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Need help in 88-108MHz preamp circuit!!

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by rahulan999, Aug 25, 2008.

  1. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Yes I know, I posted it as an example of a radio with AFC - despite the fact it's a VERY old tuner (I'm not sure how old though?).

    Quad have made some VERY nice gear over the years.
     
  2. rahulan999

    rahulan999 New Member

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    I'm not in my hometown now. When I'm going there only I'll do any experiments. I will post the pics of my receiver after a couple of weeks! Also there is some wooden board MW receivers I have made :) Everything I will post but wait.
    BTW Your new avatar is looking cute :D
     
  3. rahulan999

    rahulan999 New Member

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    Hi radiomate,
    Yesterday I picked up 4 pieces of TEA5711 easily from a component store here in Bangalore city. I enquired in just three shops. First one told that 'its Philips IC, discontinued no longer available'. Next one asked me how much you want. I told four and I got it for 50 Rupees(around 1 us dollar) per piece.
    Again I found its available in another shop also. Here I'm attaching the picture for you(mobile pic, sorry for bad quality). The top left IC is similar to what you have on your receiver and mine (Made in Taiwan). But the rest three are marked using dark golden font(not white).They told its original and showed me some duplicate chinese pieces of SONY cxa1019 IC. The part number is same but 'SONY' is not written on them. Also quality is not comparable.
    So I think the last three pieces may be the later(last) version of TEA5711.They looks more nicer than the first one.
    It seems pretty available here in India :)
    When money comes, I will pick up more and more..:D
     

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  4. dave

    Dave New Member

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  5. rahulan999

    rahulan999 New Member

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    Last 3 pieces looks exactly like this(google image!).
     

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  6. radiomate

    radiomate New Member

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    rahulan999 you sun of a gun! ;) I got the last 2 available in some store in Germany, don't know if there are more in that country.. mine were made in Taiwan, the radios are working well, so am sure they are good quality.. So what are you going to do with all those TE5711's? Just display them and tease those who are looking for them? ;) I think the next step for you is to make a Stereo receiver and be proud of your work.. You can use the close-up view on my page to get an idea of the layout.. Well good luck if you attempt this project! ;D
     
  7. rahulan999

    rahulan999 New Member

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    Thanks for ur compliments!:p
    Sorry, I'm soo excited for having these IC's..
    Actually I was sure that I could pick up it from somewhere here, because one of my friend told me that the local ready-made TEA5711 tuner boards(as what I have right now) are still available here. They may be old stock or the IC may be still available now for bulk ordering for industries.

    I have seen smd of TEA5711 in a shop.They don't have SDIP :) They told that
    it will be difficulty for me to soldering.
    But interesting thing is that they have doubled the price saying that its going to unavailable.
    Well, I'm planning to make a complete MW(530-1650KHz),FM(88-108MHz) receiver using one of this IC. I will do some research and well planning before start( goal is to pull out maximum performance from TEA5711.).I need ur suggestions also :)
    Others will be kept for future projects...
    Any performance problem for operating AM together with FM?(I heard like that).
     
  8. radiomate

    radiomate New Member

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    Don't buy the SMD TEA5711, they are a pain in the ( | ) to solder ;), even though Patrick Cambre did it. No problem having AM and FM on the same board, the IC was made for that. The TEA5711 spec. sheet shows a PC board for the AM/FM receiver with the SMD IC, you can use it to get an idea of the layout. Good luck.
     
    Last edited: Sep 29, 2008
  9. radiomate

    radiomate New Member

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    Right rahulan999, Patrick's website is up again. I don't think his receiver performs well for the following reasons:

    1) he's using a filter instead of a resonator at the detector. I tried it, the sound was badly distorted. A resonator is the way to go.

    2) his coils are not slug tuned, this is ok for the oscillator coil, he can spread or compress the coil to cover the correct frequencies, but he can't accurately peak the RF coil in this way.

    3) the trimmers on the variable capacitor can't be reached, and if he bends the capacitor to trim them, bending it back will change the values, so I don't know how he did it

    It is important to accurately peak the RF coil and capacitor trimmer to get good tracking of the RF section with the oscillator, otherwise the receiver will not be sensitive. For your information rahulan999, the RF coil is adjusted at the low end (88) and the capacitor RF trimmer at the high end (108).
     
  10. rahulan999

    rahulan999 New Member

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    If my memory is correct, in my receiver also doesn't use any box type slug tuned coils. Like what Patrick did, there's two adjacent 4-5turns plain coils I remember! For osc coil its pretty ok, stretching will do the trick for desired band coverage. But for the RF coil, I think the peak position is achieved by adjusting the 50pf parallel tuner capacitor trimmer(not sure). This way may be an alternative for avoiding the bulky slug tuned ones! My receiver is extremely sensitive and sometimes I could receive stations beyond 300Kms away!

    I have one query relating to filters and discriminator:
    They are 10.7MHz frequency, and 150Khz bandwidth right?
    Sometimes u have mentioned both resonators and discriminators in place of the two leg detector.Are they same or not?
    Here's a website:
    http://www.vanlong.com/products/ceramic.html
    They mention everything as different products.

    In my opinion, they all are basically 10.7MHz piezo resonators. So leaving the center leg of a same specification filter may act as a discriminator also. What you think?
     
  11. radiomate

    radiomate New Member

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    You don't adjust the capacitor RF trimmer IN PLACE of the RF coil. The RF trimmer is adjusted at the high end (108) and the RF coil at the low end (88) for best performance. Any other way will not give the best performance, period. Experience and the literature attest to that.

