Posts posted by walid
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
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.
I need the circuit diagram of SENAO SN-736
thank u very much
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?
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.
Now we need a limiter
now i'll search about it
can you point me to make this mission easy
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.
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
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.
(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.
Hi guruSAW filters are used for TVs.
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
How NFB decreasing Zo, increasing Zin and bandwidth?
- Stabilization of voltage gain
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
To Cabwood, thank u very much for this detailed and very clear explination.
I understood from Cabwood the mechanisim of -ve FB when there is no CE
Can u please explain how CE remove -ve FB ?
Hi monoman>also a couple of circuit diagrams would really help (I am particularly interested in Frequency modulation radio)
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.
while u r reading, you can ask about anything obscure.
Hi guruI was talking about the parallel resonant LC at the collector of the RF amplifier transistor on my FM transmitter. Its impedance is infinity at its resonant frequency without a load. But it is a terrible match to a 50 ohm antenna.
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
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
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
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 guruThe calculator you found is WRONG!
It has the wrong formula for the impedance at resonance of a parallel LC.
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)You shouldn't calculate things at such a high frequency because you don't know how much stray capacitance is in parallel with your C, and you don't know how much inductance is in the wiring of the L.
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 inductanceHere is another formula for the impedance at resonance of a parallel LC:
I calc it, using your formula, look below:
Hi guruThe 10uF capacitor is a filter so that any noise from the supply isn't amplified 50 times.
Av = R2/R1 = 220/2.2 = 100 and not 50
very good guru, u r really a professor
is this with the reverse of the figure
the 10u farad cap why?
I go to google and search for LC Resonance and one of them was:
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:
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
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?
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:When you swap the inputs of the opamp you will notice that the input impedance of the preamp circuit is only 2.2k ohms which is too low for an electret microphone. A non-inverting opamp circuit would have a much higher input impedance so that an electret mic is not loaded down.
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
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
help in using google
in Electronics chit chat
LM555 is very famous and one can find anything about it rabidly
Try MC3359 circuit and choose image, u'll get zero results