One of my local AM stations, 1380 WDLW/Lorain, OH bleeds over onto 1450 WLEC (which puts out a decent signal during the day into Lorain, about 25 miles away as the crow flies) whenever I am within about a mile of WDLW's transmitter site. However, I don't notice this interference on 1420 (which is semi-local WHK), 1430, 1440, neither of which have locals here. Also the bleedover occurs on 1310 much like it does on 1450 but not on 1320 (local WOBL) or 1330, 1340 (the latter of which is semi-local WNCO). Curious to why there is always bleedover at +/- 70kHz but not at +/- 40, 50, or 60 kHz? I have observed this in 2 different car radios.
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AM station bleedover at +/- 70 kHz
- Thread starter Buckeyes2001
- Start date
Buckeyes2001 said:
Have you tried another radio, such as a portable? Does the bleedover fade as you get further away from the WDLW tower? Does it happen at night, when their power is reduced? Your car radios could just be overloading due to too much signal from WDLW (imagine if they ran 5000 instead of 500 watts). It can happen even to good radios if you're close enough.
Sounds like they may have an old Harris PDM transmitter which uses a 70kHz square wave in their modulation scheme.
If so, the 70kHz filter in the transmitter isn't working.
If so, the 70kHz filter in the transmitter isn't working.
KeithE4 said:
I haven't tried another radio as of yet to check this out. The bleedover does fade away as I get further away from WDLW's tower. The closer I get to it, the more severe the bleedover until it completely takes over 1450 and 1310 from within about 1,000 feet of the site. Haven't noticed any interference at night except from within about 1,000 feet. Otherwise 1450 sounds like the usual graveyard mush and 1310 sounds normal for nighttime. The thing is, I haven't noticed any other station bleed over at +/- 70 kHz from being very close to their transmitter tower(s).
I've lost count of how many times I've had a station bleeding over the *ENTIRE* AM band. Even on my DSP radio (which is supposed to have excellent selectivity) I've had an AM station bleed well up to 20+ MHz. A couple examples:
http://www.youtube.com/watch?v=fEMLcEqCu3E
http://www.youtube.com/watch?v=kEIU3mP5f38
http://www.youtube.com/watch?v=fEMLcEqCu3E
http://www.youtube.com/watch?v=kEIU3mP5f38
1450-1380=70 kHz. It could also be a 2A-B or 2B-A third order intermodulation product.
I used to get a signal on 1670 with WFNT 1470 modulation as I passed the WWCK 1570 tower next to I-69 in Flint. That one was radiated, from transmitter intermod. I also used to get signals from WTRX 1330 and WFNT 1470 on 1190 and 1610, from sites about 1/2 mile apart. That was usually receiver induced, though occasionally radiated when filters were not properly tuned.
I used to get a signal on 1670 with WFNT 1470 modulation as I passed the WWCK 1570 tower next to I-69 in Flint. That one was radiated, from transmitter intermod. I also used to get signals from WTRX 1330 and WFNT 1470 on 1190 and 1610, from sites about 1/2 mile apart. That was usually receiver induced, though occasionally radiated when filters were not properly tuned.
pianoplayer88key said:
You're always way to close to AM towers, and sticking the radios next to vertically oriented metal objects, though. With a good strong 100 mV/m signal, I rarely get overload blanketing more than 100-150 kHz from AMs, and on FM, it's only all over the band when a tropo brings in a grandfathered superpowered station 10.6 or 10.8 MHz away.
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