Loading ...
Sorry, an error occurred while loading the content.

Re: PERSEUS + VHF converters

Expand Messages
  • Nelu
    Thanks a lot for very informative reply. 73, Corneliu ... at ... to ... PERSEUS ... Fujitsu ... + ... temperature ... would ... should
    Message 1 of 13 , May 31, 2008
    • 0 Attachment
      Thanks a lot for very informative reply.

      73, Corneliu

      --- In perseus_SDR@yahoogroups.com, Leif Asbrink <leif@...> wrote:
      >
      > Hi Corneliu,
      >
      > > Thanks a lot for your prompt response.
      > > I think your idea is very nice but unfortunatelly I am not good
      at
      > > programming.
      > > I would appreciate if you could include in a next release of your
      > > well known software support for FT897 and FT2000 and the below
      > > mentionned facilities.
      > > I think it will be useful for many other hams.
      > The code for commercial transceivers was written by ON5GN, Pierre.
      > I can not add code for transceivers that I do not have, I think it
      > will be necessary to verify that the code behaves correctly by
      > someone who has experience with the transceiver....
      >
      > Maybe, if you ask at the Linrad mailing list, there is someone who
      > has made a routine for FT897 or FT2000 that you might use.
      >
      > > as I know you are a very experienced EME-er so I would like also
      to
      > > ask you how much gain should have the converter in front of
      PERSEUS
      > > receiver at 28 MHz for EME work?
      > It depends on what you want to achieve.
      >
      > > I intend to use a VE3kh 144 MHz PREAMP WITH INPUT CAVITY AND
      Fujitsu
      > > 053 power fET + 4 POLES FILTER (-6bB)+ BFR 96 (+17dB) + 6 DB ATT
      +
      > > HIGH LEVEL dBM + PASSIVE DIPLEXER+ mav11 AMPLIFIER.
      > It may be easiest to compute backwards.
      >
      > The Perseus noise floor in 500 Hz bandwidth is -125 dBm. (preamp on,
      > filter on) That is -125-27=-152 dBm/Hz. A room temperature resistor
      > is -174 dBm so the noise figure is 174-152=22dB and the noise
      temperature
      > is 158*290K=45820K.
      >
      > The Perseus has an IP3 of +27 dBm (preamp on, filter on) so it would
      > be nice to use a converter that has an output IP3 of a similar size.
      > There is for example DEM Part Number 144-28 with an output IP3 of
      > +27 dBm. http://www.downeastmicrowave.com/PDF/14428.PDF
      > This converter has a conversion gain of 17 dB as I understand the
      > specifications.
      >
      > The perseus noise temperature, 45820K will look like 916K at the
      > transverter input (divide by 50 for 17dB gain) The noise of the
      > transverter itself is only 75K (NF=1dB) so the total noise at
      > the converter input would be 916+75=991K. Only 7.5% of the total
      > noise is from the transverter so the noise floor of the Perseus
      would
      > only rise by 7.5% or 0.3 dB so your dynamic range loss will be only
      > 0.3 dB and the NF at the converter input would be 5.3 dB. The input
      > IP3 would be a bit worse than +10 dBm. Maybe +8 dBm.
      >
      > It seems to me that you would not need the mav11. I do not know
      > what "HIGH LEVEL dBM + PASSIVE DIPLEXER" might stand for so I
      > can not proceed in detail.
      >
      > What you need would be an amplifier with an output IP3 that is
      > large enough to become something like +10 dBm after the attenuation
      > added by "HIGH LEVEL dBM + PASSIVE DIPLEXER". The total gain
      > of the amplifier plus "HIGH LEVEL dBM + PASSIVE DIPLEXER" should be
      > modest. Remember that the noise figure is already down at 5.3 dB and
      > you do not want to add needless noise. You might want the noise
      > contribution of this amplifier to be significant but you do not want
      > the noise of this amplifier to dominate when you look at the system
      > noise figure at its input.
      >
      > Finally the preamp (VE3KH) should dominate the noise floor
      > completely. When you connect it to the system, the noise floor
      should
      > rise by at least 13 dB. That would correspond to 5% noise NOT from
      > the preamp with a S/N loss of 0.2dB. If the noise increase is
      > 16 dB, your S/N loss would be 0.1 dB. Do not go above 20 dB. That
      > would give no improvement on S/N, only degraded dynamic range.
      >
      > In case you have a normal QTH you will not need the full dynamic
      > range that Perseus can supply. Then you can just use something
      > cheap for conversion - and plenty of gain:-)
      >
      > 73
      >
      > Leif / SM5BSZ
      >
    • DF9IC
      ... meter ... http://groups.yahoo.com/group/perseus_SDR/message/1888 I would like to have the same option. Henning
      Message 2 of 13 , Jun 1, 2008
      • 0 Attachment
        --- In perseus_SDR@yahoogroups.com, "Nelu" <conmar@...> wrote:
        >
        > Hi,
        >
        > I would like to use PERSEUS with 144/28 and 432/28 MHz converters
        > Would it be possible to display VHF frequency directly on PERSEUS?
        >
        > I mean a dialogue box where to input the converter's oscillator
        > frequency and converter gain so that the frequency readout and s-
        meter
        > indication remains correct?

