Invasion of the AM Broadcast band

[KX5JT]

So, I had adjusted my dipole legs too tightly last week.  One leg came down and I had to get it back up in the air which I did yesterday.

NOW, I can hear KROF 960 AM the Gator on 3.890 AM nearly as strong as I hear them on 960 AM.  They are only 5 miles as the crow flies from me and a mere 95 watts at night, but nevertheless, they are being heard on 3.890 now AND I hear carriers up and down the band every 5 khz, obviously other stations in the AM BC band but not as strong so I'm really only hearing carriers and some low modulation.

Where do I look?  I'm thinking maybe where that leg is attached to the 1:1 balun (w2du type) is now an intermittent connection?  Am I on the right track?  Does this mean that I could be transmitting harmonics too?

JT

[K1ZJH]

3840 would more sense than 3890... what I would do is try a preselector on the receiver, or a second receiver and see if the problem clears. The preselector will help prove whether it is receiver overload or a mixing problem due to nonlinearities in the antenna system. If it was mixing, I'd suspect you'd hear other modulation besides that of the 960 AM station on the spurious signals.  Also, make sure all of the switching power supplies in your shack are off when doing these tests.

Pete

[k4kyv]

I had a similar problem with my beverage when a bush grew and its branches touched the wire.  It would occur right after a rain.  I clipped the branches and the problem went away.

[Pete, WA2CWA]

Lots of things you can do.
As Pete said, try a different receiver.
Try a different antenna on the receiver you were using.
Check the transmitter loading when tuning up; has it changed?
Check the SWR.
Visually inspect the connections around the balun.
Check the coax connection and connector at the balun.
If the antenna wire is insulated, check to make sure you don't have a break in the wire.
Check to make sure the antenna isn't rubbing against something now.
Report back 

[KX5JT]

Great suggestions.  Something has changed.  This didn't happen before the leg came down and I put it back up.. in fact re-soldered it there at the feed-point AND not sure if the rain has something to do with it but it MIGHT.  It did rain today.  Okay, problem is I work tomorrow night, so this may be on hold until Tuesday evening or Wednesday.

SWR is normal.  I seem to be putting a normal signal out there.

It's on more than one receiver.  Preselector might actually help but that's just dancing around the symptoms, not solving them.  I'm convinced it's up in the antenna. Post hoc ergo propter hoc

JT

[KX5JT]

 

[Pete, WA2CWA]

Re-flow the solder joints at the antenna connection.
Also check the balun case for cracks to make sure no water or little critters can get in there.
If you're feeding the balun with coax, check the connector. Over time, some contamination of the metals (white powder looking stuff) can accumulate on the inside threads which could/might play havoc with your receiving. Sort of like putting a pn junction up in the air and running coax back to your receiver.

[KD6VXI]

Ever consider that he might now just have better connections than what he had before and the antenna is now rectifying the signal?

I’m saying this because when I lived back in Tulsa and put up a new 75 meter dipole using a W2DU 1:1 balun fed with coax when I first got back on the low bands after several years I had the exact same problem. Not only did it start rectifying KVOO AM radio on 1170 at my receive end, but also on my telephones and on my neighbors phones too. The antenna legs were not touching anything and there presences was somehow rectifying it. I think there may have been some connection with the power/phone lines being just a few hundred feet away from the antenna, but I was never able to fully explain what was happening for sure.

I'll back that story up.  I had an antenna fall, I put it back up, and promptly left town for the weekend (was a kid, had to do what Mom said!, screw the radio!!!).

When  I got back in to town, I had a nastygram from my neighbor / owner of the house.  Seems someone had been sitting down at the end of the driveway (a friend, he had come to see if I was home, and not being home, figured what better to do on top of a mountain but enjoy radio) talking on their radio for a couple hours.

My landlord / neighbor had a recording of about 15 minutes.  He could hear BOTH sides of the conversation!  I immediately called John and asked about his new amp in his car!  He responded nothing on his end changed, and dismissed it as my neighbor getting a walkie talkie and recording it.

