Anyone here familiar with Columbus, OH know why the WTVN directional array is such a hodgepodge of antenna styles? There are self supporters and guyed towers mixed together. Plus, the antenna heights vary greatly from west to east. I assumed the two east antennas were so short because of the old Columbus South airport...but I could be wrong. It just seems so different from other arrays I've seen.
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WTVN-AM Columbus directional array
- Thread starter Nightpattern
- Start date
All I know is the thing works & works well. The depth of their null to the west is consistent & amazing. In Indiana, when they switch at Columbus sunset, there is NOTHING left. If there is nothing else coming in on 610, all you hear is noise. WTVN puts a great signal in here during the day, but there's never a trace at night. I wish all stations were as meticulous at caring for their DA's as WTVN is.Nightpattern said:Anyone here familiar with Columbus, OH know why the WTVN directional array is such a hodgepodge of antenna styles? There are self supporters and guyed towers mixed together. Plus, the antenna heights vary greatly from west to east. I assumed the two east antennas were so short because of the old Columbus South airport...but I could be wrong. It just seems so different from other arrays I've seen.
Prior to a 1994 tornado, there were only 2 types of towers...2 tall self supporters & 1 short self supporter. When the mid one was snapped off maybe 40' above the ground, it was replaced with a guyed tower...so that's why there are 3 types. They've had many a great engineer pass through there...wouldn't surprise me if one popped in & could explain the significance of the short tower.KR4BD said:Another station with a variety of tower types (only 3, but all different) is WNDE-1260 in Indianapolis...
Here's a link to a satellite view of their site...
http://maps.google.com/maps?f=q&hl=en&q=39.86500,+-86.06194+(WNDE-AM)&om=1
When I moved to Indiana nearly 33 years ago, WNDE was the #1 station at night in Columbus,IN. When there was a high school dance, odds are the DJ was from WNDE. These days, you can't hear it there at night even though the directional pattern & power are the same as then. Did the tower replacement affect it? Or is just that there are so many stations on 1260 that either forget to reduce power at night or that don't take care of their DA's? In any case, what was once a clear night signal at 40 miles now sounds like a graveyard channel.
For those who haven't seen this array, it is two parallel rows of three towers (basically E-W) on the south side of Columbus just north of I-270. The main lobe is essentially at right-angle to the array--aimed north into Columbus.
Correct my memory if it is off, but the two SE towers are short 200' self supported towers (TVN is on 610), the NE pair and the SW towers are higher guyed towers and the NW tower is about 600', guyed tower.
That NW tower was once used for Channel 6, before it moved into the center of town (and before the digital re-arrangement of channels). It is presently used for the 93.3 station assigned to Ashville, Ohio.
Way-way back, TVN was WEAO and operated with 750 watts. Suspect this was a two-tower DA (the self-supporters) that was expanded after the war to 5 kw with the present array.
Correct my memory if it is off, but the two SE towers are short 200' self supported towers (TVN is on 610), the NE pair and the SW towers are higher guyed towers and the NW tower is about 600', guyed tower.
That NW tower was once used for Channel 6, before it moved into the center of town (and before the digital re-arrangement of channels). It is presently used for the 93.3 station assigned to Ashville, Ohio.
Way-way back, TVN was WEAO and operated with 750 watts. Suspect this was a two-tower DA (the self-supporters) that was expanded after the war to 5 kw with the present array.
A good writeup on this at the Columbus board too.
http://boards.radio-info.com/smf/index.php?topic=164687.0
http://boards.radio-info.com/smf/index.php?topic=164687.0
Try living about 5 miles west of the array and hearing the audio drop to almost nothing...it's an amazingly tight pattern. Combine that with the unusual tower arrangement and it's just always interested me.
Interesting reading on the FCC database. I too was always amazed at that antenna farm as I drove past it each week commuting to Columbus from Chillicothe.
