rfi on 80 and 40

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  • Updated 4 years ago
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First off let me say that I ONLY have rfi on 40 and 80. No amp, I only operate with Flex 6K, no amp.

Even at low power on 80 and 40 rfi is getting into the software.
Using a Flex 6.5K BAREFOOT running any mode but really a problem with JT65-JT9 running WSJT-x 1.5.0

It simply will not allow me to do anything with SSDR or WSJT till that TRANSMITTED message is complete and the Flex returns to receive mode.
For example: Once a message cycle is started in WSJT, I CANNOT move the SSDR 'RF' or 'MON' sliders.

Now I have a single point ground. (2"x4" piece of copper sheet) mounted on the wall behind the desk and all things like switches, rf filters are mounted to this thick copper sheet which is connected to my water pipe ground. (all are in the same place so all interconnections are short and direct). Multiple ferrites are employed on all cables, power supply,  keyboard, mouse, keyer. Basically anything that is wire and connected to the rig or computer has ferrites.
But still rf is causing SSDR to be unresponsive.
For instance, I can't stop sending, I can't lower the "RF POWER" in SSDR by moving the slider.
I can't lower the SSDR volume slider.
Basically SSDR is frozen and will keep transmitting till that message is completed.

I have always previously been able to find the RFI route and take steps to block it.

But this time I've been stumped.

So my question is:
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Posted 4 years ago

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Photo of George Molnar, KF2T

George Molnar, KF2T, Elmer

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Good morning, Bill. What kind of feed line are you using? Maybe an upgrade to something with a high braid percentage would help? Is there a line isolator or choke on the feeder? Sounds like it might be RF into the PC. Is the case metal? Try removing paint from touching surfaces to create a more completely shielded enclosure. Moving the PC away from the rig often helps, too. A wireless mouse may also be a big help. Good luck!
Photo of WX7Y


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what kind of Antenna? how far away from the computer is it? What mix of Fe-rite chocks are you using? sounds like your in your Antenna's "near field" and your computer is not very well shielded from RF, and YES get a Wireless Mouse / Keyboard
Bret WX7Y
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Ken - NM9P

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Experiment with a wireless keyboard/mouse combo and see if that solves some of the RFI into the computer.  Those input lines have been a source of frustration for me and moving to wireless mouse/keyboard has solved several problems.  The tradeoff is that some of these can add to RX RFI on certain frequencies.  They also have a nasty habit of the battery dying right in the middle of a contest!  In any case, it can be a temporary solution to help diagnose a problem.

Ken - NM9P
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Ken - NM9P

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Also... beware of the "bargain" clip-on ferrites you get at hamfests.  Many of these are good for VHF and most often used on computers for TVI compliance, but are almost useless for HF RFI.  

MIX-31 is your buddy for HF.  They are pretty good from 160-6 meters, and much more effective on HF than the big one-inch square clip-ons I got at Dayton in a block of 20.  (They were unlabeled, but are probably mix-46 or mix-63).  

Yes, they are more expensive when purchased from DX-Engineering and other suppliers, but worth the money.

Ken - NM9P
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Stan - VA7NF

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"which is connected to my water pipe ground"

Some water pipes, mine in a multi-unit townhouse is under (or inside) the concrete pad but "protected" by plastic pipe and has very little value as an RF ground.  A friend's is a multi-unit vertical structure and the copper pipe has a long way to go.

A little more detail please as it sounds like a grounding problem.

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Dan -- KC4GO

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I'm not a fan of water pipe grounding
. 1: as Stan said may not be a good ground because at some point it couples to plastic.
 2: When you start running it as ground for you system you may introduce stray currents that can cause electrolysis and put holes in the copper. (I have seen that happen)
3: For RF ground it should be completely removed from the RF safety ground your electrical system.

 I still struggle on 80 and 160 with some RF in the shack...at least I got 40 under control.. 
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Norm - W7CK

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I may not be much help mainly because I've adopted a less orthodox approach.  Nothing in my installation is grounded in any way shape or form.    About 35 years ago, I started out with ground rods and bonding cables running all over the place to every piece of equipment I had.  I experienced nothing but trouble.  Always had RFI in the shack, speakers, TV, phone, alarms, everything.  I ripped it all out and have never looked back.

I run everything here off of a solar installation that is dedicated just to the ham shack.  It runs everything in the room and none of it is grounded either.   I do have lightning protection though.  I only run wire antennas and use 450 ohm ladder line.  For each antenna I have a steal plate with a couple spark plugs mounted on the plate.  The plate is mounted to a ground rod outside and as close to the antenna as possible.  Each side of the LL goes to a spark plug then continues on into the shack.  The theory is If lightning hits the antenna, it will travel down the LL arc across the spark plugs to ground.   Since there isn't any ground in the shack, there isn't much incentive for it to continue in this direction.  

An added benefit is that it makes for a very quiet station.  The noise level here is usually extremely low.

