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Folded unipole antennas - why so few?

MM797 said:
I saw a three tower array in Florida, north of Orlando, in around 2002 that used those tapering corrugated galvanized pipe style free stander towers that are popular for cellular phone towers. It was right next to a railroad track so maybe the rails were bonded to the ground system and the rails ran toward Orlando so perhaps the ground conductivity worked good in that direction.
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Back in the earlier 60's WSRS 1490 in Cleveland Heights converted to WJMO and an R&B format. It was far from the Black community and only 250 watts, so they move as close to East Cleveland as they could while still doing legal coverage of Cleveland Heights, the city of license.

The new site was next to the New York Central tracks, and they welded a bunch of the guy wires to rails, thinking it would improve coverage towards the inner city. As it was, it did do a good job of covering the African American community.

I wish I had taken pictures... I was their token "white kid" and it was a hell of a great experience in both radio and life .
 
MM797 said:
Very cool. You found it. I couldn't even find it the next time I went driving around to look for it. But that was before Radio Locator and Google maps.
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I know the orlando market a ltitle bit and went looking at stations i thought had 3 towers and then brought their locations up on google maps and looked for ones near train tracks
 
MM797 said:
I saw a three tower array in Florida, north of Orlando, in around 2002 that used those tapering corrugated galvanized pipe style free stander towers that are popular for cellular phone towers. It was right next to a railroad track so maybe the rails were bonded to the ground system and the rails ran toward Orlando so perhaps the ground conductivity worked good in that direction.
Click to expand...
Had a local "engineer" try bonding his ground system to a nearby railroad track. The railroad folks found it quickly and made him unhook it. Pretty sure they threatened legal action if he ever tried it again.
 
rfburns said:
Had a local "engineer" try bonding his ground system to a nearby railroad track. The railroad folks found it quickly and made him unhook it. Pretty sure they threatened legal action if he ever tried it again.
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The way around this is to inductively couple tower ground to railroad tracks. Not as good as a hard connection, but does improve groundwave that direction. Don't ask me how I know this...
 
DavidEduardo said:
"Snow forms when tiny ice crystals in clouds stick together to become snowflakes. If enough crystals stick together, they'll become heavy enough to fall to the ground"


Or...

kids.britannica.com

snow

Tiny crystals of ice that fall to Earth are called snow. A crystal is a solid substance that has flat surfaces and sharp corners. Snowfall is made up of both single ice…
kids.britannica.com kids.britannica.com
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I remember when I was a child there was a controversy over children eating snow because of the radioactive dust from the atomic tests. Lookup nuclear fallout and you have to wonder why they continued air testing into the 1960s. They had knowledge of the Japanese blasts and the effects 15 years earlier.

Then there is always the danger of yellow snow.

But back to the unipole, IMHO except for some directional applications any class C or D AM operator who is only using the AM to "feed" a FM translator should consider a grounded tower if they can rent space on their tower.
 
Kelly A said:
The way around this is to inductively couple tower ground to railroad tracks. Not as good as a hard connection, but does improve groundwave that direction. Don't ask me how I know this...
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Didn't the FCC catch somebody using railroad tracks in their ground system back in the 1960s or early 1970's or was that just a story told after a beers?
 
If the rail tracks are used to transport hazardous shipments or passengers it most likely will have a positive train control system some of which check track conditions with a contenuity test which might not like a lot of RF. The old crossing gates used a voltage on one rail that when the steel axle on the train completed the circuit, the lights start flashing at the next intersection and the gates come down. An aluminum canoe laid across the tracks can set the crossing warning off too. A Boy Scout Troup did it to the CSX in West Virginia when they were putting in on the Tygart river. It took them 20 minutes to get five canoes down the bank and across the tracks into the river. The CSX signal guy saw the canoes in the river when he was driving up from Grafton nd figured it out. He said it happens a couple of times every summer but he got overtime to check it out on the weekend and he really didn't mind.
 
secondchoice said:
Didn't the FCC catch somebody using railroad tracks in their ground system back in the 1960s or early 1970's or was that just a story told after a beers?
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The main campus of NC State University is divided by an active set of railroad tracks. There was an often repeated story about engineering students who managed to connect one of the school's carrier-current transmitters directly to the tracks, sometime in the 60s or 70s. Supposedly the signal propagated so well that an FCC field agent in the DC area heard it, and quickly put a stop to it.

I have heard a few other stories like this, most of them probably apocryphal and embellished over a few (or several) beers.
 
awsherrill said:
The main campus of NC State University is divided by an active set of railroad tracks. There was an often repeated story about engineering students who managed to connect one of the school's carrier-current transmitters directly to the tracks, sometime in the 60s or 70s. Supposedly the signal propagated so well that an FCC field agent in the DC area heard it, and quickly put a stop to it.
.
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Rails are grounded and don’t make a good antenna. They can make up for a bad ground, though.

In Ecuador where I owned stations, most of my competitors used a couple of buried car radiators as their ground.
 
DavidEduardo said:
Rails are grounded and don’t make a good antenna. They can make up for a bad ground, though.

In Ecuador where I owned stations, most of my competitors used a couple of buried car radiators as their ground.
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Very cool David Eduardo!
 
If I had a dollar for every "they tied it in to the railroad tracks and the FCC got called in" story I've heard, especially about college carrier current stations, I'd have enough to buy an actual AM stations these days.
 
DavidEduardo said:
Rails are grounded and don’t make a good antenna. They can make up for a bad ground, though.
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Not universally. Many rail roads today use the rails for signaling. The system energizes one rail and check for continuity with the other rail. If there is continuity, that means a train is present on that segment of track. This allows the dispatcher to see direction and speed of travel, so if one train is coming up behind a slow train, they can alert the engineers to adjust their speed. And if two trains are on a collision course, the dispatcher can tell them to stop!
 
fybush said:
If I had a dollar for every "they tied it in to the railroad tracks and the FCC got called in" story I've heard, especially about college carrier current stations, I'd have enough to buy an actual AM stations these days.
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And the idea that rails are an "antenna" is even more amusing.
 
PTBoardOp94 said:
Not universally. Many rail roads today use the rails for signaling. The system energizes one rail and check for continuity with the other rail. If there is continuity, that means a train is present on that segment of track. This allows the dispatcher to see direction and speed of travel, so if one train is coming up behind a slow train, they can alert the engineers to adjust their speed. And if two trains are on a collision course, the dispatcher can tell them to stop!
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Still, any length of a conductive substance can operate as a counterpoise system, just like used to be more commonly used for stations with their tower on a rooftop.
 
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