Joe Subich, W4TV-4 wrote:
>
>
> Older (tube) radios did not have "power level controls." They
> were operated at their design power and ALC reduced the gain
> to prevent overdriving the final amplifiers.
>
> Later radios added additional comparators to the ALC system
> to sense absolute power in an earlier stage and adjust for a
> relative power level but that is not ALC it is power control.
>
>
OK. I'm not going to get into an argument over terminology. I can't even
remember what the controls were called on radios I owned 35 years ago. In
these days of SDR nothing works the way it did then anyway. But we still
tend to use the same names for things that appear to provide similar
functionality.
> The K3 operates much like the older radios except that the
> level is controlled at the output of the DSP (before the IF
> filter) and not the grid of the final amplifier. The ALC
> adjusts the DSP so that when the power control is set for 5.0
> or 50 Watts the output power is 5.0 or 50 Watts at one specific
> frequency point in the SSB filter. The DSP then adjusts its
> (peak) output as needed to maintain the correct peak level
> based on the assumption that the gain of the RF chain does
> not change.
>
That does appear to be the case when DATA mode is selected, which is why I
observed a 3dB output power variation over the range of passband that a PSK
operator might operate in. But when I transmitted tones over a range of
frequencies in SSB mode with a bit of ALC active, the output power measured
level, which suggests to me that in SSB some gain control is being applied
from after the IF filter.
> Again, you are simply asking the ALC and power control circuits
> of the K3 to do something they can not, and were not designed
> to do. The RF chain is not flat across the IF passband; as
> long as the technology uses mixers and narrow filters it will
> never be flat. If you want to be able to "click to tune"
> without manually adjusting power levels get a Flex-5000 or
> a transmitter that uses "on frequency" RF generation.
>
That may be the eventual outcome. However the K3 appears to behave as I
would expect in SSB mode. So I am not convinced that I am expecting the
impossible.
-----
Julian, G4ILO. K2 #392 K3 #222.
http://www.g4ilo.com/ G4ILO's Shack http://www.ham-directory.com/ Ham
Directory http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3
--
View this message in context:
http://n2.nabble.com/K3-pwr-out-on-digimodes-tp2163956p2176772.html
Sent from the Elecraft mailing list archive at Nabble.com.
_______________________________________________
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
