Help me to understand the MC3359P IC

[walid]

Hi
Below I attached the datasheets of the MC3359P IC.
I have a ruined cordless phone (SENAO SN736)
From this phone I’ll get that IC and the related components, and with your help and some modifications, I want to build a FM receiver.
Lets go:

(1) What the meaning of RSSI written at the beginning of the datasheets?
(2) Is this receiver possible?
(3) For the following schematic (from the datasheets) and if I use audioguru’s FM Tx as a Tx, what is the 10.7 MHz i/p connected to pin 18?

Remember that I have all the components in the schematic above from the phone itself.
Thank you a lot.

MC3359P_IC.pdf

[Kevin Weddle]

The 10.7 MHz is the carrier received from the antenna or cable, whichever. I believe the RSSI is a digital I/O of the microcontroller. They are always many I/O's, I think this is a popular one.

[walid]

thank u Kevin Weddle for fast reply

Now if audioguru's FM Tx is sending with carrier freq = 100MHz
what stage must be connected to that i/p to receive signals

thank u

[audioguru]

No Kevin,
Hi Walid,
The IC circuit is only part of a radio. The "front-end" of a super heterodyne radio is missing. The front end is the RF amplifier, local oscillator and RF mixer that converts the RF signal to the 10.7MHz IF (intermediate) frequency that is easier to amplify and filter than the VHF RF signal.

To change the RF frequency, only the local oscillator frequency (and an RF filter if used) needs to be tuned and the tuning of all the IF filters stay at 10.7MHz and 455kHz.

This receiver is "dual conversion" because it has a second local oscillator and RF mixer that has a 455kHz output that is also amplified and filtered.

Learn about how a super heterodyne radio works from articles in Google.

[Kevin Weddle]

I think in most cases, there is no intention to step down the frequency of an FM carrier. AM uses mixers. If you play with the frequency of FM, you might not be able to recover the message.

It must be an AM IF receiver.

[audioguru]

I forgot to say that this radio circuit is for narrow-band FM (telephone quality). My FM transmitter is for wideband high fidelity FM (broadcast quality).
A narrowband radio will receive wideband signals with extreme distortion.

Kevin.
Nearly all FM radios use a 10.7MHz IF amplifier. The FM sound received by TVs uses a 4.5MHz IF in North America, I think it is 5.5MHz in Europe.
10.7MHz, 4.5MHz (and 5.5MHz) and 455kHz ceramic filters and tuned transformers are used for the bandpass.
Learn about how radios work.

[AN920]

The RSSI (Received Signal Strength Indicator) is the output from a internal log detector

[walid]

Hi guru
Hi Kevin
Guru, you are the king here, at least for me.

Learn about how a super heterodyne radio works from articles in Google.

Learn about how radios work.

I’m already learned about radios.
I know u said that to escape from my 10,000 questions that will coming soon (smiling).
Look guru, I read about radios more than u expects. Theories do not suffice my requirements to be an expert like you.
During the discussions with u I got a valuable information that can’t get from hundreds of books.
So I need your help to fly together in the electronic world.
Lets start flying:
If I follow the connections in the phone’s board, I’m sure that I’ll find the remaining RF, mixer and the local oscillator.
I’ll draw the schematic by hand and scan it by a scanner and put it here for discussion.
When two signals entering a mixer, then the o/ps of the mixer are:
 The sum of the two
 The difference of them
 The same signal 1
 The same signal 2

So if sig 1 is the main i/p sig with freq = 10.7 MHz
And sig 2 from a local osc with freq = 10.245 MHz
Then one of the mixer’s o/p is the difference = 455 KHz so we use a ceramic band pass filter of 455KHz freq.
I write this to convince u that I have some basics of radios.

I forgot to say that this radio circuit is for narrow-band FM (telephone quality). My FM transmitter is for wideband high fidelity FM (broadcast quality).
A narrowband radio will receive wideband signals with extreme distortion.

(1) What the difference between wide and narrow bands  in numbers? Please    don’t disappointed from this question.
(2) Can we modify your Tx to be a narrow band?

Thank u guru and all members of this great communty.

