[BC] Changing channels

[PeterH5322]

>What is Dial-a-power?

It's a euphemism for selecting any power which makes you station work 
under the new rules.

Before the rules changes in the 80s, power could only be:

Class A: 50 kW, unless grandfathered at 10 kW,

Class B: 0.25, 0.5, 1, 5, 10, 25 or 50 kW (2.5 kW was added in the late 
60s as Canada and Mexico had been using this power for years; 0.5 kW min 
and 5 kW max for regionals, until "Rio"),

Class C: 0.25, 0.5 or 1 kW (0.1 kW was formerly allowed, and some are 
still grandfathered at 0.1 kW, but on a regional channel), and

Class D: Same as Class B.

Stability of transmitters was certainly one concern.

Sadly, there were a great many Class Bs on regional channels which could 
have been licensed at 0.25 kW, but could not meet the 0.5 kW minimum 
without a DA.

(I know of one station which went from a 1 kW daytimer on 980 to a 1 kW 
fulltimer on 1240 to a fulltimer on 980, but with 1 kW days and 0.25 kW 
nights, all over four decades, or so, and all using the same stick. I 
also know of a fulltimer on 1280 which went from 1/0.5 kW DA-N to 1/0.25 
kW ND-U, but because it installed a 225 degree stick at one point, the 
current power is 0.5/0.25 kW ND-U).

After all this, any power which met the minimum, but did not exceed the 
maximum was permissible, and this often permitted upgrades which were 
economically impossible under the old rules.

Example: ex-KRLA, Pasadena, now runs 20 kW nights into what is 
essentially its 1940's array design, since relocated to Irwindale from 
Whittier Narrows. But as there were only 10 and 25 kW as options then, 10 
kW had to be selected, as there was no allowable power between 10 and 25. 
With dial-a-power any value which maintained protection of the Class A 
was acceptable, and 20 kW did the job. Which means that 20 kW could have 
been possible from 1947 (or whenever this station became a Class II-B) 
until the 80s when the newly moved array was built.

Dial-a-power certainly faciliates "ratcheting".

Imagine a forced move of a Class A, where ratcheting would require a 50 
kW-er to reduce to 25 kW, the next lower increment under the old rules.

In that hypothetical, if 44 kW met the ratcheting rule, then that would 
be the new power, not a reduction all the way down to 25 kW.

There are a couple of Class As which have alternate antennas which are 
limited to 35 kW, not 50 kW, on account of the different vertical field 
performance characteristics of their alternate antennas.