RF causing issues

  • 1
  • Question
  • Updated 2 months ago
I'm having an issue caused by RF in my shack. Let me start by saying, this didn't always occur but I can't attach any specific event to its onset. Basically, when I use my Quadra amplifier while working FT8, I'm getting interference in the shack when A) I run over about 400watts and B) My SteppIR is pointed in the direction of the shack. Video-B shows normal operation with the antenna pointed at a right angle to the shack. Video-A then shows what happens if I point the antenna in the direction of my shack. As you can see the issue only occurs when the yagi is pointed in the direction of the shack.  If you look at my QRZ page you can see the layout. My shack is on the second floor of the garage in the picture.
Here are some other observations.

The problem doesn't seem to exist or have any impact on voice operation.
I can operate my vertical up to 1KW with no issues.
Everything in the shack is properly grounded.
I have tried adding toroids on cables in the shack but they haven't helped.
The pulsing that occurs is in the audio being sent by DAX to the radio.


Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes

Posted 2 months ago

  • 1
Photo of AH0U

AH0U

  • 250 Posts
  • 29 Reply Likes
You have got to be kidding!!! Using an amp. On FT8???
Photo of Jon - KF2E

Jon - KF2E

  • 632 Posts
  • 188 Reply Likes
Not really relevant to the issue?

Photo of Danny K5CG

Danny K5CG

  • 297 Posts
  • 43 Reply Likes
FT8 is a weak signal mode, not a low power mode like PSK.
Photo of Jerry NY2KW

Jerry NY2KW

  • 18 Posts
  • 0 Reply Likes
Sorry, the video's are not playing right for me.  Can you re-upload or check them ?
Photo of Jon - KF2E

Jon - KF2E

  • 632 Posts
  • 188 Reply Likes
They work fine for me. They are just youtube links. See if direct links work for you.

https://youtu.be/ti5cyc2pI3I

https://youtu.be/_QtlQdgdGZA
(Edited)
Photo of jim

jim

  • 26 Posts
  • 3 Reply Likes
If you are running 400 watts on FT8, I bet a lot of people are cussing you out.
Turn you power back.
Photo of Jon - KF2E

Jon - KF2E

  • 632 Posts
  • 188 Reply Likes
Look, I only use higher power when I need higher power. Isn't that the way you are suppose to operate? Where is it written that if you are trying to make a difficult contact on FT8 you can't use more power?
Photo of Dave-N9CHM

Dave-N9CHM

  • 63 Posts
  • 6 Reply Likes
You are in the extreme near radiation field of the antenna..being on the 2nd floor doesn't help as a ground that far from the actual ground is problematic..at best. You might try attaching 1/4 wave wires, laying them on the floor behind the desk, to your radio ground, in hopes of shunting some of the RF away from the radio. Tough situation, best of luck!
Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

  • 9135 Posts
  • 3462 Reply Likes
Ditto
Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes
I guess I don't understand how this will help. Since the radiation seems to be coming from the antenna and creating interference in the computer, what would stubs fix? How would they stop directional radiation from my antenna getting into my computer?
Photo of Dave-N9CHM

Dave-N9CHM

  • 63 Posts
  • 6 Reply Likes
You're probably correct, the stubs probably wouldn't work in this situation as stubs are usually used to lessen RFI from harmonics getting into other electronics. You're in such a strong radiation field when the antenna is pointed at you, that it's going to be almost impossible to shield your electronics, as you're found out. The only solution I can see is to just run <400W when pointed toward your station. You could turn your station into a SCIF by lining the walls/ceiling with RF radiation barrier, but that would be a lot of work, and probably impractical for your setup. https://tinyurl.com/yap4nser
Photo of Varistor

Varistor

  • 323 Posts
  • 73 Reply Likes
Read this

http://audiosystemsgroup.com/KillingR...

and this

http://audiosystemsgroup.com/StubPlac...

Solving your issues requires a systematic approach and some effort.

