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Re: Ultra Cheap RX Dongle for monitor stations

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  • graham787
    Sigi You could ask on the google sdr site , some there seem to have the details of the chips
    Message 1 of 5 , Aug 27, 2013
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      Sigi

      You could ask on the google sdr site , some there seem to have the details of the chips

      https://groups.google.com/forum/?fromgroups#!forum/ultra-cheap-sdr

      Have you details for this ?:-

      Ps a friend found a preamp ... 50ohms in and 200 ohms symmetrical out ...> and uses that for direct sampling instead using a balun

      Tnx-G,


      --- In O_P_E_R_A_@yahoogroups.com, "siegfried jackstien" <siegfried.jackstien@...> wrote:
      >
      > I do not know if that is the case (so just a guessing!!) ... what if the
      > sampling chip has an internal pll that is "locked" to the 28.8 external
      > clock but works with a higher clock rate (maybe 57.6 mhz or even higher)
      >
      > On the realtek hp they CLAIM that the chip can also work with an if of 36
      > megs .... so I am guessing that there is some "magical clock divider" in the
      > chip ... otherwise the chip could not work with input of 36 megs (or only
      > with lots of ghost signals)
      >
      > Sadly realtek gives no further info about whats going on in that chip
      >
      > Dg9bfc
      >
      > Sigi
      >
      > Ps a friend found a preamp ... 50ohms in and 200 ohms symmetrical out ...
      > and uses that for direct sampling instead using a balun
      >
      >
      >
      > > -----Ursprüngliche Nachricht-----
      > > Von: O_P_E_R_A_@yahoogroups.com [mailto:O_P_E_R_A_@yahoogroups.com] Im
      > > Auftrag von Andy Talbot
      > > Gesendet: Dienstag, 27. August 2013 13:34
      > > An: O_P_E_R_A_@yahoogroups.com
      > > Betreff: Re: [O_P_E_R_A_] Ultra Cheap RX Dongle for monitor stations
      > >
      > >
      > >
      > > Yes... Glad its not just me. I noticed gain fell off considerably at
      > > low frequencies - was begining to suspect my transformer at first.
      > > There's something very odd going on with those dongles. The main chip
      > > doesn't seem to take in baseband - it is as if it does an IF sampling job
      > > on a 28MHz input, since input at higher HF works OK, and an input at 28MHz
      > > behaves as if it were at zero frequency - classic alliasing in fact.
      > >
      > > Could it have in internal high pass filter specifically for first allias
      > > sampling ?
      > >
      > > I've been unable to lay my hands on a full data sheet for the Realtek chip
      > > so have no explanation for what its actually doing
      > >
      > > All pointers / data sheets greatfully received :-)
      > >
      > > Andy
      > > G4JNT
      > >
      > >
      > >
      > > On 27 August 2013 14:24, graham787 <g0nbd@...> wrote:
      > >
      > >
      > >
      > >
      > >
      > > All
      > >
      > > In support of requests for monitor stations ,
      > >
      > > Listed are a set of links to enable the £5 usb dongle to be used as
      > > SDR-RX , it will benefit from preselectors / filters / pre-amps etc , but
      > > the initial out lay of £5 is minimal compared to the results and quality
      > > of the supporting software is excellent , as well as the SDR )
      > >
      > > Performance on HF is 'good' and benefits from a ATU or better a pre-
      > > selector , The later dongle will cover 1500 MHz down to 24MHz directly
      > >
      > > A modification is needed to access the direct sample mode ,
      > > attaching a wire and cap .. the video listed is using the wire+cap method
      > > , alternative is to use a transformer , taking care the core is rated at
      > > the band is question
      > >
      > > MF and down , the 'gain' falls off , I have good results using the
      > > 500k tx-atu , the Mini-whip Ae seem's to offer a reasonable solution , and
      > > can be seen operating > http://myweb.tiscali.co.uk/wgtaylor/grabber2.html
      > >
      > > 73-Graham,
      > >
      > > SDR >>http://sdrsharp.com/
      > >
      > > Mods>>http://www.rtl-sdr.com/rtl-sdr-direct-sampling-mode/
      > >
      > > 7MHz ssb>>http://www.youtube.com/watch?v=7Le-1aW9BR4
      > >
      > > Virtual audio cable >>http://vb-audio.pagesperso-
      > > orange.fr/Cable/index.htm
      > >
      > >
      > >
      > >
      > >
      >
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