We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale.

Author Topic: Troubleshooting - 43 m tx kills wifi  (Read 496 times)

Offline Roykirk

  • Newbie
  • *
  • Posts: 16
  • Karma: +0/-0
    • View Profile
    • Email
Troubleshooting - 43 m tx kills wifi
« on: November 11, 2019, 1518 UTC »
Test #1:  Transmitting 20 watts AM, regulated power supply at 24 volts, 6925, auto-tuner, no amplifier.  Transmitter and all related gear located in the garage, with a coax feeder running out to mobile whip antenna mounted to the car. 

Test #2:  Moved the mobile whip out to the backyard (mounted on a deck railing), ran about 40' of counterpoise wire off the base.  Transmitter and all gear moved inside the house, coax feeder line running out to antenna through an open window.  MFJ-915 RF isolator at the bottom of the antenna to keep stray RF from running back in to the house. 

I've run both of these setups a hundred times before, albeit in a different house than where I am now and using a different transmitter (back then using a modified Icom 735).  Test 1 worked fine.  No problems, and could receive a clear carrier on my Tecsun.  No reports from anyone, but I didn't exactly expect that testing with a mobile whip.  Test 2, however, yikes!  Wifi in the house went dead immediately.  Checked the router and all the lights on it are blinking randomly like I just won the jackpot on a Vegas slot machine.   :o  Turned on the Tecsun to monitor and all I get is a loud hum.  Not good.  Shut everything down.  Took me awhile to get the wifi working again, but eventually it was fine.  Moved it all back out to the garage and antenna on car...everything fine again.  Tried it inside one more time with antenna out back, wifi dead. 

I've done some research on this and it seems most people feel it's unlikely for HF transmissions to interfere with wifi, especially if there are no amplifiers being used.  The only thing I'm left with is stray RF getting back in to the house, which is scrambling the wifi router/signal.  But I'm using a brand new RF isolator.  Is it possible it's just bad?  Maybe poor grounding for the antenna?  Today I'm going to test the backyard setup with the transmitter and all gear on the back deck, outside the house.  I'm guessing that will narrow it down as far as RF getting back in the house as the problem. 

Offline Σ

  • Blog author
  • Sr. Member
  • *
  • Posts: 300
  • Karma: +5/-0
    • View Profile
    • ΣSDR KiwiSDR online
Re: Troubleshooting - 43 m tx kills wifi
« Reply #1 on: November 11, 2019, 1834 UTC »
Don't dismiss that you might be interfering with the internal clock or other parts of the circuitry inside the WiFi device. It may not be harmonically related to the final output.
- Rob

CT/MA border
Afredri SDR-Net with multiband dipole at 65 ft.
Email: commsigma@gmail.com
KiwiSDR online - http://sigmasdr.ddns.net:8073/
ΣSDR Blog - https://sigmasdr.blogspot.com/

Offline Roykirk

  • Newbie
  • *
  • Posts: 16
  • Karma: +0/-0
    • View Profile
    • Email
Re: Troubleshooting - 43 m tx kills wifi
« Reply #2 on: November 11, 2019, 1844 UTC »
Definitely a possibility, but that doesn't explain why I have no problems transmitting from the garage (which is attached to the house).  The only thing I can think of is the grounding in the backyard (i.e. the car is a good ground but the counterpoise I'm using in the yard isn't) is poor or the RF isolator is crap.  I suppose another culprit could just be the distance between the antenna and the router in the two tests.  When the antenna is out on the car, it's about 30' from the wifi router, with several walls in between.  When it's in the backyard it's about 20' from the router, with nothing but a sliding glass door between.  Theory...maybe the output and the grounding are fine, it's just the proximity difference?

Offline Pigmeat

  • DX Legend
  • ******
  • Posts: 4578
  • Karma: +70/-34
    • View Profile
Re: Troubleshooting - 43 m tx kills wifi
« Reply #3 on: November 11, 2019, 2033 UTC »
I'd go with proximity just from experience. In my pirating days, cassette decks could sit directly under the antenna with no problems. If you tried it with a CD player or an early version of a digital recorder you could kiss them goodnight inside of 30 seconds. Older digital recording devices didn't like RF.

Offline Roykirk

  • Newbie
  • *
  • Posts: 16
  • Karma: +0/-0
    • View Profile
    • Email
Re: Troubleshooting - 43 m tx kills wifi
« Reply #4 on: November 11, 2019, 2209 UTC »
I'd go with proximity just from experience. In my pirating days, cassette decks could sit directly under the antenna with no problems. If you tried it with a CD player or an early version of a digital recorder you could kiss them goodnight inside of 30 seconds. Older digital recording devices didn't like RF.

