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Sound of AM back in 60s and 70s

Larry Langford at WGTO 910 has some good stories to tell about that......

Perhaps he will....

This is THE major reason that the BEST AM auto radios used an IF of 262.5 khz. (525 product instead of 910)
In this way, images fall onto a "5" instead of a "0".
Of course if you had a realy stong signal you were dealing with you could still have a 5kc birdie.
 
Aaaand...525 is just outside the tuning range of radios.

Many years ago, we had a stereo receiver with analog tuners and wanted to get the highest possible audio quality on AM. We started raising the IF frequency (tuning, peaking, tuning, peaking, etc) until we got to around that magic 525 figure just below the point where it entered our tuning range. Any higher and we would not have heard a clear signal on 540.

You said 262.5 Khz, and we do remember hearing that frequency from our youth, but it seems that an IF that low would produce a norrow (boomy, bassy) output.
 
ai4i said:
Aaaand...525 is just outside the tuning range of radios.

Many years ago, we had a stereo receiver with analog tuners and wanted to get the highest possible audio quality on AM. We started raising the IF frequency (tuning, peaking, tuning, peaking, etc) until we got to around that magic 525 figure just below the point where it entered our tuning range. Any higher and we would not have heard a clear signal on 540.

You said 262.5 Khz, and we do remember hearing that frequency from our youth, but it seems that an IF that low would produce a norrow (boomy, bassy) output.
Click to expand...

Yes, because the selectivity increases due to having the same Q in any given 455 khz designed IF transformer.....so 262.5 khz IFs
had the coils closer together physically to "overcouple" the coils.....and such coils then had the nice sharp skirts with about 25 khz bandwidth,
which in practice gave about 15 khz audio response with fine separation between channels unless the "undesired" adjacent was really strong.
You can tune up or down and "count" each "channel" easily from some particular "known" frequency to some desired dx channel, without
any worrying about the analog dial readout was. Made it real easy to hit 1430 or whatever.
 
I've heard examples of very high quality AM. However, even if that could be done again, after 35 years in the wilderness I would wish lotsa luck to anyone thinking that large numbers of people can be convinced that AM is a silk purse.
 
If were talking about AM audio today, let me nominate 740 Toronto as their audio is a delight. I was reminded of that listening last night on my Boston Acoustic Receptor radio (non-HD version with above average AM). Their audio doesn't appear to have that annoying NRSC boost but instead sounds even.
 
radiorob2.0 said:
If were talking about AM audio today, let me nominate 740 Toronto as their audio is a delight. I was reminded of that listening last night on my Boston Acoustic Receptor radio (non-HD version with above average AM). Their audio doesn't appear to have that annoying NRSC boost but instead sounds even.
Click to expand...

That's an interesting observation. Can someone on this list categorically say whether or not Canada has an AM audio bandwidth/pre-emphasis rule similar to our NRSC?

As much as I understand the reasoning behind the NRSC curve, it really is in the middle of a no-win, tail-chasing situation between receivers and transmitters.

Kind Regards,
David
 
radiorob2.0 said:
If were talking about AM audio today, let me nominate 740 Toronto as their audio is a delight. I was reminded of that listening last night on my Boston Acoustic Receptor radio (non-HD version with above average AM). Their audio doesn't appear to have that annoying NRSC boost but instead sounds even.
Click to expand...

Yes, CFZM has one of the best audio signatures (if not THE best) that can be heard today on AM. WSM is also as good.
I'm sure there are others, but this is just considering 50kw wide area signals.
CFZM is real treat for the ears, and radios. This evening I the way to work, they played "Wild Weekend" by the Rockin Rebels.
This is a song I also play on my AM 1620, and I'll be danged!
If I didn't know I was listening to AM 740, I'd think I had my own signal tuned in.
They sound every bit as good as what I can do with my station.
It's not often I can say that. I spent a good deal of time making my own audio quality as good as it is, and when I hear another signal
that is as clean, rich and full, I am very impressed. I have no doubt someone there really cares about audio quality.
It can't be that good just accidentally. There doesn't seem to be any intentional crippling of the response by rolling off the high end.

They should be very, VERY proud of their audio, and their format.
 
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