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| Richard Crowley:
--- Quote from: Circlotron on November 30, 2018, 03:45:11 am --- --- Quote from: Richard Crowley on November 29, 2018, 08:14:29 pm ---* Remember that when using a coil for direction finding, when you have a null, the source is perpendicular to the coil axis. --- End quote --- With an AM radio the null is when the loopstick axis points directly at the source. Is there some difference between an air cored loop and a ferrite loopstick in this regard? --- End quote --- It appears to be exactly the same.... --- Quote ---The ferrite rod antenna operates using the ferrite material to "concentrate" the magnetic component of the radio waves through the pick-up coil. This is brought about by the high permeability ยต of the ferrite. It means that the ferrite rod antenna has a much greater level of sensitivity than if the coil had been used on its own. The fact that this RF antenna uses the magnetic component of the radio signals in this way means that the antenna is directive. It operates best only when the magnetic lines of force fall in line with the antenna. This occurs when the ferrite rod antenna is at right angles to the direction of the transmitter. This also means that the antenna has a null position where the signal level is at a minimum when the antenna is in line with the direction of the transmitter. https://www.electronics-notes.com/articles/antennas-propagation/ferrite-rod-bar-antenna/basics-tutorial.php --- End quote --- |
| Circlotron:
--- Quote from: Circlotron on November 30, 2018, 03:45:11 am --- --- Quote from: Richard Crowley on November 29, 2018, 08:14:29 pm ---* Remember that when using a coil for direction finding, when you have a null, the source is perpendicular to the coil axis. --- End quote --- With an AM radio the null is when the loopstick axis points directly at the source. Is there some difference between an air cored loop and a ferrite loopstick in this regard? --- End quote --- If a source is perpendicular to the coil axis for a null that means it is at 90 deg to the coil axis. If a loopstick axis is pointing at the source for a null then it is not perpendicular to the loopstick axis. |
| 001:
--- Quote from: Circlotron on November 30, 2018, 05:41:59 am ---If a source is perpendicular to the coil axis for a null that means it is at 90 deg to the coil axis. If a loopstick axis is pointing at the source for a null then it is not perpendicular to the loopstick axis. --- End quote --- In fakt guitar pickup look like this. It eliminate 50Hz quite good. But not a 5kHz (Why?) How to identify problem direction? |
| Buriedcode:
The image you posted is for a "humbucking" pickup - as explained previously, these use two pickups wired in series, but placed anti-parallel to eachother, so that "interference" creates the same signal in both pickups, but at opposite polarity, so it cancels out. This should be the case for a wide range of frequencies. The clue is in the name hum - mains hum, and bucking to oppose or resist. These do not completely eliminate mains hum interference (or any other interference), merely attenuate it - often enough to make life easier for recording situations. once again, I have questions, I think I have posted these before and others have asked: What guitar is it? What kind of pickups does it have? single coils? or humbuckers? Does changing the pickup switch on the guitar change the amplitude of the noise? Is the amp set to high gain? (overdrive) or "clean" ? Are all the guitars you've tried shielded internally? Normally this doesn't' matter a great deal since most people don't experience a lot of EMI with their guitars. But in very noisy places it can make a significant difference. I'm afraid, if you've tried different amps, with different guitars, on "clean" and still get interference, then there isn't much you can do about it. There are noise-gates which are designed to cut the guitar signal out when it falls below a threshold, so that when one isn't playing it is very quiet, but these only work with low-level noise, and the noise can often be heard just before it kicks in. It just sounds to me like your friend needs to find another place to practice :/ |
| 001:
--- Quote from: Buriedcode on November 30, 2018, 02:55:31 pm ---What guitar is it? What kind of pickups does it have? single coils? or humbuckers? Does changing the pickup switch on the guitar change the amplitude of the noise? Is the amp set to high gain? (overdrive) or "clean" ? Are all the guitars you've tried shielded internally? Normally this doesn't' matter a great deal since most people don't experience a lot of EMI with their guitars. But in very noisy places it can make a significant difference. --- End quote --- Honey. You don`t want help me since Your questions are silly. You didn`t read my previous posts I posted three clean samples from humbucking guitars before It is not "guitar for beginners" tread :palm: I`m just looking for engineer who had deal with strange 5kHz sine wave |
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