Here is a pretty good read on WLW before and during their 500kw period.
The article states in part, that "WLW began broadcasting with 500KW around the
clock, in May of 1934."
https://www.neh.gov/humanities/2015/mayjune/feature/in-the-1930s-radio-station-wlw-in-ohio-was-americas-one-and-only-sup#:~:text=WLW%20was%20initially%20allowed%20to,the%20rapidly%20expanding%20national%20networks.
Don
On Monday, September 12, 2022, 07:49:42 PM EDT, Joe Subich, W4TV
<lists@subich.com> wrote:
> So, where does that drive power go while the driver(s) are being
> tuned, and the final is on standby?
Drive power is relatively low and typically dissipated in the grid
circuit of the succeeding stage. For example, the BTR1 (pair of 4-400
modulated by a P-P pair of 4-400) - one of which is in my garage - has
a single 6146 driving the grids of the 4-400s probably less than 50W
carrier drive for 1 KW carrier output.
> Based upon that description, when WLW was running a full 500KW, I'd
> assume the engineer would set the carrier around 125KW, and then 100%
> modulation would peak at 500KW.
Nope ... that 500 KW was carrier power as is typical for AM broadcast.
The RCA BTR-1 is spec'd for 1 KW AM and will certainly do 5 KW PEP (125%
positive modulation) if one were using a scope to look at the output.
73,
... Joe, W4TV
On 2022-09-12 6:06 PM, Donald Fox via Amps wrote:
> One of the things I see that is different, as I have watched videos of the
>bigger transmitters firing up, is that they can bring the driver stages
>online, and have them drawing plate current, tune them, and then engage the
>final. Obviously, there is not tx/rx relay for a plain transmitter. So, where
>does that drive power go while the driver(s) are being tuned, and the final is
>on standby? There are plenty of such videos out there that are exciting to
>watch!
>
> FM of course, does not have any 'swing", so you crank the carrier where you
> want it to be, and it just sits there. AM on other hand of course, is set for
> about 25% of max carrier, and them modulation takes it up and down from
> there. Based upon that description, when WLW was running a full 500KW, I'd
> assume the engineer would set the carrier around 125KW, and then 100%
> modulation would peak at 500KW.
>
> Any way you slice it, that is a bunch of RF up the feedline!
>
> Don N8ECH
>
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