Re: News : ARM Trying to Buy AmperComputing

On 1/30/25 11:49 PM, Robert Riches wrote:

On 2025-01-30, Charlie Gibbs <cgibbs@kltpzyxm.invalid> wrote:

On 2025-01-30, The Natural Philosopher <tnp@invalid.invalid> wrote:
>

AM is of such crap quality it is unlistenable. 30-3kHz bandwidth

>
Isn't it 5 kHz?  I can't see wasting quality on a 2-kHz guard band.
>
I've heard about AM stereo.  Is that for real?  If so, how?
>

and 40dB signal to noise? You have top be freakin' kidding me!
FM is way better,

>
As long as there isn't a hill between you and the transmitter.
And in a car you have constantly-shifting multipath interference.
All in all, though, I consider FM a win - but it's nice to have
the AM option.

 Regarding the (theoretical) audio bandwidth of US AM broadcast
radio:
      https://en.wikipedia.org/wiki/AM_broadcasting
 In the section titled "Technical information" around 80% of the
way down the article, the audio bandwidth was reduced in 1989 to
10.2kHz.  Prior to that, it was 15kHz.
 The 15kHz matches my memories from earlier studies and the manual
that came with the Pioneer TX-7800 tuner I bought in 1980-81.
That tuner has a front-panel switch for AM IF bandwidth that
yields ~5kHz vs. ~15kHz audio bandwidth, based on some filters
(ceramic, IIRC) that were pretty high tech for the time.  Sadly,
it seems some dust has become lodged in the mechanical tuning
capacitor.  It still has partial function but like when it was
young.
 Two "clear channel" stations I'm aware of are at 1160 and 1190.
IIRC, with the older 15kHz audio bandwidth standard, that means
there are no US stations centered at 1150, 1170, 1180, or 1200.
IIUC, for each clear channel station, the two adjacent center
frequencies are (or at least were) off limits.
 Another thing I have noticed is that clear channel stations seem
to have 3 call letters, while non-clear-channel stations seem to
have 4 call letters.  However, I'm not sure that's a hard and
fast rule.
 While the theoretical audio bandwidth was pretty decent at 15kHz,
now 10.2kHz, practical bandwidth depends on the receiver (as
stated in the article linked above) and on the RF S/N ratio.
Near to the transmitting antennas, the Pioneer tuner had rather
good listenable bandwidth.  Out in a rural county with a lot of
buzz-producing light dimmers and switching power supplies around
the house (and probably foil-backed fiberglass insulation in the
exterior walls), the audio S/N ratio is terrible.

   It is interesting that the original high-power transmitters
   used mechanical alternators to produce their RF sine-waves.
   Alas at only 10-20 khz the bandwidth would have been
   just miserable and huge antenna loading required to make
   both transmitters and receivers even remotely efficient.
   But, it WORKED. Proof-of-Concept.
   Lucky the triode valve came along. Thank you Dr. De Forest !
   Hmmmm ... modern tech could probably exploit sub-hertz
   frequency diffs, expanding the allowed bandwidth by
   frequency multiplication. This would not solve the
   other limitations of MW AM broadcasts however.
   Still, as I said elsewhere, ordinary AM sounds OK to
   me because that's what I grew up with. The brain knows
   how to disappear the noise and make up for the poor
   bandwidth.
   What few know is that early television goes back as
   far as 1909, with significant improvements in the
   early 1920s. Electro-Mechanical systems alas. Took
   Farnsworth to really sort it out.