Tag Archives: RFI


Here I go again, a noise hunt. Since getting the IC-7300 I have been able to observe various noise conditions on various bands. Most of what I see is broadband and pulsing. This causes horizontal stripes to appear on my waterfall. Noise blanking has no effect. There are other less frequency types that show up. Sometimes there is a “chirp” signal that will scroll across the band showing up as vertical stripes. Other times a similar chirp begins mid band and slowly works down a few kc then starts to move up a few kc. I have tried to track local noise sources in the shack with only mixed results. To devices that produce some noise are the Ipad and the 21″ monitor though these seem to be limited in range. I shut off various noise sources including the computers, drives, cable modem and Wifi hub but did not see a significant reduction in noise levels.

I decided to try something a bit different. I found a Timewave ANC-4 noise reduction unit for a decent price on Ebay and have ordered it:


The idea of these devices is to use a sense antenna to sample the local noise and then combine it with the signal from the main antenna such that the amplitude is the same but reversed 180°:


I have heard mixed reviews on these types of units dependent largely on the sense antenna and its ability to sample the offending noise. I will be giving this a try and will report on how well it works in my situation.


Insight from running 20m WSPR

The 40m vertical has been deployed for the past few months supported by a 10m SOTAbeams travel mast. It has held up well to the abuse of constant use over the summer. We had a few windy days last week and some of the seconds of telescoping pole retracted so I had to bring the whole thing down to fix. During this time I ran the 20m vertical on its own using 20m WSPR for receive only. Over this two day period I was comparing with Cliff’s (N5CEY) 20m WSPR station about 15-20 miles away near Bayview. Cliff consistently gets a larger number of unique spots as well as a larger amount of DX calls with his setup. Cliff is in a rural setting while I am in the middle of the city. What the WSPR data is telling me is that my noise floor is higher so I am not receiving as well as Cliff does out in the country. I took some measurements with the IC-7300 at various times of day and found the following noise floors:

Band Time
1800 UTC 2100 UTC 1300 UTC
80m S3 S4-S5 S6
40m S6 S6-S7 S9+5
20m S1 S2 S4-S5
17m S3 S3-S4 S5
15m S3 S1 S7
12m S2 S0 S3
10m S1-S3 S1 S5

These measurements were made with no preamp on 20m and below. All others had preamp #1 engaged. Friday night was awful, S9+ noise on 40m! Dick, WB5B said it best: “WSPR is telling you that you have a noise problem!” Doh!

Noise Raises its Ugly Head

I am seeing some weird noise on mainly the low bands here with the new vertical antenna. It is fairly broadband and the rig’s noise blanker seems to effectively null it but I would like to track down the source.The weird part is that is seems to go away on it’s own during daylight hours and return in the evening. I haven’t been able to track a specific time yet. I suspect somethjing here in the shack is causing the problem. I walked around the property yesterday with a battery powered receiver and I see the noise coming from the wall around my workstation. I suspect a bad patch cable as this has caused problems before and I did add some patch cables that may be a bit dodgy.

RFI Rears it’s Ugly Head Again

Started noticing RFI issues again after I swapped out the LDG tuner for the new MFJ. Problems were noted mainly on 40m and below this time. I also noticed the tuner would not find a good match on 15m and 17m. I checked all the connections today as well as the cable routing today. I found a subtle problem with one of the patch cables I was using in which the connector was rotating a bit. I replaced it and the RFI went away on all bands but 80m. The tuner now seems to be finding a match on 15m and 17m without any issues. Looks like everything is running well again now.

More Noise…Sigh….

Now that the RTL-SDR songle is working again as my panadapter…I noticed a lot of noise spikes on my HF spectrum. Tracked it down to the 12V 15A supply I was using for the FT-2900R. I tried to suppress the noise using ferrites but it didn’t have an effect so I am figuring the supply itself is radiating. I moved the FT-2900R to the Samlex supply and it is now sharing with the Yaesu FT-450D. Not a problem running both as long as I don’t try to transmit with both at the same time. I’ll keep the noisy supply when I try and operate the FT-2900R on the 2m Moxon when I get the mast up and running.

Otherwise, the rig is running real smooth now and playing very nicely with all my computer and USB peripherals.

The battle against RFI in the shack

I had not mentioned this before but ever since I set  up my HF station last year I have had off and on problems with RFI in various devices. This was not much of a problem when 10m was open as I spent much of my time there and my problems were showing up mainly on 20m. First there was the issue of my Eaton ACFI breakers tripping when transmitting on anything below 17m. This is a well documented problem but I lived with it until just last week when I replaced them with standard breakers and installed GCFI outlets. That settled the issue of visiting the breaker box after playing radio.

It seemed as though whenever I made even minor changes to the station wiring I would get RFI into either USB peripherals or get RF breaking the squelch on my 2m rig which I leave on when using HF. The worst problems of this type were on 20m. SSB would be relatively minor at 100W but PSK31 on 30W would drive some stuff crazy. Her’s a list of stuff that would go wacky at various times:

  1. USB Conference speaker would light up like a Christmas tree and hang
  2. RTL-SDR dongle would over load when I transmit and freeze
  3. USB keyboard would lose connection
  4. SignaLink would drop occasionally during transmit
  5. Squelch would break on my 2m rig when using PSK31.
  6. LCD computer monitor would pick up RFI during transmit
  7. Cable modem would drop internet signal.

These were the main issues and I should note that these did not always happen. The last straw came when the keyboard would lock during PSK31. Makes it hard to close a QSO when you can’t type….arrrgh!

So the battle was joined. First up I adjusted all the wiring on the radio and tuner and attempted to keep things from being to close to cables carrying RF. I added a line isolator right out of the rig. Some improvement preventing the 2m rig RFI but not much else. Off to Amazon and Ebay next to buy some snap-on ferrites. Didn’t have much luck with these initially. Today I got into it a lot deeper and found success. A snap-on ferrite on the power supply wire to the cable modem and making sure the feed-line was not in proximity to the cable line outside fixed the Internet issue. Next the USB cables. Ideally, six turns around the snap-on ferrite applied to the USB cable where it connects to the computer settled down the USB speaker. The same was done with the SignaLink, RTL-SDR dongle and mouse, keyboard USB lines.  Also coiled up the excess wire into an air-choke. The results have been very nice. Everything is behaving now. The RTL-SDR dongle was moved a few inches away from the radio and with the snap-on ferrite it no longer overloads when I transmit.

Photo Sep 06, 6 34 12 PM

AFCI and HF signals

About the time I set up my station, I updated and repaired some electrical issues around the house. Part of this was for the radio setup. I added some ground rods and bonded them to the main house ground rod. I have one rod outside my station and the other is over by the where the antenna is installed.

Inside the house, I had to replace a GFCI breaker that was faulty on my load center. This breaker controlled by outside outlets as well as the bathroom outlets. While I was at it I had the electrician add a second one to cover some outlets near the kitchen sink. All was well for a while.

I started noticing that the GFCI would trip on both new breakers. I suspected the radio but didn’t see a correlation until I started using PSK31 on 20m. I started digging around some more and found that what was installed were Eaton AFCI breakers. These are well know to be susceptible to be tripped by HF signals in the 20m to 12m range. So using 10m everything was ok. When I tried 20m PSK31 transmission the breakers tripped almost immediately. Go figure….

So my plan now is to have the electrician come back in and replace the AFCI breakers with standard ones. Then I have to replace about five standard outlets with Leviton GFCI types. That should so the trick.