Massive mediumwave interference problem at Beerus HQ.

[Beerus Maximus]

I am soliciting feedback and thoughts on a major problem I am having with an AM station causing me interference.

The station in question is approximately 6 miles (straight line) away from me and also, most of that straight line distance is over a salt water path. I never had a problem with this station, or any other AM radio station causing me interference, until January of this year.

In January, they were granted a construction permit to move from 30kw to 50kw. The problem manifests itself as carriers with audio all over HF and spaced 10, 20 or 30 KHz apart. Some of the carriers are S9, with clearly audible audio that is the same as that on the AM station. On some of the other carriers, I get some kind of mixing products and thus hear OTHER AM stations, such as WBZ (1030 KHz).

The interference lasted a few weeks in January, and then disappeared. It has resumed with a vengeance in the last week or so and seriously compromises my enjoyment of the hobby.

Some questions.

• How do I accurately characterize this problem? Is it front end overload? Or is this likely to be some kind of spurs from a poorly operating transmission system?
• Being 6 miles from this station, is it reasonable to expect this type of overload or interference?
• If this is not a reasonable expectation, would you go straight to the engineering staff of this station, or the FCC?
• Might my antennas be part of the problem? I have dipoles fed with 450 ohm open line, going to a 4:1 balun, and then a short run of coax. Would a different antenna possibly fix this?

Your thoughts and experiences with this type of problem are appreciated!

Edit: I tested with a 17m coax fed vertical and the interference is still there, which kind of eliminates my antenna system.

[Pigmeat]

Have they erected any new towers near/at the transmitter site, broadcast or other? The reason I'm asking is I had a similar problem with a local AM station when it reactivated a few years back. The problem turned out to be a cell tower erected in the years the station was dark.

The broadcaster near the top of the old MW band. The cell tower was the right height and distance away to act as a reflector. Anything to the WNW of the station's stick was getting hammered. I had the luck to be in that sweet spot.

Luckily they were still testing and discovered to their amazement that the cellphone tower reflector combined with their mighty 500 watts was interfering with both MW and ham traffic hundreds of miles to the west of them after dark. They tried an auxillary transmitter/antenna site a few miles away and the problem went away.

I switched to BOG antennas during that period. Oddly there was a kicker to that. In this case you couldn't just roll the wire onto the lawn. If the runs of wire were more than 4-6 inches above the soil itself, the noise levels shot up drastically.

I had some success with broomstick type antennas in the windows of my radio room then. You have to dick around with them when setting them up,so the polarity of the stick nulls out the noise as much as possible.

Good luck.

[Beerus Maximus]

Pigmeat, thanks for the comments. The station was sold and changed ownership; the new owners immediately got a construction permit for 50kw (from 30kw) so presumably some changes were made. Now I hear Caribbean programming up and down HF. It's a single 100 foot stick, so non-directional, according to the construction permit. I don't believe this is a change from when they were running 30kw.

[ChrisLobde]

Hi Beerus,
I feel your pain, I really do. Sometimes, when I vacation out at our island cottage, off Salem, I have similar problems with WBZ. Par Electronics makes this Hi Pass Filter in a little aluminum box, called "Broadcast Eliminate - Hi Pass Filter" part #BCST-HPF. Using that it eliminated my
problems with WBZ. Sometimes, although not recently, I've had issues with WRKO 680 kHz. Their transmitter  is about 7 miles from here, and this filter did the trick as well. So, you might want to consider buying one of these.
The station could very well have an issue with their grounding system. I remember when someone stole WILD's grounding wire, they had images all over the place.  Par's phone # is 828-743-1338

[rdla4]

How does the audio sound on these spurs? Is it "clean" sounding? Or distorted?

If "clean", I would lean toward rcvr overload as a possibility, if distorted, I would be inclined to look at something in or near their transmitter site.

Also does this QRM remain constant? or does its signal strength tend to "jump around" a lot?

What frequency are they on? I want to look a see if they are diplexed with anyone.

Nevermind, I see who they are on 1570kHz.They are not diplexed.

Edit 2. I see they were granted a CP for 50kW, but I cannot see that they have filed a license to cover for the 50kW day operation. In theory, they should still be running 30kW during the day. Going way out on a limb, my suspicion turns toward their top loading....using the top sections of the top guy wires to make that short tower look electrically taller. There may be arcing there, or some diode action going on, depending on how they have attached the top loading.

