Nighttime Protection of the Original 'Regionals' ?

[Steve Green NEPA]

This is far more of a 'retro' topic -- nostalgia -- than it is a useful or practical concern in 2017, but ....

Is there some sort of history site or sites where an elaboration can be found vis-a-vis the various agreements between big co-channel regionals so their nighttime signals didn't alarmingly overlap?

I'm thinking of examples such as 950 WWJ Detroit and WPEN Philadelphia.
Or WDRC Hartford and WSAI Cincinnati on 1360.
Or WPOP-KQV-WING on 1410.
1440 Youngstown OH and Worcestor Mass is another ..... 580 Harrisburg .... Charleston WV and (again) Worcestor MA .....

Did the Friendly Candy Company basically assign all those nighttime patterns? Were there mutual engineering agreements between the individual stations? And if the latter is the case, * when * did these mob-like territories get divvied up?

 

[Schroedingers Cat]

This is far more of a 'retro' topic -- nostalgia -- than it is a useful or practical concern in 2017, but ....

Is there some sort of history site or sites where an elaboration can be found vis-a-vis the various agreements between big co-channel regionals so their nighttime signals didn't alarmingly overlap?

I'm thinking of examples such as 950 WWJ Detroit and WPEN Philadelphia.
Or WDRC Hartford and WSAI Cincinnati on 1360.
Or WPOP-KQV-WING on 1410.
1440 Youngstown OH and Worcestor Mass is another ..... 580 Harrisburg .... Charleston WV and (again) Worcestor MA .....

Did the Friendly Candy Company basically assign all those nighttime patterns? Were there mutual engineering agreements between the individual stations? And if the latter is the case, * when * did these mob-like territories get divvied up?

Class III-A 125 uV/m 10% skywave allowable interfering signal, 2.5 mV/m normally protected contour
Class III-B 200 uV/m 10% skywave allowable interfering signal, 4.0 mV/m normally protected contour

These seem to have mainly evolved from the protection afforded by 5000 watt ND, 1000 watt ND, and 500 watt ND signals at required distances to provide this protection. Usually, when a 1000 watt ND-N station upgraded to 5000 watts DA-N, it provided protection to other stations equivalent to 1000 watts ND-N. When WWJ went from 1000 ND-N to 5000 DA-N, it protected WPEN and KPRC to the 1000 watt ND-N level. Most other drop ins of the day just kind of fit into the pattern of the others.

 

[Schroedingers Cat]

The first AM BC DA was WFLA WSUN Tampa on 620 to protect WTMJ Milwaukee. It appears that this was an agreement finally achieved between the two, and the null was quite deep. The mutual reactance and impedance interactions were not well understood then, and the null was empirically tuned to point toward Milwaukee. The DA was referred to as a shield, which along with the crude transmission line phasor, one has to wonder to what extent radio engineers influenced Star Trek terminology.

Another early DA was 500 kW WLW 700 to reduce radiation toward 50 kW CFRB on 690 (yes, 690 in Toronto) to the equivalent of 50 kW.

 

[Ai4i]

Some overseas stations use parasitic elements.
Do any North American stations do that today?

 

[davideduardo]

Some overseas stations use parasitic elements.
Do any North American stations do that today?

You mean things like non-active but tuned towers spaced at a certain wavelength from the "main" tower to nudge the signal in a specific direction?

Or do you mean negative towers in a DA?

Calling the Cat...

 

[davideduardo]

The first AM BC DA was WFLA WSUN Tampa on 620 to protect WTMJ Milwaukee. It appears that this was an agreement finally achieved between the two, and the null was quite deep. The mutual reactance and impedance interactions were not well understood then, and the null was empirically tuned to point toward Milwaukee. The DA was referred to as a shield, which along with the crude transmission line phasor, one has to wonder to what extent radio engineers influenced Star Trek terminology.

Another early DA was 500 kW WLW 700 to reduce radiation toward 50 kW CFRB on 690 (yes, 690 in Toronto) to the equivalent of 50 kW.

Was the original WSUN directional done by phased and tuned towers, or by the orientation of a center-fed "T" suspended from two support towers or masts?

Another early directional was WOR in New York. They understood that "T" antennae were directional, and they placed the antenna so that the two lobes aimed at New York and Philadelphia. They actually advertised their service to Philly well into the 30's.

 

[Ai4i]

Calling the Cat...

The former:
Grounded towers that are not fed with transmission lines
but work by receiving and reradiating RF energy.
They are called directors and reflectors in Yagi arrays

 

[davideduardo]

The former:
Grounded towers that are not fed with transmission lines
but work by receiving and reradiating RF energy.
They are called directors and reflectors in Yagi arrays

We had a quarter wave vertical a half wave from the main tower in that configuration for Radio 10, 710 AM in Buenos Aires. We wanted to nudge the signal towards downtown, which was very noisy and even 100 kw needed a bit of a boost. We got the equivalent of about 120 kw towards the city center, and the lost coverage area was not economically significant.

