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I have a Yaesu FT-101EE, D-104 Mike, MFJ-929 Antenna Tuner, 80-10 OCF Dipole Antenna with a MFJ balun.

When ever I key up for more than a few seconds, the wifi network goes down for a couple of minutes disconnecting any attached devices. A couple of minutes later after transmitting, it wifi network comes back. The router does not turn off or reset, it just seems to shut down the wifi signal.

  • The NetGear N600 router is in the house, the radio is upstairs in the detached garage. I don't believe any devices are using 5 GHz.

  • The balun is attached to a 6' horizontal pole attached to the back of the garage, approximately 25' high. The wires run from the balun across the property behind and parallel to the house and garage. There is approximately 8' of coax from the antenna tuner to the balun.

  • I have been using the 80 meter band.

Any ideas on what I can do to fix this?

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    $\begingroup$ Could you add more detail about your antenna system? Location, orientation, feed/matching/balun, and grounding are all relevant. That'll help us say whether there's improvement to be made there. $\endgroup$ – Kevin Reid AG6YO Nov 24 '18 at 17:13
  • $\begingroup$ This is the antenna I built using a MFJs balun: balundesigns.com/content/OCF%20Antenna.pdf $\endgroup$ – Roy Kees Nov 24 '18 at 17:16
  • $\begingroup$ The balun is attached to a 6' horizontal pole attached to the back of the garage, approximately 25' high. The wires run from the balun across the property behind and parallel to the house and garage. There is approximately 8' of coax from the antenna tuner to the balun. $\endgroup$ – Roy Kees Nov 24 '18 at 17:19
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    $\begingroup$ Could you also elaborate on the frequencies involved? N600 supports 2.4GHz and 5GHz; are you using both? When you key up, does it behave the same regardless of the band you are transmitting on? $\endgroup$ – Chris K8NVH Nov 24 '18 at 17:20
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    $\begingroup$ Please provide the additional information by editing your question, rather than in comments. This helps keep the information readable, organized, and editable, and allows deleting comments once things are settled. $\endgroup$ – Kevin Reid AG6YO Nov 24 '18 at 19:13
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Sounds like the router is getting front end overload. Either your OCF dipole is too close to the router, or you are getting common mode current on the coax and it is radiating along the coax.

A balun on the coax in the right place might help if it is common mode current.

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  • $\begingroup$ how would front end overload disable wifi for minutes? $\endgroup$ – Phil Frost - W8II Nov 25 '18 at 14:05
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    $\begingroup$ A soft reset could look like this, though should finish rebooting quickly. If there are a lot of devices to authenticate, that could explain the time discrepancy. A hiccup in the upstream authentication could also explain this; wifi does not shut down but needs to re-authenticate itself and all of its attached devices. That could take minutes and the device would seem shut down. $\endgroup$ – Chris K8NVH Nov 25 '18 at 15:26
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I agree with user10489's answer but would like to expand a bit on what to do about it. A signal of some sort appears to be interfering with something associated with the router and there does not seem to be enough information to pinpoint an exact cause.

As stated by user10489, adding a balun or common mode choke in the appropriate place(s) on the feed line (see http://audiosystemsgroup.com/RFI-Ham.pdf for far more information than I could possibly describe) would probably help.

A good resource on common mode chokes is http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf . Far more information than could be described here.

Also, check all of the feedline, tuner, and antenna connections. A bad connection could be the cause of the interfering signal.

Is there an ethernet wire between the wifi router and whatever is upstream of it? If so, place a common mode choke there as well since it could be the upstream device that is having difficulty. In fact, if it is the upstream device, any of the wires attached to it could be acting like an antenna.

Before adding hundreds of € worth of common mode chokes across every wire in your house, check the connections between your radio and antenna and then run the following test:

  1. Log in to your N600. Go to the "Status" screen; look for the device ethernet address and also the list of attached devices.
  2. Key up on 80 meters. (You are using the full 130 watts on SSB, right?)
  3. Observe the changes on the N600. This should give you a clue where to look.
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    $\begingroup$ Good points... I hadn't thought of it leaking into upstream devices. If your dipole is close enough and parallel to an uplink feedline, you could even get leakage into that. I've actually had that problem, had to change the dipole orientation. $\endgroup$ – user10489 Nov 25 '18 at 17:11
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To add to the excellent answers here, here's what I did here to solve this problem.

This common-mode LAN choke is 14 turns of CAT5e wound on a 2.4" OD Fair-Rite toriod core made of type 31 ferrite. Mouser Electronics and Newark Electronics stocks them, about $7 each.

These can also be used for choking any common-mode RF on the router's power supply ("wall-wart") cable.

LAN common-mode choke 1

I already have a similar coax choke at the feedpoint of my low backyard dipole, except there are fewer turns and about four of these chokes stacked.

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  • $\begingroup$ This design came from K9YC, mentioned earlier here. $\endgroup$ – Mike Waters Dec 25 '18 at 21:44
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To add one more inexpensive troubleshooting suggestion: The RF may not be coming in via any typical signal path, whether wifi or CAT5. A variety of issues such as poor mains grounding, distance from the mains ground point, faulty GFCI outlets, or just a stretch of mains wiring that happens to be a resonant length on an HF band can cause a significant amount of RF to get onto the chassis of the router.

Computers in general tend to look poorly upon intruding RF (which can look like or interfere with clock signals) on their ground plane, and in technical terms, will "freak the heck out". I could crash my wifi router at my last apartment by transmitting specifically on 15m, despite living in a new building that was up to code. In my current house, the same router has no issue with 15m due to a different antenna configuration and different mains wiring.

Adding an AC line filter to the mains supply of the router will eliminate any RF that may be on the mains, and has the added bonus of cutting down on RFI to your receiver from cheap power supplies. I usually buy an inexpensive power strip and cut the cord, then install the line filter on the power strip cord for convenience. This combined with wrapping a few feet of the router's DC power cord around a type 43 toroid fixed the problem I had with the wifi router in my apartment. If you have a lot of noise on your receiver that goes away when operating your radio via battery, you may also find that a line filter on the cord of your radio PSU helps to cut down on that noise, as it can travel both directions.

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