Notch or Bandpass Filter?

[chrissim]

As I anticipate the arrival of upgraded gear, I have one thing left to do: solve the S9++ noise issue I have confronted for the past few months. I have posted here about this before, and since then I have made some progress.

The electric company surveyed the area (these guys spent a considerable amount of time trying to solve the problem) and came to two possible conclusions. I am either plagued by an open shield from the cable company, or it's a high def television broadcast antenna spitting out hash.

Indeed, there is some type of antenna on a mountain top 11 miles away which emits a high def television signal. The electric co. guys could hear it with their antennas.

My cable company hasn't much of a clue, but they did find a leak close to my house, which they are supposedly in the process of repairing.

The recommended solution for the potential interference caused by the hi def broadcast antenna is a notch or bandpass filter. The engineer from the electric company suggested a notch filter in-line with the coax. I have no experience with such a device. Any suggestions would be appreciated.

For reference, the interference sounds like static (no electrical noise present-such as arcing), but at the 10 over 9 level. It appears on 20 and 40 meters.

Thanks in advance!

 

[nanZor]

If you can't find / fix the offending source, you may want to look into the MFJ 1026 noise canceller. It uses phase-cancellation to reduce / kill the noise. For best results, this means using an external dedicated "noise antenna", or in your case since it is so bad, you *may* be able to get by with just the included little whip - but that is rare for most.

The noise antenna doesn't have to be fancy - just enough to provide a good strong signal from the noise, and then you tune it out with the 1026 phase cancellation.

Another option which I had to revert to, was to go vertical believe it or not. If you have a receiver which you can walk around with, the objective is to find a quiet location on the property where you can successfully plant a small vertical. Sometimes just two or three feet in either direction can put you into a quiet enough zone in which to plant one. It may not be the most ideal, especially if that location is not radial-friendly, but it will keep your ears from bleeding and keep you on the air. Small mobile verticals, if done properly, can be satisfactory on a stationary basis when planted in between noise nodes.

Many don't even consider this option as they assume that all noise is vertical, yet this is exactly what one would do with an active rx antenna, typically vertical, and place it in the quietest location after some searching/listening. Something like a Yaesu FT817 makes this easy. Once you find that sweet-spot, then a larger loaded vertical may just work.

 

[chrissim]

Thanks hertz. I thought about the MFJ 1026, and unlike many, I have never had any problems with their products. I just hope it works on this type of interference.

Thank you for the suggestion. I'll call DX Engineering today.

 

[nanZor]

The standard MFJ rules apply - open case and inspect first!

If you do pick one up, don't move the internal jumpers until you read the manual and find out which setting fits your configuration.

It can take a little finesse to get the knob settings right - one can't whip them around too fast otherwise you'll zip in and out of the phase null without knowing it. See some online videos of it in action against plasma tv's.

Another alternative with a bit less twiddling is the Timewave ANC-4, although I have no personal experience with that.

 

[chrissim]

Unfortunately, after discussing the issue with DX Engineering, they seem to believe that the MFJ 1026 won't work on the hash I am receiving. It's more for pulse type noise. In fact, the rep I spoke with didn't think any type of filter would work either, considering how wide band the hash is. From 160 to 40 meters, it's anywhere from S9 to 10 over.

 

[aaron315]

Unfortunately, after discussing the issue with DX Engineering, they seem to believe that the MFJ 1026 won't work on the hash I am receiving. It's more for pulse type noise. In fact, the rep I spoke with didn't think any type of filter would work either, considering how wide band the hash is. From 160 to 40 meters, it's anywhere from S9 to 10 over.

Are you sure that the interfering signal is not coming from an electronic or electrical device in your home? It's a process of elimination and your target device could be anything. Thermostat, washer or dryer, furnace control board, doorbell power supply, bad cfl, television, computer, switching power supply, bad cell phone charger, wifi router, cable modem, and the list goes on.

How to eliminate devices in your home? Well. Here is how I would go about it. If the hf radio can be battery powered then connect a battery. Turn off every circuit breaker to the house. Is the noise still there? If the interfering noise is still there then you're done as its not coming from the house. If the interfering signal disappears then turn the breakers on one by one until the noise reappears. Once you identify the circuit the offending device is on then start identifying devices on that circuit and eliminate them one by one until the noise is gone.

 

[AK9R]

The standard MFJ rules apply - open case and inspect first!

