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Analizator stanów logicznych — 13 komentarzy

  1. many thanks, this info was exactly what I was looking for!
    question: where did you get the 479.5MHz value, and how did you know that you needed to subtract it from the calculated frequency value? I searched the SP5055 datasheet for this information yet couldn’t find it.

    • These receivers use old analog satellite tuners in which 479.5MHz is common intermediate frequency. For example you could check datasheet of this one: http://www.dpcav.com/xcart/Comtech-BSS479LAIDF-Analog-Tuner-Module.html

      So, having intermediate frequency you have only two choices: pll should make lower or higher frequency with offset of 479.5MHz to received frequency. Typically higher one is choosen. In these tuners is reasonable as it’s lower receiving frequency is about 900MHz (960-480=trouble).

  2. hi and thanks
    i want to used tuner with avr. but I do not know how and what kind of tuner should I use? (i2c)
    I think the tuner ” sharp BSFJ78G29 ” is good because pll- i2c type, but I do not know how to set : the frequency, symbol rate, vertical or horizontal,…?
    can you help me? something like notes about BSFJ78G29 i2c protocol and …..
    thanks alot

    • It looks like this tuner have SP5655 tuner which is almost the same as SP5055. If you google for ‚sharp BSFJ78G29’, you can find tuner datasheet. It clearly states that pll chip is SP5655 which is the one you should talk to via i2c. Datasheet for SP5655 is also easily found by google.

      Do you found some stock of this tuners? Narrow bandwidth is quite good feature. Maybe I could buy one or more if price is good 🙂

      About symbol rate and polarization – what do you want to do with it? It’s analog tuner and I think that almost nothing is available these days on satellite in that way. Symbol rate is domain of digital transmission. Polarisation is also another story as it is modulation of power supply for receiving head, and this is also not related with tuner iself.

  3. thanks majek
    i want to analysis some sat frequency features for example signal strength,…. but i do not know How to do it? i searched but i founded some thing like sharp tuner. In your opinion, what tuner I choose?(digital and i2c if possible)

    • Digital tuners differ a lot from analog ones. In analog almost everything important is inside tuner module, everything outside is just audio separation, equalization and control. Digital tuner is another story – much harder for hobbyist. I’m not familiar with all that demodulation, i/q things and so on (which is processed outside of tuner module), so in this part I couldn’t help you.
      So, for analog sattelite – it quite easy to use tuner module to do something (it has rssi analog output, information about frequency lock/deviation is availavle from i2c registers).
      For digital measurement I would definitely get PC satellite card – there is a lot of tools which shows signal strength, ber, transport streams, etc in real time. From my experience tuning to get maximum gain sometimes doesn’t work – it’s better to do fine tuning based on ber – and to do it you need complete receiver.

  4. thanks alot majek with you help i can set frequency but
    How to check signal information for example signal strength with sharp BSFJ78G29 tuner? (true signal or not)

  5. U mnie w tunerze (receiver dla modelarskich nadajników video 1.2G), właściwie głowicy, siedzi nie sp5055 a TA550A (toshiby) z kwarcem 4MHz i TA8804 z kwarcem 479,58 (okrągłe ustrojstwo, może to nawet generator jest).
    Miałem kłopot ze znalezieniem datasheetu od tego TA550A – może kolega pomoże.
    Dzięki z góry za pomoc.

    • Nie znalazłem nic do TA550A, ale podejrzewam, że jest kompatybilny z SP5055. Też typowo wymaga kwarcu 4MHz i raczej dziwne byłoby jakby gadał jakimś innym protokołem. Najlepiej wziąć jakiś analizator stanów logicznych i się przekonać 🙂
      Co do ‚kwarcu’ 479.58, to jest to filtr pośredniej częstotliwości. Od niego zależy selektywność odbiornika i dlatego często jest wymieniany na węższy (do satelity stosuje się szerokie, ale do bezpośredniego odbioru na 1.2G typowy jest za szeroki i łapie też dużo śmieci i sąsiednie kanały).

  6. Hi there,

    Great info! 🙂

    Did your board come with firmware to use as an analyser, or did your download/write your own?

  7. Hi All, thank you for this info.
    Finally I tried also to pilot this RX 23 cm, and it works fine on the I2C address „2C”. with a single PIC 16F84A and a F6ICX program for COMTECH receiver…
    Now I ‚m rewriting the same prog for arduino nano and I2C LCD…

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