Tackling RF in the Ham Shack

I received the following query via YouTube. Since it’s a common problem, I thought I’d address it here. Please keep in mind that English is not Billy’s first language, so please read past the minor grammar issues and look at the difficulties he’s having.

My name is Billy my call [removed for privacy] few years ago I get my ham call so was a very happy day for me when I passed my 1th exam and then 2-3 moths more got my general class.

So, really i’m new ham and always need help 🙂 In this case searching for help videos I find out one of yours videos talking about “ground” so, my question is any idea how I can ground my antenna that its place on the top building roof (3 floors) and I live in the 1th floor. I have RFI to the neightbors and I did few tests one of my problems is the antenna no have ground and is just 6-7 ft up from the roof. another thing is my rotor line when I connect and come inside of my apartament come with a lot RF I use a field strength meter so as you can get idea all cables,metals or devices get RFI ofcourse power wire lines in the while building so, for my testings remove my 10m 4 elemts antenna,3 elemts 5 band antenna and only I setup one small 3 elemets 10m yagi for have easy testings, the RFI come down when I put down the swr but still need more. again for testings controls I take off all my shack and just I have my radio and swith antennas both of them is grounded in my case I used 6 ft rod cooper and #8 wire and then for my radio #12 wire for sigle point but my problem is the antenna, as I read several notes from hams the wire or conductor we use for ground not be so long because can turn it in antenna and in anothers words more problems for me. hihi

So, my question is there any possible solution in my case? all pictures and videos of hams use towers setup directly on the soil so easy to run a grounding sistem but in my case my antenna is on a tube pipe at about 30ft high thats mean long wire come down for ground 🙁

Im sorry for very long messege but I wanna be clear for you have better idea my case and maybe you have one good option for my specific problem.

Thank you for read my lines and I hope this dont be a problem for you.

73s and happy new year (just a bit late 🙂 hi hi)

Billy

Billy, first, I sympathize with your problem – it’s no fun having RF energy in the ham shack. Let’s identify your problem. It’s not grounding, although grounding may be part of the solution. The problem is that RF energy is traveling from your transmitter, going to the antenna, and then returning into your station. This can cause all sorts of problems, such as RFI (radio frequency interference) and can even cause the rig itself to misbehave. I’ve worked hard in my shack to keep the RF away and have been mostly successful, although on 80 meters I have to shut off the computer speakers because they buzz loudly.

If I read you correctly, your station is on the 1st floor, and therefore not unworkably far from ground. It is the station that needs to be grounded, not the antenna. All the components in your station, such as transceiver, power supply, SWR meter, and antenna tuner and, in your case, the rotor control box, should be grounded to a single point. From that point, the ground wire goes out to your ground rod. I use an 8-foot ground rod in fairly dry soil. Note I emphasize “single point.” I use a short section of copper plumbing pipe. Each ground goes to this pipe. Then the pipe is connected via #2 wire to my ground rod. That’s probably overkill, but then I don’t like RF in the shack any more than you do!

The reason for the single point ground is to avoid creating ground loops. A ground loop exists when current flows between your devices by way of the grounding wire but never quite finds the ground rod. This turns that section of your ground system into an antenna!

I am assuming you use coaxial cable between your station and the antenna. The idea is to keep the RF inside the cable. If, however, there is a mismatch at the antenna, part of the reflected power can come back down on the outside of the cable. This may be what is happening in your case. You can reduce this in many ways (see the ARRL Handbook). One easy way is to roll up 10 to 20 feet of coax and tape it with electrical tape, which creates a form of a choke balun and helps keep the RF off the outside of the cable. You can also use ferrite cores—it usually takes quite a number of them. You can also repeat this where the coax comes into your station via the window. You will undoubtedly have to use multiple ferrite cores for your rotator cable. You can also purchase larger ferrite cores and wind a few feet of your rotator cable through it like a toroid.

Now there’s another way that your neighbors may be experiencing RFI, and that’s called “fundamental overload.” Lots of consumer electronic devices (like my computer speakers) don’t like to be in strong RF fields and will show signs of RFI even though your station is operating properly. Technically, if you look at the FCC statement found in the instruction manual for every consumer electronics device, you’ll find the statement that the device can’t interfere with anything else, plus has to accept interference from everything else, including interference that causes problems with the device. However, often your neighbors won’t want to hear that!

Years ago I had a neighbor who complained about very tiny amounts of RFI in his TV set. I wanted to keep good relations, so for awhile I switched from SSB to CW, which didn’t seem to bother him. I moved shortly after and went back to SSB. But this does point out a potential solution: reduce power! You can drop your power by half and that’s only a half S-unit difference to the ham on the other end. In fact, you’d have to drop your power in half again to get a full S-unit. So 25 watts is only one S-unit less than 100 watts.

Another solution, perhaps not easy, is to raise the height of your antennas. You have them quite low, so the building itself is altering the performance of the antenna. Raising the antennas by 20 feet would put the RF much further in the air.

As a final suggestion, find hams who live near you and invite them to visit your station to give suggestions. Sometimes another pair of eyes is just what’s needed. You can find a ham club near you by visiting the ARRL Club Finder web page here.

Note in all this that you’ll want to ground the towers for lightning protection reasons. The grounding line should run to a ground rod.

Good luck and 73 de Dave, KEØOG

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2 Responses to Tackling RF in the Ham Shack

  1. Dave says:

    The three coax cables can exit your shack via a single hole.

  2. Chris Honea says:

    I have a question about coax cables. I’m putting my ham shack together and I will be using 3 antennas so I will have 3 feed lines coming into my shack. Question? can I run all 3 feed lines out the same hole through my shack meaning all 3 will be touching each other or do I need to seperate each one to prevent interferance in the feed lines. Chris KG4ADG.

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