Re: [digitalvoice] Mains power Hum

[Stuart Longland]

On 16/06/13 02:22, Steve wrote:
> This is probably a function of my headset USB soundcard, but I notice it
> has a nice 60 Hz amplitude in the spectrum display.

I've found some laptops … notably Toshiba ones … generate a 50Hz (in my
experience) hum when running on mains power, even with an external USB
headset.

Sticking my finger on a bit of exposed earthed metal used to cure it.
--
Stuart Longland (aka Redhatter, VK4MSL)

I haven't lost my mind...
...it's backed up on a tape somewhere.

[cdn...@flash.net]

I have found that the small audio transformers that are used for isolation in many interface designs are very prone to induced fields from power transformers in wall warts or other equipment.  Placing these in aluminum enclosures does not work to reduce the interference.  Steel boxes and avoid placing interfaces on top of or near other transformer-operated devices can make it much better.

FYI

Curt
KU8L

On Saturday, June 15, 2013 12:22:09 PM UTC-4, Steve wrote:

This is probably a function of my headset USB soundcard, but I notice it has a nice 60 Hz amplitude in the spectrum display.

I'm not really sure what if anything can be done about that, but the thought came to mind, if FreeDV really needs to have a frequency response down to 0 Hz?

I was thinking maybe a lot of attenuation below 300 Hz probably wouldn't hurt.  Does the Codec2 need signals below 300 Hz?

73, Steve

[david]

The FreeDV modem should be immune to any signals outside of the modem
carriers, although it might affect the AGC on the waterfall. Each
carrier is tightly filtered by the demod. I just tested FreeDV with a
A/D having a big DC offset and it was OK.

- David

> --
> You received this message because you are subscribed to the Google
> Groups "digitalvoice" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to digitalvoice...@googlegroups.com.
> To post to this group, send email to digita...@googlegroups.com.
> Visit this group at http://groups.google.com/group/digitalvoice.
> For more options, visit https://groups.google.com/groups/opt_out.
>
>