EMF radiation from inverter?

[inetdog]

My primary job was to design all digital toll switching, so I know little about the step by step, number 4 crossbar, and
other mechanical systems that we replaced. But I did have some occasion to reverse engineer some analog lines.
Don't know what Originating Sleeve Control is.

The double speed rotary dial I believe was standard for operators, guess all the office equipment could handle it.
Bruce Roe

Oh, that fancy electronic stuff.

I don't think that ordinary subscriber lines could handle 20pps dialing. But for operators who needed it to make the most money for the company or for subscribers who were willing to pay it was available. It put additional restrictions on line impedance, etc. and so was not supported by default.

One note from the paper that Dereck linked, which he may find interesting:

During the ring the CO may or may not remove the loop feed DC voltage.
If Caller ID service is provided, the CO can send caller ID information between the ring pulses or prior to the ringing using FSK (Frequency Shift Keying) or DTMF signaling in the VF band. The European EN 300 659-1,2,3 standards describe the subscriber line protocol used for caller ID and other services.

So for systems that detected the AC impedance loading down the ring generator through the SLIC for off hook detection (maybe not common in the US) the 48V might actually go away.
And the DTMF or FSK Caller ID signalling might also hit the line before the first ring.

[DanKegel]

My primary job was to design all digital toll switching, so I know little about the step by step, number 4 crossbar, and
other mechanical systems that we replaced

Cool!

I helped maintain my dorm's electromechanical phone exchange back in the early '80's. It had 60 lines, and it was cool to watch the switches step as people dialled. Alas, one day it burned up. We then built a hybrid digital/analong replacement using 4x4 CMOS analong crossbar chips, controlled by a 6502. (The analog part was designed by a seriously good analog EE, who later went tp HP back when it was still HP. The digital part was designed by a guy who put himself through college by selling a spreadsheet written for the IBM5110 in machine language. I built a lot of it and wrestled the software into behaving... including cobbling together a 6502 assembler and linker for the PC.) That ran for eight or so years until it got flooded in an epic water fight, after I graduated.

Good times

[wblanford]

I also spent some time maintaining the college step by step phone exchange and telephone system that was used for all the dorms in the early '70's. Lots of time spent in the basement.

[SunEagle]

Most of you guys missed out on the fun when it came to what some of my college friends could do in the 70's with Ma Bell.

They were known as Phone Phreaks and built blue boxes to get free long distance phone calls. One of them actually went on to working for the telephone company.in research and design.

[wblanford]

Spiro T Agnew - There was the Spiro, which generated the 2500 Hz tone and the touch tone key pad with the operator frequencies for making free long distance calls. The T was a bridge rectifier which could be inserted in series with the pay phone telephone line to return your money at the conclusion of the call. The Agnew was a box with a momentary switch, a series capacitor and battery. The Agnew was placed in series with your phone. When an incoming long distance call started ringing, the momentary switch briefly shorted the line. The capacitor provided audio coupling to the phone and the battery supplied power to the phone.

[bcroe]

All that Blue Box stuff was possible because of the way the mechanical system set up calls. A local switch would signal a
toll office with the required call destination, via tones similar to DTMF. The toll office would connect to another toll office
and repeat the process, continuing across the country till the call finally connected via a local switch. So you could send
your own tones and take over the call.

We cut over the first digital toll (4ESS) in Feb 1976, a day I'll not forget after 9 years of working on it. When the whole
continent was converted, all transmission became digital. Common Channel Interoffice Signaling carried the call setup instructions.
The control chose a path across the whole network, sent commands to all the offices involved, and you instantly had a
connection, no waiting, and no chance to interject your own control. Bruce Roe

[MikeInRialto]

Did I insult you in any way?

Lmao - when I saw this. Icebox, some people are just effing jerks. Either they didn't get enough hugs when they were young, or might be tramatized because after drinking fresh milk from the cows they found out the family only had bulls. Ask all questions and some will give good answers, some will give opinions, some wok give wrong answers, and some will throw in extra crap free of charge - perhaps as a means to clense their soul of negativity they've cultivated for many many years. Just remember 30 years ago cigarettes were the in thing and they were not bad.

[icebox]

Lmao - when I saw this. Icebox, some people are just effing jerks. Either they didn't get enough hugs when they were young, or might be tramatized because after drinking fresh milk from the cows they found out the family only had bulls. Ask all questions and some will give good answers, some will give opinions, some wok give wrong answers, and some will throw in extra crap free of charge - perhaps as a means to clense their soul of negativity they've cultivated for many many years. Just remember 30 years ago cigarettes were the in thing and they were not bad.

2 People, the first to reply to most threads, felt disheartened that somebody dare 'walk' into their imaginary kingdom and ask a question that is contrary to their beliefs.