[audioguru]

I don't know how narrow is the bandwidth of wireless telephones. It might be only 6kHz. Broadcast AM stations are only 10kHz apart so their bandwidth is about 8kHz.
Broadcast FM stations have a bandwith of 150kHz.
My transmitter doesn't have a limiter so if you are too loud into its mic its bandwidth exceeds 200kHz.

[walid]

hi guru
Now we need a limiter
now i'll search about it
can you point me to make this mission easy
thanks

[audioguru]

Hi Walid,
Our new Disco-light project has a limiter circuit "stolen" from Elliot Sound Products. I haven't tried it so I don't know its range and distortion:

[walid]

Hi guru, thank u very much.
Please look at the figures below:
(1) If I introduce this limiter between the mic stage and the remaining stages of your FM Tx, then it will function as a AGC, that is it control the amplitude of my voice so that the o/p freq BW about 6KHz or so?
(2) My circuit board is SENAO SN-736, I think it have a transmitter circuit with freq different, if I can find it and modify its freq to match the 3359 receiver. I haven’t the second part of this phone. 

[audioguru]

Hi Walid,
Your transmitter and your radio circuit are very different:
1) The transmitter is wideband and the radio is narrowband. If something doesn't work properly then you don't have another narrowband station to test your radio with, and you don't have another radio to try the modified transmitter with.
2) the limiter circuit has a line-level input but the transmitter has a microphone and a mic level input.
3) The transmitter has pre-emphasis for good sound but it isn't used for narrowband.

[walid]

Your transmitter and your radio circuit are very different:
1) The transmitter is wideband and the radio is narrowband. If something doesn't work properly then you don't have another narrowband station to test your radio with, and you don't have another radio to try the modified transmitter with.
2) the limiter circuit has a line-level input but the transmitter has a microphone and a mic level input.
3) The transmitter has pre-emphasis for good sound but it isn't used for narrowband.

For these reasons I suggest to find the Tx in the same board. I know it send to another receiver but we can modify its freq to match our receiver.
At this moment I lost my scanner (acer) software, I'll find one then I can send a photo of the board to get a help from u to find that Tx
guru I fond to FM circuit, I dream to build my own walkie talkie.

NOTE: during my search i found this page, it seems to be very important, i read it but can't understand what that modifications he did to get what?
http://www.discriminator.nl/ic/index.html

[walid]

Hi guru
Finally and after some effort I can borrow a high rolsolution cam and take some photos, please look below
the first figure is for awhole SENAO SN-736 board for you to look
the second is a close view to 3359 Ic and related components.

I need your help and any help frome anyone here to enable me to take the suitable components to make a TX and Rx
To reach this target, we shall preview many important aspects.
i noticed that nearly all cordless phones have the same idea and same components with very small differences.
Where is the Tx circuit in the first figure.
Later I'll draw the shematic though it is double printed and hard to retrace but I'll do all my efforts.
thank you.

[audioguru]

I don't know how you are going to design a narrowband dual conversion FM radio without a schematic. It needs a double-sided pcb with a ground plane over most of its surface.

[walid]

Hi guru

I don't know how you are going to design a narrowband dual conversion FM radio without a schematic.

dont worry I'll draw the schematic and discuss it with you.

It needs a double-sided pcb with a ground plane over most of its surface.

I can do it, u  help me, we can do it.

now i'll draw the Rx (3359) and related parts and put it here, then u tell me where the TX part
I see the two LM567CN, i know they are for tone detection
I'll draw all pars in sequance and discuss them with you
guru I want to work hard and I need you help what u say???
yours Walid

[walid]

Hi guru

As you know if u click on th followin image it will become bigger

http://www.electronics-lab.com/forum/index.php?action=dlattach;topic=9699.0;id=6451;image

can you please tell me where the TX to draw it
thank you

[audioguru]

Hi Walid,
Is it a wireless home phone? I never looked inside one before and I have never seen a schematic of a narrowband dual conversion FM receiver circuit before. I am sorry I can't help you.
Look in its sevice manual.

[walid]

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

[audioguru]

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.

[walid]

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