hearing a voice through my rig...

[agedhorse]

That's fair... I'm just the messenger. We learn through the conversation.

Yes, agreed. I have mentioned many times that information available on the internet is often bad, and that relying on information from unknown and unverified good sources leads to this sort of thing.

I assume this is about having everything on the same earth and is just the easiest way to achieve/explain that in typical situations for people not carrying 3 phase power cabling and the associated knowledge.
I'd argue if it's all running off a single 3 phase connection then it's still all "the same electrical circuit" in this sense anyway.

The individual phases are not a problem as everything is internally isolated by a transformer of some type. This means that no piece of equipment knows what another piece of equipment's phase connection is.

In general, as long as the grounding system follows code, no current will flow in the ground conductors and there will be no voltage between ground points. In practice, this is not always 100% the case. connections to different elements of the building (via metallic conduit, boxes) can result in very small voltage differentials and leakage which can be a function of all kinds of sources. In installations where guaranteed low leakage is necessary to eliminate the effects of the circulating currents (ground loops), there is a method of grounding called "isolated ground" installations, where the ground terminal of the receptacle is carried on an insulated green wire and the mounting yoke of the receptacles (which is connected to the box/conduit system) are isolated from the ground terminal. These isolated ground wires are isolated from the conduit system all the way back to the service panel where they (or it in the case of an IG subpanel) is landed on the ground bus which is also bonded to the neutral conductor, and any other code required bonds (building steel, water piping, gas piping, CATV, Telco, Eufer, etc.).

 

[Shaggai]

My high school's PA for the gym always had a habit of capturing the local police radio transmission. No idea how it happened but every other pep rally or assembly, "Car 22, 419 at Humboldt St." and the like.

 

[Zooberwerx]

 

[CryingBass]

Not all RF transmitters/transmitee's are supposed to be sending past a certain level in a certain area.

Pirate Radio! Did you hear a Parrot squawking?

( not likely, but I could not resist )

 

[micguy]

The toughest RF intrusion issue I ever had took me quite a while to resolve. It was an instrument with an active preamp (that I had built myself). I tried cables, I tried grounding, shielding, replacing all the semiconductor devices (it was a discrete preamp), reheated all the solder joints; nothing would fix the thing. Finally, in desperation, I changed the battery. Fixed it. What? Swapped it back, yep - the battery had a bad connection between a couple of the cells, which acted as the detector. In this case, it was a very strong AM radio station nearby that crept in - RF will, if you give it an opportunity, find a way in. The odd thing about this issue is that that guitar was (for a short bit) absolutely the BEST sounding AM radio I every heard in my life.

 

[bigdaddybass12]

Paranormal activity! Start your own tv show,,,

 

[crazyBassClown]

there is a method of grounding called "isolated ground" installations, where the ground terminal of the receptacle is carried on an insulated green wire and the mounting yoke of the receptacles (which is connected to the box/conduit system) are isolated from the ground terminal.

I can't help but think this is very US centric...because "where the ground terminal of the receptacle is carried on an insulated green wire" is how all the outlets are grounded here in Australia. And it still doesn't prevent all earth loops when you join equipment on different circuits.

 

[byacey]

The toughest RF intrusion issue I ever had took me quite a while to resolve. It was an instrument with an active preamp (that I had built myself). I tried cables, I tried grounding, shielding, replacing all the semiconductor devices (it was a discrete preamp), reheated all the solder joints; nothing would fix the thing. Finally, in desperation, I changed the battery. Fixed it. What? Swapped it back, yep - the battery had a bad connection between a couple of the cells, which acted as the detector. In this case, it was a very strong AM radio station nearby that crept in - RF will, if you give it an opportunity, find a way in. The odd thing about this issue is that that guitar was (for a short bit) absolutely the BEST sounding AM radio I every heard in my life.

Frequency response wouldn't be limited by the IF bandpass, as in a conventional superhet. Did you not have a bypass cap across your 9V battery? 9V are generally a crappy power source, as the internal resistance of the cells are quite high.

