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tazmania_kid's Achievements


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  1. Hi, anyone can explain to me the differences between the attached circuits in terms of construction and their performance? The reason is: understanding more on these circuits will help me proceed with better and more complicated tx circuits. Circuit 1: http://www.geocities.com/tomzi.geo/4w_fm/4W_transmitter.htm Circuit 2: http://www.boondog.com//tutorials/rfTransmitter/rfTransmitter.htm Circuit 3: http://www.aaroncake.net/circuits/fmtrans.htm
  2. ok, I will try to make a coil myself and see what's the output :)
  3. As am new to circuit design, I thought, with coil value at 0.22uH, a 3-18pF capacitance change would in theory give you a frequency range of 80-196MHz. Too bad, it's not as easy as I think :(
  4. I didn't use an air core coil, instead I used a normal inductor which I bought from supplier. Is this possible?
  5. Hi, in regards to the circuit in the following link, I fix my inductor at 0.22uH then my variable cap at 3-18pF. So supposedly I should get a frequency of 88-108MHz right? But the tx frequency which I measured in the receiver is 50+MHz, y is this so?? I tried to use my radio as the receiver and I talked to the mic, the radio receives my voice but this is the harmonic of the tx frequency isn't it? In addition, without changing the capacitance in the tank circuit but tuning the radio to different stations (say 103-105MHz), it still can receive my signal. Why? I mean, if I transmit 103MHz, the radio should receive at 103MHz only, is this true? What is the purpose of connecting an inductor in series with the antenna? http://www.aaroncake.net/circuits/fmtrans.htm
  6. help.....i couldn't get both 2N5109 and 2SC1324 in the market... :'(
  7. Can I use other transistor instead of 2N5109? In fact, what is the criteria that will affect your choice of transistor used?
  8. Hi Alun, am now trying on the 4 transistor circuit you've posted last time. But what is 7001? An NPN transistor of what series? Simply 7001?
  9. I have a Communication Service Monitor in my U and am planning to use this equipment as my receiver. In fact, it can also be a spectrum analyser, frequency counter... and so on. Regarding the tx power, again, am using another formula to manually calculate it. But frankly speaking, I am not sure whether this works... :-\ And how you guys measure the frequency accurately? What are you using?
  10. By using the indoor path loss formula, I plug in the values like transmitted power, received power (measured by the rx), distance between tx and rx, I can compute the path loss. Path Loss=PL(d0) + 10nlog(d/d0) where PL(d0)=10log(Pt/Pr) *I take d0, the reference distance, as 1m.
  11. I use back the original circuit. Before this, I used a function generator to replace the mic as the input but i am not sure whether this is correct? And at the output, I used an oscilloscope, the result is that the waveform looked weird. Until last night, I tried to use a mic and also the antenna, and it works! ;D Next step, I should use a receiver to measure indoor path loss, hopefully it can receive my signal. By the way, how am I going to determine the max range of the transmitter? (I tried few meters range last night, it still works...)
  12. Hi all, my transmitter can finally work! I tried to talk to the mic and use the radio as the receiver, as a result, I can hear my own voice from the radio! By the way, I tried to use a 1/4 wave antenna and also a very short length antenna, the result is that the radio can receive both signal, why is this so? (as I thought the transmitter can only work at a particular length depending on the frequency we transmit?)
  13. hi alun, thank you very much for your ideas. i will try to assembly it on a PCB as soon as possible and feedback to you ;)
  14. i stick to 88-108MHz as higher frequency will create more problems n more complicated circuit. as am new to circuit construction, i would rather choose a simpler one to begin with. so with this frequency, 1/4 wave is 0.69m.
  15. hi, i wonder whether i can reduce the antenna size by a fraction of the lambda? say (lambda / 8 ), (lambda/16)? what are the pros and cons of this length? cause if i were to use lambda/4, it will be a very big antenna in which it is not practical. other than a normal wire, what type of material will improve the antenna efficiency? (my circuit is very unstable and is it due to the antenna or anything else?)
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