Good luck!
Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes
I think what is interesting/unique about this problem is that the RF causing the issue is being radiated from the antenna. That RF seems to be in some way corrupting the DAX audio stream. That data stream leaves the computer over ethernet and I am reasonably sure that the ethernet is not being corrupted. All that leaves me with as a point of failure is the audio chain within the computer. Something between when WSJT-x creates the audio and the ethernet port in the computer.
Photo of K1UO - Larry

K1UO - Larry

  • 751 Posts
  • 121 Reply Likes
have you tried grounding (or floating) your computer case?
Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes
Yes, I have tried the case both ways and it made no difference.
Photo of Jerry NY2KW

Jerry NY2KW

  • 18 Posts
  • 0 Reply Likes
YouTube video links still don't work.  I agree that FT8 even running a kW may be a weak signal elsewhere. It is not necessarily a QRP mode.  I am on second floor (no RF ground but everything bonded to single point) and directly broadside to a 140 folded dipole about 30-40' higher than me and just tried FT8 with my amp at 1.5kW and get no corruption/distortion but YMMV and there likely are other factors involved.  Are you using shielded ethernet cables plus wrapping around torroids?  Still would like to see the video  
Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes
Okay, I tried another Youtube account so we will see if this works for the videos.

Video-B  https://youtu.be/p5ULOioJFF0

Video-A  https://youtu.be/Dd-QGRjDcQk
Photo of WA2SQQ

WA2SQQ

  • 414 Posts
  • 87 Reply Likes
When you rotate the antenna in the direction which is causing the problem by chance is the SWR increasing?
Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes
No, the SWR remains good and constant.
Photo of Mike - VE3CKO

Mike - VE3CKO, Elmer

  • 343 Posts
  • 128 Reply Likes
Some may not like it here, but I'm going to use the "F-word"

In fact I'll use it 3 times, ferrite, ferrite, ferrite. I had same issue when I was on the 2nd floor but with 2m, then moved to the ground floor and when the SteppIR was pointed over the shack. Ferrites cleared that up, on every computer and audio input, output, even wall warts. I found that RF was getting into the shack from one of the many wire antennas as well so employing chokes certainly helped.

http://palomar-engineers.com/ferrite-application-experts-2/RFI-Solutions-c21312661
Photo of Robert Lonn

Robert Lonn

  • 237 Posts
  • 60 Reply Likes
Mike,,These are good folks,,, Just up the road from where I live... Have many of their products going back a LOT of years..  
Robert
Photo of Jon - KF2E

Jon - KF2E

  • 632 Posts
  • 188 Reply Likes
I have ferrites on almost everything at this point. All are Mix 31. I'm going to try adding more on the ethernet cables but I don't have a lot of hope. 
Photo of Robert Lonn

Robert Lonn

  • 247 Posts
  • 63 Reply Likes
For me the final FIX was to install an Isolator in the feeder line.. 900 Watts, SWR 1:1 to 1, SWR meter hardly moved,, but once I installed an Isolator, all problems went away and never returned.. I had a remote 4X1 antenna switch.. Different antennas caused different side affects,, but when I placed the Isolator on the output of the 4X1 Ameritron switch life was GOOD!!!! My ground system was 4 ,, 8' rods driven into the ground, and everything grounded at only one point.. Using a Fluke Megger, ground conductance was nearly perfect... Nope, had interference!! Isolator was the final fix for me..  Good Luck with solving your problem... Keep us all in the loop, we learn a lot here at Flex Group Think!!!

Robert 

https://www.ebay.com/itm/HF-antenna-Line-Isolator-1-30-MHz-Rated-3kW-stops-RFI-RF-choke-CMC-130-3K-/...
(Edited)
Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes
I already have 16 mix 31 ferrites at the feed point of the antenna. I can't imagine that isn't enough to choke any common mode currents from the feed line. I don't think that is the problem anyway or rotating the antenna wouldn't make a difference.
Photo of Varistor

Varistor

  • 321 Posts
  • 72 Reply Likes
You may want to read the reference materials. RFI could be the result of non-linear rectification in other pieces of equipment, pieces of wire, etc. If this is the case the amount of common mode choking of your feed lines is irrelevant.
Photo of Varistor

Varistor

  • 321 Posts
  • 72 Reply Likes
The feed line isolator from MyAntennas is just the garden variety of a choke, albeit very well made. Chokes are most effective when installed as close to the antenna feed point as possible. While they do offer a remedy when somewhere along the line closer to the radio, they are not as effective as at the feed point.

Of course, you can place them in many places at the same time- I use chokes at the feed point of each and every antenna, including Beverages, and then more chokes on each and every cable, not just coax, entering the shack. Then inside the shack, each and every AC power cord, computer screen or USB cable, and 12V DC distribution bus are choked.

