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Re: [softrock40] PIN Diodes

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  • Garey Barrell
    Drake used the MPN3404 throughout the TR-7. There are a total of 43 of them in the transceiver. They are still available from many suppliers. The only one
    Message 1 of 41 , Dec 2, 2006
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      Drake used the MPN3404 throughout the TR-7. There are a total of 43 of
      them in the transceiver. They are still available from many suppliers.
      The only one that has given any trouble is the one used to switch the
      calibrator signal on or off. These fail shorted, but a fairly rare
      failure. All are used for low level switching, various filters in or
      out, etc.

      73, Garey - K4OAH
      Atlanta

      Drake 2-B, 4-B & C-Line Service Supplement CDs
      <www.k4oah.com>



      Bill Dumke wrote:
      > Kees,
      >
      > Back in the late 1970's Motorola had some cheap plastic PIN diodes
      > with a long storage time. The part number was MPN3401, but they
      > worked great for switching baseband filters all the way down to about
      > 200 kHz. Also used them in a Doppler direction finder at 243 MHz.
      > Unfortunately, they weren't very reliable either. They had a tendency
      > to open up, even when used at low signal levels.
      >
      > Bill WA9PWR
      >
      > Kees wrote:
      >>
      >> Can someone provide information on the best PIN diodes for HF operation
      >> if we want to use them for electrical bandswitching. What
      >> characteristics do you look for ? Low capacitance, low inductance, etc ?
      >>
      >> 73 Kees K5BCQ
      >>
      >
      >
    • FRANCIS CARCIA
      Type 43 is very lossy at 145 MHz. Try #63 or lower perm. Giancarlo wrote: Hi Art, ... (with ... I have done tests on 145MHz while
      Message 41 of 41 , Dec 4, 2006
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        Type 43 is very lossy at 145 MHz. Try #63 or lower perm.

        Giancarlo <i7swx@...> wrote:
        Hi Art,

        --- In softrock40@yahoogro ups.com, Art <KY1K@...> wrote:
        >
        >
        > >some of these have some good
        > >switching speed their on-off time are very different.
        >
        >
        > Hi Gian,
        >
        > I have thought about switching symmetry a lot. I think symmetry
        > improvements COULD make the QSD practical at higher frequencies
        (with
        > the current technology), but probably not at 2 meters.

        I have done tests on 145MHz while experimenting with the I7SWX 2
        Transformer H-Mode Mixer with IF from 455kHz to 100 MHz, using LVDS
        squarer. The FST3125 mixer was working but the conversion losses were
        minimum -8dB (LO= RF-IF) for IFs from 4MHz to 70MHz. Transformere
        were balun core #43-2403. At 455kHz the Loss was -9dB but probably
        due to transformers core. On HF the 2T H-M Mix has a loss of -5dB or
        less with downconversion and around -5 with up conversion 70MHz IF.
        At 50MHz RF 2T was at -5dBm loss with IF at 28MHz.

        The increase of losses is certainly due to internal switch (gating
        and sw itself) unbalances, delay, phasing...who knows. When LO
        frequency is going up switches gets crazy...hi

        Table

        RF in = 145 MHz.
        IF LO = RF- IF ConvL LO = RF+IF ConvL
        MHz] [MHz] [dB] [MHz] [dB]

        0.455 144.4 -9 145.5 -9
        4 140 -8 149 -8
        9 135 -8 154 -8.5
        10.7 134 -8 156 -9
        21 124 -8 165 -10
        45 100 -8 165 -10
        70 75 -8 215 -12
        100 45 -9 244 -15

        >
        > Symmetry is perhaps more important than speed, although the current
        > generation of analog switches we use are not designed or rated for
        symmetry.
        >
        > By symmetry, I mean that the t(on) time and the t(off) times are
        > identical within each switch (they turn off and turn on at the same
        > time relative to the enable line). Also, that each individual
        switch
        > within a package turns on and turns off at the same speed relative
        to
        > the other switches in that package.

        You are right. Also components tech figures are given by marketing
        and not engineering .... often are what customers would like
        to "see".... and simulators are OK for these...hi

        >
        > In the case of the current generation of FST switches, we think
        they
        > turn on in ~1.5 nS and take ~4 nS to turn off. If we could delay
        the
        > turn on by 2.5 nS in each of the switches in the FST package, we
        > might be able to achieve better performance while using the same
        technology.

        Everything is a compromise so we have to take for good the "best
        figures" so we can be happy .... I have good friends (well known hams
        that can feel and see differences of 0.1dB or less ... for me 1 dB or
        more is the same ... I am not in business...hi

        >
        > After all, we don't care which 90 degree segment of the input
        > waveform we capture, we only care that each individual switch
        > captures a different 90 degree slice (without overlap or dead
        spots)
        > of the input wave .

        Yes. The problem is that too many "pieces" or "stages" are involved
        in those 90 degrees....

        >
        > I am not quite sure how to do this easily. But, an rc network on
        the
        > enable line would surely slow down the t(on). But, how do we make
        the
        > turn off delay on the enable line respond as though the rc network
        > wasn't there?

        You need to go inside the FST switches and see what happen ... so you
        can put anything you like to balance.

        We know that the best digital quadrature generator is the Johnson
        counter dividong by 4 the LO ... well, on paper... You maybe be OK
        with the 0° and 90° quadrature but if you use the 180° and 270° also
        you will see that these complementary waveforms are shifted respect
        the others of around 100pS ...

        We are all interested oin the Tayloe QSD but maybe we should look at
        the limits of use ....

        The SoftRock40 V7 was designed because the SDR 1000 and SR V6 were
        not performing as expected .... so it is the limit of the QSD
        configuration or the not so good quadrature signals driving it or
        both or what else? What is generating the high noise of QSD when
        going up on frequency?

        untill someone will give us a nice set of GAsFet switches with
        perfect and fast switching Ton-Toff ... we will have to accept some
        limits (HF) ...thenm we can go to SHF. The main problems will
        be ...Cases we cannot handle anymore... even the TSSOP are dying
        now ...let's collect a lot of those SOIC chips that can last us till
        end of century, at least (hope I will resist till the ..mmmm 66
        ohm) ...hi

        73

        Gian
        I7SWX
        W1-I7SWX
        F5VGU

        > Regards,
        >
        > Art
        >


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