I'm using a 60 foot center fed dipole fed with 450 ohm ladder line. And an old MFJ-941C manual tuner because the internal flex autotuner can't handle this antenna. The birdies get much smaller or even disappear on most bands when I fully “detune” the antenna with the manual tuner. But when tuned, there are tremendous spikes in every band as shown in the photos below.
One problem may be that I live in an apartment and cannot connect any RF/AC ground to the radio. The switching power supply is grounded through the AC wall plug, but nothing else so far.
If you'd be so kind, take a look at the screenshots below and let me know your thoughts. Some bands it's less obvious than below, but this pattern is visible to a greater or lesser degree on every band once that band is tuned.
Thanks! Randy Steffens
Someone from Flex, either Tim or Dudley, once told me: “ The great thing about the SDR is that you can see everything on the band. The bad thing is that you can see EVERYTHING on the band — even all the crud that you never noticed on a legacy rig. “
You will find that you now can see exactly why electronic pollution is a big issue for a lot of folks!
1) Cannot speak to the integrity of the MFJ PS -- Powerx gets superb reviews -- but consider swapping it out with a loaner PS to see if that's your problem. Switching power supplies are often the culprit.
2) Pay close attention to every cable in and out of your Flex, especially the cable delivering 12VDC to your Flex. If you're using black-red zip line with Anderson Power poles (which are great for certain applications), know that the zip line is very susceptible to RFI -- it's like a little antenna just scooping up RF and delivering it to the radio. Solution: use SHIELDED twisted line cable which you could still use with Anderson Power Poles if you want. The people who strung the first telephone lines learned this lesson: twisted cable pair discourages RFI. Shielding with all cables recommended.
3) You could try the MFJ AC line filter, https://www.mfjenterprises.com/Product.php?productid=MFJ-1164B -- but be aware you really need an Earth ground to make it 100% effective. I have two
4) Buy a ton of ferrite beads. Clamp-ons work well. Use them on every cable -- coax, audio, CAT6/7.
5) On CAT cable, in my system RFI hunt, I discovered one of the nosiest devices near my Flex was my D-Link switch which manages a dozen devices within 3-feet of the radio. So this noise-maker had 15 CAT6 cables just radiating noise. I changed every CAT6 cable to CAT7 which is heavily shielded CAT6, and added some clamp on ferrite to many of the cables especially those close to the Flex. Solved that noise.
6) One of the biggest noise makers around my Flex was the LG monitor. I love LG. There's a 4K 55-incher in my living room. But, with the Flex, the LG used a wall-wart switching power supply with an unusual 24VDC output that produced very heavy RFI near the Flex, so I could not add it to my highly filtered 12VDC West Mountain Radio Rig Runner -- http://www.westmountainradio.com/rigrunner.php -- powered by a Powerwerx PS. So I switched to a Samsung which had a more standard 12VDC system, dumped the Samsung wall-wart, and connected TWISTED PAIR and SHIELDED cable to the RIGrunner/Powerx. Noise solved. In fact, I run two monitors with the FLEX 6500. Gaming monitors -- very fast.
7) A common RF sniffing tool is an aircraft band radio which is AM roughly 108-130 MHz. Squelch it wide open and go hunting around your apartment. I had a Yaesu HT that had aircraft band. It's a real eye opener what makes RF noise.
8) And finally, look for obvious things like touch lamps made in China which are not Part 15 approved. Huge noise makers. Others: old plasma TVs, fluorescent lights, fish tank motors, etc. Someone once traced a ton of RF to an old coffee maker with an arcing connection to the heating element! Brought down the entire neighborhood.
Good luck. Any of these steps may help reduce that noise for you. Been there. Conquered it. 73s.
David Ahrendts, KK6DA, Los Angeles
But now another smaller repetitive widespread spike is evident, it's approx. every 60 kilohertz - and is especially obvious from about 14-26 megahertz.
If I zoom in on the spike, its obvious that each spike is made up of about 5 smaller spikes close together. See the photos below.
I switch off all the breakers in my house except the one powering the radio, and it's still there. Also, it's not intermittent - it's there all day, and all times of the day.
Anyone have ideas about what might be causing this?
Here are a couple samples of the signal I'm seeing scattered around different bands.
Here are two, close-up zoomed views of one of those signals.
The first step is normally to determine if in-house or not by battery power and switching off the whole house, or keeping the shack AC powered up. Don't rule out things like appliances which have variable speed motors.
I would never have found it if I had not not turned off all AC power to the Shack. The important thing is to know one way or the other if the source of the noise is coming from your house or not.
Good luck. Winston
I ran the unit off a 12V battery in my yard, outside the house, and with all the breakers in the house switched off. I see exactly the same interference, at exactly the same frequencies.
So It's definitely coming from somewhere outside of my house...
I have an RTL-SDR which is capable of receiving on the HF bands. I guess I just need to hook it up to a small directional antenna sensitive at HF frequencies and start sleuthing?