[BC] Allocation Philosophies - Was: KKGM

[PeterH5322@aol.com]

>What IS different is that in FM and TV, the tx power has to be set with 
>respect to the antenna system gain, to produce a licensed ERP in the 
>horizontal plane.

This leveled the playing field, and allowed for:

1) "table allocation" (allocation on a completely managed basis), with 
specific channels (remember, FM has channels, too) allocated to specific 
geographic locations, and to specific classes, based on *anticipated* 
need, as used by FM and TV, rather than

2) "demand allocation" (first come, first served ... whomever has the big 
bux gets the best frequency and highest power ... the emerging West be 
damned!), as is used ... to this day ... on AM.


>As Peter Haas noted, AM ERPs in the horizontal plane can 
>vary by up to ~2:1 for omni stations with same tx power, depending on their 
>antenna 'efficiency.'

A Class C can show the greatest variation: 241 mV/m minimum for 1 kW; 440 
(roughly) maximum mV/m, also for 1 kW.

440 / 241 = 1.83, but because the field ratio is a function of the square 
root of the power ratio, a 1.83 field ratio corresponds to a 3.33 power 
ratio.

There are numerous Class Cs out there with 225 degree sticks and 3,330 
watt EMRPs, for 1 kW input, at least during one mode of operation: days 
only, with nights being reduced to 241 mV/m; nights only, with days being 
reduced to 241 mV/m (or perhaps to 281 mv/m if the original stick was 90 
degrees); or days and nights.

But, try to move such a facility and you will probably be ratcheted to 
241 mV/m during either days or nights or both.


There is one Class C in my area which was dark for more than ten years 
through no fault of its own ... the city "took" the tower site under 
eminent domain ... and which was effectively "blocking" the potential 
upgrade of a first adjacent Class B.

That Class B (on a Class III channel) is now 0.4 kW days and 5.0 kW 
nights.

(Remember, before "Rio" Class IIIs had to be a minimum of 0.5 kW, period).

The Class C is again on the air, from a new (to it) Tx site, with 1 kW 
days and 0.8 kW nights, the night power representing ... somewhat ... 
that field which it produced from its 90 degree radiator before the move. 
Its new radiator is over 110 degrees.


Incidentally, the FCC allowed that Class C over 290 mV/m/kW after the 
move, nights, not 241 mV/m/kW, the minimum for the class. Days, the FCC 
allowed the full power for the class, irrespective of radiator 
efficiency, so the field is 320 mV/m/kW.

(It is that Class C's day power, with improved radiator efficiency, which 
is the limiting factor to that Class B's day operation as nights that 
Class B is running full power ... for a Class III).

The Class B got screwed, in a way, but that Class B was a "drop in", 
anyway, and should never have been allowed.

Or, the co-channel #2 market ex-Class III-A should have bought and taken 
dark that Class III-B so that the dominate station could get the 50 kW 
upgrade it deserves.

I am aware of four possible "buy and take dark" situations which would 
have allowed #2 market ex-Class III-As to upgrade to 50 kW, but only one 
was actually effected, and that particular station now has perhaps the 
best signal in the market.


Like "assembling a block", so that one may erect a 110 story building 
within a central city, one often has to do the equivalent with an AM 
allocation.

"Table Allocation", for AM, could have prevented many of these "circle 
jerks".

But, the genie was already out of the bottle.