Thanks for the kink, they confirm what I said:
"...AM waves can be blocked by walls of concrete and steel, containing pipes and electrical wires- explaining why it’s so difficult to catch AM radio inside office towers and apartment buildings ... attaching a length of wire to the radio and hanging it outside as a makeshift antenna might also help..."
I have a screened loop antenna outside and it works just fine. It's the black ring middle top in the picture below.
"...AM waves can be blocked by walls of concrete and steel, containing pipes and electrical wires- explaining why it’s so difficult to catch AM radio inside office towers and apartment buildings ... attaching a length of wire to the radio and hanging it outside as a makeshift antenna might also help..."
I have a screened loop antenna outside and it works just fine. It's the black ring middle top in the picture below.
This was known.
"CBL gave up its longtime home on 740 and moved to FM. CBL had long been plagued by radio frequency interference that made it virtually unlistenable in downtown Toronto. Despite this..." https://en.wikipedia.org/wiki/CFZM
" listeners ‘from Maine to Minnesota..
May not be far from a truth. At Raritan NJ USA, one stormy night, I was listening to traffic-weather on 1010 WINS. I did that a lot. Reception was poor behind Copper Mine Hill. But this night a different announcer was hawking a sale at a mall I never heard of. It cut back and forth with WINS. As you surely know, it was CFRB, coming the long way over the border and mountains, stronger than WINS coming up the bay.
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Technical lingo can get quite convoluted, as shown in this industrial equipment video:
But seriously, if a hifi system changes its performance with a less than an ideal power input (as long as a "120 volt" line voltage stays above 100V or so), then the system's power supply is inadequate. There's even known "flyback" buzz problems with stray inductance and common 1N4007 rectifiers, that can cause a background buzz even with a perfect sine wave input.
Don't overthink it, my advice about progressive steps in Post #23 is still valid.
The M-G set advice was the last possible treatment of your problem, and more of a prank.
It is easier to bypass the supply and build a battery operated set, connected directly to DC, and designed to use only one (battery) voltage throughout, from pre amp to power amp.
And you can disconnect the set, or not use it while the battery is being charged.
Then no noise can come except from the inputs.
The M-G set advice was the last possible treatment of your problem, and more of a prank.
It is easier to bypass the supply and build a battery operated set, connected directly to DC, and designed to use only one (battery) voltage throughout, from pre amp to power amp.
And you can disconnect the set, or not use it while the battery is being charged.
Then no noise can come except from the inputs.
Hum, crosstalk and buzz are often different manifestations of the same circuit layout issues, so whilst running on battery might eliminate hum, it does not overcome the other deficiencies in design that lead to the hum problem in the first place. But in any case, it is beyond the capability of most people to correct audio circuitry to overcome disturbances from external noise sources, and power conditioning of various types does have a place in some circumstances.
Many codes now require multiple ground rods.
I am all for whole house panel installed protectors having lost two TVs to ground strikes. My computer is still plugged into a Panamax.
So, I guess a stereo sounds better if it is not blown up. I do like big honking linear supplies and that transformer is a fantastic surge protector.
I am all for whole house panel installed protectors having lost two TVs to ground strikes. My computer is still plugged into a Panamax.
So, I guess a stereo sounds better if it is not blown up. I do like big honking linear supplies and that transformer is a fantastic surge protector.
Nice array... You clearly live in a house and by the look of the sky you don't live in an urban city area... Here is a view from my window in November. As you can see, theres no room for any of that. I don't even have a balcony.
BTW, AM reception sucks in my car, too - at least until I get to the suburbs. AM sounds fine at my fathers house 12 km from here using the built in crappy antenna in the "7 tube and 3 diodes" table top radio I keep outside in the garage though.
Attachments
I know that, but it's especially bad if they need to install a 22.4W FM repeater though because it's not just like driving under a bridge or power lines, it's a large geographic area. For all I know the Canadian Shield effects it, too.
https://en.wikipedia.org/wiki/Temagami_Magnetic_Anomaly
Big honking linear supplies are huge generators of EMI unless suitably suppressed. I know this from experience being responsible for obtaining electrical compliance certification when working for an electronics manufacturer. Frankly a transformer that protects from voltage surge is not transforming properly and should be discarded as faulty.
True, I don't live in an urban setting now, in fact I am ~100km from the nearest city. However prior to this I did in fact live in that very city, and what's more owned a hifi store where I advised and assisted customers on how to get clean AM reception. Noise free AM requires a clean RF signal no matter where the the receiver is city, country or wilderness: the laws of physics hold for everyone in every place. BTW the signal strength in the city is likely 1000 times stronger than where I am now. What is important is that the antenna is outside of the faraday cage containing internal EMI noise generators where the receiver is (AKA your building, office or house). Clean reception can almost always be obtained within the intended service area of an AM transmitting service, with a suitable external antenna. The problem is not that physics is broken, but that AM radio reception is a lost art.
