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Re: SDR station monitor, how to??

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  • warrenallgyer
    If you run the transmitter into a dummy load it will certainly reduce the stray RF pickup but, like Dave, I use mine as a true operating monitor so it needs to
    Message 1 of 15 , Nov 22, 2012
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      If you run the transmitter into a dummy load it will certainly reduce the stray RF pickup but, like Dave, I use mine as a true operating monitor so it needs to work with the transmitter at full power into the antenna. Mine does but that is at 3 watts or less and with the input terminated. At higher power levels, with unknown antenna match and ground conditions, it is hard to predict. I think, at a minimum, he needs to get it into a metal box and terminate or short the antenna connector.

      Warren Allgyer - W8TOD

      --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
      >
      >
      > ----- Original Message -----
      > Subject: [softrock40] Re: SDR station monitor, how to??
      >
      >
      > I guess Warren is saying is run your 857 into a dummy load. I think you will overload the Softrock if you have an antenna connected.
      > Or is it possible to keep the RF out Warren?
      >
      > 73 Alan G4ZFQ
      >
    • rifkum
      Thanks for the feedback... I thought that I should probably try and put the ensemble into a metal case with the case tied to the BNC ground. I have it in a
      Message 2 of 15 , Nov 22, 2012
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        Thanks for the feedback...

        I thought that I should probably try and put the ensemble into a metal case with the case tied to the BNC ground.

        I have it in a clear case (an old ipod touch crystal clear packaging box) I really wanted to be able to show my soldering handywork off to others. The simplicity and yet the feature rich functionality of the SDR is truly amazing.

        I love to be able to scan the bands for activity.

        Has anyone had any luck linking the frequency of the SDR software (I use HDSDR) to their tranciever? So that the ensemble is automatically tracking their transmitter?

        thanks
        dwight
        N7KBC
      • PeterM
        I do this as a matter of routine but and have tried a number of ways to protect the RXII while transmitting, but still looking for a better way. Disconnecting
        Message 3 of 15 , Jan 21, 2013
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          I do this as a matter of routine but and have tried a number of ways to protect the RXII while transmitting, but still looking for a better way.

          Disconnecting the antenna still produces a huge signal even with the SR in a metal box. I've been cutting power to it while transmitting...

          I'm considering some combination of the following:

          ground the metal box should help.
          wrap it in tinfoil (never tried that)?
          short the antenna
          disconnect the antenna
          cut DC power to the SR
          cut the USB connection along with DC


          Any other ideas or experience of what works best?
          I run 50 watts HF and 2M and haven't blown out the SR yet
          overload often detunes the SR or disables the USB, as does disconnection so there are downsides/risks to what I've tried.


          --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
          >
          > If you run the transmitter into a dummy load it will certainly reduce the stray RF pickup but, like Dave, I use mine as a true operating monitor so it needs to work with the transmitter at full power into the antenna. Mine does but that is at 3 watts or less and with the input terminated. At higher power levels, with unknown antenna match and ground conditions, it is hard to predict. I think, at a minimum, he needs to get it into a metal box and terminate or short the antenna connector.
          >
          > Warren Allgyer - W8TOD
          >
          > --- In softrock40@yahoogroups.com, "Alan" wrote:
          > >
          > >
          > > ----- Original Message -----
          > > Subject: [softrock40] Re: SDR station monitor, how to??
          > >
          > >
          > > I guess Warren is saying is run your 857 into a dummy load. I think you will overload the Softrock if you have an antenna connected.
          > > Or is it possible to keep the RF out Warren?
          > >
          > > 73 Alan G4ZFQ
          > >
          >
        • warrenallgyer
          I made some non-scientific tests this morning: running 1.5 watts on 40 meters from an RXTX into the dummy load in the MFJ tuner. RXII about 3 feet away
          Message 4 of 15 , Jan 21, 2013
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            I made some non-scientific tests this morning:

            running 1.5 watts on 40 meters from an RXTX into the dummy load in the MFJ tuner. RXII about 3 feet away connected to a different PC but the same 13.8 V lab supply:

            - no antenna -95 dBm on HDSDR after S9 calibration
            - Ferrite isolator on the USB line -96
            - Ferrite isolator on the 12 V and audio lines -1-2 dB
            - wrap the entire box in aluminum foil - 6 dB
            - power from batteries inside the foil -10 dB.

            So no matter what I did I could not get it much lower than -115. If you are running 50 watts that is another 15 dB so you won't get it much below -90 or about S6.

