I still don't understand the terrain shielding effect that goes on in downtown Edmonds. Yes, the hills that shield that area are 400 feet above sea level, but even KUOW is higher than that at 868 feet, and the Cougar stations are several hundred feet higher than that, so shouldn't the fm signal be able to easily make it over the smaller hills? The mountains, I agree, are the main reason, if not the only one, that Seattle fm stations don't make it to Ellensburg, but the Cascades are a lot higher than the hills that shield downtown Edmonds. Am I not understanding something?
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There are hills but...
- Thread starter bobdavcav
- Start date
bobdavcav said:
FM signals are line of sight. Sometimes, no matter how tall the transmitting tower or how high it sits, there are areas that lay just under the signal path - in some cases, even much closer to the transmitting tower than Edmonds and actually require a translator/booster in the very city of license of the station!
Think of a bowl when seen from a distance of 20 feet. You can see the bowl, but do you see the BOTTOM of the bowl? There will always be that rim that blocks your view. That's the effect in downtown Edmonds.
You could build the towers to twice or three times their current height and you may overcome it. Maybe you won't. It is what it is.
And the exact opposite for reception to the NW-with the Puget Sound right near you, NW WA/Victoria/Vancouver comes in like locals. KMPS can try and try but they will get multipathed bad by the hills.
I think the farthest East I can get a 24/7 Seattle station on FM is around Indian John Hill. After the Elk Heights area, they fade into noise (or other Eastern WA stations). KLCK and KBKS do pop up on the Manastash Ridge near Ellensburg, and KOMO-FM/KIRO-FM make it into Yakima due to Mt. Adams.
-crainbebo
I think the farthest East I can get a 24/7 Seattle station on FM is around Indian John Hill. After the Elk Heights area, they fade into noise (or other Eastern WA stations). KLCK and KBKS do pop up on the Manastash Ridge near Ellensburg, and KOMO-FM/KIRO-FM make it into Yakima due to Mt. Adams.
-crainbebo
D
Darth_vader
Guest
Hmmmmm, well.....
Consider that you're standing outside in the open talking to somebody a couple yards away. You can hear him just fine, and he can hear you.
Now consider that the two of you are on either side of a big brick wall. You're trying to talk to the guy on the other side of the wall, but since the bricks reflect sound and not conduct it, the guy on the other side can only very faintly hear whatever little bit of your voice manages to overcome the wall, if he can even hear you. Now, you could stand up on a chair or a ladder and try to talk over the top of the wall, but the wall's just tall enough that it still manages to block most of the sound going over it. That'd be like the "line-of-sight" phenomenon--the wall is blocking the signal (your voice) from reaching its destination (the other guy's ears.) On the other hand, if there were a microphone on your side of the wall to pick up your voice and an amplifier and loudspeaker on the other side to pass it onward, that'd be like a translator or a signal booster.
(I'm sure there are others who could come up with more accurate analogies than that, but that should be the general idea.)
Consider that you're standing outside in the open talking to somebody a couple yards away. You can hear him just fine, and he can hear you.
Now consider that the two of you are on either side of a big brick wall. You're trying to talk to the guy on the other side of the wall, but since the bricks reflect sound and not conduct it, the guy on the other side can only very faintly hear whatever little bit of your voice manages to overcome the wall, if he can even hear you. Now, you could stand up on a chair or a ladder and try to talk over the top of the wall, but the wall's just tall enough that it still manages to block most of the sound going over it. That'd be like the "line-of-sight" phenomenon--the wall is blocking the signal (your voice) from reaching its destination (the other guy's ears.) On the other hand, if there were a microphone on your side of the wall to pick up your voice and an amplifier and loudspeaker on the other side to pass it onward, that'd be like a translator or a signal booster.
(I'm sure there are others who could come up with more accurate analogies than that, but that should be the general idea.)
