Yaesu probably spent more money on metal and ferrite, but when I had a HF Icom it received carriers on specific frequencies
from it’s own silicon, be it from clock or a produced frequency like a harmonic of the display update frequency, etc.
My FRG-7 wouldn’t receive the same carriers.
This has also happened when I connected a frequency counter to an analogue radio.
When you think about it a processor in the radio probably won’t be running faster than 30MHz,
and it’s own generated noises will be slower than it’s clock speed.

That probably contributes to why I’m suspect about making more switching things.

I've been a ham for 11 years and have simply not encountered any trouble from the switching power supplies that I have used in my own shack

I have only been for about 2, and I think I became old fashioned quickly!
Some of the older guys though run their sets from batteries, and I can only assume they are even more unreasonably pure than me.
So you do get ripple free supply of juice and no possible surges from mains. Then I guess you only have an antenna to watch out for.

 

Back in the sixties when switching power supplies first came on the scene the switching frequency was low (1 to 20 KHz) and RFI/EMI control was minimal. That is when switchers, deservedly, got their bad reputation. Now with switching frequencies increasing to 100 KHz and higher, coupled with excellent noise control, switchers don't deserve the bad reputation for being noise generators. But, like a wayward girl, reputations follow more than performance.

One example I overlooked; In car audio - the basic BTL amplifier can put about 17W into 4 Ohms, but some people want a lot more.

There's a big market for switch mode converters that generate plus and minus rails, typically about 50V. The amplifier is then not very different to what you might find on a Hi-Fi stack indoors.

 

One example I overlooked; In car audio ...

Another example I overlooked - CARS. As in the Kettering ignition system, a classic flyback switching DC/DC converter, now over 100 years old and only a billion or so produced over the century. Imagine an all analog DC/DC converter that makes tens of watts at 20,000 volts over a 200 degree F temperature range in a very high vibration environment - for $10.

ak

 

Another example I overlooked - CARS. As in the Kettering ignition system, a classic flyback switching DC/DC converter, now over 100 years old and only a billion or so produced over the century. Imaging an all analog DC/DC converter that tens of watts at 20,000 volts over a 200 degree F temperature range in a very high vibration environment - for $10.

ak

They didn't have much choice - a 20kV battery would've been a tad unweildly!

But valves to switch it to the plugs would've been at least feasible.

 

IIRC, the Kettering patent predates the triode.

ak

 

<.....SNIP......>
Many audio products have switching supplies, including almost all high power automotive products. Because it is easy for switchers to operate above 100 kHz, it also is easy to keep heterodyne products and image frequencies out of the audio passband.

<.....SNIP......>

ak

I just finished repairing (with wonderful help from many of you!) the SMPS in an automotive audio amplifier, and I learned a ton. Just for an example data point; the SMPS oscillator runs at 35kHz. With 13.5Vdc input, the high side of the toroidal transformer is about 80V. Output power is around 250Wrms.

It has a feature where if multiple amplifiers are in use, the SMPS clocks can all be synchronized by making one the master and the others all slaves, for the purpose of reducing heterodyne noise. I understand that heterodyne is the mixing of 2 frequencies to create a 3rd, and this can happen when you have multiple circuits running at "almost" the same frequency. But it's not clear to me why this would cause more noise than just one frequency? Here's the excerpt from the manual:

 

They idea of synchronisation is try to maintain both smps oscillators at the identical frequency, so there wont be any beat frequency, a slight difference of 1 khz would be picked up on the audio amp, and produce an irritating whistle, just like listening to an AM radio at night.

 

Ahh I get it.. So with two oscillators at almost the same frequency you don't actually get "more" noise, you just get noise at the beat frequency (caused by the interference between the two original signals), with frequency matching the difference between the two original frequencies, and which can easily be in the audible frequency range. Thanks!

 

Technically, with two oscillators you do get more noise. But if it all stayed ultrasonic it wouldn't matter. When two frequencies combine you get both sum and difference products, so 34 kHz and 35 kHz signals combine to produce 1 kHz and 69 kHz in addition to their own frequencies. Guess which one matters?

Another trick is for the slave to invert the master clock signal, so when one amp is switching up the other is switching down. This phase cancellation can make a significant improvement is the overall system noise levels. Some high power high density DC/DC converters run at 500 kHz. With two converters running in sync, the system sees the same noise peak amplitude as with one converter, but at 1 MHz, something relatively easy to filter.

ak