            BTW... the RXII will overload at around -35 dBm. Actually I think it is the audio input card that overloads...... but I have local stations that put 0 dBm coming out of my antenna tuner and this has not harmed the RXII. I suspect it will actually take several watts to do any damage..... one of those "push the envelope until it breaks" tests that I will do one of these days.

            I think so long as you don't have a direct connection to your transmitter you are unlikely to do any harm. On the other hand, if you want to actually use the RXII to monitor and measure then you need to find a way to get the input down to at least -40 dBm, S9 +33 or so.

            Warren Allgyer - W8TOD

            --- In softrock40@yahoogroups.com, "PeterM" wrote:
            >
            > I do this as a matter of routine but and have tried a number of ways to protect the RXII while transmitting, but still looking for a better way.
            >
            > Disconnecting the antenna still produces a huge signal even with the SR in a metal box. I've been cutting power to it while transmitting...
            >
            > I'm considering some combination of the following:
            >
            > ground the metal box should help.
            > wrap it in tinfoil (never tried that)?
            > short the antenna
            > disconnect the antenna
            > cut DC power to the SR
            > cut the USB connection along with DC
            >
            >
            > Any other ideas or experience of what works best?
            > I run 50 watts HF and 2M and haven't blown out the SR yet
            > overload often detunes the SR or disables the USB, as does disconnection so there are downsides/risks to what I've tried.
            >
            >
            > --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
            > >
            > > If you run the transmitter into a dummy load it will certainly reduce the stray RF pickup but, like Dave, I use mine as a true operating monitor so it needs to work with the transmitter at full power into the antenna. Mine does but that is at 3 watts or less and with the input terminated. At higher power levels, with unknown antenna match and ground conditions, it is hard to predict. I think, at a minimum, he needs to get it into a metal box and terminate or short the antenna connector.
            > >
            > > Warren Allgyer - W8TOD
            > >
            > > --- In softrock40@yahoogroups.com, "Alan" wrote:
            > > >
            > > >
            > > > ----- Original Message -----
            > > > Subject: [softrock40] Re: SDR station monitor, how to??
            > > >
            > > >
            > > > I guess Warren is saying is run your 857 into a dummy load. I think you will overload the Softrock if you have an antenna connected.
            > > > Or is it possible to keep the RF out Warren?
            > > >
            > > > 73 Alan G4ZFQ
            > > >
            > >
            >
          • Roger Critchlow
            ... Warren, you wouldn t be admitting you need a 24 bit sound card to increase your dynamic range, would you? Just kidding, -- rec --
            Message 5 of 15 , Jan 21, 2013
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              On Mon, Jan 21, 2013 at 8:14 PM, warrenallgyer <allgyer@...> wrote:
               

              BTW... the RXII will overload at around -35 dBm. Actually I think it is the audio input card that overloads...... but I have local stations that put 0 dBm coming out of my antenna tuner and this has not harmed the RXII. I suspect it will actually take several watts to do any damage..... one of those "push the envelope until it breaks" tests that I will do one of these days.


              Warren, you wouldn't be admitting you need a 24 bit sound card to increase your dynamic range, would you?

              Just kidding,

              -- rec --
            • Alan
              ... Subject: Re: [softrock40] Re: SDR station monitor, how to?? ... But a 24 bit card will still overload with excessive input, as will the Softrock opamps. To
              Message 6 of 15 , Jan 21, 2013
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                ----- Original Message -----
                Subject: Re: [softrock40] Re: SDR station monitor, how to??


                >
                > Warren, you wouldn't be admitting you need a 24 bit sound card to increase
                > your dynamic range, would you?
                >

                But a 24 bit card will still overload with excessive input, as will the Softrock opamps.
                To gain the advantage of 24 bits the Softrock gain needs to be reduced.
                Lower noise is the answer.

                73 Alan G4ZFQ
              • warrenallgyer
                Roger Hmmmm.... that is an interesting thought. Do you have some numbers on the 24 bit card? From a practical standpoint I have put attenuators in all of my
                Message 7 of 15 , Jan 22, 2013
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                  Roger

                  Hmmmm.... that is an interesting thought. Do you have some numbers on the 24 bit card?

                  From a practical standpoint I have put attenuators in all of my Softrocks to reduce the input level so that I only get 6-8 dB rise in the noise floor when the antenna is connected. In the lower bands this ends up being 15-20 dB so my overload point with my "cheapie" cards is around -15 dBm or so, and the minimum detectable signal is unaffected.

