Nighttime DX on FM and TV

[Gregg.]

We know how day vs. night conditions affect the AM dial. But most people think that doesn't apply to FM or TV signals. My family owned a lakeside cottage 100 miles north of Boston for many years. And I was always impressed with Boston FM and TV reception after dark.

Being at lakeside, our elevation wasn't very high. But I reliably was able to get several Boston FM stations at night, just using the antenna on my AM/FM/cassette box. When Howard Stern was on 104.1 WBCN, airing him from 8pm to 12am, I could pick it up reliably most nights. Luckily there was no nearby NH or Maine station nearby on 103.9 or 104.3. This was also true of some other Boston FMs, reliable at night, non-existent by day.

Boston TV stations were not as easy to get. We had a large TV antenna on the roof with an electric rotator, so we could point it right at Boston. Some nights we could pick up a couple of Boston TV stations, some nights none. But some nights, all the Boston stations would come in plus a couple from Providence, 150 miles away. And this was true in both analog and digital TV days.

We know that AM signals bounce off the ionosphere. But what about FM and TV? What makes those broadcasts carry farther at night?

 

[SomeRadioGuy]

We know how day vs. night conditions affect the AM dial. But most people think that doesn't apply to FM or TV signals. My family owned a lakeside cottage 100 miles north of Boston for many years. And I was always impressed with Boston FM and TV reception after dark.

Being at lakeside, our elevation wasn't very high. But I reliably was able to get several Boston FM stations at night, just using the antenna on my AM/FM/cassette box. When Howard Stern was on 104.1 WBCN, airing him from 8pm to 12am, I could pick it up reliably most nights. Luckily there was no nearby NH or Maine station nearby on 103.9 or 104.3. This was also true of some other Boston FMs, reliable at night, non-existent by day.

Boston TV stations were not as easy to get. We had a large TV antenna on the roof with an electric rotator, so we could point it right at Boston. Some nights we could pick up a couple of Boston TV stations, some nights none. But some nights, all the Boston stations would come in plus a couple from Providence, 150 miles away. And this was true in both analog and digital TV days.

We know that AM signals bounce off the ionosphere. But what about FM and TV? What makes those broadcasts carry farther at night?

AM signals bounce off the ionosphere because at night a layer that attenuates them and keeps them from bouncing disappears

FM and TV signals are carried farther not because of that but because of weather .. its not an exact science.. but it often has to do with temperature in versions. Sometimes clouds play into it. .and sometimes big storms do.. when I was in PA.. one day i had a bunch of FM signals from Nebraska and as the big big big thunderstorms and rain started moving east, so did what I was logging.

 

[Gregg.]

That's happened at the cottage too. One day, TV stations from Memphis and Kansas City were coming in for a time. We weren't having a storm then but there was a line of thunderstorms around Ohio.

But this is something different. It's not weather-related because those Boston stations come in almost every night. Some nights stronger, some nights not at all. But I'd say five out of seven nights for Boston TV and virtually every night for WBCN (now WWBX). Summer and winter. So something else is causing FM and TV signals to carry after sunset. Sometimes, it would last until an hour or two after sunrise, then they'd fade to nothing.

 

[kevtronics]

What you're experiencing is tropospheric ducting:

Tropospheric propagation - Wikipedia

en.wikipedia.org

At sunset the upper air cools, as does the surface temperature, but at different rates. This produces a boundary or temperature gradient, which allows an inversion level to form -- a similar effect occurs at sunrise. The inversion is capable of allowing very high frequency (VHF) and UHF signal propagation well beyond the normal radio horizon distance.

 

[gr8oldies]

That's happened at the cottage too. One day, TV stations from Memphis and Kansas City were coming in for a time. We weren't having a storm then but there was a line of thunderstorms around Ohio.

But this is something different. It's not weather-related because those Boston stations come in almost every night. Some nights stronger, some nights not at all. But I'd say five out of seven nights for Boston TV and virtually every night for WBCN (now WWBX). Summer and winter. So something else is causing FM and TV signals to carry after sunset. Sometimes, it would last until an hour or two after sunrise, then they'd fade to nothing.

It's not the same phenomenon as medium wave. There is usually cooling in the evening most places and that may create enough of an inversion layer to enhance regional reception

 

[ZantennaG1]

It sounds like you was close to the ocean, so you can get tropo off of that, especially at night. Not to mention that inversions in the evening and morning causes stations to come in from further.