No, shake the device and listen for solder balls and loose parts rattling inside the case. Then open the case and inspect. And, make sure your inspection includes looking carefully for solder bridges.

 

[chrissim]

Before the guys from the electric co. came by, I turned the power off at the mains and ran the radio battery powered. There's nothing in this house that is causing this problem. Sure, there are a few things I can improve, but it seems to be a relatively quite house. The noise is most definitely being emitted from an outside source. On 160 meters, it's actually 20 over. Imagine?

Often, I can turn on the transceiver and I'll have an S3 noise level, then within 15 seconds, it rises to S9 and continues to do so until it reaches it's resting spot, about 10 over on average. Regardless, it's 24 hours a day - constant.

I hoped it was the transceiver, but I've connected the antennas to two other receivers I have and same thing. I've also tried different antennas from a G5RV to a resonant dipole cut for the bands.

I have a hex beam en route and it should be here by the weekend. I hope between the new antenna, new transceiver, new coax, and new everything else that it somehow magically fixes the problem, but i know better.

Thanks for the replies.

 

[WA0CBW]

Just because you killed the power to everything doesn't mean everything has been shut off. I came across a defective remote control (UHF) that was causing interference on the HF bands. It had an internal battery and as soon as I removed the battery the interference went away. I have also found UPS's that caused interference. Again I had to pull the battery to completely shut off the device. I once found a "sonic" jewelry cleaner that was battery operated that caused interference even when turned off. Can you take the radio mobile? If you drive several miles away from your house do you still hear the noise? That might help you determine if the noise is being generated in or around your house or neighborhood..

 

[chrissim]

The process that the electric co. guys went through was exhaustive. The first guy came out and couldn't find anything in the home. He wasn't convinced so he called a guy in from another city. Although the additional person was not a ham, he is an avid shortwave/utility listener. He knows his job and I have confidence in him.

He searched every crevice of the house with different specialized sniffers. He identified one or two things and we disabled them and doing so made no difference.

They heard strong hash up the road as well as a strong broadcast signal, as I mentioned in a previous post. The HD signal being emitted from a mountain 11 miles away, according to them, is spitting out some type of hash. See, the most difficult thing to explain is that it's not your typical garden variety electrical noise. No arcing sound or similar. Tune to an unused frequency and listen to the static. Ordinarily you should hear no more than perhaps an S3 (some have S0 - S1). Mine is that static sound amplified 10 over 9 or even 20 over. Washes out nearly everything on 160 through 40. 20 meters is S7, 17 and 15 meters is S5, and 10 meters a comfortable S3. Nearly identical readings on various other receivers. All antennas are resonant dipoles with the exception of an OCF, which pulls the same noise in on the same bands.

Thanks again for the input.

 

[w2xq]

Wirelessly posted (Moto Droid Bionic: Mozilla/5.0 (Linux; U; Android 4.1.2; en-us; DROID BIONIC Build/9.8.2O-72_VZW-22) AppleWebKit/534.30 (KHTML, like Gecko) Version/4.0 Mobile Safari/534.30)

if you are a member of the ARRL you might be able to get someone interested in helping you. If other hams in your area are also receiving "hash" from that suspect tower at that distance, I would think the local FCC office may be interested. Are you a member of an area hsm club? Many voices may carry more.weight. Unfortunately a noise problem can be tough to solve.

 

[prcguy]

I can't imagine an HD TV transmitter generating or causing interference to the HF bands. You can get an Intermod mix from a TV station and another transmitter or two on the same mountain but I can't see that ending up in the HF bands either.

Corrosion on a tower near a high power transmitter can rectify signals and create all sorts of signals, its basically Intermod mixes. If the TV station is part of the problem you should see the characteristic profile of a 6MHz wide digital signal raising out of the noise floor with a spectrum analyzer.

I would think you could pinpoint or at least get an idea of the direction or location of the interference using a spectrum analyzer and directional HF antenna like a medium size loop with preamp. Do you know anyone who has a spectrum analyzer? I have everything needed to do the job, where are you located?
prcguy

 

[chrissim]

I'm in South Carolina. The guys from the electric co. had a nifty portable spectrum analyzer and directional antennas. I am a member of the ARRL and have considered contacting someone there for advice. I'm certain this isn't a typical scenario where unplugging something, wrapping wires around ferrite cores, or replacing batteries is going to help. This is a huge and robust source.