                  I am for anything that expands dynamic range..... as long as it is CHEAP! ;-)



                  --- In softrock40@yahoogroups.com, Roger Critchlow wrote:
                  >

                  >
                  > Warren, you wouldn't be admitting you need a 24 bit sound card to increase
                  > your dynamic range, would you?
                  >
                  > Just kidding,
                  >
                  > -- rec --
                  >
                • PeterM
                  Thanks Warren - I ve concluded that trying to keep enough stray RF out of the softrock to use it to monitor the station transmitter(s) is impractical unless
                  Message 8 of 15 , Jan 22, 2013
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                    Thanks Warren - I've concluded that trying to keep enough stray RF out of the softrock to use it to monitor the station transmitter(s) is impractical unless there was a lead-lined or at least foil lined separate chamber in the shack. I'd settle for using the softrock to monitor everyone but myself. This must have been covered before but I can't seem to get the right search going so I'll start a separate thread - RXII and SDR as a second station receiver, how to?

                    mahalo,
                    Peter

                    --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
                    >
                    > I made some non-scientific tests this morning:
                    >
                    > running 1.5 watts on 40 meters from an RXTX into the dummy load in the MFJ tuner. RXII about 3 feet away connected to a different PC but the same 13.8 V lab supply:
                    >
                    > - no antenna -95 dBm on HDSDR after S9 calibration
                    > - Ferrite isolator on the USB line -96
                    > - Ferrite isolator on the 12 V and audio lines -1-2 dB
                    > - wrap the entire box in aluminum foil - 6 dB
                    > - power from batteries inside the foil -10 dB.
                    >
                    > So no matter what I did I could not get it much lower than -115. If you are running 50 watts that is another 15 dB so you won't get it much below -90 or about S6.
                    >
                    > BTW... the RXII will overload at around -35 dBm. Actually I think it is the audio input card that overloads...... but I have local stations that put 0 dBm coming out of my antenna tuner and this has not harmed the RXII. I suspect it will actually take several watts to do any damage..... one of those "push the envelope until it breaks" tests that I will do one of these days.
                    >
                    > I think so long as you don't have a direct connection to your transmitter you are unlikely to do any harm. On the other hand, if you want to actually use the RXII to monitor and measure then you need to find a way to get the input down to at least -40 dBm, S9 +33 or so.
                    >
                    > Warren Allgyer - W8TOD
                    >
                    > --- In softrock40@yahoogroups.com, "PeterM" wrote:
                    > >
                    > > I do this as a matter of routine but and have tried a number of ways to protect the RXII while transmitting, but still looking for a better way.
                    > >
                    > > Disconnecting the antenna still produces a huge signal even with the SR in a metal box. I've been cutting power to it while transmitting...
                    > >
                    > > I'm considering some combination of the following:
                    > >
                    > > ground the metal box should help.
                    > > wrap it in tinfoil (never tried that)?
                    > > short the antenna
                    > > disconnect the antenna
                    > > cut DC power to the SR
                    > > cut the USB connection along with DC
                    > >
                    > >
                    > > Any other ideas or experience of what works best?
                    > > I run 50 watts HF and 2M and haven't blown out the SR yet
                    > > overload often detunes the SR or disables the USB, as does disconnection so there are downsides/risks to what I've tried.
                    > >
                    > >
                    > > --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
                    > > >
                    > > > If you run the transmitter into a dummy load it will certainly reduce the stray RF pickup but, like Dave, I use mine as a true operating monitor so it needs to work with the transmitter at full power into the antenna. Mine does but that is at 3 watts or less and with the input terminated. At higher power levels, with unknown antenna match and ground conditions, it is hard to predict. I think, at a minimum, he needs to get it into a metal box and terminate or short the antenna connector.
                    > > >
                    > > > Warren Allgyer - W8TOD
                    > > >
                    > > > --- In softrock40@yahoogroups.com, "Alan" wrote:
                    > > > >
                    > > > >
                    > > > > ----- Original Message -----
                    > > > > Subject: [softrock40] Re: SDR station monitor, how to??
                    > > > >
                    > > > >
                    > > > > I guess Warren is saying is run your 857 into a dummy load. I think you will overload the Softrock if you have an antenna connected.
                    > > > > Or is it possible to keep the RF out Warren?
                    > > > >
                    > > > > 73 Alan G4ZFQ
                    > > > >
                    > > >
                    > >
                    >
                  • warrenallgyer
                    Oh I don t think you should give up Peter. I am pretty sure if you put a shorting plug on the antenna connector you can get the level down to where it won t
                    Message 9 of 15 , Jan 22, 2013
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                      Oh I don't think you should give up Peter. I am pretty sure if you put a shorting plug on the antenna connector you can get the level down to where it won't overload. Try also reducing the PC audio input gain a bit. This will help if the audio card is overloading.... it will not help if the receiver itself is overloaded.