You could hear the overload in the recording equipment, funny thing...  It WASN'T an audio recording, it was RF.

Took the aluminuluminum antenna down, put up fibercrap and problem ceased to exist anymore.


--Shane

[K1ZJH]

Ever consider that he might now just have better connections than what he had before and the antenna is now rectifying the signal?

I’m saying this because when I lived back in Tulsa and put up a new 75 meter dipole using a W2DU 1:1 balun fed with coax when I first got back on the low bands after several years I had the exact same problem. Not only did it start rectifying KVOO AM radio on 1170 at my receive end, but also on my telephones and on my neighbors phones too. The antenna legs were not touching anything and there presences was somehow rectifying it. I think there may have been some connection with the power/phone lines being just a few hundred feet away from the antenna, but I was never able to fully explain what was happening for sure.

Yes, but it still involves a non linearity somewhere, either in his antenna system, or in a close by wire junction that has oxidized.  There is a very remote possibility that the problem is in the station end as well. Bad coax splice, etc. or receiver overload. That's why I suggested a preselector as one troubleshooting aid if nothing was found on the outside plant.  Being an RX problem, I'd look at the outside connections first, especially if rain was involved.   A spectrum analyzer would be ideal here.

Pete

[Steve - WB3HUZ]

Why would a "good" antenna rectify anything?

[The Slab Bacon]

If it has been a wet or rainy day, my wife swears that she hears my voice coming out of the rainspouts / downspouts when she's sitting on the front porch and I am on the big rig.   

[flintstone mop]

Why would a "good" antenna rectify anything?

OHH boy. Look out. Brian might be "watching this thread"
strange and mysterious things

fred

[flintstone mop]

If it has been a wet or rainy day, my wife swears that she hears my voice coming out of the rainspouts / downspouts when she's sitting on the front porch and I am on the big rig.   

And when I was a pirate on 6955 with a kilowatt of A.M. I heard my modulation in the metal A/C ducts in the attic!!!

Fred

[KD6VXI]

If it has been a wet or rainy day, my wife swears that she hears my voice coming out of the rainspouts / downspouts when she's sitting on the front porch and I am on the big rig.   

And when I was a pirate on 6955 with a kilowatt of A.M. I heard my modulation in the metal A/C ducts in the attic!!!

Fred

I remember about a year and a half ago my kids came RUNNING into the house.  I had been on AM with about a 200 watt carrier.

"DAD, DADDY!!  WE CAN HEAR YOU THROUGH YOUR ANTENNA!"

I had an aluminum vertical, and one of the fasteners that joined two pieces of aluminum on the matching network had come loose....  Broken, really.

It was better at night...  You actually got a light show!

Another time, kinda related, I had about 50 watts of carrier, and a neighbor with a solar water heater.  The power supply was located in a closet in her bedroom (of all places).  It had a small neon light that indicated AC power was applied and it was hot.  Well, neon LOVES RF, especially when it's overmod CB garbage signal.

Lady thought her house was haunted.  I'd be up until all hours of the night (was a kid then, during summer) babbling incessantly, not knowing it was driving her up the wall and she couldn't figure out WHY their was a ghost in her closet, much less one that had such a slanted view of things (as only a teenager could have!).

Once we found out what was happening, Mom made me go apologize.  From that point forward, ANYTHING in the neighborhood that was "unexplainable" or made TVs or radios go fuzzy was attributed to my radio. 

Incidentally, that install (neon light) is the same one that I spoke of earlier where I was out of town and a friend was bleeding from / through / whatever my antenna from his mobile.  I always chalked it up to the antenna acting like a parasitic element.  Made sense to me, anyway.  I know I had issues once with a mobile install and MASSIVE amounts of noise.  Grounding the tailpipe at both ends and in the middle eliminated the noise.  It was a quarter wavelength at 10 meters....  Incidentally, my RX and TX strength increased at the same time, close to an S Unit.