        http://groups.yahoo.com/group/perseus_SDR/message/1888

        I would like to have the same option.

        Henning
      • DF9IC
        ... Seems I do not have a normal QTH :)
        Message 3 of 13 , Jun 1, 2008
        • 0 Attachment
          > In case you have a normal QTH you will not need the full dynamic
          > range that Perseus can supply. Then you can just use something
          > cheap for conversion - and plenty of gain:-)

          Seems I do not have a normal QTH :)
        • Nelu
          I have plenty of GSM and VHF industrial transmitters (taxi stations) at abt. 20 meters distance from my antenna when I turn the antenna in that direction and
          Message 4 of 13 , Jun 1, 2008
          • 0 Attachment
            I have plenty of GSM and VHF industrial transmitters (taxi stations) at
            abt. 20 meters distance from my antenna
            when I turn the antenna in that direction and using an FT897, the
            background noise level increases by abt 20 dB....
            that's why i expect that PERSEUS high dinamic range will help...

            73 Corneliu




            --- In perseus_SDR@yahoogroups.com, "DF9IC" <whrech@...> wrote:
            >
            > > In case you have a normal QTH you will not need the full dynamic
            > > range that Perseus can supply. Then you can just use something
            > > cheap for conversion - and plenty of gain:-)
            >
            > Seems I do not have a normal QTH :)
            >
          • Leif Asbrink
            Hi Corneliu, ... I do not think so. GSM is far above 144 MHz and I guess the taxi stations are several MHz away from the two meter band. The important thing is
            Message 5 of 13 , Jun 1, 2008
            • 0 Attachment
              Hi Corneliu,

              > I have plenty of GSM and VHF industrial transmitters (taxi stations) at
              > abt. 20 meters distance from my antenna
              > when I turn the antenna in that direction and using an FT897, the
              > background noise level increases by abt 20 dB....
              > that's why i expect that PERSEUS high dinamic range will help...
              I do not think so. GSM is far above 144 MHz and I guess the taxi
              stations are several MHz away from the two meter band.

              The important thing is your preamplifier. Even if it has a cavity
              input, its attenuation at GSM frequencies is limited. Note that
              the antenna as well as the preamp are very far from 50 ohms well
              outside the two meter band and that you can not assume that
              you will have the combined frequency response of the antenna
              and preamplifier.

              Assume a taxi at 160 MHz. Your cavity preamp may have 20 dB
              attenuation in a 50 ohm system. In case your antenna has an equally
              high SWR as the preamp at 160 MHz you may not have any attenuation
              at all if you have bad luck with the cable length. Then your preamp
              would see the full power at 160 MHz with saturation as a consequence.

              You should find out what the saturated power output from your
              cavity preamp is at all frequencies of interest. Then measure
              at the output of the cavity preamp with a spectrum analyzer in
              peak hold mode for a long time. If any signal that you can see
              outside 144 - 146 MHz is above 1% of the saturated power
              (10% amplitude) you need some additional filter between the
              antenna and the cavity preamp.

