I have had S7 power line noise (RFI) on 160 m for several months now (as measured on inverted-L antenna). I spent almost a month collecting observations and search for possible RFI sources nearby.

The first step was to characterize the noise source. I first observed that the noise goes away during rain, which is expected for arcing power lines. Otherwise it was constantly on 24/7 but its intensity varied slightly from day to day. During heavy winds the noise sometimes showed erratic behavior, like a bad contact. Setting my radio to AM mode on 160 m band and checking the WSJT-X water fall (starting from 0 Hz rather than the usual 200 Hz), one could clearly see peaks at 120 Hz plus its multiples. Occasionally weaker 60 Hz and multiples were also seen. All this is consistent with power line arcing. So, now I knew what I am looking for.

To locate the source, I first used my 160 m receiving antennas to get the approximate direction and then concentrated the search in that approximate direction. Since it could only be heard on the 160 m band, it is likely not very close to me (> 1 mile distance). Google Earth is a great help in mapping out the search area. When I eventually drove near the RFI source, the noise showed up on my car AM radio but then I failed to observe it on portable 120 MHz AM radio, which indicated that I could not get very close to the troublemaker (private properties with barbwire fences, animals etc.). Unfortunately, AM radio observation is often not very reliable because the noise can be conducted through the power line wires (antenna) and radiate over a large area. Fortunately, in this case the information I provided turned out to be sufficient for the power company to locate the problem.

I detailed all the findings (including proof that the RFI is not from my property) and sent a letter to the power company (Craighead Electric). They received the letter and responded the same day (9/28). Even though I was not able to pin point the exact source of the RFI, they found the problem & fixed it in just a couple of hours (9/30)! The actual broken equipment was located using ultrasonic microphone equipped with a parabolic dish. The RFI was caused by arcing of this jumper (see the brown piece on the left where some wire has evaporated):

Over time this would have led to power line failure since the wire was getting evaporated slowly. When it gets thinner (increased resistance), it begins to heat more (on top of the heat produced by arcing) and this accelerates the failure process. This broken equipment was located 2.2 miles east from my QTH. There is still a smaller issue in another location but they promised to search for it soon. This RFI source I am able to hear with my 120 MHz AM handheld radio, which can determine the location more exactly. Interestingly, it can only be heard weakly on the 10 m band at my QTH, mainly because of the higher natural noise floor on the lower bands. It is approximately located 2 miles northeast from me. I used my 10 m yagi to get the direction for the search (signal maximum & side null). It has the same signature as the 160 m noise (120 Hz + multiples and goes quiet when it rains).

Now my day time noise floor sits neat at S3 on 160 m. It turns out that the grandfather of the electric company technology chief is a ham and that probably helped.

Excellent service from Craighead Electric!

My Acom 2000A amplifier started complaining “bias too low at power on -56 V” when turning it on. I pulled out the tubes (GU74B / 4CX800A) and did some simple resistance checks, nothing stood out. Then based on the advice from Acom (fast and good customer support) and a local ham, I decided to put in another pair that was known to work. Well, the amplifier came back on without any issues. Here is the amplifier with the new tubes put in:

And these are the old tubes (of which at least one is bad):

Now I need to finish plate current calibration and I should be all set to go again! If you have to change your tubes, drop Acom an email and ask for instructions. They have a very nice writeup on how to do the procedure. Even though Array Solutions is cooling down their operations (retirement), Jay can still do tube testing. However, there is a bit conflicting information on “gettering” this type of old tubes. On the internet most people say that one must do this for old Russian GU74b’s whereas Acom technical support said that it is not needed. Go figure… Just to be safe, it is probably a good idea to getter them before using.

Except then leads of one of the temperature sensors snapped. This has LM335GE label on it. Now need to replace that. According to Acom, LM335Z will work. I will try to put flexible leads on them in order to avoid breaking them again.

Update: New LM335Z is in and the amplifier seems happy. Also the “new old” pair of tubes look produce full power output.

In order to better catch 6m DX conditions, I wrote a small program to alert me about the band openings (called ealert). I have WSJT-X Improved running 24/7 with filters set to DX only, so it will broadcast only those decodes (see WSJT-X network settings). The program then catches those UDP multicast messages, parses them, and forwards them either to a given email address or XMPP address (using Gajim). The latter works better for me since it does not litter my email box. It has a simple GUI that allows turning the alerts on/off. I have XMPP client (Conversations app) on my cell phone that catches the alerts.

Even when I am not at the radios, I can use my cell phone to run VNC remote desktop to my station and run FT8 QSOs. This combined with the alert system should improve my presence on 6m whenever the band opens up.

Installed Morgan M-303 lightning protection to all coax cables:

It is not fully weatherproof so decided to install the first one inside the shack:

with grounding outside the shack:

The other two units are outside and just in case I wrapped everything with electrical tape:

I always disconnect all cables during lightning stroms but this is just to protect against those random strikes…

One interesting feature of this unit is that it fully blocks DC. This is important during rain/snow/sleet precipitation when static electricity can develop at the antennas and appear at the coax cable. I experienced this last winter when my K4 suddenly started flashing overload!

Note: This unit can handle full legal power on 6m band unlike most other surge protectors (e.g., polyphaser).

