Geoff wrote:
Gary Schafer wrote:
By "legal power out of the 813's" I assume you mean 375 watts carrier?
Why assume something that is false??
That statement is -designed- to put you on edge, Gary. Perhaps it's
just my perception, but it simply appears as if you're not paying
attention.
NO WHERE does it say that 375w of carrier is the 'legal' limit.
The LEGAL limit is 1500w PEP output. It's just a point of reference,
that if you modulate a 375w signal with a sine-wave to 100% audio, then
you will reach 1500w pep output. The truth of the matter is, we don't
-speak- in sine-wave. Our voices are rather asymetrical. Some of us
have voices that are rather 'peaked'. In order for the audio amplifying
equipment to properly modulate 375w of carrier, instead of needing to
only be 50% of the carrier, or 187.5w of needed audio, you -might- wind
up needing an audio system with the capability of producing upwards of
600w of AUDIO.
(ref: http://w5omr.shacknet.nu/~wa5bxo/asyam/Amplitude%20Modulation.htm)
THIS IS NOT TO SAY that you'll be pushing your positive peaks that high,
but in order to keep your signal clean, and well within "good
engineering practice", you certainly don't want any flat-topping or
distortion. Anything in the audio system that does -not- allow your
audio to be clean and free of distortion then, by definition, wouldn't
be operating within "good engineering practice".
While I'm at it, I'll say, again, that if I wasn't covered up
with neighbors, I'd run my rig at around 500w DC Input (around
1500v @ 350mA), make sure that the modulator was capable of
cleanly modulating the signal, and let the positive peaks float
up to wherever they like, -as long as- my negative peaks don't
pinch/cut the carrier. If it's 2500w PEP, then so be it.
(where'd I leave my black cowboy hat and six-shooter? ;-))
As it is, with neighbors on *ALL* sides of me, during the
day-time, I limit the power output of the 250TH final to 100w
OUTPUT (and probably reaching 500+wpep out) and between midnight
and 6am, it's at 200w carrier (around 800wPEP out, w/o cutting
the carrier off, with negative peaks)
73 = Best Regards,
-Geoff/W5OMR (aka: AM Outlaw)
(p.s. Does anyone (other than K4KYV) remember the phrase:
"When AM Kilowatts are outlawed, then Outlaws will run AM
Kilowatts!"?)