              At the preamp output you will add a 4-pole cavity filter.
              Neither taxi nor GSM will pass through it so what comes
              after the cavity filter is not critical in terms of IP3
              unless you have strong signals from friends on 144 MHz.
              The Perseus will allow good copy very near strong local
              144 MHz stations (if they have pure signals) and that is
              sometimes very important:-)

              73

              Leif / SM5BSZ
            • Nelu
              Hi Leif, You are right. The strongest offending stations are around 156 MHz. However there are some stations also around 146.500 MHz (but not so strong) I hope
              Message 6 of 13 , Jun 1, 2008
              • 0 Attachment
                Hi Leif,

                You are right. The strongest offending stations are around 156 MHz.
                However there are some stations also around 146.500 MHz (but not so
                strong)
                I hope it will help also with local stations during contests as I
                have about 6 strong neighbours in a radius of abt 1 Km or less.
                I will experiment with PERSEUS and converter and will report later
                about results.

                73 Corneliu

                --- In perseus_SDR@yahoogroups.com, Leif Asbrink <leif@...> wrote:
                >
                > Hi Corneliu,
                >
                > > I have plenty of GSM and VHF industrial transmitters (taxi
                stations) at
                > > abt. 20 meters distance from my antenna
                > > when I turn the antenna in that direction and using an FT897, the
                > > background noise level increases by abt 20 dB....
                > > that's why i expect that PERSEUS high dinamic range will help...
                > I do not think so. GSM is far above 144 MHz and I guess the taxi
                > stations are several MHz away from the two meter band.
                >
                > The important thing is your preamplifier. Even if it has a cavity
                > input, its attenuation at GSM frequencies is limited. Note that
                > the antenna as well as the preamp are very far from 50 ohms well
                > outside the two meter band and that you can not assume that
                > you will have the combined frequency response of the antenna
                > and preamplifier.
                >
                > Assume a taxi at 160 MHz. Your cavity preamp may have 20 dB
                > attenuation in a 50 ohm system. In case your antenna has an equally
                > high SWR as the preamp at 160 MHz you may not have any attenuation
                > at all if you have bad luck with the cable length. Then your preamp
                > would see the full power at 160 MHz with saturation as a
                consequence.
                >
                > You should find out what the saturated power output from your
                > cavity preamp is at all frequencies of interest. Then measure
                > at the output of the cavity preamp with a spectrum analyzer in
                > peak hold mode for a long time. If any signal that you can see
                > outside 144 - 146 MHz is above 1% of the saturated power
                > (10% amplitude) you need some additional filter between the
                > antenna and the cavity preamp.
                >
                > At the preamp output you will add a 4-pole cavity filter.
                > Neither taxi nor GSM will pass through it so what comes
                > after the cavity filter is not critical in terms of IP3
                > unless you have strong signals from friends on 144 MHz.
                > The Perseus will allow good copy very near strong local
                > 144 MHz stations (if they have pure signals) and that is
                > sometimes very important:-)
                >
                > 73
                >
                > Leif / SM5BSZ
                >
              • DF9IC
                ... Hi Corneliu, pleae do not expect an exceptional VHF performance from Perseus with a low noise (= high gain) converter. If you care about total noise figure
                Message 7 of 13 , Jun 1, 2008
                • 0 Attachment
                  --- In perseus_SDR@yahoogroups.com, "Nelu" <conmar@...> wrote:
                  > I hope it will help also with local stations during contests as I
                  > have about 6 strong neighbours in a radius of abt 1 Km or less.

                  Hi Corneliu,

                  pleae do not expect an exceptional VHF performance from Perseus with
                  a low noise (= high gain) converter. If you care about total noise
                  figure you have to use a converter gain well above the noise figure
                  of Perseus which in turn reduces its dynamic.

                  Let us assume a 32 dB converter gain (22 dB NF + 10 dB). Then the
                  saturation will occur around -37 dBm whith a total RX noise figure of
                  1...2 dB.

