#1
Hi, I would like some help finding the inductance and impedence of my pickups.

A Google search didn't give me what I was looking for.

I am attempting to build a low pass filter that will block out receiving the local clear channel 50kw MW transmitter at night. I live 15 miles away from the WBBM transmitter and I don't want to hear it at night on my amp anymore.

In order to know the capacitance value to choose for the capacitor to buy from RadioShack, I need to know what the total impedence load is and even the inductance to find what the resonant frequency with the inductance is.

I know that the volume pot has an impedence load of 100k-500k. I am ignoring the load of the tone pot for now. I need to know the load of the pickups.

I have humbucker pickups. My pickups say Switch on them and they also say Stinger on them. No search results for Switch pickups or Stinger pickups.

Please help point me in the right direction to find the impedence and inductance value of my pickups, thanks.
#3
Quote by dietermoreno
Hi, I would like some help finding the inductance and impedence of my pickups.

A Google search didn't give me what I was looking for.

I am attempting to build a low pass filter that will block out receiving the local clear channel 50kw MW transmitter at night. I live 15 miles away from the WBBM transmitter and I don't want to hear it at night on my amp anymore.

In order to know the capacitance value to choose for the capacitor to buy from RadioShack, I need to know what the total impedence load is and even the inductance to find what the resonant frequency with the inductance is.

I know that the volume pot has an impedence load of 100k-500k. I am ignoring the load of the tone pot for now. I need to know the load of the pickups.

I have humbucker pickups. My pickups say Switch on them and they also say Stinger on them. No search results for Switch pickups or Stinger pickups.

Please help point me in the right direction to find the impedence and inductance value of my pickups, thanks.


How do you know its the pickups? When you move around does the transmitter interference vary with the orientation of the guitar?

I ask because a significant amount of MW transmitter energy comes from the transmission ground wave, which can get into your home through its ground and then into your amp. Before you go mucking about with your guitar internals, beg, borrow or buy a EMC/EMI filter box for the power outlet to clean up the power supply to the amp first.

As a minimum try different power outlets in a few different rooms and see if the interference changes
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#4
Quote by Roc8995
Buy a multimeter.


I have an analog multimeter than does not measure inductance.


Quote by Phoenix V
How do you know its the pickups? When you move around does the transmitter interference vary with the orientation of the guitar?

I ask because a significant amount of MW transmitter energy comes from the transmission ground wave, which can get into your home through its ground and then into your amp. Before you go mucking about with your guitar internals, beg, borrow or buy a EMC/EMI filter box for the power outlet to clean up the power supply to the amp first.

As a minimum try different power outlets in a few different rooms and see if the interference changes


No, moving the guitar in a different direction does not effect the radio interference for the MW station, but the guitar also picks up the local FM station 5 miles away that is much quieter than the MW clear channel station and holding the guitar perdendicular to the direction of the station seems to pick up that FM station the best.

I didn't even consider the outlet ground bringing in ground wave propogation. This mostly is worse at night, and I thought at night the propogation mode that is improved is sky wave propogation.


Hhm...now that I think about it...adding more capacitance to attenuate RF just is a bad idea for a guitar, since the capacitance of the cable and the impedence of the volume pot already form a cut off frequency in the audio frequency range, and adding more capacitance would cut off high end response.


So this makes me think that 300pF 10 foot long cable and 500k volume pot should already be a low pass filter that attenuates signals at a greater frequency than audio frequencies, and adding further capacitance would just give less of a treble response.

So I guess that crystal receiver schematics should not be applied to guitar electronics.

So the only thing my 1000pF capacitor is good for is building a crystal radio.

So I could wrap my cables in aluminum foil to block out the RF, since we have established that adding more capacitance to a circuit with high capacitance won't do anything other than kill high end response; but then that would just increase the capacitance and kill the high end response, since aluminum foil wrapped around an insulated conductor is I have built a capacitor.

