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/diy/ Do-It-Yourself

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Anonymous 2015-01-10 01:26:57 No.753451

[Missing image file: ]

Hi, DIY. I want some advice and help. Long ago I built a Power supply (with lm317, 2n3055 and shit) and it works flawlessly. The only problem now is that I want to test some RF circuit I built. The RF circuit is OK. It works without any noise on the battery, but on my power power supply it is noisy as hell.
The pic attached is the RF circuit (ugly I must say. I built it 4 years ago when I was learning to build circuits on boards). It is a VHF receiver for amateur radio.
If anyone knows a good filter for my case, I will be verry happy to implement it on my power supply.

Anonymous 2015-01-10 03:13:25 No.753497
LC filter. Surprised you'd have to ask, if you're capable of building a receiver like that.

Anonymous 2015-01-10 03:23:11 No.753504
Thanks, but Only a LC? I already have one inside my power supply. I used a coil of a old switched power supply.

Anonymous 2015-01-10 03:25:35 No.753507
>I used a coil of a old switched power supply
Probably not enough inductance.

Do you have a 'scope? Look at the output of your supply, it might not be as clean as you think it is. Also what sort of 'noise' are we talking about, here?

Anonymous 2015-01-10 03:28:10 No.753509

>not enough inductance
OK. Ill check that.

>sort of noise
like a radio out of tune. on the battery I get no noise

I dont have a scope.

Anonymous 2015-01-10 03:28:56 No.753510
Got a schematic of both your power supply and the radio?

Anonymous 2015-01-10 03:33:18 No.753511
here is the radio.
The power supply I dont have because I I add caps and coils to the schematic but I will atach the original circuit of it

Anonymous 2015-01-10 03:34:29 No.753513
power supply

Anonymous 2015-01-10 11:25:19 No.753636
how can an npn work with negative Vbe

Anonymous 2015-01-10 11:38:16 No.753639
>measuring a VHF oscillator with a multimeter
You can expect funny readings. Or maybe it's just a typo.

What happens if you connect the radio ground and the PSU ground, but run the radio from a battery?

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