A radio wave is attenuated when passing through materials/earth. First, a portion is reflected when it encounters the transition from free space and the earth. Probably the greatest loss. Then, there is a loss as it passes through a hill or building. There is an additional reflection/loss when the radio wave encounters the transition back to free space on the other side of the solid wall as it bounces off a wall or building sometimes you will get a multi-path signal. All of the losses are frequency dependent to this. (example) (Your neighbors stereo is blasting,you can't hear the highs but the bass is booming.)You may get a clear spot where if you move the signal will be lost. Take into consideration that Am signals bounce off the ionosphere and earth where as fm shoots straight,good example fm signal turn your water hose and point it at something, once it hits the object it will stop and splatter to the other side, you may get a good flow or just sprinkles.
Another point am towers are usually standing in soggy/damp ground for better conductivity whereas fm towers are high and dry.
I know this is a pretty shallow explanation, but I hope it helps.
I'm a little rusty on this so someone correct me if I'm wrong...PLEASE!!
Another point am towers are usually standing in soggy/damp ground for better conductivity whereas fm towers are high and dry.
I know this is a pretty shallow explanation, but I hope it helps.
I'm a little rusty on this so someone correct me if I'm wrong...PLEASE!!
You guys are basically saying what I already know, I just didn't understand the bottom of the bowl thing that Bongwater I think it was pointed out. Darth's annalogy of the brick wall is exactly the same principal that I have understood for some time about why stations don't make it over to Ellensburg at least very well and the splattering effect that the last poster pointed out.
OK water hose example again, but this time put a bowl anywhere underneath the stream.
You will get a splatter in the bowl or just shoot straight over it. Most likely if you get splatter you have a bad transmission line somewhere. FM is just not as flexible as am. It will not bend over the hill.There are antenna that compensate for this, but where most towers are located for Seattle it would be a fruitless effort. Am signals you can bend,that's why you see 3-6 antenna towers for am....example..(imagine am is 1/4 inch fm is 1 inch which is easier to bend. Ever notice where KCMS tower is? It's there for THAT reason as Edmonds is the col and would never hit there from cougar mt.
With the terrain that most Seattle signals travel from is Cougar/Tiger this would intensify the effect of the bowl theory. (I think)
I believe this was the main propose for translators.
You will get a splatter in the bowl or just shoot straight over it. Most likely if you get splatter you have a bad transmission line somewhere. FM is just not as flexible as am. It will not bend over the hill.There are antenna that compensate for this, but where most towers are located for Seattle it would be a fruitless effort. Am signals you can bend,that's why you see 3-6 antenna towers for am....example..(imagine am is 1/4 inch fm is 1 inch which is easier to bend. Ever notice where KCMS tower is? It's there for THAT reason as Edmonds is the col and would never hit there from cougar mt.
With the terrain that most Seattle signals travel from is Cougar/Tiger this would intensify the effect of the bowl theory. (I think)
I believe this was the main propose for translators.
Also want to add that frequency and wavelength. FM's wavelength is too small. The higher the freq the smaller the wavelength.
To this day U.S subs can still run an antenna that's a mile long cause the bigger the w/l and the lower the freq it's easier to tx/rcv through the dense salt water.
Same theory applies to hills/buildings.
To this day U.S subs can still run an antenna that's a mile long cause the bigger the w/l and the lower the freq it's easier to tx/rcv through the dense salt water.
Same theory applies to hills/buildings.
I think if a couple of stations that are fuzzy in the Edmonds "bowl" had translators on the south part of Whidbey island, or near Kingston, they'd get good signals along the coastal areas that are shadowed from many of the Seattle FMs. KIRO-FM is a lot of multipath. But the high power Olympia area signals come in strong. KUOW is trash in Edmonds and along Puget Sound (as it is almost anywhere outside central Seattle). But good luck finding a frequency now if you're not going to try making a same-channel booster work. Drive north-sound along the ridge that is 100th St SW aka 9th Ave and you'll get a really good shot at the Victoria signals before the Seattle ones fuzz up on your way down to the ferry terminal.