So then my "project" is a waste of time, and there's nothing I can do to remove radio interference if I don't want my treble response to be affected other than (in order of lowest cost) (with the exception of the RF in the ground of the wall outlet, but I don't know yet if that is that case of what is happening to me):
(1) don't record at night if don't want to record WBBM.
(2) instead of building a low pass filter to attenuate RF, build a noise gate that only allows the strong signals generated by the guitar strings vibrating in the magnetic field of the pickups to pass and attenuates weak noises such as RF noises.
(3) install electric outlets into my basement and record in the basement (probably not a good idea for me to mess around with mains since I'm new to this).
(4) build a one transistor short range super regenerative FM guitar transmitter and receiver tuned to a frequency not used for broadcasting and add in the damn low pass filter to attenuate RF in the radio receiver.
(5) buy a noise gate.
(6) buy a wireless guitar system to eliminate the capacitance of the cable altogether and make sure that the wireless receiver has a low pass filter to attenuate RF and use a 6 inch guitar cable to connect the wireless receiver to the amp.
(7) buy a better amp that was designed to remove RF.
(8) buy out Star 105.5 and WBBM and turn off their transmitters whenever I want to record.
Last edited by dietermoreno at May 22, 2013,
#5
Quote by dietermoreno
I have an analog multimeter than does not measure inductance.


No, moving the guitar in a different direction does not effect the radio interference for the MW station, but the guitar also picks up the local FM station 5 miles away that is much quieter than the MW clear channel station and holding the guitar perdendicular to the direction of the station seems to pick up that FM station the best.

I didn't even consider the outlet ground bringing in ground wave propogation. This mostly is worse at night, and I thought at night the propogation mode that is improved is sky wave propogation.


Hhm...now that I think about it...adding more capacitance to attenuate RF just is a bad idea for a guitar, since the capacitance of the cable and the impedence of the volume pot already form a cut off frequency in the audio frequency range, and adding more capacitance would cut off high end response.


So this makes me think that 300pF 10 foot long cable and 500k volume pot should already be a low pass filter that attenuates signals at a greater frequency than audio frequencies, and adding further capacitance would just give less of a treble response.

So I guess that crystal receiver schematics should not be applied to guitar electronics.

So the only thing my 1000pF capacitor is good for is building a crystal radio.

So I could wrap my cables in aluminum foil to block out the RF, since we have established that adding more capacitance to a circuit with high capacitance won't do anything other than kill high end response; but then that would just increase the capacitance and kill the high end response, since aluminum foil wrapped around an insulated conductor is I have built a capacitor.

So then my "project" is a waste of time, and there's nothing I can do to remove radio interference if I don't want my treble response to be affected other than (in order of lowest cost) (with the exception of the RF in the ground of the wall outlet, but I don't know yet if that is that case of what is happening to me):
(1) don't record at night if don't want to record WBBM.
(2) instead of building a low pass filter to attenuate RF, build a noise gate that only allows the strong signals generated by the guitar strings vibrating in the magnetic field of the pickups to pass and attenuates weak noises such as RF noises.
(3) install electric outlets into my basement and record in the basement (probably not a good idea for me to mess around with mains since I'm new to this).
(4) build a one transistor short range super regenerative FM guitar transmitter and receiver tuned to a frequency not used for broadcasting and add in the damn low pass filter to attenuate RF in the radio receiver.
(5) buy a noise gate.
(6) buy a wireless guitar system to eliminate the capacitance of the cable altogether and make sure that the wireless receiver has a low pass filter to attenuate RF and use a 6 inch guitar cable to connect the wireless receiver to the amp.
(7) buy a better amp that was designed to remove RF.
(8) buy out Star 105.5 and WBBM and turn off their transmitters whenever I want to record.


FM? How would your amp discriminate FM, demodulate it and provide the audio component? AM MW I can understand.

Your guitar cable is shielded. Yeah it has capacitance but unless its complete rubbish cable it may have less than 30pf per metre. Hardly treble killing, unless you're using 20+ metres of it. You actually want to have good quality shielded cable I might add.

I think youre over thinking this too much. If the MW interference doesnt change much regardless of the guitar orientation then it suggests ground wave interference.

But to be sure disconnect the guitar, but leave the lead on the amp. Short the ground and hot on the open end and see if the amp still picks up MW. If so, then remove the lead altogether.

If the amp alone with nothing plugged into the input socket still picks up MW, you will need a EMI/EMC filter block between your power outlet and your amp.

Start testing
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#6
Quote by Phoenix V
FM? How would your amp discriminate FM, demodulate it and provide the audio component? AM MW I can understand.

Your guitar cable is shielded. Yeah it has capacitance but unless its complete rubbish cable it may have less than 30pf per metre. Hardly treble killing, unless you're using 20+ metres of it. You actually want to have good quality shielded cable I might add.

I think youre over thinking this too much. If the MW interference doesnt change much regardless of the guitar orientation then it suggests ground wave interference.

But to be sure disconnect the guitar, but leave the lead on the amp. Short the ground and hot on the open end and see if the amp still picks up MW. If so, then remove the lead altogether.

