m718 said:I am trying to amplify extremely small signal(around 200 nanovolt) from a coil of wire on a ferrite to make a gaussmeter, I've seen some FM transmitter schematics online that I want to connect this signal to, Would a FM transmitter be able to work with a signal this low?
I tried amplifying with op amps(OP07) but the noise was more than signal.
thank you
Basicaly I'm trying to make a gaussmeter that is VERY sensitive I would like the frequency range to be 100 to to about 4000 hz , for S/N ratio I need the signal amplitude to be atleast 20 times higher than the noise I don't know what db that is. And if you could tell me what transistors and other components to use for least noise possible I would really appreciate it.skeptic2 said:You would need to amplify it substantially before you could use it to modulate a carrier. Using a 200 nV signal will be difficult but not impossible. However you need to answer a few questions.
What frequency is your signal? Over how wide a frequency range do you need to detect the signal? How good a signal to noise ratio do you need in order for it to be useful?
Opamps are not the way to go. You'll need very low noise transistors and good filtering. This will not be a trivial project.
vk6kro said:Maybe it would be possible to improve the probe?
I am trying to amplify extremely small signal(around 200 nanovolt) from a coil of wire on a ferrite
Could you describe what you are using here? Is it a ferrite toroid or a short bar or something else? How many turns of wire are you using?
skeptic2 said:Your range of input frequencies is so wide (over 5 octaves) I recommend a narrowband tunable input filter to reduce noise. Perhaps you could combine this with your pickup coil. As for the transistor, do some searches on the internet for very low noise transistors and see what you can learn about them and low noise amplifiers in general.
One question I forgot to ask is what is the maximum voltage you expect to see at the input?
m718 said:I'm using 7 inch 1 cm ferrite rod 38 gauge magnetic wire 6000 turns. The output is high at close distance.
skeptic2 said:Questions:
How did you measure the voltages?
Were the measurements at the input or output of your 3 opamps?
What is your power supply voltage?
What voltage do you see at the outputs of each of your opamps with no signal applied (input shorted to ground)?
Do you have any diodes, transistors or other potentially non-linear elements in your circuit besides opamps?
What is the opamp you're using?
m718 said:I think the easiest way is to use a gaussmeter that I already have the only problem is that it has a DC output I need to somehow modify the circuit to make it AC output.
I will draw a schematic from the board and post it and i'll see if anyone can tell me what changes to make to get AC output. Do you think you would be able to make the changes to make it AC ?, the circuit has ,op amps, PNP NPN transistors, diodes, one MC14046BCP and ofcourse resistors and caps.
I'm making a schematic of the gaussmeter, I won't make my own amp if I can make this AC output. AC so I can also get frequency of fields.skeptic2 said:A schematic would certainly help. Is the schematic of your amplifier or of the gaussmeter? Why do you need an AC output?
FM transmitter sensitivity refers to the ability of a transmitter to accurately and efficiently transmit a signal over a given distance without interference or loss of quality. It is a measure of how well the transmitter can pick up and amplify weak signals, and is typically measured in decibels (dB).
FM transmitter sensitivity is important because it directly affects the quality and range of a transmitted signal. A higher sensitivity means the transmitter can pick up weaker signals, resulting in a clearer and more consistent transmission. This is especially important for long-distance broadcasts or in areas with a lot of interference.
FM transmitter sensitivity is typically measured using a signal-to-noise ratio (SNR) test. This involves comparing the strength of the transmitted signal to the amount of background noise present. A higher SNR indicates a higher sensitivity.
There are several factors that can affect FM transmitter sensitivity, including the quality of the transmitter components, the frequency and modulation of the signal, and the surrounding environment. Interference from other electronic devices, weather conditions, and physical obstructions can also impact sensitivity.
To improve FM transmitter sensitivity, it is important to use high-quality components and properly tune the transmitter. Additionally, choosing a frequency with less interference and ensuring a clear line of sight between the transmitter and receiver can also help improve sensitivity. Using amplifiers or other signal boosters can also be effective in increasing sensitivity.