I put an FM on the air in the 1990s that was 120 watts at about 700+ feet, 2/3 of the way up a mountain, about 30 miles from the city of license. Hot sunny days (in California) would create temperature inversions where the signal would be overtaken by another station on the same freq downhill 80 miles, and we couldn't hear outselves in the city of license. Same was true with a class B FM in the gently rolly terrain of the midwest - even much higher wattage and a lower tower there found many a summer's afternoon where other class Bs on the same freq 130 miles away competed for in-car listeners, and when a thunderstorm knocked us off for awhile, one of the other stations came in on the studio monitor loud and clear.
I also think barometric pressure may have some impact on FM and TV signals. Certainly storm fronts do. Having a lower wattage station with a high tower location on a crowded FM dial gives you lot of variation in signal strength. Rainy and humid weather seemed to boost the reception. Nighttime always did a bit, too.
I put an FM on the air in the 1990s that was 120 watts at about 700+ feet, 2/3 of the way up a mountain, about 30 miles from the city of license. Hot sunny days (in California) would create temperature inversions where the signal would be overtaken by another station on the same freq downhill 80 miles, and we couldn't hear outselves in the city of license. Same was true with a class B FM in the gently rolly terrain of the midwest - even much higher wattage and a lower tower there found many a summer's afternoon where other class Bs on the same freq 130 miles away competed for in-car listeners, and when a thunderstorm knocked us off for awhile, one of the other stations came in on the studio monitor loud and clear.
I also think barometric pressure may have some impact on FM and TV signals. Certainly storm fronts do. Having a lower wattage station with a high tower location on a crowded FM dial gives you lot of variation in signal strength. Rainy and humid weather seemed to boost the reception. Nighttime always did a bit, too.
It's been my experience that contrary to the popular notion that clear days are best for FM radio reception, I agree rainy, humid days seem to be the best. Especially for AM (daytime ground wave gets a heck of a boost.) But oddly for FM/TV too. I somehow get Cougar Mountain stations like KJR-FM and KPLZ a lot better on rainy days.
It's VERY noticeable with cell phones signals. On clear days, I get more signal breakups on my cell phone than on wet rainy days. DTV, for some strange reason seems to be an exception to this rule. Clear days seem to work better.
It's VERY noticeable with cell phones signals. On clear days, I get more signal breakups on my cell phone than on wet rainy days. DTV, for some strange reason seems to be an exception to this rule. Clear days seem to work better.
Hmm, I haven't noticed rainy days being best, in fact I have noticed the exact opposite. When it has been raining, I notice that cell signals sound pretty broken up, though I don't talk on my phone much, usually I've noticed this when my dad has his on speaker. I do notice however that when there is ducting, there will be some stations not audible at all on some radios, while they will be stronger on others. Two prime examples of this are KOMO-FM and CBUF, and KKBW against Sonic. When there was even slight ducting last summer, I could get Sonic, no sign of KKBW. Up here, the radio actually seems to be in a pretty good spot for 97.7, but that signal has quite a bit of static downstairs, though I don't think that radio is quite as good. When there is ducting however, that radio gets 97.7 just fine. However, on my BrailleNote on days when there is ducting, I can move the headphones one way and get CBUF as clear as KOMO typically is, and if I move the headphones the other way KOMO's signal is significantly degraded. I don't think I'll ever forget the day when for a brief second, I got CFBT in stereo on that radio from here at home.
So -- If the FCC ever allowed the spectrum from 54 - 88 Mhz (TV channels 2 - 6) to be used for standaed FM broadcasting -- what would coverage be like in the new lower band be like ???
Pretty similar, with fringe coverage slowly improving as you go lower. Note that channel 2 generally gets out better than channel 6.
But the FCC has shown no interest in making this happen. Their current policy appears to be geared to moving everything to your cellphone as the access device for all info.
But the FCC has shown no interest in making this happen. Their current policy appears to be geared to moving everything to your cellphone as the access device for all info.
Yes, the lower frequency 88.1 would get out a bit further thatn 107.9. If you recall the FCC authorized 100kw for tv stations channels 2-6 and 316 KW for 7-13 (channel 6 ended just below 88 and channel 7 was arount 176mhz. UHF Stations have 5000kw maximums- all in an attempt to equalize coverage.
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