softrock40@yahoogroups.com, "Alan" <g4zfq@...> wrote:
                        >
                        >
                        > ----- Original Message -----
                        > From: "vk7oo"
                        > > - Softrock with dummyload in place of antenna = -145dBm
                        > > - 20m band is quiet at the moment = -123dBm
                        > > Remember these numbers are relative as I haven't properly
                        calibtrated
                        > > PowerSDR
                        > > I've also discovered that the computers in the shack are often
                        the
                        > > major source of noise around the band
                        >
                        >
                        > Steve, If that -123 does not actually include computer noise it
                        looks like
                        > you've confirmed what Christos said.
                        > With a good setup the Softrock has ample sensitivity.
                        > You'd better look out for a decent skyhook!
                        >
                        > 73 Alan G4ZFQ
                        >
                      • Alan
                        ... From: vk7oo ... Steve, Well if you are not convinced then try a pre-amp. The one I suggested can be built with a low gain of about dab. It is very
                        Message 11 of 16 , Nov 4, 2008
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                          ----- Original Message -----
                          From: "vk7oo"
                          > I often get the noise floor around -130dBm, at the moment it's -
                          > 126dBm on a noisy part of the panadapter
                          > Never the less, on real signals the Softrok is just slightly less
                          > sensitive than my Icom 731
                          >

                          Steve,
                          Well if you are not convinced then try a pre-amp.
                          The one I suggested can be built with a low gain of about dab. It is very
                          similar to the one used in my OAR 7030 so it should be of good performance.
                          I would be interested to know what you find.
                          Whatever you use make sure it is of good quality, a cheap, high gain one
                          will certainly not help.

                          73 Alan G4ZFQ
                        • picnet2
                          It should be sensitive enough to show when you have something plugged into it... In 2006 I tested the V6.1 board and write an article showing how to modify the
                          Message 12 of 16 , Nov 4, 2008
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                            It should be sensitive enough to show when you have something plugged into it...

                            In 2006 I tested the V6.1 board and write an article showing how to modify the icom
                            ic1500 receiver to use it with the softrock as a panadapter, during that time I tested
                            it with a 20 dB attenuator and signal generator at -127 dBm,

                            http://urlme.net/455khz/tests/winrad-147dBm.jpg

                            Could of been that the attenuator was leaking rf, or it really was that sensitive.

                            http://www.qrpradio.org/pub/softrocks/manuals/softrock%20v6.0/V6%20IF%20applicatio
                            ns/softrock-ICR1500-455khz.pdf

                            Should also be somewhere in the files section in this group...

                            -Mike.





                            --- In softrock40@yahoogroups.com, "Alan" <g4zfq@...> wrote:
                            >
                            >
                            > ----- Original Message -----
                            > From: "vk7oo"
                            > > I often get the noise floor around -130dBm, at the moment it's -
                            > > 126dBm on a noisy part of the panadapter
                            > > Never the less, on real signals the Softrok is just slightly less
                            > > sensitive than my Icom 731
                            > >
                            >
                            > Steve,
                            > Well if you are not convinced then try a pre-amp.
                            > The one I suggested can be built with a low gain of about dab. It is very
                            > similar to the one used in my OAR 7030 so it should be of good performance.
                            > I would be interested to know what you find.
                            > Whatever you use make sure it is of good quality, a cheap, high gain one
                            > will certainly not help.
                            >
                            > 73 Alan G4ZFQ
                            >
                          • Alan
                            ... From: picnet2 To: Sent: Tuesday, November 04, 2008 10:44 PM Subject: [softrock40] Re: Softrock
                            Message 13 of 16 , Nov 5, 2008
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                              ----- Original Message -----
                              From: "picnet2" <picnet@...>
                              To: <softrock40@yahoogroups.com>
                              Sent: Tuesday, November 04, 2008 10:44 PM
                              Subject: [softrock40] Re: Softrock sensitivity


                              > It should be sensitive enough to show when you have something plugged into
                              > it...
                              >

                              Mike,

                              Thanks for your reply.
                              I have an old AVO signal generator and have also produced amazing
                              performance figures figures from a Softrock. However, using the same
                              techniques I have produced considerably better figures for a Yaesu FT840.
                              Like you I was using a DSP program to detect the signal.

                              Rather than using my dubious test methods I have done checks on the air with
                              real signals.
                              For a long time I have been monitoring the UK 5MHz beacons for the RSGB
                              experiment.
                              I was using an Icom R70 with G3PLX's DSP program which monitors and records
                              the signal/noise figures. When he brought out a version that took I/Q
                              signals a few years ago I got my first Softrock, a 6.1 lite for 5MHz. When
                              testing I realised that in quiet periods the Softrock was showing a lower
                              S/N ratio than the Icom system.
                              This was "rectified" by adding an 8db preamp. The Softrock had a TLV2462
                              op-amp, I later replaced that with an LT6231 and found the preamp was not
                              then needed.
                              These tests were all done using on-board sound, It is very likely that
                              results would be different with better quality cards.
                              I must get round to trying similar tests with different cards and higher
                              frequencies.

                              As Christos says, to get the best results it is necessary to have the best
                              soundcard and be certain eveything else is correct. I am just saying that
                              my practical tests on my inferior system resulted in a higher s/n without
                              any obvious drawbacks.

                              73 Alan G4ZFQ
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