                      The sign of overload on my Softrocks is spurious signals every 10 KHz of so in the frequencies near the transmitter. If you can get down to where you don't see these then the RXII can be a very useful monitor.

                      Warren Allgyer - W8TOD

                      --- In softrock40@yahoogroups.com, "PeterM" wrote:
                      >
                      > Thanks Warren - I've concluded that trying to keep enough stray RF out of the softrock to use it to monitor the station transmitter(s) is impractical unless there was a lead-lined or at least foil lined separate chamber in the shack. I'd settle for using the softrock to monitor everyone but myself. This must have been covered before but I can't seem to get the right search going so I'll start a separate thread - RXII and SDR as a second station receiver, how to?
                      >
                      > mahalo,
                      > Peter
                      >
                      > --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
                      > >
                      > > I made some non-scientific tests this morning:
                      > >
                      > > running 1.5 watts on 40 meters from an RXTX into the dummy load in the MFJ tuner. RXII about 3 feet away connected to a different PC but the same 13.8 V lab supply:
                      > >
                      > > - no antenna -95 dBm on HDSDR after S9 calibration
                      > > - Ferrite isolator on the USB line -96
                      > > - Ferrite isolator on the 12 V and audio lines -1-2 dB
                      > > - wrap the entire box in aluminum foil - 6 dB
                      > > - power from batteries inside the foil -10 dB.
                      > >
                      > > So no matter what I did I could not get it much lower than -115. If you are running 50 watts that is another 15 dB so you won't get it much below -90 or about S6.
                      > >
                      > > BTW... the RXII will overload at around -35 dBm. Actually I think it is the audio input card that overloads...... but I have local stations that put 0 dBm coming out of my antenna tuner and this has not harmed the RXII. I suspect it will actually take several watts to do any damage..... one of those "push the envelope until it breaks" tests that I will do one of these days.
                      > >
                      > > I think so long as you don't have a direct connection to your transmitter you are unlikely to do any harm. On the other hand, if you want to actually use the RXII to monitor and measure then you need to find a way to get the input down to at least -40 dBm, S9 +33 or so.
                      > >
                      > > Warren Allgyer - W8TOD
                      > >
                      > > --- In softrock40@yahoogroups.com, "PeterM" wrote:
                      > > >
                      > > > I do this as a matter of routine but and have tried a number of ways to protect the RXII while transmitting, but still looking for a better way.
                      > > >
                      > > > Disconnecting the antenna still produces a huge signal even with the SR in a metal box. I've been cutting power to it while transmitting...
                      > > >
                      > > > I'm considering some combination of the following:
                      > > >
                      > > > ground the metal box should help.
                      > > > wrap it in tinfoil (never tried that)?
                      > > > short the antenna
                      > > > disconnect the antenna
                      > > > cut DC power to the SR
                      > > > cut the USB connection along with DC
                      > > >
                      > > >
                      > > > Any other ideas or experience of what works best?
                      > > > I run 50 watts HF and 2M and haven't blown out the SR yet
                      > > > overload often detunes the SR or disables the USB, as does disconnection so there are downsides/risks to what I've tried.
                      > > >
                      > > >
                      > > > --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
                      > > > >
                      > > > > If you run the transmitter into a dummy load it will certainly reduce the stray RF pickup but, like Dave, I use mine as a true operating monitor so it needs to work with the transmitter at full power into the antenna. Mine does but that is at 3 watts or less and with the input terminated. At higher power levels, with unknown antenna match and ground conditions, it is hard to predict. I think, at a minimum, he needs to get it into a metal box and terminate or short the antenna connector.
                      > > > >
                      > > > > Warren Allgyer - W8TOD
                      > > > >
                      > > > > --- In softrock40@yahoogroups.com, "Alan" wrote:
                      > > > > >
                      > > > > >
                      > > > > > ----- Original Message -----
                      > > > > > Subject: [softrock40] Re: SDR station monitor, how to??
                      > > > > >
                      > > > > >
                      > > > > > I guess Warren is saying is run your 857 into a dummy load. I think you will overload the Softrock if you have an antenna connected.
                      > > > > > Or is it possible to keep the RF out Warren?
                      > > > > >
                      > > > > > 73 Alan G4ZFQ
                      > > > > >
                      > > > >
                      > > >
                      > >
                      >
                    • Alan
                      ... Subject: [softrock40] Re: SDR station monitor, how to?? ... Warren, My understanding is that theoretically a 24 bit card could have more dynamic range than
                      Message 10 of 15 , Jan 22, 2013
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                        ----- Original Message -----
                        Subject: [softrock40] Re: SDR station monitor, how to??