Most info posted is accurate- the big tower, basicly a .4 wave is their daytime omni and did support the chan 6 TV antenna back then. Their night pattern is non-standard and has lots of augmentations to fine tune it to protect a whole slew of stations east, west, and south and eke out just a little more signal to reach Chillicothe and Circleville at night (the extended south lobe). The two mid sized towers are about .25 wave, but the three electrically short towers are top loaded. Click on their application list, apparently the coordinates and heights of the towers were slightly off from what was on the license. They filed to correct those discrepancies and included some neat photos and maps.
I was working at WCOL at the time (another big daytime signal on 1230 with only 1000 watts but from a .5 wave tower over on Greenlawn) but my friend was doing overnights at 610 and he told me he had regular listeners well up into Canada!
Most info posted is accurate- the big tower, basicly a .4 wave is their daytime omni and did support the chan 6 TV antenna back then. Their night pattern is non-standard and has lots of augmentations to fine tune it to protect a whole slew of stations east, west, and south and eke out just a little more signal to reach Chillicothe and Circleville at night (the extended south lobe). The two mid sized towers are about .25 wave, but the three electrically short towers are top loaded. Click on their application list, apparently the coordinates and heights of the towers were slightly off from what was on the license. They filed to correct those discrepancies and included some neat photos and maps.
I was working at WCOL at the time (another big daytime signal on 1230 with only 1000 watts but from a .5 wave tower over on Greenlawn) but my friend was doing overnights at 610 and he told me he had regular listeners well up into Canada!
I read somewhere that the different height towers were intentionally designed to change the vertical pattern null profile for WTVN. This has been done in a lot of places, not just WTVN. This is often done to keep a shallow null at ground level and a deeper one at a higher elevation to protect a relatively nearby station.
Slight dog leg, but almost linear arrangements, make the pattern asymmetric, so that rather than the same depth null on either side, one null is deep and the other is shallow. This is also being done more with new arrays. Often it would take more towers to get the necessary pattern, and the nulls would be deeper than they have to be in many directions.
Slight dog leg, but almost linear arrangements, make the pattern asymmetric, so that rather than the same depth null on either side, one null is deep and the other is shallow. This is also being done more with new arrays. Often it would take more towers to get the necessary pattern, and the nulls would be deeper than they have to be in many directions.
Sorry, I didn't realize that Dan had already discussed some of this on the Columbus thread.
The Columbus (WTVN) to Philadelphia (WIP) skywave path would be short enough to have a signigicant elevation angle, as stated.
I have also noticed the same phenomenon mentioned of previously well protected stations that are a mess at night.
I think all of the factors mentioned, patterns not being maintained, not changing to night pattern and power, and also the current extended low sunspot activity have contributed to this.
The Columbus (WTVN) to Philadelphia (WIP) skywave path would be short enough to have a signigicant elevation angle, as stated.
I have also noticed the same phenomenon mentioned of previously well protected stations that are a mess at night.
I think all of the factors mentioned, patterns not being maintained, not changing to night pattern and power, and also the current extended low sunspot activity have contributed to this.
Schroedingers Cat said:Sorry, I didn't realize that Dan had already discussed some of this on the Columbus thread.
The Columbus (WTVN) to Philadelphia (WIP) skywave path would be short enough to have a signigicant elevation angle, as stated.
I have also noticed the same phenomenon mentioned of previously well protected stations that are a mess at night.
I think all of the factors mentioned, patterns not being maintained, not changing to night pattern and power, and also the current extended low sunspot activity have contributed to this.
So..for us laymen..is that why the towers decrease in height from west to east...to emphasize protection towards WIP?
Nightpattern said:So..for us laymen..is that why the towers decrease in height from west to east...to emphasize protection towards WIP?
