FM/AM Tuner

[jeje]

Hello everybody,

I am looking for ideas concerning FM decoder(s).

I have seen some circuits about this with tubes and transistors. I don't know the quality of electronic.

But I can find it. I am sure I have it, where???

Jerome

[dangus]

FM stereo decoding can be done with a PLL (phase locked loop); there are (or were) some ICs that did this. Here's a page with some options:Ake's Audio

[oshifis]

There used to be an ambitious product in the early 80's by the late Orion radio factory in Hungary, the ST-240 AM/FM tuner. The designers incorporated every advanced circuit solutions of that time (discrete MOS-FET front end, TOKO linear-phase LC IF filters, LC phase discriminator FM demodulation, LC multiplex filters, etc). The result was an ugly monster that is still the reference of many fellow-countrymen of mine...

Here is some description and pictures (sorry it is Hungarian only):

http://oldradio.tesla.hu/rajzok/radi...rion_st240.htm

And the full circuit diagram, it is possible to get some ideas from it:

http://oldradio.tesla.hu/rajzok/radi...er/fmtuner.jpg
http://oldradio.tesla.hu/rajzok/radi...tuner/fmkf.jpg
http://oldradio.tesla.hu/rajzok/radi...amvalaszto.jpg
http://oldradio.tesla.hu/rajzok/radi...d_muszerek.jpg
http://oldradio.tesla.hu/rajzok/radi...net_am_tap.jpg

The linear phase filters were also available in electronic parts shops over here. Linear phase in FM domain is amplitude linearity in the audio domain. I have a Marantz tuner with simple ceramic filters, and I replaced them with those linear phase LC blocks (on a small PCB with some additional circuitry). I understand they were also used in the Klein + Hummel high-end tuner "Telewatt FM 2002" and also by Rohde & Schwarz. Now it sounds good!

[jeje]

Hello,

Ok, I 'll see that.

Thank you.

[dxer_87]

Hi everyone!

I have a few questions about my simple design. I want to build IF circuit with CA3189 and AN7470 (stereo MPX).

I want to start with typical application from the datasheet and connect it to a RF+PLL module. Also I have a kit with RDS, but my simple question is where's the pin with mpx signal?

I have CF filters and polish Coil with these parametres:


frequency:10,7 MHz
inductance: 2,43uH
Q>=75
I winding: 8+7 turns
II winding: 2 turns
internal C: 82pF

The TOKO coils are unavailable here in Poland in a small quantity. Would it work out with this one?

The main question is which transistors should i use to gain IF? Any ideas or another application circuits for CA3189 would be very helpful.

TIA, Przemek

[rayfutrell]

Hi Dxer,

Maybe this spec sheet will help. It shows an application of the IC. http://www.515ic.com/view-656.html

Regards,
Ray

[dxer_87]

This application is incomplete, I'm asking what transistor (Q1, Q2) should I use? There is also note 'bout coil (TOKO one).

I see, that I just have to try different transistors. Maybe Mr. Kiraly have some info about this circuit?

Heh, look what pretty tuners they build:

http://larsholt.dk/Brochurer.htm

I can see, that CA3189 and LM4500A (TCA4500A) were very popular in the late 80's Hi-Fi receivers.

If this project fails (with universal PCB), I must try something different. I build the complete HiFi system, and what's funny, in my country there's no kit available to build a good tuner.

I need complete IF + MPX circuit, maybe I can do it another way?

[mako1138]

I think just about any modern small-signal transistor will work for Q1 and Q2... I recall building a radio kit that was all 2N3096. BC547 or BC549 would provide better performance.

[dxer_87]

Hi Mako,

This info can be very helpful. I'll work with my soldering station and PCB, and then I'll tell if it works ok

Maybe only a few or less know about what tuners we produce in 80's:

Have a look at this:

www.radmory.za.pl/

They have a very good front-ends and function called '0 detector'. Only the MPX is as noisy as my grandma while sleepin'

[gpapag]

Mr. Kiraly had suggested to me BF240 ("F" denotes High Freq.) for Q1, Q2.

But as mako1138 suggested, in this place (IF=10.7MHz) almost any modern small-signal transistor will work for Q1 and Q2. Even the humble not modern BC109 will do. See some data sheets on the links.
Look for ft (in MHz).

I have used BF240 (readily available) and works fine.

http://www.pira.cz/pdf/BF240.pdf
http://www.datasheetcatalog.org/data.../BC546_7_8.pdf
http://www.datasheetcatalog.org/data...ens/BC109B.pdf

Best Regards
George