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Why is thing happening? KEXP+KUOW on 99.5

S

speer360

Perhaps the smarted RF heads can explain something for me.

I moved to Capitol Hill in Seattle during december. Right next to the Tower Trio on the hill hosting KUOW and KEXP among other broadcasters.

I have noted within a good half a mile or so of the tower I can hear both KEXP and KUOW combined into a single broadcast on 99.5. Multiple radios, Broken RDS even comes thru.

Is something broken or is this some RF science explanation?
 
KCGY 95.1 and KUWR 91.9 are 100kw from 2 different towers just a few dozen yards form each other, neither has filtering for each other.. and in laramie, youll get KUWR RDS and KCGY audio on 98.3
 
If you were to take the inverse, and calculate (2)90.3 - 94.9, would you hear the same phenomenon on 85.7? Provided you had a radio that could tune that frequency?

I always thought this phenomenon was nothing more than multipath reflection, or the signal overloading the radio.

Cheers to a genuinely fascinating topic that we all can learn from.
 
Perhaps a similar situation on AM here: I live very close to the daytime AM tower for KCIS AM 630, and have noticed for years that their signal combines with one from KVI AM 570 and override the signal from CBU on AM 690. On all radios, in my car and house. So it's probably not the fault of the radios. Noticed this for 20 years.
It's a different effect from having radios that spread out nearby signals too far from their main frequency. The two signals competing with CBU is noticeable to some degree for about a mile from the AM 630 transmitter site. Any ideas on what's happening with this? I'd like to know what to call it, if I were to try to contact their designated engineer to ask them to address it.
 
Goldilocks94941 said:
Perhaps a similar situation on AM here: I live very close to the daytime AM tower for KCIS AM 630, and have noticed for years that their signal combines with one from KVI AM 570 and override the signal from CBU on AM 690. On all radios, in my car and house. So it's probably not the fault of the radios. Noticed this for 20 years.
It's a different effect from having radios that spread out nearby signals too far from their main frequency. The two signals competing with CBU is noticeable to some degree for about a mile from the AM 630 transmitter site. Any ideas on what's happening with this? I'd like to know what to call it, if I were to try to contact their designated engineer to ask them to address it.
Click to expand...

mixing/re radiating spurs is what id call it.

When i was in WY, i was about 1 1/2 miles from KOWB 1290. KHAT 1210 was 1/2 mile further away from 1290

Neither had filters for each other... and there were spurs and mess all over the band... it was caused by the lack of filters and because 1290 was picking up 1210 somewhere in their transmission system and re radiating it
 
The 570 site and 630 site are at least 20 miles apart. Half of that is over salt water. With 20 miles of separation there probably was no requirement for 630 to install a filter or 570
 
I experience something similar all of the time at my place in BC. I’m probably within a few miles of almost all of the major AMs. You can scan across the dial and hear duplicates of the same signal (but on different frequencies).
 
fordranger797 said:
I experience something similar all of the time at my place in BC. I’m probably within a few miles of almost all of the major AMs. You can scan across the dial and hear duplicates of the same signal (but on different frequencies).
Click to expand...

some of them are almost that strong here

i keeeeddd i keeeedd.. not quite........ but kinda close.. lol especially 1600
 
I'm not sure if this is the same situation, but Rapid City SD is terrible. I thought that this was caused by overload as well, but potentially not. Rapid City is an interesting situation, with many high powered stations really close to town on relatively short sticks. I wonder if this is why a few of the rimshots in that market have in city translators? I remember one of my radios having the scan tripped on 99.9 with nothing there in that market, and my other radio, which has a dead spot on 98.3, being full of stuff there. I don't know how a radio like the G8 would handle that market.
 
bobdavcav said:
I'm not sure if this is the same situation, but Rapid City SD is terrible. I thought that this was caused by overload as well, but potentially not. Rapid City is an interesting situation, with many high powered stations really close to town on relatively short sticks. I wonder if this is why a few of the rimshots in that market have in city translators? I remember one of my radios having the scan tripped on 99.9 with nothing there in that market, and my other radio, which has a dead spot on 98.3, being full of stuff there. I don't know how a radio like the G8 would handle that market.
Click to expand...
Overload certainly is a factor -- intermodulation products increase with signal strength. Essentially, what happens is that when the front end of your radio receiver overloads, the amplifier circuitry in your radio becomes non-linear. And that non-linearity generates a rich assortment of harmonics for all the signals that are present at the front end. That non-linearity also turns amplifiers into mixers, which means that you'll see sum and difference products on a whole bunch of different combinations of all those harmonics that were generated.
 
TexasTom said:
Overload certainly is a factor -- intermodulation products increase with signal strength. Essentially, what happens is that when the front end of your radio receiver overloads, the amplifier circuitry in your radio becomes non-linear. And that non-linearity generates a rich assortment of harmonics for all the signals that are present at the front end. That non-linearity also turns amplifiers into mixers, which means that you'll see sum and difference products on a whole bunch of different combinations of all those harmonics that were generated.
Click to expand...
That might explain why this phenomenon is only observable on stations that transmit from the city of Seattle itself. The Cougar Mountain stations are cranked up to 100kw, but there’s probably not enough people in close enough proximity to notice anything like that. Also, I would imagine that there’s little power being directed directly down from that location.
 
Seattle is a bit of a unique case because its main transmitters are so far out of the market. I can't help but wonder what overload and harmonics are like in places like Issaquah. My sister for instance had a friend in high school who lived on Cougar Mountain. I've never actually been to her house, but I would imagine there would be harmonics all over the dial there. I also wonder about the residential areas around the towers in Portland. I suspect that those are actually not as bad since the towers are 200+ meters tall, but it certainly would be interesting to DX from there. Back to Seattle for a second, I did definitely notice that the signal of KXXO was significantly degraded coming through Issaquah on I-90 one time coming back from eastern Washington. That station tripped the scan on the car radio at the top of Snoqualmie pass and we carried it all the way home.
 
Speaking from experience, the Cougar signals in the Sky Mtn. neighborhood (on Cougar) are pretty awful. Full of multipath. I have been told the main signal goes over their heads and they are mainly getting reflections. The Tiger stations come in fine from there, at least.
 
When I lived in Queen Anne in the mid-90s, I would faintly hear 100.7 (then KIRO-FM) in the background on my landline phone. If I’m not mistaken, their transmitter at the time was atop Queen Anne Hill.
 
DrJerry said:
When I lived in Queen Anne in the mid-90s, I would faintly hear 100.7 (then KIRO-FM) in the background on my landline phone. If I’m not mistaken, their transmitter at the time was atop Queen Anne Hill.
Click to expand...
Working there was a pretty decent gig because TV Master Control engineers monitored the FM readings, etc.! They had to do it for the TV transmitter anyway.
 
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