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Hello,

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starting from strange LO signal I de-solder one wire of trifilar T401 to IC408 pin 9.

To verify I touch every pin of IC 403 and IC402 with the Ohm-meter.

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Power -on: LO-Signal at BNC vanished and wistles get weaker.

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Connecting wire of T401 again: Noisefloor at 6m reduces from 25 dB to 5 dB and wistles are reduced.

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Side-Band of LO at BNC vanished, only LO Signal is detectable.

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My conclusions:

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Either I have a fine closure in T401 or a cold soldering point at IC 403.

I guess one pin of IC 403 was not connected properly, touching with the Ohm meter established connection.

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All pins of IC403 will be soldered in case wistles are remainig.

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vy 73 Michael

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Hi Michael,

hmm -‘solved’? What were your RF plots like before and after on 6m? Surely if you had a bad connection this would have shown up as an off tune response?

My plots are fine so i am not convinced you have found the root cause of this whistle on 6m. Others have reported the same problem so we cannot all have the same poor joint at that location.

Despite that, thanks for your input.?

73 Ken g4apb?

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