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Re: [softrock40] Re: Ensemble RX2 VHF - Zener diode D4 replacement

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  • Sylvain AZARIAN
    Bob, I share your opinion regarding these old rigs ... that s why I kept mine ;-) I made some measurements yesterday at my working place with an Agilent signal
    Message 1 of 10 , Jan 29, 2011
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      Bob,

      I share your opinion regarding these old rigs ... that's why I kept mine ;-)
      I made some measurements yesterday at my working place with an Agilent signal generator. I tried two signals :
      - one at 145.605 at -90 dBm
      - second one 100 hertz away, 40 db lower...

      I could see the two signals on waterfall after fine adjust of the trimmer caps (I gained 20 db....). This confirms your sensivity estimation better than -100 dBm. I did not perform the full MDS test but saw following interesting things :
      - my I/Q balance is very bad, image rejection around 20dB. Seems the Op amps resistors do not have exactly the same values... needs further investigation
      - I've seen unstable sampling frequency on the laptop embedded sound card, could see a drift over time of both (still equidistant) signals on waterfall. I've seen that on a MacBook and on a HP Laptop.
      - poor reverse isolation with LO.
      - Frequency precision of the shipped si570 was not that good. After precise check on R&S spectrum analyzer, had to correct the freq. to see the waterfall at the right place.

      nothing really new, just to confirm your sensivity estimation & trimming procedure.
      I am now playing with Baudline under linux and this tool is nice to display waterfalls...

      Regards
      73 from F4GKR - sylvain  

      2011/1/25 g8voip <g8voi.reeves59@...>
       

      Hi Sylvain,

      Both Bodo Schultz DJ9CS and I built and tested beta versions of the Ensemble VHF RX for Tony, and we got very similar results. The 2m version has a MDS of around -140dBm, so certainly not lacking sensitivity and is almost comparible with most typical VHF transceivers.

      I also built and tested versions for 6m and 4m, and the performance was very similar.

      I also compared the performance against my 6m, 4m and 2m plug in VHF converters for the SoftRock v9.0 RX, and all are very similar, not too surprising as it is the same design.

      It sounds perhaps of you still have some problems either with your hardware or the AVR firmware configuration.

      73, Bob G8VOI



      --- In softrock40@yahoogroups.com, Sylvain AZARIAN <sylvain.azarian@...> wrote:
      >
      > Good evening,
      >
      > My Ensemble RX2 VHF is working with the original zener modified (4.2V
      > instead of original 3.3v)
      >
      > The overall sensivity is quite poor... I don't think it comes from that
      > modification (zener). My opinion is that the op. amp. chain gain is too
      > small.
      > I've made several tests today and... well I need to boost the receiver
      > somehow because it is difficult to get weak stations out.
      >
      > Something else : the Si570 Lo is radiating a lot... I can receive the
      > carrier two or three meters away from the receiver with a handheld yeasu
      > tuned on LO or LO+FI (received freq.)
      >
      > Any suggestion to improve the receiver ?
      >
      > regards
      > sylvain
      >
      > Re: [softrock40] Ensemble RX2 VHF - Zener diode D4 replacement
      >
      > Tony,
      >
      > thanks for reply. Honestly I am quite sure I lost it... the two others (d1 &
      > d2) were in the bags...
      > I am trying with other voltage and I will let you know...
      >
      > 73 from F4GKR - sylvain
      >
      > 2011/1/16 Tony Parks
      > <kb9yig@<http://groups.yahoo.com/group/softrock40/post?postID=aKjS28JJnDMXdgcIDf4muTAk0KdRCbfXyF4UAwFEZmAAhOJbfZLrw7Gf6YeIiaGSaoBLC7JyIzAE>

      > >
      >
      > >
      > >
      > > Hi Sylvain,
      > >
      > > The 3.3 volt zener diodes should have been included in the bag with the
      > > resistors. If missing, let me know and I will send them to you.
      > >
      > > Thanks and 73,
      > > --
      > >
      > > Tony Parkskb9yig@ <http://groups.yahoo.com/group/softrock40/post?postID=Ez5a3gQLBLiAyHJ0avUXZvuh7L_ADC9I_a35GNMYnTZBCb89cJC4SQN_uy9GOgTBqX7jyGNS1g>http://www.kb9yig.com

      > >
      > >
      > >
      > > On Sun, 2011-01-16 at 16:37 +0100, Sylvain AZARIAN wrote:
      > >
      > >
      > >
      > > Good evening,
      > >
      > >
      > >
      > > While assembling my kit received weeks ago, can't put an hand on 3.3V zener
      > > D4. This one is used to set voltage at gate G2 of Q1.
      > >
      > > My junk box is full of 4.2V zener diodes... any advice ?
      > >
      > >
      > >
      > > Thanks
      > >
      > > F4GKR - Sylvain
      > >
      > >
      > >
      >


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