If the amp alone with nothing plugged into the input socket still picks up MW, you will need a EMI/EMC filter block between your power outlet and your amp.

Start testing



This dude has an MG and used an Un-shielded cable last time he posted. Do t waste your time with him.
Quote by DeathByDestroyr
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Last edited by R45VT at May 22, 2013,
#7
We've been down this road before, just get a better amp and move on.
“Ignorance more frequently begets confidence than does knowledge.”
Charles Darwin
#8
Well its not unheard of for crappy guitar amps to demodulate FM. I've seen dozens of YouTube videos of it happening if you live close enough to the station. but it is much much quieter than MW and is only heard in the recording very quietly and not heard on the guitar speaker. I think the detection method is slope detection. It only happens for the FM station that is 5 miles away from me and night doesn't change anything for it, but position in the room does change it to not be heard, while position in the room does not change the clear channel MW being heard at night.

Okay I will begin the tests that you said and tell you the results.

Yes it is the MG 15. Apparently its cheap enough to not have the guitar input jack designed to remove RF and not have the power supply designed to remove RF.
#9
You're wayyyyyyyyy overthinking this man. You're turning a very simple problem into a NASA project.

1: Clean up your power source.
2: Get yourself a legitimate shielded cable.
3: Ditch the amp, get a Vypyr 15 or Mustang I
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#10
Just to give you an idea of the broad band interference on the FM dial from Star 105.5, at my house in my car radio I can hear the station at about half volume and distorted at 105.3 MHZ and 105.7 MHZ. Then when I drove my friends home who live in McHenry, when I got to their house on the west side of McHenry which is about 2 miles away from McHenry Community College (MCC) where the transmitter is, at 105.3MHZ and 105.7MHZ I heard the station at full volume just distorted (must be the AGC on my radio that makes the volume the same), at 106.4MHZ I heard the station at about one-tenth volume distorted, at 104.3MHZ I heard the station at about one tenth volume distorted, and at 97.3MHZ I heard the station at a quiet distorted volume about the same sound quality as my FM penny radio I described in a previous post. So 2 miles away from the transmitter essentially I hear the station on every frequency in the FM band that has static when I am at home. OMG why does Mylie and Madonna have to be on every frequency why can't I live in Pleasant Prairee, WI where the rock station 95.1 is probably on every frequency.

My college, College of Lake County (CLC), also has an FM station, but it is a low powered transmitter since it is not-for-profit and student run. So the radio station at CLC is always played on the loud speakers in the school cafeteria, but probably can't travel much farther than the campus ground.

I suppose Star 105.5 probably also started out as a student-run station and then it was bought out and transmitter power was increased to spam the FM spectrum near MCC with pop variety hits.

I suppose that at MCC you can probably have a crystal radio in your pocket and listen through crystal ear phones to the campus station at volume as loud as a transistor pocket radio.

I never picked up Star 105.5 in my recording when I lived in Wauconda just a few miles east of Island Lake. As soon as I moved to Island Lake it is picked up quietly in every recording.

Funny thing is that when I look on a map of the transmitter, I found that I misestimated the distance to the transmitter from my friend's house in McHenry, and I found that the transmitter is the same distance as from my house, which is 5 miles. So it appears that what is just as important to radio interference from one station is that there are no other stations nearby. Island Lake is closer to radio stations in Lake County in the Chicago suburbs, but McHenry in McHenry county has that as the only station in McHenry county.


I tried every outlet in the upstairs music room, the news is heard no matter what outlet is plugged into, and I found that the news is only heard when my guitar volume is up and I mute the strings.

When I have the volume on my guitar at minimum so that all if is doing is providing a source of ground so that mains hum is not heard, I've found that its actually the FM radio stations that are every where. When I face due west I hear the dreaded star 105.5 in my emulated headphones and when I face slightly east of north I hear the more desired 95.1 THE ROCK STATION. So the guitar has nothing to do with FM reception and the guitar is only involved in MW reception.

So its not an outlet grounding problem, just the air in the Chicago area is that saturated with MW and FM stations.

So could I try building a noise gate to attenuate the weak rectified radio signals?

I didn't try using another instrument cable yet. I only have one uncoiled 10 foot instrument cable. I've found that my 20 foot instrument cable makes a real good FM antenna and my coiled instrument cable makes a real good MW antenna. So yeah, I can't try another instrument cable because all of my other cables are even worse.

Even the worst yet is using a tip ring shield cable instead of a guitar cable, removing the guitar, shorting tip to shield with aluminum foil, and making a loop antenna to receive both the vertical and horizontal polarized components of the wave by wrapping the cable around 2 coat holders and the door knob on the door to the balcony which the balcony is facing due west of the transmitter.