 

[Schroedingers Cat]

The WFLA WSUN DA sounds like it's a driven array using transmission lines as a crude phasor. Here's the story by Barry Mishkind.

http://www.oldradio.com/archives/stations/tsp/WSUN-WFLA.pdf

I think many of the early arrays were designed by 1) Carl Smith, 2) The predecessors of Kear and Kennedy, and 3) The predecessors of Bob Jones and/or Donald Markley, at least in the Midwest. There were about 40 DAs sometime right after World War II. The Bath, OH contingent, Carl Smith did WGAR, WTVN, CKLW, and WTAC from what I can gather. They are additive patterns, physical layout parallelograms, 5, and 6 tower arrays. The rectangular paralellograms seem to be from the LaGrange-Peoria, Illinois contingent, WIND, WGES, WMBD, are a few of those. The three tower in line endfire arrays seem to originate from Kear and Kennedy and predecessors. The History Cards usually only show the Attorney, not the Consulting Engineer. I'm going by the different designs, but it is mainly intuitive speculation, along with tidbits of memorabilia and anecdotes from engineers along the way.

The biggest trigger for DA installation seemed to be increasing power from 1000 to 5000 watts, particularly at Night. The History Cards do back that up.

 

[davideduardo]

The WFLA WSUN DA sounds like it's a driven array using transmission lines as a crude phasor.

I did one of those in Ecuador where we had two coax runs out of the transmitter and they were measured in length and characteristics to create a true north-south pattern that fit the population centers of the Andean zone. No phasor... just precise measurement of the coax runs.

 

[Ai4i]

The WFLA WSUN DA sounds like it's a driven array using transmission lines as a crude phasor.

Just this little sidenote, or big sidenote:
Those early phasors were "crude" in the sense that they were simple by today's computerized models,
but an engineer from who's knowledge and experience I learned much, shared with me that
when an array is aligned as much as possible by adjusting the lengths of transmission lines,
rather than by the quick and easy method of big coils and caps, it will be much flatter across the full channel.
Use the coils and caps for fine tuning and do it as much as possible at the LTU shacks,
not the transmitter room, and the entire system will be less reactive along the transmission lines.
Big coils and caps exhibit much higher Q's and narrower bandwidths than long lengths of cables.
I participated in an antenna proof of performance and was very impressed at how undistorted the station was,
even in its deepest nulls, and they were and are deep, it was completely undistorted.
In other words, the sidebands across the channel were just as suppressed as the carrier
and the audio was good in all directions.

 

[gar hi]

Was the original WSUN directional done by phased and tuned towers, or by the orientation of a center-fed "T" suspended from two support towers or masts?

Another early directional was WOR in New York. They understood that "T" antennae were directional, and they placed the antenna so that the two lobes aimed at New York and Philadelphia. They actually advertised their service to Philly well into the 30's.

And to this day, WOR still has the strongest signal in the Philadelphia area of all the NYC stations.

Wouldn't quite call it 'Local' strength but close.

 

[Ai4i]

WOR still has the strongest signal in the Philadelphia area of all the NYC stations.

Here!

 

[gar hi]

I used to think the reason for WOR's directional signal was to not interfere with 710 in Miami but I can't find much on the history of the old WGBS, so I would think WOR started their signal pattern long before the Miami station first came on the air.

 

[davideduardo]

I used to think the reason for WOR's directional signal was to not interfere with 710 in Miami but I can't find much on the history of the old WGBS, so I would think WOR started their signal pattern long before the Miami station first came on the air.

Miami is a very recent allocation compared to WOR. WGBS did not go on 710 until the beginning of 1945, and when they did it was at 10,000 watts.

 

[Schroedingers Cat]

According to Rich, the pattern of the Hammock T Antenna is nondirectional, despite the symmetry of the wires and the fact that this is counterintuitive. In any event, a T antenna is NOT a horizontally polarized dipole. It is vertically polarized. The horizontal wires are top loading.

The pictures and post cards you see of these antennas are old school photoshopped, as the wires are drawn in, as they would not be visible otherwise. The center vertical wire is the vertical radiator.

 

[davideduardo]

According to Rich, the pattern of the Hammock T Antenna is nondirectional, despite the symmetry of the wires and the fact that this is counterintuitive. In any event, a T antenna is NOT a horizontally polarized dipole. It is vertically polarized. The horizontal wires are top loading.

The pictures and post cards you see of these antennas are old school photoshopped, as the wires are drawn in, as they would not be visible otherwise. The center vertical wire is the vertical radiator.

The actual close up photos I have seen show the vertical component to generally be 4 or 5 wires in a square or hexagon with dielectric spacers for rigidity. There was some form of the concept that bandwidth and fidelity improved with a vertical component that had a broader face.

 

[Schroedingers Cat]

The actual close up photos I have seen show the vertical component to generally be 4 or 5 wires in a square or hexagon with dielectric spacers for rigidity. There was some form of the concept that bandwidth and fidelity improved with a vertical component that had a broader face.

I think that was the idea behind self supporting towers being better for fidelity also. The two extra dimensions in some sense have waveguide like properties in that the a range of resonance is wider. There are more quantum solutions to the wave equation. A single wire will have a sharp resonance.

 

[davideduardo]

I think that was the idea behind self supporting towers being better for fidelity also. The two extra dimensions in some sense have waveguide like properties in that the a range of resonance is wider. There are more quantum solutions to the wave equation. A single wire will have a sharp resonance.

I wonder whether the theory was understood in the 20's, or whether trial and error led to the discovery that the extra dimensions just sounded better.

 

[Ai4i]

So, we had the T which grew into the the short, top loaded verticle,
the quarterwave, the 5/8 wave, the modified Franklin, the full Franklin,
and finally the Crossfield glorified capacitor dummy load antenna.