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Old 14th Jan 2019, 5:35 pm   #21
bikerhifinut
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Default Re: "The Works" Crystal Radio

A quick google suggests the ST4148 is a zener diode but I think it's as everyone says a 1n4148 100V 1A rectifier. The datasheet says 1V Vf. I think the ST prefix probably indicates the manufacturer?

I'm going to have a look in town on wednesday while we are in and I might buy one out of curiosity. If nothing else I think it could be possible to mod it with a variable capacitor and I might see if there are any strongish signals here in the frozen wilds.
A.
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Old 14th Jan 2019, 6:19 pm   #22
paulsherwin
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Default Re: "The Works" Crystal Radio

The 1N4148 isn't a rectifier, it's a general purpose silicon switching diode, probably the cheapest diode of any type available.

https://en.wikipedia.org/wiki/1N4148_signal_diode
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Old 14th Jan 2019, 6:34 pm   #23
bikerhifinut
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Default Re: "The Works" Crystal Radio

My mistake Paul. Got distracted by the Reverse voltage and current data when I did a quick google.
I wonder if its a batch of discontinued stock as ST microelectronics don't list it.

Or more likely something swept off a production line in a Chinese knock off plant.

A.
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Old 15th Jan 2019, 4:19 pm   #24
ionburn
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Default Re: "The Works" Crystal Radio

Quote:
Originally Posted by bikerhifinut View Post
A quick google suggests the ST4148 is a zener diode but I think it's as everyone says a 1n4148 100V 1A rectifier. The datasheet says 1V Vf. I think the ST prefix probably indicates the manufacturer?

I'm going to have a look in town on wednesday while we are in and I might buy one out of curiosity. If nothing else I think it could be possible to mod it with a variable capacitor and I might see if there are any strongish signals here in the frozen wilds.
A.
I am not sure about all this buying, but everyone has been warned lol. It's nice to have a kit, but I get far better results with my 84mm ex Superdrug moisturiser jar with multi-tapped 24SWG coil, good old fashioned tuning capacitor, Germanium diode, (probably) 2k ancient headphone plus 1nF capacitor with the same aerial / earth. I was surprised to receive a German speaking station yesterday, but probably just a one off. Cost is perhaps double although sourcing would be trickier.

I plotted a curve for my ST4148. It spot reads about 0.6mA forward at 0.6V (starts conducting around 0.4V).
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Old 15th Jan 2019, 7:18 pm   #25
duncanlowe
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Default Re: "The Works" Crystal Radio

I just had a look out of curiosity. I laughed out loud!
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Old 16th Jan 2019, 1:36 pm   #26
Nuvistor
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Default Re: "The Works" Crystal Radio

While on the subject of crystal sets, this may be of interest.

https://www.americanradiohistory.com...l-Sets-v12.pdf
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Old 16th Jan 2019, 1:55 pm   #27
Ian - G4JQT
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Default Re: "The Works" Crystal Radio

Circuit 7 from Frank's "The Boy's Book of Crystal Sets" worked very well. Four MW stations and R2 on LW - all in 1973-ish. Maybe I was lucky that at the time, in Bury Lancs, all the strong stations were nicely spread out across the band.

That is one of the circuits that spurred me on the more investigation; adding transistors, and - eventually - a career in radio...!
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