walid

Hi look at this link it may help you: http://www.electronics-lab.com/forum/index.php?topic=3911.0

I read this:"a small signal diode of the 1N914 type commonly used in switching applications". I know thast 1N914 like 1n4148 is a small signal diode but what are the switching applications, give me some example on how to use diodes to switch between ON and OFF thanks

Thank you very much Audioguru I understand it very well this is really good answer thanks again walid

Hi Ante I found this very interesting thank you very much Walid

I read this statement somewhere in the web, can you please explain this with practical example circuit. thanks very much.

Ok guys, I'll tell you the story I have a small telephone device, it is very simple, I try to understand its circuit, it contains this circuit in it, this is the 4069 IC. When I follow the diagram I found that pin 14 of 4069 which is the Vcc of the IC is connected to the phone lines via a cap (1u 250V) and a rectifier bridge and a ripple filter (22u 16V cap) and a zener diode as shown in the circuit below. The idea is when a ring signal (AC) come into the line it pass through C1, rectified and then regulated through BR1 and ZD1. The resultant DC connected to pin 14 of the 4069 IC which acts as a ringer circuit, the o/p of the ringer is connected to an audio transformer and finally to 100 ohm speaker. All what I said is clear and simple, the hard thing is the ringer circuit itself, why it appear so complex. When I connect a 9 VDC directly across the 4069 IC (+ve to pin 14 and -ve to pin 7) I hear like horse sound from the 100-ohm speaker. Now we all know that the circuit in the fig above is a ringer used in a telephone circuit and the question is: can you please explain it step by step for me. thanks. yours Walid. NOTE: You can ask me about anything related to what I discuss above.

Hi all This circuit shown below consists of 6 inverters (NOT gates), that is using the 6 gates in 4069 IC, these gates are connected as shown with 5 resistors, 3 caps and one diode the o/p is as shown. can you please tell me what is this o/p. I think it is an oscillator, but it is very complex to be! I see many oscillators using NOT gates, they use only 2 NOT gates and one cap + 2 R. What the function of the diode? thanks very much. WALID.

Hi autir I think you cannot achieve these extrem limits in practicle but i think to have a maximum power transfer the impedances between the stages must be equal

i think this is not the problem..... A switched mode power supply (SMP) uses a ferrite core transformer, how you will get it . If I in place of you i get this psu from a used computer monitor and modified it , or simply analyze it and understand the design.

There are many general purpose transistors like what audioguru said and 2n2222, 2n2907 i 'll tell you what i do; i get some electronic board from say radio or any other not used device and get all the transistors from it then get their datasheets and put them in boxes for future use. this makes me familiar with many of these transistors.

Yes, thank you very much. walid

hi friends here are you

Hi 1st Mil-Tech you mentioned a very important subjects, can you point me to any web pages that discuss these subjects tank you.

How the Q of the coil affected by its shape what is Q of the coil???????????

Where are you alun????????????????????

Wow! Thanks, that's great.

Thank Audioguru i'll take my time to discuss what you said with myself then ask you. thanks

hi 1st Mil-Tech tanks for this, can you tell me more

I'll read that articale very well but I'll ask you about what is hard to understood

Hi AUDIOGURU this is a good answer hehe .... imagine that in that stations they cotrol the mod.index using var.R it is a very good jok heeeeeeeeeeeeeeheeeeeeeeeeeee

thank you all for your responds I know that any antennat may do the job, but i think that there are some formulas aid in proper design, that when i want to explain this to someone i depend on it. i can't say this general speaking.

exactly it is grounded to exactly the same point as the mains, and used the same wires to the equipments. we notice the following: if we disconnect the main circuit breaker of the digital studio either it is oprating or not, the hum is reduced to 90% or more note also we have two other analog studios and hese not contribute to the broblem. this problem appears only the last 3 monthes and at that time we had the same conditions we have now, only we as i told you enhance the grounding abnd the problem remain. thanks very much.

hi boys, thank you for your interst , in the last few days we have an expert who seperate between the earth of the main power and the generator earthing , but the problem is not solved , so i want to summarize the problem as follow : when our equipments operate on local authority main power there is no hum on audio or video , but when our equipments operate on our generator ( 500 kva ) there is a strong hum on video signal. thank you for the help walid

Thank you Audioguru

Hi Bjorn if i have a FM Tx transmitting at 100MHz tell me what antennat is suitable for this Tx, wire length, diameter and its impedance and tell me how you calculate it please note that my antenna is simply a wire not dipole or yagi thanks