[Moon-Net] RFI from laptop via USB cable

Charles g3wdg at moon-net.eu
Thu Apr 22 08:41:37 CEST 2021


Hi James

It sounds like the QRM is coming in at the IF.  Do you have any 
attenuation in circuit between the transverter and the 817?  If so, I 
would take it out so that the noise from the transverter (and preamp if 
you have one) might be at a higher level so the QRM is then sufficiently 
masked.

Another alternative might be to try to connect the 817 directly to the 
audio input of the PC.

73

Charlie G3WDG

On 22/04/2021 06:09, James Morris via Moon-net wrote:
> I'm wondering if anyone has experience dealing with RFI from a laptop (or
> other computer) when connecting audio via USB?
>
> I have a Kuhne 3cm transverter, an FT-817, and a Rigblaster (which uses a
> USB audio connection to my laptop). This has been working fine for
> terrestrial contacts, but I'm running into issues trying to receive the
> DL0SHF beacon.
>
> When the USB cable is connected, there's a bunch of interference on ~144.0
> MHz, with sidebands extending up at least 25kHz, which makes a mess of the
> spectrum at the beacon frequency (144.025 at the IF radio, +/- doppler).
> I've tried adding ferrites to the USB cable but with no effect.
>
> The laptop is a Thinkpad T470s which has otherwise worked fine with weak
> signals at higher frequencies in the band. This is running on batter
> power, also.
>
>
> Any ideas / suggestions?
>
>
> - James W7TXT


More information about the Moon-net mailing list