 

[nanZor]

Unfortunately, after discussing the issue with DX Engineering, they seem to believe that the MFJ 1026 won't work on the hash I am receiving. It's more for pulse type noise......

That's unfortunate that they say that, since this is basically utilizing a phase-array technique, and not any sort of noise-blanking. While this technique is used mostly for noise control in the MFJ, it can also be used in a normal fashion for phase-array directional control of other antennas if one wanted to do that.

It does not differentiate between pulse-type noise, nor hash - nor does it know the difference. All it does is phase-out offending signals by utilizing two antennas.

You might be interested in this writeup:
MFJ-1025/1026

A bad analogy would be similar to using a rotatable loop, but instead of rotating the antenna mechanically, it does so by phasing two antennas to provide the directional control. Quite slick.

 

[chrissim]

hertz:

I watched some videos on youtube that gave a fair representation of the 1026. It does look promising. I'd be using a KIO hexbeam. The plan was to take down the five dipoles I have now and replace them with the hex. I assume I could leave up the 40 meter dipole (that's the 10 over offender) and likely use that as the receiving antenna. It would be about 20 or so feet away from the hex. What do you think about that?

Thanks for all the replies. I feel like I'm making progress.

 

[Cataddict]

I see you've tried multiple receivers. Good.

Remember if you end up with a bandpass or notch filter, you need one capable of handling your transmitter power.

It would be really good to find the source of interference rather than to brute force filter, if that would even work. Is there anybody you can borrow some tunable filters from just to try? For just receive, they would not have to handle any power. I'm fortunate that I can borrow some things like this from where I worked.

It sounds like the interference is 24/7? In a way that's good, because you can try to find it any time. Intermittent sources are difficult.

In the absence of a spectrum analyzer and portable directional antennas, you can try finding it yourself. If you said, I missed it, but can you go mobile with your reciever? Hopefully, and with an S-meter. Kludge up an antenna on your car - something that receives the noise at your house. Something close to omni-directional would be best for driving around it you don't have a portable directional antenna that you know where the lobes are. (example: using my 2m beam on 440, the front of the antenna is NOT the direction of strongest signal. You can find models of examples like this). With that strong of signal, you also need to have a way to attenuate the signal down as you get closer. Selecting AM mode (not SSB) gives me the best results.

This is a crude way of finding things like this, and can be time consuming, but can work. I've had intermittant noise at my house for a couple of weeks now (VHF) and so far I've identified I think 9 noise sources within two blocks of me - all power line. They have fixed the hottest one on my property and will scan the rest of the neighborhood in a week or so.

So you may have multiple hot spots. There are a lot of thngs that can produce noise - power lines (usually lightning arrestors), large well pumps, communications centers, etc.

I don't think it would be as broad as what you have, but intermod can be real troublesome. I live down in a deep hole, and the hills around me are real close, and are full of power lines, cell towers, and public service (fire/police/commercial) repeaters. The number of 2 meter frequencies being trashed by intermod seems to grow monthly, and the "noise" is very strong. It sounds like a bunch of digital signals on top of each other. I need to track them down next.

I had an intermittent noise problem last year that was S9+, sounded exactly like power line noise, but was band limited to about 140 - 150 MHz. Weird. I started tracking it, using an HT I found a spot on the street behind me with no house or pole on it where the HT went nuts. As soon as I started walking around to REALLY pin-point it, it stopped. And hasn't came back. Go figure.

Good luck. If you can find it, it may be something that the "source" may be legally required to fix. I feel your pain.

 

[W3DMV]

Any chance you could record the noise and post it for us to hear.
Some types of interference have very distinctive sounds and there is
several people on here with a very good ears..... Good luck....

 

[chrissim]

Recording the noise? That's a great idea. I'll do that in the morning and post it. Thanks for the suggestion.

 

[chrissim]

Hopefully this works. It's a 20 second recording of the 9++ hash on 40. What do you think?

40 meter noise

 

[W3DMV]

Recording is fine. Used I-Tunes player.. Kept re-running it for about
30 minutes and to my ear, sounds like normal back ground low level
power grid noise and atmospheric noise.. About 6 guys in the local
radio club here have listened to the recording and agree with me, but you
said it was very strong (+10db). On the recording it doesn't sound
that strong.... What mode is your receiver in and what receiver ?