The problem is that the high angle lobe brings down ground/sky cancellation closer to the transmitter. That makes the 180° to 195° tower the best option.
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AM Frequency of the week: 650
- Thread starter cyberdad
- Start date
The problem is that the high angle lobe brings down ground/sky cancellation closer to the transmitter. That makes the 180° to 195° tower the best option.
The Horizontal radiation efficiency only increases up to about 225 degrees. Then it goes down. By about 240 degrees, the secondary lobe above the vertical elevation null becomes very large. Since 5/8, or 5/4 effectively with a ground plane wavelength doesn't represent a true standing wave height with end nodes, and 225 degrees may be an empirical maximum including the tower architecture and tower base under the insulator as part of the height, and anyone I've ever talked to couldn't come up with why it is theoretically 225 degrees, I suspect it might be theoretically the inverse of the golden ratio, 0.618 wavelength or about 222.5 degrees where the maximum is reached. Past discussions in old publications show it as ABOUT 0.6 or 0.62 wavelength. No one has ever shown me a theoretical argument for 225 degrees. Considering that so many equations can't be integrated mathematically but only numerically also leads me to this conclusion. If you can find a theoretical mathematical argument for exactly 225 degrees, let me know. And even then, it would only apply to an infinitely thin conductor, and "spherical chickens in a vacuum".
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Should have specified monopoles along with infinitely thin spherical chickens.
Most actual circa 225 degree monopoles were done with Class IVs which had the 250 watt and later 1000 watt limitations. That also helped with early higher HAAT FM facilities for stations not coowned with TV stations. You can also really hear that high angle lobe on WFUR 1570 (A clear channel relatively sparse graveyard frequency now) Grand Rapids, MI, which is 230 degrees I believe. That lobe, along with the high frequency and poor real conductivity, makes it boom in at the relevant skywave angle distances without fading from groundwave interference. It makes it a Critical Hours regular in the skywave lobe annulus.
Most actual circa 225 degree monopoles were done with Class IVs which had the 250 watt and later 1000 watt limitations. That also helped with early higher HAAT FM facilities for stations not coowned with TV stations. You can also really hear that high angle lobe on WFUR 1570 (A clear channel relatively sparse graveyard frequency now) Grand Rapids, MI, which is 230 degrees I believe. That lobe, along with the high frequency and poor real conductivity, makes it boom in at the relevant skywave angle distances without fading from groundwave interference. It makes it a Critical Hours regular in the skywave lobe annulus.
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I am looking for the Col. Sanders joke here.
The company I was with had a Class IV with that height on 1340 in Lake City. The height was amended to just under 200° when the FM was taken off the tower and moved, resulting in the removal of a pipe-style mast. At the same time, it was converted to a unipole. For a Class IV, it did very nicely and the co-channel interference came in well before any skywave cancellation set in.
I have seen several of those over-half-wave Class IV towers reduced to under 200 feet to save money on lighting and painting.
I thought the tall-tower stations would be the deep-pocketed fifty kilowatters.
What about expanded band stations above 1600, or has the quarter wave been written in stone.
In more recent decades, the commission seems to be more into ERP and less accepting of special antennæ.
The tallest radiating mast of them all stood at the purely reactive height of one-half wavelength.
A 646m halfwave at 227/225 KHz, it rose over the rural fields of central Poland in 1974 but came crashing down in 1991.
We dedicate this little movie tune in their memory.
What about expanded band stations above 1600, or has the quarter wave been written in stone.
In more recent decades, the commission seems to be more into ERP and less accepting of special antennæ.
The tallest radiating mast of them all stood at the purely reactive height of one-half wavelength.
A 646m halfwave at 227/225 KHz, it rose over the rural fields of central Poland in 1974 but came crashing down in 1991.
We dedicate this little movie tune in their memory.
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Days:::: An respectable 21.4KW KSTE out of Sacramento. Its not the strongest listenable station, but if I set my radio down just in the right spot, its fine. It's finding that "sweet spot".
Nights:::Its a noisy mess. I can barely hear KSTE, as they have to drop power down to 920 Watts, and there signal pattern changes north. The surprising visit every 5 minutes or so is 900 Watt KMTI out of Manti, Utah. Its somewhat weak, but I can listen to it for a bit before it fades out. Besides, I like country music, so its nice to hear it coming in. Tonight its coming in quite good on my Sangean PR-D5, with a little KSTE underneath. They trade blows as the night wears on.
Unfortunately, no sign of WSM, Nashville. I'm just to far away....
Nights:::Its a noisy mess. I can barely hear KSTE, as they have to drop power down to 920 Watts, and there signal pattern changes north. The surprising visit every 5 minutes or so is 900 Watt KMTI out of Manti, Utah. Its somewhat weak, but I can listen to it for a bit before it fades out. Besides, I like country music, so its nice to hear it coming in. Tonight its coming in quite good on my Sangean PR-D5, with a little KSTE underneath. They trade blows as the night wears on.
Unfortunately, no sign of WSM, Nashville. I'm just to far away....
Not too far away, just too many stations. Several decades ago when 650 was a clear channel WSM was listenable on the west coast.
From Carrollton, MO.
Daytime: Nothing.
Nighttime: WSM, Nashville, TN.
Daytime: Nothing.
Nighttime: WSM, Nashville, TN.
Keep after it!
As radioman alluded to, the WSM signal is no stranger to the west coast. Just more pests in the way. The legendary Blaw-Knox antenna puts out a fabulous groundwave AND skywave signal. I'd fully expect that on several occasions this coming winter DX season, WSM will be able to rise up on top of whatever is out there blocking it.
WSM and WHAS run into both terrific and pretty bad ground conductivity. Go north, and both can be heard 300 miles during the day. Go other directions and their signal is greatly reduced. WHAS may have the greatest non salt water path disparity by day; Lower Michigan to the north (300 miles) and spent by Nashville (170 miles) to the south.
In areas where mountains aren't an issue, I'd give at least an "Honorable Mention" to KFGO. What happens when 5kw non-directional on 790 hits prairie on three sides. Lousy conductivity to the east. https://radio-locator.com/cgi-bin/pat?call=KFGO&service=AM&h=D
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