They misunderstood the intent of my question anyway, foul is on them.

[DanKegel]

Sunking's really useful on battery questions, so people put up with his quirks.

To the question "do solar inverters emit an unsafe level of electromagnetic radiation", the answer is "no", I think, based on looking at sources like

http://www.who.int/peh-emf/publications/facts/fs322/en/

To the question "do solar inverters emit enough RF to interfere with with nearby radio and TV reception", the answer is "sometimes, maybe; if it happens, document it and add countermeasures like RF chokes".
The FCC puts limits on emissions, see http://www.edn.com/design/systems-de...ns-and-options for a wall of info about that from the designer's point of view. But problems can still occur, see e.g.
https://www.reddit.com/r/amateurradi...hey_gifted_me/
or
https://www.solarpaneltalk.com/forum...radio-stations
Avoiding interference probably depends on the installer adding RF chokes.

So, how well shielded are SolarEdge inverters? Here's a photo of one with the door open:
https://goo.gl/photos/aNJDinEASa5ssBMT7
I don't know if the outer case is shielded, it looks plastic, but there could be a conductive layer inside it. Still, that leaves the seams and exit ports for RF to leak out.
The silvery block near the top looks like a well-shielded section. I bet the high-power switching stuff is in there, and care was taken to prevent leakage.
The DC input and AC output wires exiting at the bottom have large RF chokes not mentioned in Solar Edge's documentation, so I bet they were added by the installer to reduce interference. (Good for him!)

I tested whether my SolarEdge inverter interfered with radio reception just now by walking around with a portable AM radio (Sony ICF-SW7600G).
Standing a few inches away from the inverter, I was still able to receive WWV at 15.00 MHz from several states away clearly.
And it didn't interfere with local stations like KFWB, either.
Now WWV's pretty powerful, but I'm in Los Angeles, and it's in Colorado, so if I can hear that clearly, things aren't so bad.
Turning the inverter off reduced the noise slightly, so there is a little interference, but so far it hasn't bothered me.
For comparison, even with the inverter off, just being near our gutter downspout caused far more interference - I guess the downspout acts like a big antenna.

But of course, inverters are only one possible source of RF energy; the optimizers could emit it, too, and I haven't tested that yet.
So can LED lights, CFL lights, computers, cordless phones, set-top boxes, video games, and basically everything that has an integrated circuit in it these days, which means everything that uses electricity.

As Madge said, "you're soaking in it!" https://www.youtube.com/watch?v=H7BvEldVEHU

[jflorey2]

I helped maintain my dorm's electromechanical phone exchange back in the early '80's. It had 60 lines, and it was cool to watch the switches step as people dialled.

We had one of those at MIT called Dormline. We built it out of surplus switchgear from local CO's. It was always breaking down and needed a three wire connection to all the phones, but on the plus side you couldn't trace calls through it.

[DanKegel]

Three wire connection? Strange! I think ours (BTE, in Blacker House at Caltech) only needed two wires to each phone.

[wblanford]

We had one of those at MIT called Dormline. We built it out of surplus switchgear from local CO's. It was always breaking down and needed a three wire connection to all the phones, but on the plus side you couldn't trace calls through it.

I also worked on those in the early '70 at MIT. I do not recall needing a three wire connection to the phones.

[jflorey2]

I also worked on those in the early '70 at MIT. I do not recall needing a three wire connection to the phones.

This was late 80's. I don't know what changed but it was always a pain in the butt to pull new wire, since you couldn't use the really cheap stuff.

[inetdog]

Three wire connection? Strange! I think ours (BTE, in Blacker House at Caltech) only needed two wires to each phone.

Three wire connection to phone usually is actually two line wires, one of which is grounded most of the time, and a ground. Where the ground is needed for some oddball ringing options instead of across the line ringing.

[Sunking]

Three wire connection? Strange! I think ours (BTE, in Blacker House at Caltech) only needed two wires to each phone.

Back in the days when there were party lines, it required 3-wires for the Ringers to work. Back in those days the Telco applied Ring Voltage between Tip-Ring, Tip-Ground , and Ring-Ground, or 3-mode at Frequencies of 20, 30, 40, and 50 Hz. That allowed them to put 12 homes on a single party line. Stilll used in some remote rural areas like Indian Reservations.

But today for most of us with private lines it is all 2-wire 20 Hz Ring circuits called Tip and Ring. FWIW Ring Conductor has nothing to do with Ring Voltage. It has to do with the Operator old switch board cross-connect cable just like you phono Jack you plug into your cell phone for ear buds. Tip for the end of the plug electrical contact, followed by and insulator, and then Ring electrical connections completing the return circuit.