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Re: PowerSDR LF limit?

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  • Don
    Thanks for the tip on securing the toroids. Got another question, but will open a new topic. Don
    Message 1 of 5 , Mar 2, 2011
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      Thanks for the tip on securing the toroids. Got another question, but will open a new topic.

      Don


      --- In softrock40@yahoogroups.com, "g8voip" <g8voi.reeves59@...> wrote:
      >
      >
      > Hi Don,
      >
      > Must admit it did make me think a bit! Having said that, I had only just got out of bed, had breakfast and a few minutes to spare before heading off to work :)
      >
      > When I tested one of the beta Ensemble LF kits for Tony, I mainly used Winrad and Rocky, cannot remember now if I tried PSDR or not. Anyway, the main thing is there is an explanation for what you were seeing and it is the correct operation.
      >
      > As for protecting the coils and transformers, this was mentioned in another thread yesterday, its a good thing to do as you are pretty certain at some point to knock or drop something on the PCB if you run it out in the open on your bench.
      >
      > I used 2 part epoxy adhesive on all of mine, works fine, but of course would present a little problem if I ever wanted to remove any of them.
      >
      > The other choices are RTV or Silicon rubber, only thing to watch out for are those containing acetic acid (vinegar smell) as they can react with copper. There are plenty of types available that are available which are suitable, Dow Corning etc, but they tend to be expensive.
      >
      > Another alternative mentioned yesterday is a hot melt glue gun, that has the advantage that it can easily be heated up again if you want to remove the component.
      >
      > There are no issues to worry about with dielectric constants etc affecting performance with any of the above at HF frequencies.
      >
      > 73, Bob G8VOI
      >
      >
      >
      > --- In softrock40@yahoogroups.com, "Don" <don1mh@> wrote:
      > >
      > > Hey Bob,
      > >
      > > You have explained the situation very well. I know now what I see with PSDR at the low end, is a function of the application, and not the RX. I was going to waste time messing with the options of PSDR to get it to go lower. No need now. It's just the way it is.
      > >
      > > I shouldn't do this, change subject, but maybe once. Broke connection of a toroid right at board. All of them are so prone to move with the slightest jarring of the board.One too many times of bending over, and they are going to break connection. I'm going to get a tube of GE Silicone II and a tooth pick and lightly dab all of them at the base. I don't think uH's will change. GE is pretty inert. That should stabilize them mechanically. What do you think?
      > >
      > > Thanks, Don
      > >
      > > --- In softrock40@yahoogroups.com, "g8voip" <g8voi.reeves59@> wrote:
      > > >
      > > > Hi Don,
      > > >
      > > > The lower limit for the Si570 will be around 3.5MHz divided by 16 so should be able to set the LO down to around 218kHz.
      > > >
      > > > PowerSDR works in a different way to Rocky. PSDR uses a 'pseudo'IF, set to 9kHz by default, so the lowest you can tune will be around 218kHz + 9kHz = 227kHz, close to what you are seeing which is correct.
      > > >
      > > > PSDR uses the IF to shift the point you are receiving away from any centre frequency spike or hum and noise etc.
      > > >
      > > > In Rocky and Winrad it is possible to tune lower as they use a different method, i.e. the LO (centre frequency) can be set to around 218kHz, then you can tune down further depending on the sampling rate, up to 48kHz if you have the sound card sampling rate set to 96kHz. So in theory with Rocky and Winrad you can tune down to around 170kHz.
      > > >
      > > > The PSDR has a number of benefits, more so for transmitting where as the fixed centre frequency used in Rocky does allow it to use a nice system for image rejection that is not possible with PSDR.
      > > >
      > > > 73, Bob G8VOI
      > > >
      > > >
      > > >
      > > >
      > > >
      > > >
      > > > --- In softrock40@yahoogroups.com, "Don" <don1mh@> wrote:
      > > > >
      > > > > Maybe, my observation is known, but I don't have the answer. I playing around at LF using Ensemble II, LF Option. I have constructed a 39" square loop just for this band, 180 to 480 KHz. I can receive very well, even inside, the NDB beacons and other "stuff". I'm using PowerSDR v1.19.3.15 from SV1EIA as the GUI.
      > > > >
      > > > > However, at about 228 KHz, I can't go any lower in frequency. I see a "crossover" effect of signals and junk. The frequency numbers do go down, but I hear no real signals below this 228 KHz point.
      > > > >
      > > > > But, if I switch to good old Rocky 3.6, and set center frequency to 220 KHz, I can continue past 228 KHz, all the down to 180 KHz, hearing real signals, and seeing no "crossover".
      > > > >
      > > > > So, what is going on with PowerSDR, not being able to go below 228? I suppose the Si570 quits, but why? Not so with Rocky.
      > > > >
      > > > > Don
      > > > >
      > > >
      > >
      >
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