Even worse is taking the above set up, adding in a 6 inch instrument cable to connect from nickle to amp, connecting a short wire from shield to shield to provide ground, connecting the TRS cable to the green spot on a nickle (all of my pennies that are semi conductors are dark but not green yet), and connecting the 6 inch instrument cable to the clean part of the nickle. Now I hear Star 105.5's shitty adult pop rock half as loud as the side band at 105.3 MHZ on the car radio when I'm in my driveway. So now I have built a crystal radio.

I could make the bad music even louder if I used an insulated antenna wire (insulated so it doesn't ground itself) instead of the TRS cable so that the 300 pF capacitance of the cable doesn't block out RF, but I think I'll stop now.
Last edited by dietermoreno at May 24, 2013,
#11
You're helpless
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#12
WTF is all this shit.

All you had to do were some simple tests. The whole process of elimination thing.

Not coming back to this.
'It takes 100 guitar players to change a light. One to change the light and 99 to stand around pointing, saying..."Yeah man, look...I can do that too"...'

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Last edited by Phoenix V at May 24, 2013,
#13
strike a note to which you know the frequency. measure the resistance of the output of the pickup.

Z(L) = +jwL
= +j(2)(pi)(frequency)(L)

L = 1/jwZ
=1/wZ

not entirely sure if the formula for L is correct since I did it off the top of my head without any paper to keep track and Im a bit rusty on this topic. but if the formula is correct, and the frequency applied is more or less constant enough for you to read a good value on the multimeter, it should work. keep in mind that building a low pass filter into your guitar would affect tone.

and before you go messing with filters in your guitar, make sure its properly shielded. the electronics cavity should be shielded as well as the signal wires. incorrect/no shielding may result in pickup of radio signals.
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#14
^You're wasting effort with this guy, he's not going to be satisfied until he has a Faraday cage constructed around his MG15 with a book of paperwork to justify the dimensions, internal volume, material, and color of said cage.


Call the radio station and demand they use a lower power transmitter, it's interfering with the performance of your amp.
Endorsed by Dean Guitars 07-10
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2006 Fender All-American Partscaster
SVK ELP-C500 Custom

1964 Fender Vibro Champ
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[thread="1166208"]Gibsons Historic Designs[/thread]
#15
Carefully puts a few pickups, a rockman, some solar cells, a battery charger, rechargable batteries, and some headphones into a faraday cage.

Waits for the zombiepocalypse.
Last edited by HowlerMonkey at May 24, 2013,
#16
Make sure it's not coming from your power supply.

Past that take and install a 68k resistor from your input jack signal to the PCB or first gain stage. It will attenuate radio frequencies. If you input jack is not directly mounted to the PCB make sure the wiring is shielded.

If you would buy a better amp you would not be worrying about this and instead would be able to focus on school.

Quote by DeathByDestroyr
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Last edited by R45VT at May 25, 2013,
#17
Resoldered guitar jack and problem solved. So it was the loose solder connection that was creating the rectifying junction, NOT the amp (although the amp still has a rectifying junction, just it is much much quieter).

That's why there was not a noticeable difference of using a green oxidized penny connected to an antenna wire instead of a guitar, because the loose solder connection was the same effect of using a green oxidized penny connected to an antenna wire.

Actually, the much much quieter rectification heard is probably more loose solder connections, so I should resolder all connections in my guitar and then there will be no more radio heard on my amp.
#18
^umm, do you know half of what you are saying?

how exactly was a loosly wired guitar jack creating a rectifying junction(a diode)?
how is specifically a diode supposed to catch radio signals?
youre amp should have a few diodes in it(if its tube), a alot if its solid state.
you should drop the belief that there is any effect of rectification in your guitar.

if you look at a wired guitar jack, youd see there's 2 wires soldered onto it. one is a copper wire which is for the guitar signal. the other is a shield that is supposed to be grounded. that shield is for keeping noise and interference out of your signal. as a few people and I have already pointed out, improper guitar shielding may lead to radio pickup. theres no need to resolder everything, just make sure the electronics cavity is properly shielded.
Marty Friedman is GOD!

curently in a SEX MACHINEGUNS and X JAPAN phase AND Galneryus AND Anthem phase

damn J-Metal, why you so awesome

My Gear:

Schecter Hellraiser V-1 fr
Ibanez RG321mh
Fender GDC-200sce
Peavey Vypyr 30 w/ sanpera 1