<div dir="ltr"><div>Hi John - by doing your own DC distribution you can do a much better job of RFI suppression.</div><div><br></div><div>- Consider using coaxial cable to distribute the DC power.</div><div>- Common-mode filters on the DC coax can help the cable do a good job of keeping the RFI inside.<br></div><div>- RFI can come from either (or both) ends of the circuit, Low pass filters on both ends can reduce that problem.</div><div>- Use of ferrite beads in the series DC+ filters can reduce the higher frequency components of the noise because</div><div> the bead itself usually has low parallel capacitance compared to some other inductor types. You may need to worry</div><div> about saturation of the bead at higher currents.<br></div><div><br></div><div>-- Tom, N5EG</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div>- <br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Feb 27, 2024 at 12:31 PM John Ackermann N8UR via TangerineSDR <<a href="mailto:tangerinesdr@lists.tapr.org">tangerinesdr@lists.tapr.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi Tom --<br>
<br>
I think you're absolutely right on #3. After fiddling with the cables <br>
that noise seems to have largely gone away. But we have other noise <br>
sources in the building, and moving the radio 100 or so feet away can't <br>
hurt. And besides, it sounds like a cool idea!<br>
<br>
A DC power line would go along with the fiber. It would be regulated <br>
and filtered at the far end to provide the required voltages. Hopefully <br>
with shielded twisted pair, good PSRR regulators etc., you could keep <br>
that from contributing much noise.<br>
<br>
I don't know if the cable I linked to is anything like the best choice; <br>
more research would be needed on that. There are solutions that cost <br>
from <$100 to >$1500. There are also 10 Gbit and even some 20 Gbit <br>
converters available if 5 Gbit isn't enough.<br>
<br>
73,<br>
John<br>
----<br>
On 2/27/24 15:05, Tom McDermott via TangerineSDR wrote:<br>
> Hi John - some things to consider about the USB extender cable:<br>
> <br>
> 1. How will the RX888 be powered when using this cable?<br>
> 2. In the one review - the extender was being used to bring back data <br>
> from an HDMI switch to a computer.<br>
> HDMI switches are usually powered from the HDMI cables or via a local DC <br>
> input, thus not needing power from the USB port.<br>
> 3. I'm guessing much of the hash is due to the DC USB power from the <br>
> computer radiating as RFI on the cable<br>
> when the shield is making poor or no contact.<br>
> <br>
> -- Tom, N5EG<br>
> <br>
> <br>
> On Tue, Feb 27, 2024 at 8:26 AM John Ackermann N8UR via TangerineSDR <br>
> <<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank">tangerinesdr@lists.tapr.org</a> <mailto:<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank">tangerinesdr@lists.tapr.org</a>>> wrote:<br>
> <br>
> I had the idea last night that we could put an RX888 and GPSDO at the<br>
> base of our active antenna and run an optical USB3 cable back to the<br>
> host computer. That would move the radio far away from all the<br>
> computers<br>
> and other noise in the shack. The only copper connection would be for<br>
> power, and we could filter the hell out of that.<br>
> <br>
> Something like this:<br>
> <a href="https://www.amazon.com/Elecan-Extension-Extender-Transfer-Keyboard/dp/B0BNGW5225/ref=asc_df_B0BNGW5225" rel="noreferrer" target="_blank">https://www.amazon.com/Elecan-Extension-Extender-Transfer-Keyboard/dp/B0BNGW5225/ref=asc_df_B0BNGW5225</a> <<a href="https://www.amazon.com/Elecan-Extension-Extender-Transfer-Keyboard/dp/B0BNGW5225/ref=asc_df_B0BNGW5225" rel="noreferrer" target="_blank">https://www.amazon.com/Elecan-Extension-Extender-Transfer-Keyboard/dp/B0BNGW5225/ref=asc_df_B0BNGW5225</a>><br>
> <br>
> might do the trick. (Note -- I don't know if 5gbps is sufficient for<br>
> the<br>
> RX888, but if not there are 10 and 10 gb cables available for more<br>
> money.)<br>
> <br>
> A challenge is powering the transceiver at the far end, but that<br>
> shouldn't be too hard to do.<br>
> <br>
> Has anyone considered this?<br>
> <br>
> 73,<br>
> John<br>
> <br>
> -- <br>
> TangerineSDR mailing list<br>
> <a href="mailto:TangerineSDR@lists.tapr.org" target="_blank">TangerineSDR@lists.tapr.org</a> <mailto:<a href="mailto:TangerineSDR@lists.tapr.org" target="_blank">TangerineSDR@lists.tapr.org</a>><br>
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> <br>
> <br>
<br>
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</blockquote></div>