    My ceramic filters are centered at 10.7Mhz with 150Khz band width. My resonator is centered at 10.7Mhz. Yes leaving the filter center pin may make it act like a make-shift resonator, but that didn't work for me, the sound was distorted. Using a resonator, the sound was very clean. Why should anyone use a filter with center pin removed if they can use a resonator? In any case, why don't you check your TEA5711 receiver and see what they use, and let me know ;)
     
    Last edited: Oct 1, 2008
  12. rahulan999

    rahulan999 New Member

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    Surely they have used a two leg discriminator resonator only :). Everything I'm telling abt my receiver is from memory when I thoroughly checked it before a couple of months. It's in my hometown only as I'm far away from there for my job purpose. I will come back with more details and pictures sometimes later.

    My new TEA5711 receiver planning and parts collection will go on here, but for assembly I have to return back to my home ;)
    I think now I'm confident and quite familiar with the receiver section.
    Can u suggest me a good stereo pre-amplifier for the receiver with a low frequency boost? It should not distort at the strong signal output of the IC.
    A wonderful performing AM/FM receiver, thats on my plan..and TEA5711 is quite eligible for that :rolleyes:
     
  13. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The datasheet for the LM386 has a bass-boost circuit that can also be done with an opamp.

    The TEA5711 radio iC was not wonderful, it had a simple circuit with not very good sensitivity.
    Also its stereo separation wasn't very good. Its max distortion was horrible.
     
  14. rahulan999

    rahulan999 New Member

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    Audioguru,
    The IC may not be wonderful in datasheets. But practically it do awesome! When I bought my receiver 3 yrs back itself I particularly noticed the audio clarity. It sounds excellent! Regarding sensitivity, I don't have much words - it catches a lot of stations that is not possible for my SANYO audio system radio tuner. If my receiver board was not performing well then I would have thrown it away as what happened to my other old CXA1019 boards(It may be a good one, but not for me :))
    What do u think about this pre-amplifier?
    http://amplifierlab.com/?p=15

    Is it compatible with the audio out of TEA5711? How's the performance regarding tone controls and audio quality. If its ok, then it will be followed by a stereo power amplifier both running on 12V supply except receiver section on a 3v battery-pack.
    Also radiomate,
    that 1uf cap in place of original .1u at 2&3 pins on ur circuit may affect the originality of audio when I extend it for the AM part right? That along with the tone control section may sound too bassy when operating on AM.
     
    Last edited: Oct 1, 2008
  15. radiomate

    radiomate New Member

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    I made the TEA5711 receiver and listened to it for months. rahulan999 you have 2 boards with the TEA5711, and you've listened to it too. So hands on experience talks here, not premonitions. The separation is 30dB, not the highest, but it is very good, I made a stereo decoder with 45dB separation and I can't really tell the difference, and the 5711 has better separation than my Sony ICF-SW7600G! This says a lot.

    I increased the caps at pins 2 & 3 to boost the base response. it all depends on how you will listen to the receiver. You can stay with the 0.1uF caps with acceptable base performance. The 0.012uF de-emphasis capacitors at pins 2 and 3 depend on the pre-emphasis used by the FM stations in your region (75uS or 68uS I think). I used 0.01uF caps since it is 68uS where I am. Check the net for info on this subject-----The highs and lows in my headphones (Koss Pro35A) are excellent.

    Don't expect excellent performance on AM. The IF section uses only 2 tuned circuits at 455KC, so the selectivity will be mediocre, but the sound quality will be real good (!). You can add a narrow bandwidth 455KC ceramic filter ahead of the first IF transformer to improve the selectivity, but the audio quality will suffer.

    Don't use the LM386 IC, they have high hiss when a capacitor is connected between pins 1 and 8 to increase the output power. I use these ICs with pins 1 and 8 always open with acceptable audio performance. I am using the TDA7050 in my FM receivers with very good audio performance.
     
  16. rahulan999

    rahulan999 New Member

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    Hi radiomate,
    What about TDA1524 tone controller? Its also from Philips. Check out the above link for its circuit.
     
  17. radiomate

    radiomate New Member

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    I looked at the TDA1524 spec. sheet, looks like a good performer, but why do you want to use it and complicate your life with the 5711 receiver? If I were you, I would use the 5711/7050 combination for a portable receiver with good headphones (Koss) and be satisfied ;)
     
  18. rahulan999

    rahulan999 New Member

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    :D
    Actually I'm not a 24hr experimenter, bec basically I'm a software engr ;)
    I didn't do any complicated projects till now but I wish to. I really want to make this complicated as a perfect achievement dont know whether I will get time for any other such projects in future.
     
  19. radiomate

    radiomate New Member

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    Software Engineer... interesting, I do Visual Basic programming myself. 2 years ago I wrote a ray tracing application that creates photorealistic pictures, 17000+ lines of code with pretty advanced features. If you haven't seen it on my website, have a look here:
    http://www.midcenturyradios.com/miloraytracer.html

    Back to the radio, I suggest you build the 5711/7050 combination with 4.5V supply (like my 1st receiver) and make it a portable receiver you can use anywhere.. believe me, contrary to what some guys insist on stressing, it is a very good performer, and when you have built it, aligned it and received stereo stations on a radio you made yourself, the satisfaction will be great, and you will not want to stop using it :D
     
  20. rahulan999

    rahulan999 New Member

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    7050 also I have :)
    I dont like a headphone bec continues use is not good for ears! :D
    I'm planning to place the my whole non-portable receiver on a polished wood-board with receiver-preamp-poweramp section with connection terminal for speakers.
    People should scare on seeing it! That is my primary objective :D
    BTW, your ray-tracer is freeware or not????
     
  21. radiomate

    radiomate New Member

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    My ray-tracer if free-nothing :D I worked 2 years on it, so it is not freeware or open-source. Cheers
     

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