Help me to understand the MC3359P IC

[walid1]

Hi guru
Ok, I understand that you have never looked inside one before and u have never seen a schematic of a narrowband dual conversion FM receiver circuit before. But also I know that u still have the ability to help me. I need you theory information to help me in my trip inside that cordless phone.
I the fiq below, I’ll concentrate on the 2sc2314 transistor, in its datasheets I read: 27MHz CB Transceiver Driver Applications
1) What the meaning of CB?
2) Is 27MHz mean that the operating freq of both TX and Rx is 27MHz?
3) What you understand from using that transistor?

Thank you



2sc2314.pdf

 

[audioguru2]

Hi Walid,
I think you have an old cordless phone, the 1st generation. Google doesn't talk about its frequencies anymore. A phone must transmit and receive at the same time so they use different frequencies for transmit and receive. The 1st generation used 27MHz (CB or Citizen's Band) for one frequency and 1.7MHz (if I remember correctly) for the other frequency. One is AM and the other is FM but I can't find out which was which. I had a phone like that about 30 years ago. Now my cordless phones are 900MHz and much higher frequency ones are sold now.

The old frequencies became used by many people and there was lots of interference.

I don't know why your phone uses a power transistor for its RF driver or output since the power is very low.

 

[walid1]

Hi guru
thank you for fast reply

I don't know why your phone uses a power transistor for its RF driver or output since the power is very low.

In my country, there is a puplic open market, they sold scrap, half a telephone 1/4 radio part of vedio recorder..etec
every month, i go to this market any by some boards
i have this 1/2 phone, it is senao, it is at least 10 km long.

After this discussion with you, now i don't want to take parts of this phone and reconstruct it to a Tx and Rx. but you open my eyes to new things merit to look at and discuss
i gained till this moment some important information about narrow and widebands and can imagine now how modulation process takes place (sorry for bad grammar)

Now my cordless phones are 900MHz and much higher frequency ones are sold now

Why manufatures go to a higher freqs, is it better?

The 1st generation used 27MHz (CB or Citizen's Band) for one frequency and 1.7MHz (if I remember correctly) for the other frequency. One is AM and the other is FM but I can't find out which was which.

this is a good information and from it i can diduce that mine is transmit at 1.7MHz AM and receive at 27MHz FM.

CB or Citizen's Band

what the range of freqs of Citizen's Band?

at this time I'm near to finish the drawing of the o/p section starting from the antenna, the filter is very complex series and parallel combinations of caps and air coils (look at the last photo), i'll put it here to discuss it with u to learn new things.

thank you guru