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Re: [softrock40] Re: Switching BPFs

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  • Pete Smith
    Interesting, Philip - I am switching 4 lines of the 5 - only the center taps of the transformers are in parallel. As you can see my level disparities really
    Message 1 of 21 , Aug 1, 2008
      Interesting, Philip - I am switching 4 lines of the 5 - only the center
      taps of the transformers are in parallel. As you can see my level
      disparities really don't get that much worse, nor do the phase errors
      follow a frequency-dependent pattern that I can see. But it sure ain't
      working.

      73, Pete

      At 11:31 AM 8/1/2008, philiplock wrote:
      >--- In softrock40@yahoogroups.com, Pete Smith <n4zr@...> wrote:
      >Hi Pete.
      >
      >I also tried to switch the BPFs with a 3 pole 4 way switch
      >and had the same problem as you had.
      >I had a look at the outputs of the filter with a scope and found that
      >the level of one output get lower as I went up in frequncy.
      >if I swapped the outputs of the switch the inbalace stayed the same.
      >I give up in the end I just could not workout what was happening.
      >
      >Philip g7jur
      >
      >
      >
      > >
      > > At 09:01 AM 8/1/2008, John H. Fisher wrote:
      > > >We are providing three binary bits to be used by a hardware BPF
      > > >switching board. The three hardware outputs represent memory
      >locations
      > > >100-199, 200-299, 300-399... depending on the most significant
      >digit 1-8
      > > >= 000-111. The actual BPF hardware will use those three lines to
      >select
      > > >a one of eight filters based on the memory location. This was an
      >add on
      > > >Kees thought of to use the last three pins on the chip. Seems like
      >a
      > > >good idea :-) Best of luck with your relay BPF board. I'm sorry the
      > > >Si570 controller can't help you out with that particular problem:-)
      > >
      > >
      > > What you have there is really neat, John - I am wondering if anyone
      >has a
      > > hardware implementation of the BPF switching that will work with
      >the Lite
      > > 8.3, or if the 5-lead BPFs it uses are unique and difficult to
      >interface
      > > to. My problem seems to be related to lead lengths (maybe), and
      > > secondarily to an apparent imbalance in both phase and gain in my
      >Lite
      > > 8.3. I can remotely locate the BPF on 160 and 80. By 40M I'm no
      >longer
      > > able to get the I/Q balance corrected reliably - sometimes it works
      >and
      > > sometimes not. Above 40, the auto balance routine won't even run.
      >Here
      > > are some examples:
      > >
      > > All of the following tests were run using Rocky 3.5, eyeballing the
      >signal
      > > levels off the spectrum display. All the image rejection tests
      >were run
      > > with the fundamental at x025 KHz - 1825, 3525, etc. and a local
      >oscillator
      > > frequency of x046 - 1846, 3546, etc. Levels expressed are high/low
      > > extremes across 96 KHz audio bandwidth
      > >
      > >
      > > Band BPF location Image Rej (dB) Phase error (deg)
      >Gain ratio
      > > (one channel as % of other)
      > >
      > > 160 orig. >60 -.93 to -
      >.33 .62-.64
      > > remote >60 1.4 to
      >4.1 .61-.65
      > >
      > > 80 orig. >60 6.2 to
      >7.1 .59-.61
      > > remote >60 4.1 to
      >7.2 .69-.70
      > >
      > > 40 orig. >60 7.3 to
      >8.1 .70-.71
      > > remote no data at this and higher - auto I/Q
      >balance
      > > would not work
      > >
      > > 20 orig. >70 5.8 to
      >6.44 .66-.78
      > >
      > > 15 orig. >60 3.9 to
      >5.2 .74-.76
      > >
      > > 10 orig. >60 8.7 to
      >9.2 .77=.78
      > >
      > > 73, Pete N4ZR
      > >
      > > ...who is going to put this aside for a while and see if he can get
      >his
      > > scope working.
      > >
      >
      >
      >
      >------------------------------------
      >
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      >
      >
      >
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