Re: QCX LPF 60m adjustments

ian liston-smith

Thanks for the info guys.

I did measure all the LPF toroids on a peak LCR meter to be on or slightly under the inductance value in the table for 60m. I tweaked the windings a bit with the display module removed, but it didn't make much difference.

QCX inbuilt RF power meter says 4.54 W (but also 2.58 W on receive!) but both 50MHz scope and power meters give about 1 watt RF output on 60m.

Some of the LPF caps get very warm...


Ian, G4JQT

From: <> on behalf of Hans Summers <hans.summers@...>
Sent: 29 April 2020 21:51
To: <>
Subject: Re: [QRPLabs] QCX LPF adjustments
Hi Ian

Yes, you can remove the LCD and power-up, once you are confident everything is working fine. I do this all the time, for making adjustments to the LPF toroid spacing. QCX works fine without the LCD; it only talks at the LCD, it does not check for any answer back. So if the LCD is not present, the firmware doesn't notice or care. 

73 Hans G0UPL

On Wed, Apr 29, 2020 at 11:34 PM ian liston-smith <> wrote:
Quick question:

Can the display module be removed so the LPF coils can be poked and tweaked for adjustment? Does removing the display module and powering up cause any problems? Will the rig still work so adjustments can be made?

If so it will make spacing/squashing the toroid turns with a cocktail stick for maximum power much easier.



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