Having said all that, I can’t emphasize enough the point of identifying other possible sources that are re-radiating RF. I just built a new station on the Caribbean and found out that the RG6 for cable TV and internet was causing enough RFI that to slow down the rate on the second radio, despite the extensive use of high power BPFs and a 70lb suitcase full of chokes. Now I am having the CATV coax choked in many different places and buried in the ground. I am also walking around the house with an AM radio to look for other sources of RFI to make sure I squash them all at once.

Last but not least, if your RFI disappears below certain power level, you are dealing with non-linear rectification/re-radiation rather than the garden variety RFI. It will take you some time to track the source down and remediate it. In fact, you may find out that you have several trouble spots.

Good luck.
(Edited)
Photo of Ria - N2RJ

Ria - N2RJ, Elmer

  • 2252 Posts
  • 875 Reply Likes
It sounds more like RF is getting into your computer. I had a problem with my icom where the CAT port would reset whenever I used CW on 80m. I put a choke balun at the antenna and problem solved. Depending on how close the antenna is to your house you may need more drastic measures. Rudy’s suggestions of reading audio systems group links (K9YC, who basically wrote the book on EMC) is very sound advice.

You won’t see it on SSB because the power peaks are very brief versus FT8 where it’s sustained. I run 1500w on FT8 often but only on 80/160 and 6m. You tend to need the power for those bands. Has netted me Japan, India, Australia, China which I could never get with only 100w.
Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes
I agree the problem is RF getting into the computer. Today I'm going to try unplugging everything from my computer with the exception of the power cable and the ethernet cable. I will also make sure those cables have ferrites at both ends. Then I will use team viewer to operate the radio remotely. If I still have RF getting into the audio chain of the computer I'm going to be stumped. 
Photo of Bill -VA3WTB

Bill -VA3WTB

  • 2668 Posts
  • 597 Reply Likes
The lan cable is a great antenna
Photo of Varistor

Varistor

  • 323 Posts
  • 73 Reply Likes
By the way, this is what a truly effective choke looks like; note the amount of ferrite being used:

(Edited)
Photo of N5LB - Lionel B

N5LB - Lionel B

  • 126 Posts
  • 23 Reply Likes
The Ethernet cable from the radio to the computer was the weak point with RF into the computer and/or the 6400 port.  Choked the Ethernet cable - all fixed. 

I use a non resonant dipole, open feedline, and feedline choke for coax into the shack and this is problematic-easy to get RF into everything on some bands unless good equipment grounding and chokes on all cable applied.  Following best practices from links in this thread eliminated the RFI.
Photo of Al / NN4ZZ

Al / NN4ZZ

  • 1702 Posts
  • 579 Reply Likes
Hi Jon,
I had RF problems a few years ago that sound similar.  In addition to grounding and chokes I also added a short fiber link in the shack to eliminate RF from getting into the radio and PC from the LAN cables which are like antennas.  It will also protect both the PC and flex from power and lightning surges.  It easy to do and not too expensive ($100 - $150)

Here is a link to my fiber setup.

http://nn4zz.com/FLEX6700.htm#Ethernet_Lightning_Protection

And a link to my other RF mitigation steps:

http://www.nn4zz.com/FLEX6700.htm#RF_issues_and_solutions 

Regards Al / NN4ZZ
Photo of Jon - KF2E

Jon - KF2E

  • 634 Posts
  • 188 Reply Likes
Okay, after disconnecting everything from my computer and operating it remotely with teamviewer nothing changed. I still had the interference. After reading Al's note I went back and revisited the ethernet cable from the Flex to the switch. I had previously added one mix 31 ferrite to each end of the cable but I decided to try a new cable and a bigger ferrites that allowed me to get three turns. Problem solved!

I'm going to take Al's advice and add a fiber link between the radio and switch. I had been meaning to do that since my previous 6500 took what was believed to be fatal surge through the ethernet port that left the radio unrepairable.

Thanks to everyone who helped with their comments.
Photo of Dave

Dave

  • 2 Posts
  • 0 Reply Likes
In my case it turned out to be the power supply for the Fiber optic to digitle converter. Useing my spare astron 35m did the trick. W8XO