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Old 12th Apr 2014, 2:38 pm   #1
mole42uk
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Default Chinese valve FM receiver kit

Hi,

I bought a receiver kit from Aliexpress in China. It's cheap, has a single valve and claims to be an FM receiver...

The circuit is attached.

My question is, can anyone interpret the coils at L1 & L2? There is a piece of 1mm enamelled copper wire in the kit, so I first thought that L1 was 2 turns and L2 was 5 turns, but I'm not sure what the number 4 relates to.

Any ideas?

Richard
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Old 12th Apr 2014, 3:53 pm   #2
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Default Re: Chinese valve FM receiver kit

Best of luck! this may work within 10 miles of Wrotham. At a guess 5 turns for the Japanese FM band, 4 for us as the Japanese band is a bit lower then ours. I have no idea what the Chinese band is.
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Old 12th Apr 2014, 4:20 pm   #3
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Default Re: Chinese valve FM receiver kit

I think the Chinese band goes from around 70 to 90 Mhz. Many years ago, someone brought a Chinese Hi Fi system round to me because they said FM didn't work and would only just about get R2


Rich
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Old 12th Apr 2014, 7:14 pm   #4
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Default Re: Chinese valve FM receiver kit

It's a variant on the quadrature detector. THe multi-grid valve is used as a multiplier and its inputs are the signal and a phase-shifted version of the signal, shifted by the input coils and capacitors.

There won't be significant limiting so it'll receive AM as well.

Oh boy! what will they sell next?

David
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Old 12th Apr 2014, 7:15 pm   #5
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Default Re: Chinese valve FM receiver kit

The Chinese used to use the Soviet FM band, but they may have switched as Russia mostly has now.

That valve is a Russian mixer a bit like a DK96 and I'd be astonished if it worked all the way to 108, but you never know.
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Old 12th Apr 2014, 10:10 pm   #6
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Default Re: Chinese valve FM receiver kit

A bit of amusement here -

I was using an app on my phone which uses the camera to look at Chinese characters and produces a translation.

The top line on the circuit diagram, which starts with 1A2 and ends with FM
translated as "Be Reborn"

It took me a while to realise that it really meant "Regenerative"

The line below that translates as "Radio Electric Circuit" which I take to mean "Receiver"

So, we'll see if I can make this one-valve kit into a '1A2 Regenerative FM Receiver'!

Richard
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Old 13th Apr 2014, 1:17 am   #7
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Default Re: Chinese valve FM receiver kit

I thought it might be a superegen design. There were lots of these around in the 50s and 60s, but they didn't work very well and chucked out lots of RFI. Interesting to build as an experiment though - obviously nobody is going to build one of these for serious FM listening given the availability of dirt cheap scanning FM radios from places like Poundland complete with earphones, and high end FM tuners available on Freecycle/Freegle.
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Old 15th Apr 2014, 7:48 am   #8
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Default Re: Chinese valve FM receiver kit

Quote:
Originally Posted by mole42uk View Post
can anyone interpret the coils at L1 & L2?
Well, I've been playing with Google Translate which has a method of drawing Chinese characters on-screen.

I now know that L1 is 2 turns of 1mm wire.

L2 translates as "1mm wire on the 5th battery 4 turns air-cored". I have improved the Google output a little, but I'm stumped as to the word 'battery'!

I wonder if there's something in that instruction to mount the 4-turn coil directly on the tuning capacitor - that would make some sense!

Richard
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Old 15th Apr 2014, 9:24 pm   #9
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Default Re: Chinese valve FM receiver kit

Well a variable capacitor could be said to be a battery of vanes rather than cells.
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Old 16th Apr 2014, 3:42 pm   #10
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Default Re: Chinese valve FM receiver kit

Have you got any pictures of the kit? I'd be interested in what you got for how much and where from. You deserve a pint if you get it working!
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Old 16th Apr 2014, 4:29 pm   #11
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Default Re: Chinese valve FM receiver kit

Here's the website:

http://www.aliexpress.com/item/Free-...377073663.html

I'll take a couple of photos of the actual kit and upload later.

