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Old 27th Nov 2017, 1:03 pm   #1
Andrew2
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Default Another Tesco radio.

I couldn't resist this as it was beautifully marked and up-wind. Just 8.

https://www.tesco.com/direct/tesco-r...?source=others

The one in the link is FM only. Note it says 'no longer available'. NOT surprised! Mine is AM and FM but looks exactly the same and has the same model no. Of course we shouldn't expect much at this price and not much is exactly what we get.
Both bands are dreadful. On AM, the radio is very insensitive and prefers to pick up its own processor noise. Even on strong signals the audio sounds distant. Tuning is in 9KHz steps and there is a lengthy muting period at every click so you can't tune around like you would on an analogue radio. The ferrite antenna is tiny and appears to be untuned.
There's a local oscillator which seems to run about 500KHz high. IF selectivity is poor - I can't see any hardware IF filters so I assume it is done digitally.

On FM the story is similar. Poor gain, noises off and generally irritatingly bad. Again no filtering hardware and I couldn't find a LO signal.

The chip that does the radio duties is a C9631:

http://aitendo3.sakura.ne.jp/aitendo...EN_aitendo.pdf

I was thinking of taking it back, but it's chucking it down outside so I'll keep it as a plaything. I may see what it says to my big tuned ferrite sleeve antenna. That'll fix it's clock...

Avoid unless you have eight quid burning a hole in your pocket and you fancy something to fiddle with.
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Old 27th Nov 2017, 1:12 pm   #2
paulsherwin
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Default Re: Another Tesco radio.

It's odd how variable these cheap chip based radios are. They all use similar technology and you'd expect the performance to be much of a muchness, but some are much better than others. I suppose some are just bodged together from datasheet examples with an absolute minimum of components.
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Old 27th Nov 2017, 2:52 pm   #3
Refugee
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Default Re: Another Tesco radio.

The RAD-108 is much better apart from the antenna having a tendency to fall to bits.
It also has short wave.
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Old 27th Nov 2017, 2:55 pm   #4
Andrew2
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Default Re: Another Tesco radio.

Yes, I've got a RAD108 and it's far, far superior to this heap of junk. My 108 is an early one with a standard polyvaricon tuning cap and analogue circuitry, but as there is a lengthy thread on this subject I'll shut up. Oh, the top section of the aerial went missing long ago!
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Old 27th Nov 2017, 4:55 pm   #5
merlinmaxwell
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Default Re: Another Tesco radio.

Saved me 8 quid, thank you (always a sucker for a silly electronic thing from Tesco).
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Old 28th Nov 2017, 8:15 am   #6
Neil Purling
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Default Re: Another Tesco radio.

I tried the first link....

Favourite music in impressive quality

It said. "We no longer sell this product" I wonder why?
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Old 30th Nov 2017, 2:41 pm   #7
colourking
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Default Re: Another Tesco radio.

Quote:
Originally Posted by Andrew2 View Post
On FM the story is similar. Poor gain, noises off and generally irritatingly bad. Again no filtering hardware and I couldn't find a LO signal.
With other similar radios on FM (having 'low-IF'), the Local Oscillator is approximately just 0.125kHz either above or below the received frequency.

So for example tuned to a station on 100.0 MHz, the LO is likely on approx either 100.125 or 99.875 MHz

Very little leaks out, but a narrowband receiver, such as a scanner in NFM mode, will likely receive the LO carrier holding it close to the radio (I found on a similar radio - the Tesco RAD108, the 4th harmonic of the LO could be detectable over a significantly greater distance).

Last edited by colourking; 30th Nov 2017 at 2:55 pm.
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