Tropospheric DX Modes

 

[cyberdad]

My unscientific observation and experience seems to point to normal FM and TV propagation typically being at least slightly better around sunrise and sunset. But also subject to broad variances. By 'normal, I mean absent tropo or e-skip events.

 

[tvnut]

The evening inversion in the summer of 1969 or so allowed me to watch the WTMJ 4 Milwaukee late night lineup most every night from some 120 miles away in the southwest suburbs of Chicago. A local talk show following Tonight, and I think a movie after that. It went on for weeks.

 

[cyberdad]

The evening inversion in the summer of 1969 or so allowed me to watch the WTMJ 4 Milwaukee late night lineup most every night from some 120 miles away in the southwest suburbs of Chicago. A local talk show following Tonight, and I think a movie after that. It went on for weeks.

As I posted not long ago in another thread, growing up in Wauconda (12 miles east of where I live now), WTTW. Public TV Chicago Channel 11 was off on Saturdays until the late '60s. The result of that was WLUK-TV from Green Bay often coming through. Distance was roughly 140 miles.

 

[KeithE4]

As I posted not long ago in another thread, growing up in Wauconda (12 miles east of where I live now), WTTW. Public TV Chicago Channel 11 was off on Saturdays until the late '60s. The result of that was WLUK-TV from Green Bay often coming through. Distance was roughly 140 miles.

Until it blew down in a winter storm, and my neighborhood was wired for cable a few months later, I had a big antenna with a rotator and preamp when I lived in Wauconda. This was late 1983 and early '84. All three Green Bay VHFs were snowy but viewable when I turned the antenna north. The Chicago VHFs were almost completely nulled out when I did that, save for Channel 7.

 

[Schroedingers Cat]

I used to hear more FM stations at Night after other stations used to sign off at 10, 11, 12 Midnight, etc. After about 1980, that changed, with more stations on each frequency, and 24 hour operation for many more stations. Sometimes, there were dominant stations that were quite strong but captured by a closer stronger signal. As the stations signed off, other solid signals would capture. Same with TV stations that used to sign off. When there were tropospheric events, some 24 hour Class A stations were heard 200 miles away very clearly, even on a telecoping whip antenna on a good receiver.

 

[Harvey_Dogg]

My TV antenna is 80 feet up on a tower. But my rotor is stuck. Darn it! So, I can't get the PBS station 30 miles away. But I can get the PBS station that's close to 100 miles away.

 

[Harvey_Dogg]

STL's that operate at 950 MHz can be received at considerable distances when tropospheric conditions are right. I received WKRQ in Cincinnati's studio transmitter link at 200 miles out. They were only putting out a couple Watts in my direction.

 

[gar hi]

When I grew up in south Jersey, the New York TV stations were usually better many nights and early mornings and that happened mostly in spring and summer, not much in fall and winter.

For distances around 100 miles or less, I believe the reason is tropospheric enhancement which is different from ducting.

And sometimes it would be the Baltimore stations instead of New York.

 

[r388yh]

STL's that operate at 950 MHz can be received at considerable distances when tropospheric conditions are right. I received WKRQ in Cincinnati's studio transmitter link at 200 miles out. They were only putting out a couple Watts in my direction.

Cool! What receiver and antenna did you use? Do you often tune around up that high looking for STLs?

 

[gr8oldies]

STL's that operate at 950 MHz can be received at considerable distances when tropospheric conditions are right. I received WKRQ in Cincinnati's studio transmitter link at 200 miles out. They were only putting out a couple Watts in my direction.

That's one aspect of DXing I've never done.

 

[tvnut]

As I posted not long ago in another thread, growing up in Wauconda (12 miles east of where I live now), WTTW. Public TV Chicago Channel 11 was off on Saturdays until the late '60s. The result of that was WLUK-TV from Green Bay often coming through. Distance was roughly 140 miles.

WTTW was also off on Sundays until 5 p.m. or so into the early 1970s. So when CBS was forced to black out a Black Hawks home game, we would go to my grandmother's house, which had a better antenna than ours, and watch the Hawks with a fuzzy-to-good picture on Milwaukee's WISN 12, then a CBS affiliate.

 

[Schroedingers Cat]

Back in 1970, both WLS-TV and WTTW were 316 kW ERP. I got them once in Genesee County, MI in early July during a very strong tropospheric event. WTTW was very clear, because WTOL was much weaker and easier to null. WLS-TV, which was probably just as strong but had cochannel interference from WXYZ-TV, which was 42 miles away. WGN-TV was 112 kW, and was noticeably weaker. WMAQ-TV and WBBM-TV were weaker still, but also seen.