Update: If you have antenna that has elevated SWR (greater than 2), the DC block circuitry in the unit can heat up and cause gradual increase in SWR when using full power (1500W) on digital modes like FT8. There is a beefier unit in preparation, model 305, but that does not support 6m like the 303. It is possible to bypass the DC block in 303 to avoid this issue. Or even better, tune the antenna properly…

My NW/SE BOG suddently went dead. It had 30 dB less signal than on the NE/SW BOG. After inspection, I found the obvious reason:

and then this one was the “final straw”:

Added a fresh piece of cable there and all is well again. However, I definitely need to get better/thicker cable for my BOGs so that mice can’t chew them through.

Update: There are apparently wire coatings that are either rodent proof or have some chemical added that they taste bad. Need to look into this.

Update 2: I installed conduit in the area where the critters were feasting:

Update 3: The mice got falsely blamed for this – it was the rabbits! It is now wabbit season….

Due to humid summers and “cold” winters in Arkansas, I need to keep an eye on how the temperature and humidity are in my shack. So, I decided to use Adafruit SHT4x Trinkey M0 USB half-key device for this purpose. It costs about $10. The GTK+4 code (Linux) that I wrote can be found from github. This is what the device looks like:

Since it is USB A half-key, I used electrical tape to secure it to the USB extension cable. Here is what the simple GTK+4 widget looks like:

I will probably add graphing to it at some point but this will enable me to monitor my shack from remote locations. Too bad that there is no USB device that can get rid of insects! One had crawled inside the LCD display of my amplifier and now I have to figure how to get it out 🙁

Well, here is the graphing added to it:

“Bad weather” pretty much summarizes the contest for me. Both in the ionosphere and lower. Poor propagation overall and thunder storms circling my QTH. The poor propagation also drove people to other bands (except those of us who had decided to do single band). Whenever the band opened slightly to some direction, for sure there was a thunder storm in that direction and terrible QRN. My ears are still ringing from those lightning crashes – volume had to be turned up and APF on in order to copy stations. I do not want to wear headphones for a while… One could argue that it must be the lightning that fires up the ionosphere 🙂

Finally, late on Sunday afternoon the band opened to EU but then the QRN prevented me from working most of the stations. Nothing more frustrating than hearing a bunch of people calling but I can’t copy them. Then there were some minor episodes like losing the power for a bit during the contest, AC leaking condensed water into my ham shack and me being attacked by a fly swarm while trying to work. The latter was very annoying and distracting! They must have been attracted to my “contest aroma” (sweating with the AC off and no shower). And when the contest was almost over (1.5 hour left), I hear a loud rumble through my headphones and realized that a thunder storm had just developed almost exactly above my QTH. Turned off everything and pulled cables off. I kept waiting for it to go away but no, it decided not to go anywhere (game over). The timing of WPX is really bad for us due to the storm season but what can we do?

But I still managed to get 1252 QSOs and 706 prefixes. However, I am pretty sure that there are tons of copy errors because of the QRN and poor band condx (very weak signals) but that’s life…

Here is an example where in one QSO (SP5EXA) RX A decoded the first message and RX B the following message. So, the QSO would not have completed (or, well, could have after retries) without the two RXs.

Here RX A was connected to inverted L and RX B to BOG-NE. The ! sign indicates that the decode was received only with that RX.

My half empirical points for successful BOG antenna deployment:

• Poor ground conductivity is good for BOGs especially when the wire is directly on the ground. Elevating the wire will reduce influence of the ground and the results will become more consistent between different QTHs. My QTH has rocky / poor conductivity ground, so longer BOGs work well. At locations with higher ground conductivity, BOGs should be shorter.
• If you install radials, make sure that they are not too long. Three 40′ radials per end point seems to be good for 60/80/160. I also have ground rods at each end of my reversible BOG (KD9SV setup).
• Lengths of 150′ – 300′ have been typically used. I have tried 150′, 200′ and 300′. 300′ worked best in my case. It has a good pattern on 160 m, 80 m, and 60 m. I have not tried it on 40 m since I have a 3 element beam there. Distance between the BOG wire and ground affects the wire velocity factor: closer to the ground makes it electrically longer whereas elevating it reduces its electrical length (but increases the overall signal strength). My BOG is elevated slightly (4″ from ground) and hence the optimum wire length is somewhat longer than cited elsewhere (typically approx. 225′). If rising the wire more, it will eventually become a regular Beverage antenna (and needs a longer wire).
• Termination resistance: Elevating the BOG and increasing its length may require using a larger value termination resistor than the usual 240 ohm (in the KD9SV box). I have not observed any self-termination effects of my BOGs but I have not gone beyond 300′ in length.
• Having the BOG elevated slightly helps prevent accumulation of leaves etc. on the wire, which can degrade the performance. This can also reduce the chance of mice, rats, squirrels etc. eating the BOG wire. It would be best to use critter resistant wire!

There are many stories online where some people say that BOGs work great and others that have absolutely no success with these antennas. This is presumably due to different ground conductivities at the locations. It took me a while to test various setups but now I finally have a working system. It easily beats my inverted L in receiving on 160/80/60 especially when lightning is present somewhere. But I use both when receiving on the low bands (see other posts on “multi”).