At my dad's house 12 km from here, I can use a garbage tie as a loop antenna and receive lots of AM in his living room on an 80's Pioneer system... I can receive AM outside but it isn't clean - there is 60Hz coming from everywhere when you live within a two minute walk of 20 condo towers 😀
The only way I could get a loop outside here would be to hang it out of the window on the wires and that would result in a letter from management asking me to remove it. Luckily, there's nothing on AM radio I can't stream or get on FM. They aren't even including AM in some new radios.
The only way I could get a loop outside here would be to hang it out of the window on the wires and that would result in a letter from management asking me to remove it. Luckily, there's nothing on AM radio I can't stream or get on FM. They aren't even including AM in some new radios.
Almost cinemas built before WWII had them. Usually a large AC electric motor driving an equally large DC generator. The low voltage/high current DC was used to light the carbon arc in the film projector. High current rectifiers were not available at the time, so you had to make your own DC.
But for home use, you'd want 50/60Hz AC, of course. They are not cheap and are somewhat noisy. Not nearly as noisy as one driven by an internal combustion engine, but not silent, either. The main problem for electrical noise is the generator (alternator) itself. I've looked at the waveform of some, including one we had at home. A horrible waveform! You would be much better off with mains AC. At work we often use generators for show power, and the good ones are crystal locked. However I've never peeked at the waveform of these fancy generators. Hopefully it's clean, as it never seemed to cause much trouble for audio PA or sensitive video gear. But you'd need to be careful, AC coming from a local generator could be far worse than your mains.
Most diesel electric locomotives are nothing more than a big diesel generator set on wheels... I used to run a Nintendo from an M-G set I made from a 1/4 HP motor, an IBM floppy drive spindle motor, and a rubber band. Neat idea, but unnecessary. Any device designed to run from line power should be designed to work with and filter out noise. For me, even going to balanced connections from single ended is past the point of diminishing returns. A power conditioner, inverter UPS, or otherwise wouldn't improve anything enough to bother spending time and money IMHO. Most electronic things are powered by converting AC to DC. If they do it properly, it shouldn't matter what the AC looks like - it will become DC.
Well that's the idea, anyway. 
I find that grounding problems are much more audible and troublesome than any mains noise.
Yes, I've done balanced power and the medical isolation transformers.
I find that grounding problems are much more audible and troublesome than any mains noise.Yes, I've done balanced power and the medical isolation transformers.
I would posit that you have a faulty or perhaps terribly-designed receiver... If there's no signal, you should get static not hum. 60Hz is way outside the band to which such a receiver should be sensitive.
The 60Hz and its harmonic frequencies could be finding their way to the audio section from the power supply. Not from the RF section.
Faulty design, poor screening, maybe a cap not put...many reasons.
Even dirty switches can cause problems.
Check that the transformer casing is earthed.
And to pinpoint the fault, if possible, use a different supply to the RF section, a wall wart or SMPS as a temporary supply, that should help find the fault. And without RF, the amp section should be quiet, as it has no input.
Here for the past many years even SW was missing, now the new receivers are FM only.
Some transmitters here are converted from TV use, so they have 1 and even 10kW outputs, clear out to 150 km. Typical is 100 W, and most transmitters use the same mast, easier for users to point their antenna.
Faulty design, poor screening, maybe a cap not put...many reasons.
Even dirty switches can cause problems.
Check that the transformer casing is earthed.
And to pinpoint the fault, if possible, use a different supply to the RF section, a wall wart or SMPS as a temporary supply, that should help find the fault. And without RF, the amp section should be quiet, as it has no input.
Here for the past many years even SW was missing, now the new receivers are FM only.
Some transmitters here are converted from TV use, so they have 1 and even 10kW outputs, clear out to 150 km. Typical is 100 W, and most transmitters use the same mast, easier for users to point their antenna.
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Drive your car under power lines or a bridge and tell me whet you hear on AM radio 🙂 Nothing wrong with the tuner. No AM radio receives in here.
What I don't get is hum. RF attenuation leading to a higher noise floor after AGC for sure, but the receiver doesn't ever produce a 50Hz tone.
I disagree. Power transformers will convert those HF spikes into broader humps easily dealt with. Yes they generate EMI. LF EMI. We know how to deal with that too. Never lost electronics on well built linear supplies. Have lost several on SMPS and on TV's that just rectified the line.