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LZ1AQ using BFU590QX transistors

 

I just finished building 5 LZ1AQ loop amplifier boards, 4 of which I used? 2SC5551 transistors. The 5th one I used BFU590QX transistors.
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Running sweeps on the 2 looking at both impedance and gain, one with 2SC5551s and the other using BFU590QX, I saw very little difference between the two. Both boards were supplied 3.8VDC, the 2SC5551 board ran at 142mA, the BFU590QX board ran at 130mA.
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I checked both boards with my SA and saw no signs of oscillation on either board.
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Everett N4CY
 

Hi Everett,
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Can you compare the noise level of the 2 variants with the input shorted? Not a true noise figure measurement, but a relative comparison.
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73, Mike AF7KR
 

Everett,
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Do you mean 13.8VDC? I think there is a typo.
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Mike M
 

Sorry about that, yes it is 13.8VDC

In a message dated 10/29/2024 10:04:09 AM Central Daylight Time, groups@... writes:
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Everett,
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Do you mean 13.8VDC? I think there is a typo.
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===================================================================
Mike M
 

Mike,
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With the inputs shorted they both were 105dBm at 1MHz.
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Everett

In a message dated 10/29/2024 10:01:59 AM Central Daylight Time, 3ym3ym@... writes:
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Hi Everett,
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Can you compare the noise level of the 2 variants with the input shorted? Not a true noise figure measurement, but a relative comparison.
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73, Mike AF7KR
 

Hello Everett

Between these two versions of transistors, have you changed any component values on your PCB

Best regards

Bernard
 

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Hi Bernard,

I changed nothing, both boards had the same components.

Everett

On Oct 30, 2024, at 3:47?AM, Bernard Malet via groups.io <malet-bernard@...> wrote:

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Hello Everett

Between these two versions of transistors, have you changed any component values on your PCB

Best regards

Bernard

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