Hi again Pieter. That is very interesting. Yes I suppose 3kHz would fit the
MW/LW "grid" of 9kHz frequency allocation spacing for BC stations. The
design objectives may look odd, particularly to those of us who are older,
but it is ineresting to look at the design in terms of manufacturability and
cheapness. Labour is the most expensive item in electronics and technical
labour is almose unaffordable for consumer items. So I think they design to
avoid the need any manual setting up.......no trimmers or coils to adjust.
Key pads are expensive and prone to fail, a potentiometer and a scale
silk-screened on the knob or the case, is easier and probably indepenent of
language, since the main supply target for these type of units is counties
in Africa, S. America and Asia. Sale to Tesco is probably at a premium and
help keep 3rd world prices down. Strangely though I think only Europe has LW
BC stations.....and those are closing one by one.
Maybe the maker bought a bin full of surplus chips when a big manufacturer
ceased production, and designed a product to use them up?.
Alan
G3NYK
----- Original Message -----
From: "Pieter-Tjerk de Boer" <[email protected]>
To: <[email protected]>
Sent: Saturday, January 14, 2017 9:04 PM
Subject: Tesco 113B radio [was: Re: LF: Smart noise cancelling?!?]
A couple of months ago, there was some discussion on this list about the
cheap Tesco 113B kitchen radio performing very well on longwave (see
below).
This made me curious, particularly since it looked like a simple analog
radio, the circuit diagram of which might teach us something, so I got
myself one during my recent UK holiday.
Opening it up showed that it is not analogue at all. It's built around
an AKC6952 chip, of which a Chinese datasheet is at
+http://travelx.org/dsp6952.pdf .
This is a complete radio chip, presumably entirely digital, like e.g. the
SiLabs Si48xx series.
I knew such chips existed, but hadn't realized they were so cheap that
nowadays even the cheapest "analogue looking" radios use them, although
in hindsight it does make sense.
Technically it seems a bit silly though: tuning a nicely synthesized radio
via a mechanical potentiometer with a rather imprecise mechanical scale,
just because that's how kitchen radios are supposed to look.
I did some measurements on this radio using an AM signal generator.
It seems to tune in 3 kHz steps, and if the incoming signal isn't quite
on the tuned frequency, it seems to automatically make one such a 3 kHz
step either way. This explains why it seems to suddenly "lock" onto a
signal, as David wrote.
Its AM detector seems to be a standard envelope detector, not a
synchronous
detector, judging by the distortion when I notched the signal generator's
carrier.
I don't know why it would be more immune to noise than other radios.
Its digital filters may well be much steeper than those of cheap real
analog radios, thus keeping some noise out.
Also, the google translation of the datasheet promises "Precise digital
demodulation", whatever that means...
Regards,
Pieter-Tjerk
On Thu, Nov 03, 2016 at 05:34:50PM +0000, David Hine wrote:
Hi Alan, I am certain you are correct, but this Tesco set is much much
quieter
than my Eton G3, which also has sync detection. There must be something
else
too in that Tesco £9 cheapie -but what is it?? I know another user of one
of
these he bought for TMS on R4 LW, and he says it's the only LW radio he
can use
anywhere without any interference. Perhaps get one before they disappear
from
the shelves? I bought several, as they are so cheap, with the view to one
day discovering this radio's 'secret'. I feel this 'secret' could be
valuable
to know for other LF applications. Perhaps someone in this group has the
answer? Very kind regards, David.
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From: Alan Melia <[email protected]>
To: [email protected]
Sent: Thursday, 3 November 2016, 17:14
Subject: Re: LF: Smart noise cancelling?!?
Hi David, what describe (jump to frequency as you tune a station in)
sounds
like a little bit of sophisticated radio electronics. It suggests that
the unit
employs synchronous detection, somtimes called enhanced sideband
detection I
think. I dont have details to hand but it would allow a clear signal to
be
received in a much narrower receiver bandwidth than the 18kHz of the bog
standard diode detector usually used on cheapies. It also has the
advantage
that it greatly reduces the effects of fading (apparent over-modulation)
on the
audio quality.
It may sound unlikely at first sight at that price But sophisicated MSF
synching clocks are available for about the same price.
Alan
G3NYK
----- Original Message -----
From: David Hine
To: [email protected]
Sent: Thursday, November 03, 2016 4:32 PM
Subject: Re: LF: Smart noise cancelling?!?
Hi Stefan, Although this is a bit different, but also to do with
noise, I
bought a very cheap kitchen broadcast radio from Tesco for £9. It has
Long
Wave on it, and I am amazed it is the only LW radio I have that can
receive
all the stations that still are on LW without any background noise
once a
station is tuned in. It can be mains powered and next to a computer
or TV,
and still no local noise!! The model number of this Tesco kitchen
radio is
RAD - 113B. On tuning to a station, it suddenly 'locks on' to it with
a
small 'jump'. Then the local noise totally disappears, leaving only
the
required LW programme interference free!! Why is this? -could it be
the way
this very cheap radio detects the signal? If so, the detection method
used
in this cheap radio would be very useful for LF work, in which local
mains
noise is always a big problem. Perhaps someone here also owns this
Tesco radio, and can answer why it is so quiet indoors where all my
other
Long Wave (and much more expensive) receivers are all swamped by
local
noise when used indoors?? I hope this is useful. Regards, David.
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From: DK7FC <[email protected]>
To: "[email protected]" <[email protected]>
Sent: Thursday, 3 November 2016, 13:22
Subject: LF: Smart noise cancelling?!?
Hi all,
Last night i thought a bit about noise cancelling on LF/VLF.
Depending
on the band and distance and strength of the QRN, different settings
for
a noise blanker are used, or optimal. Different rise times, treshold
levels and so on.
I thought about propagation changes and different shapes of QRN
bursts
in the time domain, requiring different blanker settings.
Is it possible to program an 'intelligent' noise blanking system that
is
evaluating the input spectrum, looking at the shape/type of a sferic
and
automatically sets individual dynamic noise blanker parameters for
each
burst?
Or do i miss something here?
Just a thought. I guess i'm not the first one who has this idea :-)
73, Stefan
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