I think the problem being alluded to is a burst of RF (at full output) from the
transmitter/transceiver which happens before the ALC can cut in and reduce it
to the proper level. If the designer does pay attention, it is easy to have
happen - the RF turns on abruptly while the ALC loop has too long of an attack
time so there is a bit of time before the ALC loop can come into play (delay
time in the ALC loop). It certainly could, in some units, be exaggerated when
running at lower RF levels because you have further for the ALC loop to ramp
the output back.
The latter problem is also affected by the fact that the RF amplifier has a
maximum RF level (i.e. the RF is clipped or limited). If your normal RF level
is just a bit below the maximum then the 'burst' is not (relatively speaking)
not that much higher. For example, if your amplifier is only capable of 150 W
and you normally run 125W then the burst is only 25W possible. If, on the
other hand, you are running 25W normally then the burst is 125W! Quite a
difference.
Hope this helps a bit.
73
Bob, WA2CKY
Blue Springs, MO. 64014
----- Original Message ----
From: Win <w0lz@winlyn.us>
To: Amps@contesting.com
Sent: Monday, March 19, 2007 10:17:08 PM
Subject: Re: [Amps] drive power
I hate to come back to this subject, but I am not sure I understand the
problem. Is the overshoot a product of the ALC outputted from the exciter
to the amp, or is it caused within the transceiver at significantly reduced
power settings.
In either case I should be able to see the overshoot if I put a scope across
the meter in my power meter. Is that correct?.
I currently reduce my FT-1000MKV from 200 to 50 watts, when driving my old
SB-220 amp on CW.
Win, W0LZ
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