<div dir="ltr"><div>Hi John - you can try shielded Cat cable. Using the twisted pair for DC and return can achieve cancellation</div><div>of radiation to a good extent. Coax is better, but can be overkill in many situations.</div><div><br></div><div>Breaking the shield (i.e grounding at only one end) often helps at audio and lower frequencies, I've found times it<br></div><div>makes things worse at RF. It depends on the exact antenna configuration, the antenna feed method, the antenna</div><div>ground reference, and the power feed method. Experimentation is often needed to find out.<br></div><div><br></div><div>-- Tom, N5EG<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Feb 27, 2024 at 3:08 PM John Ackermann N8UR <<a href="mailto:jra@febo.com">jra@febo.com</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">Thanks for those tips, Tom, especially the last one about saturation. I <br>
wouldn't have thought of that.<br>
<br>
I was thinking that it might work to run shielded CAT-something ethernet <br>
cable with the conductors paralleled to make one balanced pair, and <br>
ground the shield at one end. Do you think that plain coax would be a <br>
better bet?<br>
<br>
Thanks,<br>
John<br>
----<br>
<br>
On 2/27/24 16:39, Tom McDermott wrote:<br>
> Hi John - by doing your own DC distribution you can do a much better job <br>
> of RFI suppression.<br>
> <br>
> - Consider using coaxial cable to distribute the DC power.<br>
> - Common-mode filters on the DC coax can help the cable do a good job of <br>
> keeping the RFI inside.<br>
> - RFI can come from either (or both) ends of the circuit, Low pass <br>
> filters on both ends can reduce that problem.<br>
> - Use of ferrite beads in the series DC+ filters can reduce the higher <br>
> frequency components of the noise because<br>
> the bead itself usually has low parallel capacitance compared to <br>
> some other inductor types. You may need to worry<br>
> about saturation of the bead at higher currents.<br>
> <br>
> -- Tom, N5EG<br>
> <br>
> <br>
> <br>
> <br>
> <br>
> <br>
> -<br>
> <br>
> On Tue, Feb 27, 2024 at 12:31 PM 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>
> 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. <br>
> 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<br>
> data<br>
> > from an HDMI switch to a computer.<br>
> > HDMI switches are usually powered from the HDMI cables or via a<br>
> 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>><br>
> <mailto:<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank">tangerinesdr@lists.tapr.org</a><br>
> <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<br>
> GPSDO at the<br>
> > base of our active antenna and run an optical USB3 cable back<br>
> 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<br>
> would be for<br>
> > power, and we could filter the hell out of that.<br>
> ><br>
> > Something like this:<br>
> ><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>> <<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<br>
> sufficient for<br>
> > the<br>
> > RX888, but if not there are 10 and 10 gb cables available for<br>
> 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>
> <mailto:<a href="mailto:TangerineSDR@lists.tapr.org" target="_blank">TangerineSDR@lists.tapr.org</a><br>
> <mailto:<a href="mailto:TangerineSDR@lists.tapr.org" target="_blank">TangerineSDR@lists.tapr.org</a>>><br>
> ><br>
> <a href="http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org" rel="noreferrer" target="_blank">http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org</a><br>
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> > <br>
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> ><br>
> ><br>
> <br>
> -- <br>
> TangerineSDR mailing list<br>
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> <br>
</blockquote></div>