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Re: ULTRA CHEAP DONGLE OFF AIR MONITOR

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  • graham787
    Rich, Well all I can say , is take a wire to pin-1 and see what happens ! If stations want to leave a monitor running , this is a good £10/£6 option
    Message 1 of 3 , May 1, 2013
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      Rich,

      Well all I can say , is take a wire to pin-1 and see what happens !
      If stations want to leave a monitor running , this is a good £10/£6 option , stability is good and results are excellent , it meets the JR criteria of 'no pre filtering' as well , I was monitoring 14.103 over the weekend and decoding signals not showing on the w/fall , using virtual audio cable as the data link

      Pull the pass band to 20khz usb and with dream software , good copy of HF DRM stations with 10KHz data b/w

      No need for the up-convertor , and with the mixer and conversion oscillator out of the cct , noise factor is -very- low , the 8 bits is misleading , as once post processed your close to 60 dB dynamic range , OP4 dropped another 2/3 dB in the first test on 472

      As for a shoot out , low bands direct sample , with hdsdr it gives the ft897 a good run .ok the racal ra6790gm with the LF front end , no preamp has round 120 db dynamic range but that's driving the first mixer with 5 to 7 watts of rf .

      73-G


      Signal path variations

      direct sample

      Ae <> A/D

      Quad sampling

      Ae <>[mix]<>A/D

      With up convertor

      AeHF<>[mix]<>vhf<>[mix]HF<>AD



      --- In O_P_E_R_A_@yahoogroups.com, "Richard B Georgina" <wd4rbx@...> wrote:
      >
      > Hi Gram,
      >
      > Just add an upconverter and listen for signals below the AM broadcast band such as 474.2 KHz. and up...No matter what band you want to monitor you need a good antenna.
      >
      > I have the cheep USB TV dongle and the Ham it upconverter and love it. For well under $100 US you can have a good RX station. Don't expect the dongle to RX as good as your ham rig...! I have to admit it RX damn good for the money...! I have the Yaesu VR-5000 and if the dongle and upconverter were available at the time I would have saved myself $400.
      >
      > I highly recommend this approach.
      >
      > Rich
      > WD4RBX
      >
      > >>ULTRA CHEAP DONGLE OFF AIR MONITOR
      >
      > No need to tie up a radio now to monitor off air , with the latest versions of the `Ultra cheap dongle' project , the R820T dongle offers good sensitivity from 24 MHz to pas 1000 MHz and is cheaper than the E4000 based version (£15 in uk), which fails round 60 MHz and is no longer in production.
      >
      > Slightly out side its published limits the latest R820T based USB-2 dongle provides direct access to 12 , 10 , 6 , 4 , 2 Mtrs and 70 23 CM
      >
      > The addition of a connection to `Pin 1' of the A/D chip, via a 0.1 uF , allows `Direct Sample' mode from round 24 MHz down to well past 136 KHz , in this mode , the addition of a suitable ATU improves performance
      >
      > The SDR sharp software has features that compliment `data' use , simple set up , good spectrum and waterfall and drag-configurable bandwidth , up to 20 KHz in SSB
      > Click qrg selection , there are other sdr packages , perhaps more suited to ssb/cw use , but with the up-date facility , sdr-sharp offers a good `fit and forget' package
      >
      > Dongle mode selection is via the `controller' application , available by clicking the `configure' button , the SDR app must be `stopped' first , giving Quadrature sampling , for normal use , or Direct sampling (I Branch) for modified LF>HF
      >
      > Once the mode is selected , then the appropriate frequency correction (ppm) can be inputted , this slews the recovered frequency from the Dongle for netting purposes , further correction may be applied in the main software , with the `shift ` function
      >
      > Access to AGC and Gain control is also part of this `pop up' menu
      >
      >
      > Results
      >
      > Using a co linera , comparable results to the ft897 are obtained on VHF
      >
      > 70/50 MHz , gives better performance than my 144/70 transvertor , giving equal signals from gb3bux on 50 MHz and 70 MHz at 50 miles range
      >
      > Quad sample mode, 24/28 MHz , using tuner and 14 MHz H Ae , excellent results
      >
      > HF , direct sample , using 40 vertical and tuner , compatible to the ft897 but lower `noise' due to the removal of the mixer chip R820T from the signal path , noting that minimum decode levels are based on s/n , lowering the system noise ,
      >
      > NB , this is a `Ultra-Cheap' 8 Bit solution , large carriers will cause problems , there are the odd `spur' but for £6 / £10 , it provides a effective off air monitor !.
      >
      >
      > Audio from the sdr software may be shared by selecting the common windows sound driver , or by one of the `virtual' audio link software's
      >
      >
      > The latest version of the SDRsharp software may be found :-
      >
      > http://sdrsharp.com/index.php/downloads
      >
      > This software has a dos based installation scrip that recovers the latest versions of the file set from the web and unpacks them , making updates nice and simple , re-run and reload driver , job done , even the icon links remain !
      >
      > http://sdrsharp.com/downloads/sdr-install.zip
      >
      > There are various help files etc , but once un-packed , all that is needed is to use the windows based drive installation tool zadig.exe , to load the driver and that's it
      > [noting the USB port forms part of the address , so the dongle needs to be in the port interned for use]
      >
      > More than one device may be installed in the same machine and addressed via the software control and device selection panels, one standard and one modified , gives 'dc to 1500 MHz coverage for very little outlay and may addressed in the same pc by two sessions of a sdr software
      >
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