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Hi guru LM555 is very famous and one can find anything about it rabidly Try MC3359 circuit and choose image, u'll get zero results

hi all sometimes i want information about IC It is easy for me to write its number and get the datasheets I want circuits that uses that IC, what to do. can anyone help thanks

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.

Hi I need the circuit diagram of SENAO SN-736 thank u very much

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

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.

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

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

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

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

Hi guru what are SAW filters?

Practical Benefits of the Negative Feedback Most practical amplifier circuits use negative feedback for the following practical benefits: Stabilization of voltage gain Decreasing output impedance Increasing input impedance Decreasing distortion Increasing bandwidth How NFB decreasing Zo, increasing Zin and bandwidth? thanks

Hi guru two weeks ago, i discussed and write an article about a very simple FM transmitter, the one whose circuit is appear at the top of this topic- in an arab community. my discussion was depending

Hi To Cabwood, thank u very much for this detailed and very clear explination. To audioguru I understood from Cabwood the mechanisim of -ve FB when there is no CE Can u please explain how CE remove -ve FB ? thank u

Hi monoman The following link is a practical book full with transmitters and receiver circuits if u read it carefully, you will find all what u need to know about FM also AM and antennas I hope it help u. http://www.mikroe.com/en/books/rrbook/rrbook.htm while u r reading, you can ask about anything obscure.

Hi guru I can't understand or accept that the LC impedance is infinity at its resonant frequency. Here is your formula: At resonance XL = Xc in magnitude and if they cancle each other because of phase.................... Yes Yes its impedance is infinity at its resonant frequency. But still some point obscure: If U GURU, for example, want to replace your C14 (=22p) in your FM Tx with a Pi C-L-C network as in that site: http://hem.passagen.se/communication/antenimp.html you have to know the Zout of the RF amplifier transistor (Q3) to match it with the 50 ohm antenna using the calculated values of caps and coil. May I worgly understood what the above link want to say, may be he want to tell me that the Pi C-L-C network match any Tx at 50MHz. so tell me what you have to do if u decide to use that network. thank u guru

hi guru If they cancel then the Z is zero not infinity I know it is not zero the ohmic resistance of the coil wire and cap materials .. etec please look, the man who do this: http://hem.passagen.se/communication/antenimp.html say: the matching between Zout and the 50 ohm antenna using Pi C-L-C filter if Zout is infinity, how can he put the matching network to design the Pi C-L-C filter you must know Zout?? Your last answers on this topic were not very good it takes me up then down, I'm confused now thank u

hi guru IF i apply audio sif to the input cap of 10uV, then I'll fet it from the o/p (before the volume) as 100*10u = 1mV or 50* 10u = 0.5mV????????????

Hi guru yes I agree, it It has the wrong formula and they calc it as 220 and i calc it the first time as 110 and mistake when tell you it 220 ( I was hurry) yes, I know, but still must calc it to know the o/p impedance to correctly fit the matching network, then may modify it lettle to compensare for the stray capacitance and inductance I calc it, using your formula, look below:

Hi guru Av = R2/R1 = 220/2.2 = 100 and not 50 correct me

very good guru, u r really a professor but please is this with the reverse of the figure and the 10u farad cap why? thanks

Hi guru I go to google and search for LC Resonance and one of them was: http://www.pronine.ca/lcf.htm It is a calculator substitute L=330n and C=6.7p u will have f=106 MHz and Zo=220 ohm as i calculate it, it is not nearly infinite ohms It is very important to me to correctly calc the o/p Z of the oscillator because i want to discuss with u the pi C-L-C filter between this osc and the 50 ohm antenna from this site: http://hem.passagen.se/communication/antenimp.html and to ask u why u don't use it in your FM Tx don't worry i understand 95% of what he said but still to know how to cal the o/p Z of the oscillator to match it with the antenna I make a page in MATHCAD for quickly calculations thank u guru

Hi aProgrammer thank u for fast reply Yes I agree, there are a mistake, the + and - inputs are inverted If they are Av = 1 + (R2/R1) but why they connect the (+) i/p [the -ve in the figure] to adivider that half of VCC applied to it, why not simply connect R4 to ground and omit R3? thanks To guru whose reply reached me just now Are u agree that there are a mistake, the + and - inputs are inverted I read your reply and I'll analyze it now: from this i deduce that someone can swap the inputs of the opamp to get low input impedance if he want, and that the circuit as its work. For a very low resistance source, the gain at low audio frequencies of the inverting preamp circuit is R2/R1= 100. The impedance of the mic is in series with R1 so reduces the gain. thank u guru

Hi guru lets do it again at 106MHz, L =330nH and C=6.8pf, we have XL = 2 pi f L = 220 ohm XC= 1/(2 pi f C) = 220 ohm (resonance) Ztot = (XL*XC)/(XL+XC) = 110 ohm I think it is wrong calc, Ztot must be zero because XL = j w L and XC = -1/j w c I don't know what to do............ IF the LC impedance = 110 ohm as before, and the antenna impedance = 50 ohm 110/50 = 2.2 the turns ratio = sqr(2.2) = about 1.5:1 which equivalent to 3:2 = 6:4 if the coil was 6 turns then the tap must be at the fourth turn and not the fivth turn to have better impedance matching. please guru correct me

Hi For the circuit shown below I want: to calculate the o/p gain to know what the function of C1 I noticed that there are something strange in it, the feedback is connected to the noninverting i/p and the voltage divider to the inverting i/p thank u in advance