--Shane

[k4kyv]

Reminds me of a story from Otis, K5SWK in Houston.  His AM kilowatt was getting into the superstitious Mexican lady next door's electric stove oven.  She came knocking on his door at 2 AM one one night while he was on the air.  She didn't know that the radio had anything to do with it.  She was frightened because she heard voices coming out of her oven and thought there was an evil spirit in her kitchen stove.

[k4kyv]

John, WA5BXO told me he is still alive, but doesn't get on the air any more.  I think his vision and hearing are failing and he doesn't feel like working on his homebrew rig, which has had some minor crap-out, but he doesn't want anyone else to work on it for him.

[KX5JT]

Reminds me of a story from Otis, K5SWK in Houston.  His AM kilowatt was getting into the superstitious Mexican lady next door's electric stove oven.  She came knocking on his door at 2 AM one one night while he was on the air.  She didn't know that the radio had anything to do with it.  She was frightened because she heard voices coming out of her oven and thought there was an evil spirit in her kitchen stove.

HAHA, That's a great story!!!  Being here in south Louisiana and many of my fellow AMers are from East Texas, I've heard a lot about Otis.  They often talk about going see him and checking on him.  He must have made a great impression and been a hell of a character.

JT

[ke7trp]

Join the club.  I have disney at 50KW north of the house. Its full scale in here. I can tune it to the third octave and hear it clearly. 

The R390A model hears this station all over the ham bands.. Especialy when I Spot tune the transmitter. It mixes loud and blows you out of your chair.

The R390 non A does not hear this nearly as bad. Now thats a real mystery to me as the A should be better.  The SX28 does not seem to care about this station much. At least where I use it.

A few years back this was a real problem for me.. But recently, I have heard this station less and less through the bands. I wonder sometimes if they Dropped the power or changed Transmitters. 

Everyone told me that more then likely some aspect of the antenna or house was causing this station to come in and rape my RXers.  Some mentioned gutters and feedlines ect..   My ZEP is not nearly as bad in this respect going through the KW matchbox. If I bypass the KW and RX directly, some portions of the band are not usable.  Of course, The Icom Pro never heard this station anywhere.. But when it came to the old rigs.. Look out!

C

[W2VW]

But does he still drink coffee?

John, WA5BXO told me he is still alive, but doesn't get on the air any more.  I think his vision and hearing are failing and he doesn't feel like working on his homebrew rig, which has had some minor crap-out, but he doesn't want anyone else to work on it for him.

[ka3zlr]

eeney beany chili beany
the spirits of the stove are
about to speak.....

Are they friendly spirits..?

[KB2WIG]

Whatt? why not just place a few chicken bones on their front doorstep?  Works for me.


klc

[KX5JT]

Just an update here about the AM BC stations being heard after the antenna repair.......

... it simply just went away after a couple days and hasn't come back....

SWR normal on the same range of 75 and 40 meters.  (It's a parallel 75/40 meter dipole)

I'm leaving well enough alone for now and will just enjoy operating unless it comes back.

John KX5JT

[K5UJ]

Sounds like it might be a wx related problem.  Did you notice any change in moisture level?  Has it been a dry spell for several days giving something time to dry out?  Or the other way around?

If we have extremely wet wx here and the ground saturates and everything outside is covered with dew I notice some weird antenna problems I can never track down because the problem goes away after a few hours and I never get close to figuring it out in time.   Then the problem goes away and does not come back for 6 or 12 months and by then I have forgotten what I did before so I have to start all over again.  It's usually in the morning and by mid-day it's gone.

[KX5JT]

Heck Rob, this is South Louisiana.... It goes from scorching hot and dry to wet for a week!  Nah, this is weird but it only happened those first couple days after the repair and we've had all manner of dry and wet days alternating... mostly wet but it has dried out a few days too.  Cautiously operating and staying vigilant for any changes, John

[KX5JT]

Hi Brian.  We've had rains from hurricane Alex and normal Gulf Coast afternoon summer thunderstorms that have inundated our area off and on since the initial problem and after this just went away it never came back whether all dried up or soaked in rain sooooo

I suppose not all things need an explanation no matter how much that KILLS ME! LOL.

John