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Old 3rd Jan 2019, 10:44 pm   #101
m0cemdave
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Default Re: More Chinese AM radio kits

Quote:
Originally Posted by samoca58 View Post
The dome is way off centre...
The dome is only there as a cover, to keep dust and debris out of the voice coil. So being askew shouldn't affect performance, although selling a product with such an obvious cosmetic defect is extremely unwise. It speaks volumes (pun intended) to the supplier's attitude to quality control, and gives a warning as to how much confidence we should have in their products.
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Old 3rd Jan 2019, 11:04 pm   #102
Philips210
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Default Re: More Chinese AM radio kits

Hi

Perhaps the person that assembled it was equally as eccentric as the loudspeaker itself or maybe had a few too many Christmas drinks before starting work

Regards
Symon.
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Old 3rd Jan 2019, 11:29 pm   #103
Jolly 7
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Default Re: More Chinese AM radio kits

As the driver and output transformers are highly unreliable, I am thinking of making and fitting a 3 volt amplifier in place of them. This could either be IC or transistor based. I have a couple of LM386Ns somewhere, so they might do the trick.
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Old 4th Jan 2019, 10:00 am   #104
Neil Purling
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Default Re: More Chinese AM radio kits

There's a HX108-2A. This uses the TDA2822 8-pin IC. I also have ordered one of these.

I note that the HX102 received Kingstown Radio well in Hull. This is located in the Hull Royal Infirmary, the transmitter being a merely 45 watts.
At night the sky wave brings in other transmissions almost on top of it. One of which being Manx Radio.
I haven't tried this radio at night yet. I am waiting for the CR123 batteries I ordered to arrive.

m0cemdave: That speaker further reinforces my suspicion that these kits are assembled from QC rejects.
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Old 5th Jan 2019, 11:57 am   #105
Jolly 7
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Default Re: More Chinese AM radio kits

Would it be correct to say that transistor V1 is acting both as an oscillator and a mixer in the HX108-2 ?
Some superhet radios have separate oscillator and mixer transistors if I am not mistaken ?
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Old 6th Jan 2019, 8:08 am   #106
Neil Purling
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Default Re: More Chinese AM radio kits

The first transistor is always a self-oscillating mixer in all of these kit radios. Unless it uses a IC of course.
Nothing new has arrived since Christmas/New Year. Still waiting for more bits & a total of eight kits.
I already had several HX-6B kits, so I assembled one of those yesterday. I made a mistake around V3 which I need to sort out.
It is oscillating, I know this after testing with another radio.
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Old 6th Jan 2019, 12:06 pm   #107
Jolly 7
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Default Re: More Chinese AM radio kits

Thanks Neil. I am trying to build a superhet without a circuit diagram on an old unused radio PCB, so it helps to know. So far I have figured out where all the coils and the first transistor go.
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Old 7th Jan 2019, 2:11 pm   #108
Neil Purling
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Default Re: More Chinese AM radio kits

The six transistor radio is very deaf, compared to the 7 transistor HX108-2. The S66E, which is the 6 transistor radio has audio that sounds like the speaker has sand in the voice coil. It is not the OEM speaker, but a 50mm plastic-coned water resistant driver.
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Old 7th Jan 2019, 11:35 pm   #109
Jolly 7
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Default Re: More Chinese AM radio kits

In spite of only two IF stages in the S66E, someone set the IF to 475 kHz and reported very good results. I haven't tried building the kit myself yet.

The HX108-2 uses the fourth transistor configured as a detector.
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Old 8th Jan 2019, 8:11 pm   #110
Neil Purling
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Default Re: More Chinese AM radio kits

The plastic coned speaker I used lasted all of two weeks before it sounded like Lee Marvin performing Wandrin Star with a sore throat. I put the bog-standard speaker back.
The HX108-2 is worth getting, but there is so little precision in the tuning that it is impossible to find Manx Radio at around 1370 Khz above Kingstown Radio on 1350 Khz.
There's all sorts of stuff that appears after dark on the sky wave.
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Old 11th Jan 2019, 9:47 am   #111
Neil Purling
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Default Re: More Chinese AM radio kits

I didn't like the dial window of the HX108. At the high frequency end of the band it was rendered opaque by the strip of adhesive.
So I got busy with the scissors & re-used part of a HX-6B dial. It is not pretty, but who cares anyway?
No new kits have arrived yet.
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