The only logical conclusion is yes. But someone a lot smarter than I am will have to prove it to you. The distance from WTVN to WIP is 417 miles; the distance from WTVN to KCSP is 624 miles--about 1.5 times the distance to WIP. With a two- or three-tower in-line "end-fire" array of unequal-height towers, designed to send the strongest signal along the line of towers and the weakest signal in the opposite direction (also along the line of towers but 180 degrees from the strongest signal), you'd want the taller towers "behind" the pattern--that is, in the direction of the signal minimum. This is the configuration that optimizes the vertical radiation pattern. If done the other way (taller towers in front of the pattern), you get a high-angle lobe that produces phasing that causes unwanted "self-interference" during critical hours and at night. The WTVN array is a six-tower side-fire parallelogram, however, and I do not have the tools or the knowledge to apply the lessons of the simpler two or three tower array to it.
The way to understand it is probably to consider it as a two tower pattern multiplied by a three tower pattern perpendicular to it. If the parameters are not exact, they are probably close enough to aprroximate it.
Schroedingers Cat said:The way to understand it is probably to consider it as a two tower pattern multiplied by a three tower pattern perpendicular to it. If the parameters are not exact, they are probably close enough to approximate it.
To a certain extent, that analysis is pretty straightforward. Taken alone, the three towers in the north row (#s 1, 5, and 6), with zero phase difference among them and field ratios of 1:2:1, produce a side-fire figure eight with minima to the east and west along the row and maxima to the north and south (normal to the row). The same is true of the three towers in the south row (in which the field ratios are 1.1:2.1:1.1. Taken alone, each north-south pair, which consists of towers 100 degrees apart and phased approximately 90 degrees apart with the south tower in each pair leading the north tower and a slight field imbalance with the south tower producing a slightly larger field, would produce a slightly detuned cardioid. The product of the "east-west" and "north-south" patterns is, then, an upside-down figure eight, in which the north lobe of the figure eight is much larger than the south lobe. That is, in fact, what the actual standard pattern looks like. But then we get to the subtleties of what the vertical radiation pattern looks like (which was the question I was trying to answer). Are there minima to the east at whatever the critical angle is for 417 miles (distance to WIP) and to the west at whatever the critical angle is for 624 miles (distance to KCSP)? I don't know and I wouldn't even know how to start getting the answer. I do know that for several thousand dollars, you can buy software that will predict and plot the vertical pattern.
No doubt there would be an exact solution with enough work and enough towers, given there were just those two stations to protect. Remember in those advanced calculus and engineering classes where they talked about "degrees of freedom" and "degrees of constraint" or something along those lines? They involved solving several simultaneous equations. It gets even more complicated when you throw a few trigonometric functions into the equations. Ideally, the person designing an array would have a hands on understanding of how you would do the whole intereference study and arrray design by hand, as well as being familiar with the capabilities and limitations of the software.
Nostalgia said:And to expand a bit on what S Cat mentioned, remember back when that array was designed you can bet it was done by a guy with a slide rule and a bunch of charts, not a super computer!
If we didn't know that from the age of the array, there would be other give-aways that this is not a modern design. The spacing between towers in the east-west rows is exactly 180 degrees; the rows are perfectly straight; the spacing between the north and south rows is exactly 100 degrees. Even with older six-tower side-fire parallelograms, you generally find the spacing between towers in the long rows is a little greater than 180 degrees. I think that if you look at side-fire three-tower arrays, which are the prototypes for six-tower arrays like WTVN's, the best-looking figure eights are produced by arrays in which the tower-to-tower spacing is about 190 degrees--not 180. Two textbook examples are on 1090: KAAY (188 degrees) and XEPRS (185). The only thing that is not obvious about the WTVN design is the characteristic that started this whole thread--the towers are of unequal heights. I am surprised that, of the pair at the west end, the northern tower is the taller of the two. I would have expected the tall one to be the southern tower in the pair. I will take it on faith that the actual arrangement produces a "better" vertical pattern, but it would be interesting to know the details of how a modern method-of-moments design would differ from this classic.
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