                        > Do you have some numbers on the 24 bit card?
                        >

                        Warren,

                        My understanding is that theoretically a 24 bit card could have more dynamic range than something like a Softrock could ever use.

                        However it seems to me that most, if not all of the advantage will have to be at the bottom end.
                        Maybe a professional grade card will accept higher inputs? The Softrock opamp may need greater headroom, especially if the inputs
                        are unevenly matched as some are. (Mixer DC balance).

                        My limited tests seem to show most soundcards will see the opamp noise from a Softrock. So to gain any advantage from a lower noise
                        card then the opamp gain must be reduced.
                        I think the Softrock is ideal for 16 bit cards.

                        Some time ago I did investigate, most remarks I got were like "24 bit is better so my SDR is better" without any real facts to back
                        this up.
                        I eventually found some in the Mobo group who had looked into this and gained some more dynamic range by reducing the gain of the
                        opamps.

                        Really that's as far as I've gone.

                        I'm reminded of a comment made on this group. Something to the effect that without testing all the parameters of a Softrock it is
                        pointless spending a lot of money improving just one of them. But if it makes someone happy...

                        73 Alan G4ZFQ


                        > From a practical standpoint I have put attenuators in all of my Softrocks to reduce the input level so that I only get 6-8 dB rise
                        > in the noise floor when the antenna is connected. In the lower bands this ends up being 15-20 dB so my overload point with my
                        > "cheapie" cards is around -15 dBm or so, and the minimum detectable signal is unaffected.
                        >
                        > I am for anything that expands dynamic range..... as long as it is CHEAP! ;-)
                        >
                      • warrenallgyer
                        My stock RXTX overloaded on 40 at -35 dBm. My antenna noise floor was roughly -110 dBm and my rig noise floor (op amp? sound card?) was about -147 dBm. So I
                        Message 11 of 15 , Jan 22, 2013
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                          My stock RXTX overloaded on 40 at -35 dBm. My antenna noise floor was roughly -110 dBm and my rig noise floor (op amp? sound card?) was about -147 dBm.

                          So I put a 20 dB pad in the receiver line after the IO switching. After recalibrating for S9 = -73 dBm I now overload at -15 dBm, my antenna noise floor is still -110 dBm, and my rig noise floor is -127 dBm.

                          So I think the only effect a wider dynamic range would have, after re-calibration, would be to increase the level at which the receiver would overload. That would be OK but I would not pay a lot of money just to have a receiver that could take 0 dBm in as opposed to -15!

                          Maybe someone smarter than me has an input on this?

                          Warren Allgyer - W8TOD

                          --- In softrock40@yahoogroups.com, "Alan" wrote:
                          >
                          >
                          > ----- Original Message -----
                          > Subject: [softrock40] Re: SDR station monitor, how to??
                          >
                          >
                          > > Do you have some numbers on the 24 bit card?
                          > >
                          >
                          > Warren,
                          >
                          > My understanding is that theoretically a 24 bit card could have more dynamic range than something like a Softrock could ever use.
                          >
                          > However it seems to me that most, if not all of the advantage will have to be at the bottom end.
                          > Maybe a professional grade card will accept higher inputs? The Softrock opamp may need greater headroom, especially if the inputs
                          > are unevenly matched as some are. (Mixer DC balance).
                          >
                          > My limited tests seem to show most soundcards will see the opamp noise from a Softrock. So to gain any advantage from a lower noise
                          > card then the opamp gain must be reduced.
                          > I think the Softrock is ideal for 16 bit cards.
                          >
                          > Some time ago I did investigate, most remarks I got were like "24 bit is better so my SDR is better" without any real facts to back
                          > this up.
                          > I eventually found some in the Mobo group who had looked into this and gained some more dynamic range by reducing the gain of the
                          > opamps.
                          >
                          > Really that's as far as I've gone.
                          >
                          > I'm reminded of a comment made on this group. Something to the effect that without testing all the parameters of a Softrock it is
                          > pointless spending a lot of money improving just one of them. But if it makes someone happy...
                          >
                          > 73 Alan G4ZFQ
                          >
                          >
                          > > From a practical standpoint I have put attenuators in all of my Softrocks to reduce the input level so that I only get 6-8 dB rise
                          > > in the noise floor when the antenna is connected. In the lower bands this ends up being 15-20 dB so my overload point with my
                          > > "cheapie" cards is around -15 dBm or so, and the minimum detectable signal is unaffected.
                          > >
                          > > I am for anything that expands dynamic range..... as long as it is CHEAP! ;-)
                          > >
                          >
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