Yeah, that's what I was afraid of.  Working off the car in the driveway seems to pass muster, but an 8' vertical sitting on top of the car isn't exactly stealth.  Can't move it anywhere farther away in the back yard either because there's no space.  Might have to poke around and see if there's somewhere else I can put the router, perhaps up on the second floor.  A small loop on the second floor might work as well.  A bit more focused with a nice sharp null on the sides that might shield the router.  I forgot that half the fun is the experimenting.   ;D 
« Last Edit: November 11, 2019, 2347 UTC by Roykirk »

Offline Josh

  • DX Legend
  • ******
  • Posts: 4064
  • Karma: +10/-0
    • View Profile
Re: Troubleshooting - 43 m tx kills wifi
« Reply #5 on: November 12, 2019, 0002 UTC »
Some guys who got knocked offline using dsl have wrapped their modem loosely with foil, some even grounding the foil, and it kept them online. You'd have to be concerned with cooling when a modem's wrapped with foil.
We do not encourage any radio operations contrary to regulations.

Offline Pigmeat

  • DX Legend
  • ******
  • Posts: 4578
  • Karma: +70/-34
    • View Profile
Re: Troubleshooting - 43 m tx kills wifi
« Reply #6 on: November 13, 2019, 0518 UTC »
Try the second floor. A friend has two hardcore gamers under the roof and doesn't want them underfoot. He banished them to two upstairs rooms w/ the router in the same place it's been for nearly a decade. They haven't complained.

His Dad is a ham. When he got sick he moved in radios and all. No problems, the guy was directly above the router.

Offline Roykirk

  • Newbie
  • *
  • Posts: 16
  • Karma: +0/-0
    • View Profile
    • Email
Re: Troubleshooting - 43 m tx kills wifi
« Reply #7 on: November 13, 2019, 0909 UTC »
Try the second floor. A friend has two hardcore gamers under the roof and doesn't want them underfoot. He banished them to two upstairs rooms w/ the router in the same place it's been for nearly a decade. They haven't complained.

His Dad is a ham. When he got sick he moved in radios and all. No problems, the guy was directly above the router.

I investigated and found there are no places to move the router on the second floor that wouldn't require spending several hundred dollars to have the phone company come in and rewire.  Right now I'm leaning towards putting a mag loop on the second floor right by a window.  I don't think there will be problems with killing the router that way given its location.  Not exactly keen on operating an antenna indoors, but it's definitely stealth and as long as I stay off the second floor while transmitting I think it'll be fine. 

Offline ThaDood

  • Sr. Member
  • ****
  • Posts: 449
  • Karma: +3/-0
  • There
    • View Profile
    • Extreme Part #15!
    • Email
Re: Troubleshooting - 43 m tx kills wifi
« Reply #8 on: November 13, 2019, 1959 UTC »
I did not catch what your source for internet was. DSL, CATV, satellite??? Reason I ask is, if it's DSL most phone lines are not shielded and that drop line from the utility pole to the house could be a big antenna with RF that overwhelms the DSL MODEM. What can be done? What I have had to do was wind ferrite chokes on the phone line that plugs into the DSL MODEM. DSL is a type of Carrier-Current transmission, where a medium wave carrier is coupled to the long-ass phones lines, and the DSL MODEM takes it from the phone line itself. Another example of that are those FM intercoms, that use the house wiring at around 175kHz. Anyway, several ferrite chokes will suppress the 43M band, but pass medium wave. BTW, I've also had to choke off the Eithernet cables and DSL wallwart where I am, since this MODEM that I have spurs on VHF badly. Another contemplation, (Not thought, since I don't want to strain myself.), is that newer CATV and satellite MODEM's use cheap switching power supplies, and no more step down power transformers, which worked great as RF suppressors. Depending upon what you have for a MODEM, you may have to choke the power cords as well.   
I can't decide upon what's worst, young and stupid, or old and chemically dumbed down.

Offline Roykirk

  • Newbie
  • *
  • Posts: 16
  • Karma: +0/-0
    • View Profile
    • Email
Re: Troubleshooting - 43 m tx kills wifi
« Reply #9 on: November 13, 2019, 2249 UTC »
All good questions that I may not be the smartest person to ask.  I do know that at both houses where I've broadcast that I had "high speed fiber optic internet" from the same provider.  However, at the old house the router was plugged in to the house's wired coax cable and at this house the router is plugged in to a phone line jack on the wall.  As noted earlier, I never had a problem with my router screwing up at the old house (and I was running up to 500 watts at times!).  Here at this house I'm causing chaos with 20 watts.  After reading your post I'm wondering if that's because this house's router seems to get its signal from a phone line and the other house got it from a (shielded) coax cable?  This might all be starting to make a lot of sense.  I do know that none of our utilities are overhead here, they all come in underground.  So I have a utility pedestal in front of my house, and it serves my house and the house next door.  I sure hope I was scrambling only my own internet and not also the neighbor's.   :o
« Last Edit: November 13, 2019, 2253 UTC by Roykirk »

Offline Roykirk

  • Newbie
  • *
  • Posts: 16
  • Karma: +0/-0
    • View Profile
    • Email
Re: Troubleshooting - 43 m tx kills wifi
« Reply #10 on: November 16, 2019, 0024 UTC »
Fixed, thanks to ThaDood!   :D  Wrapped a couple ferrite chokes around the phone line input in to my broadband wifi router.  Started out at 20 watts and everything was fine.  Then ran it up to 40 watts and everything still fine.  I also took note of all my neighbor's visible wifi networks before and after and none of them disappeared.  I think we can consider this problem solved!