 |
RFI noise antenna issue
20 June 2021 | by I have decided to give my MFJ 1026 noise canceller a call to action and combat this RFI I have been having. In the past, I did own a 1026 and used it with great success to remove RFI our plasma TV was giving me. With the MFJ 1026, you need to have what is called a noise antenna and it has to hear the same RFI your main antenna is hearing. When I used this device to remove the plasma TV issue I had no problem getting the noise antenna to receive the RFI loud and clear.
This brings me to my head-scratching moment with the RFI issue I am having now. The first noise antenna I tried was my H-800 active antenna. I picked up nothing, I then placed it from vertical to horizontal without success. I then moved it around the property and still I was not able to hear the RFI. I then tried a long wire in the horizontal plane fairly close to my Endfed antenna and I picked up nothing. Again I moved this long wire around the property without success again.
I do have a spare Endfed that I used for portable use and I ran some coax outside to set up the Endfed close to the main Endfed and low and behold I picked up the RFI BUT it was way too close to my main antenna. The MFJ unit (via an internal light/fuse) was indicating far too much RF was making its way down the noise antenna.
The other thing I tried was the change the length of coax that feeds my main Endfed antenna but this made no change to the RFI issue. In July we are getting a new aluminum gutter installed and I may try using that as the noise antenna and see if that works. Up to this point I have not been able to pick up the RFI that the main antenna is picking up.....well other than almost putting a noise antenna ontop of the main antenna that as I said did not work out very well.
14 Responses to “RFI noise antenna issue”
 Ham Radio Deluxe |
 Ham Radio Prep |
 KB3IFH QSL Cards  Hip Ham Shirts  HamRadioAuctions Reliance Antennas Enigma Shop |  morseDX  Ni4L Antennas  R&L Electronics antennas.us Ears to Our World |
- Matt W1MST, Managing Editor
MIKE –
Have you listened on your portable battery-powered SW receiver near each end of your EFHW transmit antenna? If either end is quite near to the noise source within your residence (directly in the near field) it will pick up MUCH higher levels than would normally be observed. Possible sources can include ‘wall-wart’ power supplies for clocks, rechargeable razors, internet or CATV modems, cordless phones, HVAC thermostats, etc.
Beware using your new aluminum rain gutter system as an antenna. All of the crimped joints and seams will become oxidized at the first rainstorm and become “soggy diodes” capable of rectifying local RF. Driving screws into each joint doesn’t help because of the junction of dissimilar metals when using either brass or steel screws on aluminum gutters.
73 and happy Canada Day coming soon.
Hi Mike,
In my experience, for the noise canceller to be effective, the sense antenna should be some distance from the receive antenna. Ideally, both the sense and receive antennas should be orthogonal to the noise source, but of course you need to know the direction of the noise source. If the RFI is propagating over the power line, it is difficult to tune out because it arrives from multiple directions. In addition to WA8NVW’s list, I would add computer monitors and wired ethernet as primary culprits.
Gud Luck OM
Mike,
You did not mention if you have proper common mode chokes installed on the coax of your EFHW. This type of antenna promotes common mode current on the coax so it will also couple local RFI into your receiver. You should place one about 3 meters from the EFHW transformer and one before the coax enters the shack. Each should have >4k ohms of resistance (not simply impedance) on the bands of interest.
– Glenn W9IQ
Good morning Karl and thanks for taking the time to send me a reply, no I have not used the SW at each end to listen and I will try that today and see that the results are. I wanted to get the Icom down into the MV AM band and see exactly where the RFI was as it’s not all across the band but in certain segments only. This way when I do go out hunting I can have the SW radio set to the same section of the AM band that the Icom is picking up the RFI on. We have a few days of rain coming so I can do some indoor RFI hunting. As for the gutter listening antenna yes I am aware of the issues. I had one at my old QTH and did end up have to overcome some issues.
Thanks very much again for the advice and I will keep the blog world posted with how things are working out.
73,
Mike
VE9KK
Good morning Ken, thanks for your input and taking the time to read the post and leave a comment. I am going to get out my AM battery radio and start hunting again.
Thanks and have a good week,
73,
Mike
VE9KK
Good morning Glen, very nice to hear from you, I do have a common mode choke made by Balun Designs. The Endfed manufacturer mentioned for the antenna that I have it should be placed at or about the 10m mark. Having said that, I do have a second Endfed antenna that I connected to the same coax that was feeding my permanent Endfed antenna. I placed this Endfed alongside our home (about 10 feet from the permanent Endfed and I have no RFI. This temp Endfed was the same polarization and height as the permanent Endfed.
As I move forward with troubleshooting the RFI I am left scratching my head more and more.
I am going to keep trying and thanks for your input,
73
Mike
VE9KK
I do recommend two common mode chokes with that antenna, Mike. Changing antennas and using the same coax may not be a meaningful comparison as they will have differing levels of common mode subseptibility.
Do check carefully the integrity of your coax and connectors. Even a small fraction of an ohm can cause significant RFI issues. Also open the autotransformer box for the antenna and inspect the connections and the condition of the core and its windings.
– Glenn W9IQ
Good evening Glen very nice to hear from you again, that will be one of my steps in trying to figure this out. Thank for your additional input.
73,
Mike
VE9KK
Mike – please describe the noise you are receiving – not sure if there’s a way for you to record the noise or not but that would be helpful. My email is [email protected] if you can.
Also, since it is summer, does the noise change when it rains?
Steve W
Good morning Steve, sorry for taking so long to get back to you but I found your comment in my junk file for some reason. For sure I will be able to email you a recording of the noise. I can get that off to you today or tomorrow the latest.
Thanks for your help and taking the time to leave a comment,
73,
Mike
VE9KK
Hello,
Add common mode chokes to your feedline, just below the transformer on the EFHW, and one at the entrance to the home as well. I went thorough a total rebuild of my home entry area and shack woring and removed a lot of RFI. See:
https://www.nk7z.net/rfi-now-house-cleaning/
Good afternoon David and thanks for the link and stopping by to leave a comment, At this point in time I have not added a common mode choke to the feedline at the antenna end. I very quickly looked over the website but will be going more for a closer look this eve. Thanks very much for the link.
73,
Mike
VE9KK
Had no RFI problems when living in rented apartments all over Arlington VA. Bought a condo which is built with concrete and ribar. hvac unit devastates all attempts to suppress RFI. Turn off all electrical noise sources and neighbors generate total RFI. Have to take Grungig SW receiver 100 feet tocommunity mail boxes ti escape RFI.Makers of noise suppressions kits and devices are adverized as suppressing all RFE. Not so. In no way. Had Nordmende Globetraveler radio in car in Warsawand noise suppression was perfect. In new car (VW) back in States, it was long effort to reinstall noise suppression. Maybe manufacturers are not selling me a bill of goods re their suppression kits. Only one way to find out.
Good morning Joel, thanks for stopping by and sharing your not-so-good run-in with RFI. When I was in my condo and it too was concrete and rebar I was fortunate that the RFI that was there was not too bad.
73,
Mike
VE9KK