So I live close enough to Canada to get CBC OTA on my tv. Problem is I lose signal in the evening after the sun goes down. Research indicates it's something called the digital cliff that happens when temps drop. The antenna is an older roof mounted big antenna that's over twenty years old. Should I look at a new antenna. The broadcast tower is less than 150 miles away as the crow flies.
150 miles?! I'm amazed you get any signal.
Tv antenna technology hasn't really changed, I can't imagine you seeing too much improvement with a new purchase.
Yeah, 150 miles is pretty impressive for digital tv. I would think your options are antenna with higher gain, physically higher, and/or amplified. I'm not sure I like the odds of success.
CBC is available live stream but is geofences. The work around is a VPN that closes your true location.
Gaining some altitude of the antenna would help with you being that far from the source.
You can use this as a pretty good reference to see what's possible:
https://www.tvfool.com/
We're at 1000 feet altitude on a north facing slope. I checked CBC for the location of their towers and there are two at about 90 miles from us according to TVfool.
I read something recently about antennae for long vs short wave reception. Apparently most were not designed to get the shorter wave channels, which affected getting some local channel favorites. Might be worth investigating.
If you really want to fall down the rabbit hole...
https://www.digitalhome.ca/forums/antenna-research-development.186/
Start building your own antennas,
One last question from reading your profile is there a specific type of programming you seek?
As the initial posted pointed out I'm watching CBC. Mostly for the hockey coverage. We don't have cable or satellite and I don't want either. And the NHL package has too many rules on blackouts.
VHF and UHF signals like TV go in pretty much a straight line. Since you get a regular fall-off of signal at night I suspect you're getting signal from a bit of atmospheric refraction bending the signal down to you instead of going off into space.
That makes it hard to improve so far away. A much higher antenna might work. More antenna or amplification probably won't help. The subscription may suck but it's cheaper than an antenna tower 
Canadian broadcast signals drop power at sundown. They have to legally. Many US radio and TV stations do as well, but I don't think it's regulated the same.
When the sun is up, the atmosphere is flooded with intense radiation and all kinds of interfering RF signals so broadcasts have to boost. At a prescribed time, they drop Tx power significantly. My guess is that your problem has nothing to do with temps and air density, it has to do with the channel dropping from 40kw to 22kw when they don't have to compete with the sun's radiation.
The same exact thing happens when I'm at our farm in WV. We get two channels poorly during the day and zero after dark. WDTV and WBOY both drop wattage at sundown.
Good cable from antenna to TV can make difference. If you get a new antenna, one with an antenna mounted preamp, powered through the coax, will negate any cable losses and will give you the best opportunity to grab any available signal. Height helps as well.
The FCC has a nice writeup on power reduction by broadcasters: https://www.fcc.gov/media/radio/am-stations-at-night
During the day signals on the AM band frequencies (aka MF, medium frequencies) work about like the higher VHF/UHF frequencies and travel direct from the broadcast antenna to your antenna, and otherwise out into space. That means a broadcast radius of 100-ish miles. When the sun goes down, the ionosphere changes and starts to reflect lower frequency waves. MF signals can bounce around the ionosphere (or between the earth and the ionosphere) and skip for hundreds and thousands of miles. Reducing power at night reduces the chances of AM stations interfering with stations far away.
The atmosphere is very different for the higher VHF and UHF frequencies used by FM radio and TV. The ionosphere is pretty much transparent to VHF and UHF, but those frequencies can bounce around other atmospheric layers. FM, VHF TV and UHF TV operate in distinctly different bands, with different fun atmospheric effects, almost all of which are transient.
So why regularly lose TV at night if the station doesn't change power? My bet is that there's a little bit of atmospheric refraction happening during the day - maybe a temperature inversion - that goes away at night. Not a huge change to signal propagation but when you're at the very ragged edge it doesn't take much signal loss to go from enough to digitally decode to not enough (the digital cliff).
To get past that you need more signal to the receiver. Height is always your friend with radio signals. At 1000 feet ASL on a slope you might already have a clear path between antennas.
Your big old analog TV antenna might actually be superior to a newer one if you're trying to receive on a lower channel, since the newer ones focus on the higher frequency channels. New or old, the long, arrow-like antennas are pretty directional, so you want to point it dead-nuts on to the heading for the transmitter. A good preamp up at the antenna definitely worth a try to maximize what's available. You also want to minimize losses, so the recommendation for good fresh coax is excellent. High quality RG-6 coax and decent connectors are pretty cheap. Remove any devices that you can from the coax between antenna and TV, especially splitters, as they reduce signal. Don't be afraid to pull any old amplifiers out of the signal path, too - even if they still work they may provide more noise than signal.
Couple things:
Okay, this seems serious. I need to research all that jargon regarding splitters and pre amps and such. Odd, the last game I watched had no loss of signal. Weird. Oh yeah, Let's Go Rangers!
Try aligning the antenna and running fresh cable first. Basically, you want the shortest possible length of antenna cable, with as few interruptions (ie things that are not cable) as possible in between the antenna and the receiver box. With that done you're giving the receiver as much signal as possible from the antenna. If you still need more you can try a preamplifier mounted on the antenna.
In reply to paddygarcia :
I do have a splitter in there between two different TV's and it's not coax either, but traditional TV antenna cable. I will look at it tonight.
I was going to post a few pics to see what you might have, but there's a wealth of info here: https://otadtv.com/cables/index.html
93gsxturbo is spot-on about optimizing. The splitter at best is dividing the received signal strength in half, maybe more if it's old with corroded connectors. Pulling it out will double the input signal right away. Clean connections and good cable could easily get another 2x, if your old cable is as sun- and weather-damaged as it usually gets.
paddygarcia said:I was going to post a few pics to see what you might have, but there's a wealth of info here: https://otadtv.com/cables/index.html
93gsxturbo is spot-on about optimizing. The splitter at best is dividing the received signal strength in half, maybe more if it's old with corroded connectors. Pulling it out will double the input signal right away. Clean connections and good cable could easily get another 2x, if your old cable is as sun- and weather-damaged as it usually gets.
What do I do to feed two tvs then?
There are switches, so you could feed the full signal to one TV or the other. Also powered splitters which have an amplifier.
Before choosing between those or other options, see if you can get reliable results to one tv with as few things in the signal path as possible. Then you can make changes that you know worked.
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