Richard
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Old 16th Apr 2014, 5:40 pm   #12
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Default Re: Chinese valve FM receiver kit

And here's what's in the kit:

The supplied valve is a 1A2, which is equivalent to a 1R5 or a DK91

Richard
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Old 16th Apr 2014, 7:37 pm   #13
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Default Re: Chinese valve FM receiver kit

Quote:
Originally Posted by paulsherwin View Post
The Chinese used to use the Soviet FM band, but they may have switched as Russia mostly has now.
No they don't and never had. The Chinese use the standard FM band. There is also a "college band" around 65MHz that features on some Chinese radios. The Japanese use 76 to 90MHz but many radios in Japan actually cover 76 to 108MHz. Japan analogue TV channels 1 to 3 are in 90 to 108MHz so these radios can also get some TV sound.
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Old 20th Apr 2014, 6:56 pm   #14
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Default Re: Chinese valve FM receiver kit

I've printed it out to see what my wife can make of it!

Fred
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Old 20th Apr 2014, 7:56 pm   #15
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Default Re: Chinese valve FM receiver kit

Could the "4" be 4mm - the length the 5 turn coil should occupy?
That seems about right for the 100 Mhz region of the spectrum, given the number of turns and the value of the tuning capacitor. Just a guess though! Tony
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Old 21st Apr 2014, 9:53 am   #16
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Default Re: Chinese valve FM receiver kit

Quote:
Originally Posted by boxdoctor View Post
Could the "4" be 4mm - the length the 5 turn coil should occupy? Tony
I've looked at the Chinese text using several different translate engines, and they are all pretty much of the opinion that it's '4 turns'. The line above always translates as '1mm wire 2 turns' and the symbol after the number 2 is the same as the symbol after the number 4 on the next line.

I have seen another photo of the kit where the 1mm copper wire was supplied coiled. It looks like it was wound on a former about 6.35mm diameter, the turns spaced about half a wire diameter apart.

I've been doing LC calculations to try and arrive at something which seems to work as a starting point for a 100Mc/s receiver but I'm not sure how to factor in the valve capacitance so I'm making rather wild guesses at the moment!

I think I'll probably just put it together with a best guess coil and see what frequency it tunes to.

Richard
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Old 21st Apr 2014, 9:57 am   #17
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Default Re: Chinese valve FM receiver kit

Quote:
Originally Posted by dodgy-dxer View Post
I've printed it out to see what my wife can make of it!
Ah, thanks Fred! It would be good to have someone look at it who might know what it's all about.

That could work. The text in the top right, next to the valve base diagram, seems to read as 'the valve base viewed from underside, counted clockwise'.

I've got 'Audio Output' next to the 10nF capacitor and B+ and B- by the 67V marking.

The text at bottom right seems to read "Dragon Electronic"

Richard
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Old 21st Apr 2014, 12:39 pm   #18
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Default Re: Chinese valve FM receiver kit

Quote:
Originally Posted by mole42uk View Post
The text in the top right, next to the valve base diagram, seems to read as 'the valve base viewed from underside, counted clockwise'.
Which makes perfect sense as to how to interpret the base pin numbers.....
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Old 21st Apr 2014, 12:45 pm   #19
dodgy-dxer
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Default Re: Chinese valve FM receiver kit

Hello Richard

My wife is from Hong Hong and says this is "Simple" Chinese which she is not so good at.

However it says number 5 battery, not 5th battery

A "number 5 battery" in China is what we call an AA cell

She says the last 2 characters mean "take out". The first part says the 1mm wire "goes on top of the number 5 battery"

So putting a technical spin on it (ie a guess!) it could be that L2 is wound from 4 turns of 1mm wire around an AA cell which is then removed?

Unfortunately I don't deal with Huawei as part of my job any more or maybe I could find someone who reads simple Chinese better AND understands the technicality!

73 Fred
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Old 21st Apr 2014, 12:57 pm   #20
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Default Re: Chinese valve FM receiver kit

This is getting somewhere!

One of my attempts at translation got to 'AA battery' too - I think you are correct in suggesting the coil is wound on an AA battery which is then taken out - as I found out, the last part translated literally as 'bodiless' which I took to mean "air-cored"

Thank you, and please thank your wife! I'm getting more confident that I might get something out of this radio soon. I just ordered a pack of ten PP3 batteries for the HT supply (ebay 5.75 for the ten including post!!).

Richard
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