|[AMRadio] AM Amps|
w5omr at w5omr.shacknet.nu
Tue Jan 11 20:04:23 EST 2005
> 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
> 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
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