Oooh eee Oooh aaah aaah ting tang walla walla bing bang coming out my friend's parents intercom speaker, the back side of which was OB into their garage, next to the door frame. Their intercom had FM, while ours was AM only.
I've worked on radio chips a lot. It's not unusual for the AM audio bandwidth to be limited to about 2 kHz, for example by using the 75 us American FM de-emphasis filter on AM audio. The customers are obsessed by the sensitivity numbers and the sensitivity is defined as the carrier level at which the signal-to-noise ratio is 26 dB related to 30 % modulation, so the narrower the bandwidth, the better the sensitivity.
The radio ICs I've designed parts of were not intended to be used with output transformers.
Probably CFTR, another hit music station at the time. CKLW was mentioned earlier in the thread. I started my radio career at CKLW in the Big 8 days as a bench tech and wrapped it up designing and building the studios for the four station radio cluster containing CFTR, now 24/7 news.
As a child our family spent Sundays at a park on the north shore of Lake Erie picnicking with other WW2 Italian refugee diaspora. The drive took us past the CKLW transmitter site and there was always a moment of child anticipation waiting the the car radio's front end to blow in the site's main power lobe. That art deco building with massive front windows glowing orange at night was a source of wonder for a kid.
I think he´s explaining why 5kHz compromise was reached back in the day when the worldwide AM system and standards were established in the 1920´s
Not many ICs available and every amplifier used an OT.
99.9% of which were cheap non interleaved.
And an expensive "Radio Grammophone Combination" would at best sport a 12" speaker.
As an example Heathkit's 1950s BC1A receiver is capable of at least double that with a 10 kHz notch. Every Canadian AM in my professional experience broadcasts to 10 kHz with the one exception of a station with a first adjacency 10 kHz away.
Not in North America. It's 10 kHz with an emphasis/de-emphasis curve receiver manufacturers with few exceptions ignore.
https://www.nrscstandards.org/standards-and-guidelines/documents/standards/nrsc-1-c.pdf
Attachments
Could be, but that remark about audio bandwidth and output transformers came right in the middle of a discussion about the 2 kHz audio bandwidth of modern AM receivers.
1. A little more accurate history of US AM radio:
In the middle years of AM radio in the US, there were clear channel AM stations, their station occupied 20kHz for the 10kHz upper and lower sidebands.
Yes, they had audio bandwidth of 10kHz.
That meant that in the US, with a good tuner such as the Eico AM tuner, which had a narrow band/wideband IF switch, and a 10kHz Notch filter (to notch out the adjacent station's carriers that beat with the desired stations carrier).
I remember listening to those stations (on several radios, including the Eico AM tuner), the stations really did broadcast decent audio signals.
The stations prided themselves with wide bandwidth and fairly low distortion.
The US government in their effort to "improve" things, made everything worse.
If you like what you have, enjoy it, before it is taken away.
Just my Opinions and my Experience.
2. Ford got lots of feedback on their decision to take out the AM radios for new vehicles.
They re-considered, and may put the AM radios back into the vehicles.
In the middle years of AM radio in the US, there were clear channel AM stations, their station occupied 20kHz for the 10kHz upper and lower sidebands.
Yes, they had audio bandwidth of 10kHz.
That meant that in the US, with a good tuner such as the Eico AM tuner, which had a narrow band/wideband IF switch, and a 10kHz Notch filter (to notch out the adjacent station's carriers that beat with the desired stations carrier).
I remember listening to those stations (on several radios, including the Eico AM tuner), the stations really did broadcast decent audio signals.
The stations prided themselves with wide bandwidth and fairly low distortion.
The US government in their effort to "improve" things, made everything worse.
If you like what you have, enjoy it, before it is taken away.
Just my Opinions and my Experience.
2. Ford got lots of feedback on their decision to take out the AM radios for new vehicles.
They re-considered, and may put the AM radios back into the vehicles.
Not surprising. The one tuner I believe implemented it was the Denon TU-680NAB from the early 1990s. Lack of a 10 kHz notch filter limits its nighttime utility unfortunately. No AM broadcaster to my knowledge doesn't adhere to the NRSC standard.
Most contemporary radios - Tecsun, CC Crane, Sangean, etc. - appear to be designed around DSP chips like the Skyworks Si4730/31. https://www.skyworksinc.com/en/Products/Audio-and-Radio/Si4730-31-AM-FM-Radio-Receivers They can be capable of pretty remarkable performance but the chip doesn't embed NRSC functionality so radio manufacturers design the top end 'by ear'. Even so to my ear radios like the CCRadio Solar Digital easily exceed the AM audio performance of legends like the GE Superadio with better selectivity and sensitivity.