RadioRon said:The next step to fix these problems is to change the connection point of R1 and of R2. For example, with R1, you should disconnect it from the top of L1 and create a "tap" on L1 about 1/10 from the bottom (that is, 10% of the total number of turns of wire) and then connect R1 to that tap. Similarly, disconnect R2 from C5/L3, create a tap on L3 at the same height as you did for L1, and reconnect R2 there.
Harros said:By the way, I did not assign the Q of the coils during simulation, will it cause my simulation to be inaccurate? Should i do the simulation without coupling the source impedance and load impedance?
RadioRon said:Your sim is probably inaccurate. What Q does the sim assume? Infinite?
How would you do the sim without a source?
Harros said:I guess so. There is no such an option to allow me to set the Q factor of the inductor that i use in simulation. The freq response of the filter now is much better. But the bandwidth is uneven as i can see a wider band at upper freq. What should i do?
Harros said:I can observe that the quality factor for most of the inductors sold in the market are around 35 to 45, should i put the corresponding Q of the particular inductor rather than the Q of 80? I am now working on designing the amplifier, is it alright for me to use 2n3904 in the amplifier?
I am now satisfied with the filter response (please refer to the pics, and circuit)... How do you think? I made the capacitors in the CL tank to be in parallel as i cant get a component with such a exact value , is it alright for us to do so?
Again, whats the type of connector that i should use to connect all the modules?
Harros said:The tx antenna that i am going to use is a ferrite core loop antenna, which can be found in the old radio. Is it alright to use this type of antenna? By the way, there is another documentation that i found yesterday, it is about the work done by the inventor of this distance measuring tech, but the prototype is working at 10.7MHz. What a coincidence, he use the same phase detector!
**broken link removed**
For the rx Rod Antenna, can I just implement this impedance buffer amplifier without redesigning it? **broken link removed**
Harros said:Hi, back to the 1MHz Oscillator, the output of the 1MHz Crystal Oscillator seems to be a square wave rather than a sine wave... Is there anything can be done to produce sine wave from this crystal oscillator. By the way, i cant find a 1MHz crystal in my place but the 1 MHz Crystal Oscillator. The lowest frequency of the crystal at my place is 1.8MHz (for UART communication use)... I am now out of idea on the sine wave oscillator that i should build...
I have an idea where the output of the crystal oscillator is connected to a 5th order Cheybyshev LPF to filter out all the harmonics and obtain the pure sine wave. I have done the simulation, it seems working fine (It functions just like a Pierre Oscillator here). However, i used a pulse voltage source to replace the crystal oscillator in simulation (this is because i cant find a crystal oscillator in the simulator). Is there any inaccuracy of this simulation? From the simulation, the waveform is located at the positive part of the v versus time plot. Should we do clamping on it to move down the waveform?
I cant find the data about output current of the crystal oscillator from the data sheet, how can i know the output current of the crystal oscillator?
Besides, i have got the rx loop antenna for H field detection. It is a AM loop antenna made by AIWA. I have enclosed the diagram here. Any comment on this antenna?
RadioRon said:As you have discovered, it is commonly done to build a square wave oscillator and then simply filter out the harmonics. Your simulation is correct and your approach is good. Clamping is not necessary, you only need to use a DC blocking capacitor, ceramic type.
The crystal oscillator is rated to drive 50 pF capacitance of 10 TTL loads. The term "TTL load" is a standard way of saying how much current this device can deliver. See this thread:
https://forum.allaboutcircuits.com/showthread.php?t=8471
and read the post from Papabravo.
That AM loop will work OK. You can also use a ferrite rod AM antenna as is usually found inside small portable receivers. This has the advantage of being smaller than your antenna.
Harros said:I have used the ferrite rod AM antenna for the transmitter antenna. Is it alright to use the same antenna at the receiver as well?
RadioRon said:You remind me that it may be inappropriate to use a ferrite rod antenna for transmitting. The reason is that the ferrite rod may saturate with the amount of magnetic field that your transmitter will send out. For this reason, I think it may be best to avoid the ferrite rod for your transmitter and use your air-core loop antenna for that instead. The receiver, on the other hand, is receiving very tiny amounts of power, amounts too tiny to allow the rod to saturate, so the ferrite rod is very well suited to the receiver. After all, it is commonly used in this way.
Harros said:By the way, i am thinking of making the transmitter antenna to be in small sized (portable preferably). So, should i build the air core loop antenna on my own? Do you have any reference on the formula of the number of turns for the air-core loop stick antenna? What type of wire that i should use to wind the loop stick antenna?
How to infer the impedance of the crystal oscillator?
Harros said:I am going to add the secondary loop, as the primary loop will be terminated using a tuning capacitor... But i cant get a variable capacitor with high capacitance range. Can i add a fixed capacitor in parallel to the variable capacitor, and use that variable capacitor to fine tune the selectivity of the loop antenna? How can i determine the value of the fixed capacitor?
I am thinking of using the pvc pipe to build this antenna core. Is it alright to do so?
Regarding the output impedance of the crystal oscillator, the impedance is quite high: 4.7V / 16mA = 293k ohm....Am i correct in calculating the output impedance?
Harros said:Yes, you are correct. I misread "mili" as "micro"...
I am going to couple energy to the loop using a secondary loop, I have used the inductance calculator to calculate the number of turns needed. There are 43 turns for the loop with 1 inch diameter and 4 inch length. Does the size of the enameled copper wire used affect the inductance of the loop?
How can i infer the number of turns needed for the secondary loop? How should i calculate the input impedance of the secondary loop?
By the way, for a 10uH inductor, a 2.5nF capacitor is needed for frequency tuning. However, the value of a variable capacitor ranges from few pF to about 100 pF... So, should i increase the inductance of the inductor in order to reduce the capacitance of the capacitor used?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?