 

[byacey]

In installations where guaranteed low leakage is necessary to eliminate the effects of the circulating currents (ground loops), there is a method of grounding called "isolated ground" installations, where the ground terminal of the receptacle is carried on an insulated green wire and the mounting yoke of the receptacles (which is connected to the box/conduit system) are isolated from the ground terminal. These isolated ground wires are isolated from the conduit system all the way back to the service panel where they (or it in the case of an IG subpanel) is landed on the ground bus which is also bonded to the neutral conductor, and any other code required bonds (building steel, water piping, gas piping, CATV, Telco, Eufer, etc.).

This is common in hospitals, and "technical ground" often found in sound studios and performance theatres.

 

[fdeck]

The occasions when I've observed radio pickup, it was caused by a dodgy ground connection at the input jack of the amp, such as a broken solder joint.

 

[Rojd]

A couple of years ago I bought a pedal that was a lightning rod for a Spanish language radio station. As soon as I put the pedal on my board and powered up, there was the Spanish radio. I could not get rid of it which made it unusable for me. I took it off the board, no more Spanish radio. I sent it back to the maker.

 

[agedhorse]

I can't help but think this is very US centric...because "where the ground terminal of the receptacle is carried on an insulated green wire" is how all the outlets are grounded here in Australia. And it still doesn't prevent all earth loops when you join equipment on different circuits.

No, the difference in an IG installation is that there is no bond between the green wire ground and the conduit system, each is independently returned to the ground bus at the service.

Most residential installations do not use conduit here (there are exceptions in large (or high rise) apartments, condos, etc) so there is no separate set of ground paths. The green or bare wire ground is then the only ground.

Ground loops generally happen because there is current leaking into the grounding system, this can be normal low level leakage (that's tested for when equipment is designed) or it can be higher level leakage from a fault, or an improper connection (such as a neutral and ground touching somewhere in the system other than the bond at the service panel).

 

[LowActionHero]

I had a guitar amp that picked up a radio station a couple times. This was many years ago, hasn't happened since. The funniest thing was - it was a German talk station. Could have been shortwave I suppose. It would disappear and come back as I rotated the amp.

 

[FunkyFlashFive]

One of my bands in high school often rehearsed in the drummer's basement which was a few blocks from the local AM sports broadcast tower. When the lead guitarist ended a particular song, as his note faded out the baseball game would fade in and we'd wait to get the score before starting the next tune.

 

[micguy]

Frequency response wouldn't be limited by the IF bandpass, as in a conventional superhet. Did you not have a bypass cap across your 9V battery? 9V are generally a crappy power source, as the internal resistance of the cells are quite high.

That's a good question, but we're talking about something from quite a while ago - I don't recall the particulars of what value I used for the power supply bypass. The lab (where I worked) where I built that circuit originally is right next to another strong AM station, so any circuits we designed there were generally very good at RF rejection. This one was just fine with a good battery, but I managed to find a bad battery.

 

[crazyBassClown]

No, the difference in an IG installation is that there is no bond between the green wire ground and the conduit system, each is independently returned to the ground bus at the service.

The "conduit system" as you call it here in australia is not a ground bus given it is plastic if it is used...

 

[agedhorse]

The "conduit system" as you call it here in australia is not a ground bus given it is plastic if it is used...

Here, due to hazardous smoke in the event of a fire, there are limits to where PVC conduit is allowed. In most installations where conduit is used, it’s steel and must be bonded to safety ground. How it’s bonded is what an IG installation addresses.

 

[Ductapeman]

Growing up in Seattle we were big fans of Sonics basketball-- the year they took the championship (1979? damn I'm old) we were rehearsing in an unheated basement freezing our backsides off when we discovered we could pull in the ball games on our guitarist's amp-- getting scores between songs made that place a little more bearable--

 

[Mannyinnewyork]

A couple of years ago I bought a pedal that was a lightning rod for a Spanish language radio station. As soon as I put the pedal on my board and powered up, there was the Spanish radio. I could not get rid of it which made it unusable for me. I took it off the board, no more Spanish radio. I sent it back to the maker.

¿entonces lo retiró sin hacer preguntas?

 

[lowendrachel]

When I used to live in an apartment. Whenever I practice through my combo. I hear a Christian radio station.