Bill;
The KPA100 is less efficient at lower power levels. Most amplifiers are
designed to have their best efficiency at their maximum power output.
Some digital modes do not transmit 100% power even when the transmitter is
sending a continuous character stream. PSK31 is an example; it is both
phase and amplitude modulated. For other modes, such as any FSK mode
including RTTY, the transmitter is running full power output continuously.
These modes should only be run at 25 watts unless you can supply better
cooling to the KPA100 heatsink.
-John
KI6WX
----- Original Message -----
From: "Bill Coleman" <[EMAIL PROTECTED]>
I'm just starting to get into RTTY with my K2 and I'm wondering how much
power I should use.
The KPA100 manual recommends 40 watts, with 25 watts for "higher-duty
cycle modes such as MFSK".
Now, this statement confuses me for two reasons. First, where does 40
watts come from? The KPA100 is rated for 100 watts of CW. Since CW has a
50% duty cycle, it would seem that the raw heat dissipation of the KPA100
should handle 50 watts of the 100% duty cycle of RTTY.
So, how do we arrive at 40 watts? Is the KPA100 less efficient when
producing 40-50 watts than it is producing 100 watts?
Second question -- how can one have a "higher" duty cycle than 100%? Can
someone explain how MFSK can produce more of a strain on the amplifier
than being directly keyed down on a single tone continously?
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