Diode action on anything near that site may cause an issue. Including that ball park thru the woods~

They have to do an NRSC proof on that station once a year---unfortunately---that does not have to be in the public file, so it may be tough to get a peak that that document. Any idea who does contract engineering for them?

[staticlistener]

Certifying engineer's contact info is at the bottom of the page:
http://fccinfo.com/CMDProEngine.php?sCurrentService=AM&tabSearchType=Appl&sAppIDNumber=1516234&sHours=D

[Pigmeat]

Hi Beerus,
I feel your pain, I really do. Sometimes, when I vacation out at our island cottage, off Salem, I have similar problems with WBZ. Par Electronics makes this Hi Pass Filter in a little aluminum box, called "Broadcast Eliminate - Hi Pass Filter" part #BCST-HPF. Using that it eliminated my
problems with WBZ. Sometimes, although not recently, I've had issues with WRKO 680 kHz. Their transmitter  is about 7 miles from here, and this filter did the trick as well. So, you might want to consider buying one of these.
The station could very well have an issue with their grounding system. I remember when someone stole WILD's grounding wire, they had images all over the place.  Par's phone # is 828-743-1338

It's interesting you mention the high pass filter Chris. When I was having the noise issues mentioned above,one of the few tricks that worked was using a MFJ random wire tuner in line w/ the receiver. I could tune out most of the images that way. The harmonics stayed nice and loud,of course,but I learned to live with it.

[Beerus Maximus]

How does the audio sound on these spurs? Is it "clean" sounding? Or distorted? Also does this QRM remain constant? or does its signal strength tend to "jump around" a lot?

It's not clean sounding. It's very muffled on the random spurs. On the harmonics (like 4710 KHz) its a little cleaner sounding but still quite muffled.

Chris: thanks for the information about the PAR filter. I'll keep that as an option. I'd really like this to just stop, however. I have never had this problem... never ANY mediumwave products, in the 7 years I have been at this location. And then BOOM, one day in January it starts.

Update: I took a portable (Tecsun PL-380) with me to a spot about 3 miles from my shack. The same stuff is notable there. Very loud odd harmonics of 1570 KHz (e.g. 4710 KHz) and spurs and images everywhere else. Granted not quite as strong as on my shack rigs, but those are probably much more sensitive and have larger antennas. I know, now, that it's not a problem specific to my shack. Still, a discouraging situation. Ideas on how to proceed?

[redhat]

A broadcast station has an obligation to correct any interference caused by a change to its licensed facilities for a period of one year from the filing of its license to cover its construction permit.  Ask nicely to speak with a representative of the engineering department and explain your observed changes and what you have tried to remedy the situation.  They should assist you in remediating the problem.  If they don't want to help, you can always file an interference complaint with the FCC referencing their license changes.  As others have noted, there has been no license to cover filed, and thus if they are operating at 50KW per the construction permit, this must be filed for them to do so.

Do some research and see if you fall within their 1V/m contour, know as the "blanketing contour."  If so, they have to help you fix it, pursuant of CFR47 part 73.88

http://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&SID=c6b795492159c04be4712cffd92eae0d&rgn=div8&view=text&node=47:4.0.1.1.2.1.1.29&idno=47

Good luck,

+-RH

[curious george]

I also feel your pain, as I have a 5 kW station about a mile from me.  My solution was similar to Chris's but I used the Kiwa equivalent of the PAR filter (PAR wasn't making them at the time of my purchase).  I don't think they manufacture the Kiwa filter any longer, so the PAR is probably the way to go.

Also, I feed my dipoles with coax, but I use RF chokes on the feedlines, as recommended by John Bryant in this article:

http://www.dxing.info/equipment/coax_leadin_bryant.pdf

Here are some links to the PAR and Kiwa filters:

http://www.universal-radio.com/catalog/filters/4426.html

http://www.kiwa.com/bcb.html

http://www.universal-radio.com/catalog/filters/3449.html

[Tuco]

Beerus, just curious to see if there was any change? From reading your description of the problem, it sounds like it's on the broadcaster's end and they should fix it.