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Proximity to QRO HF antenna?

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k1zk
Proximity to QRO HF antenna?
New to AREDN & thinking of putting an AREDN antenna at the top of my 50-foot tower.  I have an HF beam there that's plugged into my 1.5 kW amp.  Any experience on how AREDN gear tolerates proximity to QRO HF signals?   Running a Mikrotik BaseBox2.

73 from Vermont de K1ZK
w6bi
w6bi's picture
QRO HF & AREDN
I had a friend with a Nanostation in proximity to his high power HF station antenna and he was unable the keep the two peacefully coexisting.  YMMV obviously.  I suggest:
  • At least single-shielded Ethernet cable.  Double-shielded if you can swing it.
  • Make sure to use shielded Ethernet connectors on both ends of cables.
  • Lots of clamp-on ferrite cores at both ends of the Ethernet cable(s).     Also on coax to HF beam.
  • You didn't mention how you were going to link the AREDN node into your shack.  Most folks use an Mikrotik hAP to nicely integrate the AREDN network with their home network.  If you do so, apply some clamp-on cores to the wall wart's cable.
  • Follow good grounding practices, of course.
Hope this helps!

Orv W6BI
K7EOK
Orv, I was waiting for
Orv, I was waiting for someone to reply to this question.  Can you share more specific information from your friend's experience?  What exactly was "not peacefully coexisting"?  Did the HF transmissions cause noise on the ethernet cables, did the microwave transmissions cause noise or issues on the HF?  What was observed and did the friend resolve the issue with mitigation steps like you describe?

I'm about to put AREDN on the same rooftop as a HF station for a county EOC and this is very relevant.

Ed
 
w6bi
w6bi's picture
Interference
In this particular case, when running his HF amp, his old Nanostation would stop.  It's been a while but I believe it reset the node back to 'just installed' status. He finally just stopped using AREDN, as he was moving soon anyway.  He's since left the area.

Orv
 
KR7O
RFI mitigation to mesh antennas
No direct experience with this but will be dealing with this in the future.

There are two issues, RFI to/from the router.  RFI from the router can potentially be mitigated. 
     -Keep everything possible in a metal box (charge controllers, POE injectors, etc) and use metal boxed equipment if possible.
     -Use shielded network cables with metal RJ45 connectors.
     -Keep all cables as short as possible, especially if not in a shielded box
     -If running POE up the tower, toroid cores at the device and after the injector may help.  Clamp on ferrites will not typically be effective at HF.  Refer to the RFI articles from K9YC which covers this extensively.  You need to select the correct core material with an appropriate number of turns for effective choking at the problem band(s).
     -Use shielded twisted pair cables where possible for external cables. 

The above should also help with RFI to the router/antenna.  Fundamental overload is also a potential from QRO HF transmissions.  Physical separation is the only real solution for this.  The TP-Link antennas that I have claim a 15KV ESD and 6KV lightning rating, so hopefully fundamental overload will not be an issue.

I am hoping that my 60' tower will make the link that I need since it functions solely as as a 630M transmit antenna.  If i have too use the taller tower, it will hold antennas for various bands all at legal limit, plus 900, 1.2, 2.3, 5.7 and 10G antennas for weak signal work.

73, Robert

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