I do have an amplifier that I switch in line occasionally and it runs off of the commercial power.  I do not have any special bonding to the amp and at 1500 watts - no RFI.
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I agree with Norm. Plug it in and operate. No rfi, tvi, bci.  I had a friend with similar RFI TVI problems. Went over and disconnected all his stuff from rod and it all disappeared.  Years ago with all antennas disconnected and laying on the ground, a close hit fried all my gear, computers, everything connected to a ground rod triad. Only thing in the house to get burned. Never again.
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Norm - W7CK

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The only time I get RFI is when I have a bad piece of coax.  I went to HRO several months ago and bought a few 3' patch coax cables.   Every one of them had poor shield connections.  I redid the connectors and all is good now!

Just something to check.
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John n0snx

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 That dang RFI is tricky stuff....here one day gone the next and back again.... In my case almost every time the issue was with a coax jumper... I switched all my jumpers to LMR 240 jumpers and havent had any issues since I did...  oh by the way.... I run computer with wireless mouse & keyboard, 2 Flexes, 2 monitors, legal limit amp, LP100a and a remote MFJ antenna switch to switch between radios....mic pre-amp all with  no grounding ... RFI galore with all the grounding. unhooked all the grounding and RFI was much easier to control. It worked for me.... your outcome may vary.
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Bill W2PKY

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I had this issue with a USB Ethernet adapter. Are you able to try another computer or Ethernet connection? Finally my earphone jack was sensitive to RF. Especially with a long extension cable.
Palomar Engineers have some good solutions for RFI. http://palomar-engineers.com/
Hope this helps.
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Pat - WH6HI

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It is very important to start from the point of view of wave length.  The longer the ground run the more problems will pop up in the station.  Trying to beat the RF to death with ferrite is a very big chore and in the end may not solve the problem.  In the shack, make sure all cables and connectors are functioning properly.  Reroute some cables if necessary, keeping audio and RF as far apart as possible.  The best place to start though is right at the antenna.  RF has a bad habit of coming back at you and your shack via the outside of the RF line going to your antenna.  And again this is a function of wave length as to how bad this RF affects your shack.  Use wire or ferrite or antenna isolators on each of the antennas.  This type of RF incursion to the shack is common mode.  Next source of RF in the shack is the length of the station ground.  Again wave length is an important consideration.  This is also important for lightning protection as lightning acts much like RF.  Some times this can only be solved by placing the shack in a location that provided as short of a ground run as possible.  Remember that a long ground run also can become an antenna as  I have said before wave length rules!  At lower frequencies ground length problems are less pronounced, but is still a consideration.  At higher frequencies, it is a must that the ground run be as short as possible.  I had a second floor shack at one time and I ran very High power station. but on 10, 15 and 20 meters I had bad RF in the shack.  There was no way to shorten the ground, but wave length can be your friend.  What I did was I ran 1/4 wave length radials out the window from the grounding point were the ground went outside and fanned them out at about 30 degrees apart.
This put the high voltage part of the RF out away from the shack completely eliminating the RF in the shack.  40 and 80/75 were not a problem as the ground did its job even at 20 feet of 1.5 in copper braid to the ground rod.  Any I hope you get my point to analyze your station setup as a complete system from antenna to ground using wave length as you guide. 

Thanks for reading my long post.

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Luis del MOlino

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Coaxial cable are famous acting as a triple conductor: The central conductor, the internal copper braid and the external coaxial braid. We have to avoid that RF circulates by the external side of the coaxial braid returning to the shack. The only good solution to avoid this is using a good balun at the feeding point of the antenna, be a dipole or a vertical. It constrains the RF to pass through the inside ot the coaxial cable with two exactly equal corrents going in opposite direction in the central conductor and the internal side of the coaxial braid.

If you do not have a balun in the feeding point of the antena, the worst method to elliminate RF in the shack is to place a common ground that taks RF to earth. When you add it, you are suppliying another path to the RF circulating through the outer side of the braid.

Then you have some RF been radiated inside the shack through this ground cable. Now this ground cable is forming part of your antenna, But you have to think that it works too as an antenna in reception and as an antenna it gets all noises radiated inside the shack.

If you have (you must have one) a common ground earth for electrical protection, you should place ferrite beads in the ground cable to avoid any RF circulating through it.

Another source of RF could be the outer braid acting as a receiving antenna and carring some RF to the shack. This could be avoided placing an un-un as MFJ-915 just at the output of your transceiver.

Another source of RF could be any rotor cable coming from your Yagi for hiigher bands  capturing RF and taking it into the shack. Place ferrite cores in it to avoid this to happen.

And that's all folks.  

73 Luis EA3OG
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I have always found that a field strength meter is the easiest way to find the path RF is following whenever ingress is an issue. They are cheap and extremely effective. Key your rig on a clear frequency on one of your problem bands and hold the field strength meter near every lead that is connected to equipment at your operating position. The hot leads that are problematic will usually peg the little meter.