                  I use 2x11 on 144 from a good QTH. In a contest situation I have
                  signals at the antenna up to -25 dBm from stations up to 30 km away,
                  and up to -10 dBm from the closest station in 3 km distance near LOS.
                  Always assumed is high power at the TX station (as it is) and
                  antennas pointing to each other.

                  So you see that for such situations Perseus is 30 dB too bad. BTW,
                  other radios are, too, but with a well selected and optimized
                  analogue RX (FT1k + TVTR, IC275) you can at least handle up to -25
                  dBm levels if they are not too close in frequency.

                  But Perseus is a nice tool to monitor your own TX. For this purpose
                  you should use a converter with low gain, e. g. 0 dB, to keep the
                  original dynamic range.

                  73 Henning
                • Nelu
                  HI Henning, Thanks for advice. I expect a total converter gain of no more than 20 dB as the first device is a low noise power FET. I will provide some
                  Message 8 of 13 , Jun 1, 2008
                  • 0 Attachment
                    HI Henning,
                    Thanks for advice. I expect a total converter gain of no more than
                    20 dB as the first device is a low noise power FET.
                    I will provide some attenuators at the output to reduce converter
                    gain in contest situations. As I am living in the center of a big
                    city i will not be able to use noise figures of 1 db or less in 144
                    MHz. but I hope that the overall improvement over the present FT897D
                    to be dramatic anyway.

                    73 Corneliu


                    --- In perseus_SDR@yahoogroups.com, "DF9IC" <whrech@...> wrote:
                    >
                    > --- In perseus_SDR@yahoogroups.com, "Nelu" <conmar@> wrote:
                    > > I hope it will help also with local stations during contests as I
                    > > have about 6 strong neighbours in a radius of abt 1 Km or less.
                    >
                    > Hi Corneliu,
                    >
                    > pleae do not expect an exceptional VHF performance from Perseus
                    with
                    > a low noise (= high gain) converter. If you care about total noise
                    > figure you have to use a converter gain well above the noise figure
                    > of Perseus which in turn reduces its dynamic.
                    >
                    > Let us assume a 32 dB converter gain (22 dB NF + 10 dB). Then the
                    > saturation will occur around -37 dBm whith a total RX noise figure
                    of
                    > 1...2 dB.
                    >
                    > I use 2x11 on 144 from a good QTH. In a contest situation I have
                    > signals at the antenna up to -25 dBm from stations up to 30 km
                    away,
                    > and up to -10 dBm from the closest station in 3 km distance near
                    LOS.
                    > Always assumed is high power at the TX station (as it is) and
                    > antennas pointing to each other.
                    >
                    > So you see that for such situations Perseus is 30 dB too bad. BTW,
                    > other radios are, too, but with a well selected and optimized
                    > analogue RX (FT1k + TVTR, IC275) you can at least handle up to -25
                    > dBm levels if they are not too close in frequency.
                    >
                    > But Perseus is a nice tool to monitor your own TX. For this purpose
                    > you should use a converter with low gain, e. g. 0 dB, to keep the
                    > original dynamic range.
                    >
                    > 73 Henning
                    >
                  • DF9IC
                    ... There will be an improvement of more than 20 dB at 20 kHz offset, and still at least 15 dB in 50 kHz offset, compared to a FT897. Far off (200 kHz) the
                    Message 9 of 13 , Jun 2, 2008
                    • 0 Attachment
                      --- In perseus_SDR@yahoogroups.com, "Nelu" <conmar@...> wrote:
                      > but I hope that the overall improvement over the present FT897D
                      > to be dramatic anyway.

                      There will be an improvement of more than 20 dB at 20 kHz offset, and
                      still at least 15 dB in 50 kHz offset, compared to a FT897. Far off
                      (200 kHz) the difference in RX performance is less than 10 dB even at
                      low converter gain.

                      But please be aware that the true problem is usually not the RX (LO)
                      noise but the TX noise. If the other stations also use FT897 or similar
                      radios there will be no improvement at all, with large in-band signals.

                      Henning
                    Your message has been successfully submitted and would be delivered to recipients shortly.