[TangerineSDR] In pursuit of low noise: fiber USB cables?

[John Ackermann N8UR]

Thanks for those tips, Tom, especially the last one about saturation.  I 
wouldn't have thought of that.

I was thinking that it might work to run shielded CAT-something ethernet 
cable with the conductors paralleled to make one balanced pair, and 
ground the shield at one end.  Do you think that plain coax would be a 
better bet?

Thanks,
John
----

On 2/27/24 16:39, Tom McDermott wrote:
> Hi John - by doing your own DC distribution you can do a much better job 
> of RFI suppression.
> 
> - Consider using coaxial cable to distribute the DC power.
> - Common-mode filters on the DC coax can help the cable do a good job of 
> keeping the RFI inside.
> - RFI can come from either (or both) ends of the circuit, Low pass 
> filters on both ends can reduce that problem.
> - Use of ferrite beads in the series DC+ filters can reduce the higher 
> frequency components of the noise because
>     the bead itself usually has low parallel capacitance compared to 
> some other inductor types.  You may need to worry
>     about saturation of the bead at higher currents.
> 
> -- Tom, N5EG
> 
> 
> 
> 
> 
> 
> -
> 
> On Tue, Feb 27, 2024 at 12:31 PM John Ackermann N8UR via TangerineSDR 
> <tangerinesdr at lists.tapr.org <mailto:tangerinesdr at lists.tapr.org>> wrote:
> 
>     Hi Tom --
> 
>     I think you're absolutely right on #3.  After fiddling with the cables
>     that noise seems to have largely gone away.  But we have other noise
>     sources in the building, and moving the radio 100 or so feet away can't
>     hurt.  And besides, it sounds like a cool idea!
> 
>     A DC power line would go along with the fiber.  It would be regulated
>     and filtered at the far end to provide the required voltages. 
>     Hopefully
>     with shielded twisted pair, good PSRR regulators etc., you could keep
>     that from contributing much noise.
> 
>     I don't know if the cable I linked to is anything like the best choice;
>     more research would be needed on that.  There are solutions that cost
>     from <$100 to >$1500.  There are also 10 Gbit and even some 20 Gbit
>     converters available if 5 Gbit isn't enough.
> 
>     73,
>     John
>     ----
>     On 2/27/24 15:05, Tom McDermott via TangerineSDR wrote:
>      > Hi John - some things to consider about the USB extender cable:
>      >
>      > 1. How will the RX888 be powered when using this cable?
>      > 2. In the one review - the extender was being used to bring back
>     data
>      > from an HDMI switch to a computer.
>      > HDMI switches are usually powered from the HDMI cables or via a
>     local DC
>      > input, thus not needing power from the USB port.
>      > 3. I'm guessing much of the hash is due to the DC USB power from the
>      > computer radiating as RFI on the cable
>      > when the shield is making poor or no contact.
>      >
>      > -- Tom, N5EG
>      >
>      >
>      > On Tue, Feb 27, 2024 at 8:26 AM John Ackermann N8UR via TangerineSDR
>      > <tangerinesdr at lists.tapr.org <mailto:tangerinesdr at lists.tapr.org>
>     <mailto:tangerinesdr at lists.tapr.org
>     <mailto:tangerinesdr at lists.tapr.org>>> wrote:
>      >
>      >     I had the idea last night that we could put an RX888 and
>     GPSDO at the
>      >     base of our active antenna and run an optical USB3 cable back
>     to the
>      >     host computer. That would move the radio far away from all the
>      >     computers
>      >     and other noise in the shack. The only copper connection
>     would be for
>      >     power, and we could filter the hell out of that.
>      >
>      >     Something like this:
>      >
>     https://www.amazon.com/Elecan-Extension-Extender-Transfer-Keyboard/dp/B0BNGW5225/ref=asc_df_B0BNGW5225 <https://www.amazon.com/Elecan-Extension-Extender-Transfer-Keyboard/dp/B0BNGW5225/ref=asc_df_B0BNGW5225> <https://www.amazon.com/Elecan-Extension-Extender-Transfer-Keyboard/dp/B0BNGW5225/ref=asc_df_B0BNGW5225 <https://www.amazon.com/Elecan-Extension-Extender-Transfer-Keyboard/dp/B0BNGW5225/ref=asc_df_B0BNGW5225>>
>      >
>      >     might do the trick. (Note -- I don't know if 5gbps is
>     sufficient for
>      >     the
>      >     RX888, but if not there are 10 and 10 gb cables available for
>     more
>      >     money.)
>      >
>      >     A challenge is powering the transceiver at the far end, but that
>      >     shouldn't be too hard to do.
>      >
>      >     Has anyone considered this?
>      >
>      >     73,
>      >     John
>      >
>      >     --
>      >     TangerineSDR mailing list
>      > TangerineSDR at lists.tapr.org <mailto:TangerineSDR at lists.tapr.org>
>     <mailto:TangerineSDR at lists.tapr.org
>     <mailto:TangerineSDR at lists.tapr.org>>
>      >
>     http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>     <http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org>
>      >   
>       <http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org <http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org>>
>      >
>      >
> 
>     -- 
>     TangerineSDR mailing list
>     TangerineSDR at lists.tapr.org <mailto:TangerineSDR at lists.tapr.org>
>     http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>     <http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org>
>