Joe
I take your point entirely which is why I said
"ALC is an analog signal for gradually reducing drive, which
might not be appropriate for shutdown."
Shutdown for me is for protection against gross overload and for this
another signal might be more appropriate. Since many users do not connect
ALC, some other signal for protection should/could be provided. The problem
yet again is that users might still ignore what the manufacturer offers, so,
the amplifier must protect itself.
David
G3UNA
----- Original Message -----
From: "Joe Subich, W4TV" <[EMAIL PROTECTED]>
To: "'David Cutter'" <[EMAIL PROTECTED]>; "'Elecraft Reflector'"
<[email protected]>
Sent: Tuesday, December 04, 2007 2:03 AM
Subject: RE: [Elecraft] linear amp shutdown (was ALC)
2 ALC has its problems and thus not always connected, but
everyone uses PTT which can be very easily disabled (allow
the rig to self protect) or tx inhibit, tx enable, or others?
I STRONGLY disagree ... I WANT a graceful foldback if the antenna
SWR is slightly out of range. 10% reflected power should not take
an amplifier off line. However there should be some way to cause
the exciter to reduce its power output so the amplifier does not
generate voltages or currents that will cause the demise of the
active devices.
Unless one has an amplifier and exciter that share a common
control microprocessor with data feedback or the amplifier has
an extremely sophisticated and FAST attenuator in the drive
line, ALC (e.g., an external gain control) is the appropriate
means of reducing power gradually.
Sure, if the reflected power is so high that it indicates an
antenna failure (50% reflected power), the appropriate action
is to disable the amplifier and potentially even the exciter
but that's over the top for 10% reflected power (2:1 SWR) or
even 20% reflected power (3:1 SWR).
73,
... Joe, W4TV
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of David Cutter
Sent: Monday, December 03, 2007 5:55 PM
To: Elecraft Reflector
Subject: [Elecraft] linear amp shutdown (was ALC)
In my view there are 2 issues here:
1 in my view the amplifier should be self-protecting
against overloads, eg
antenna fault (I am mindful of virtually any other equipment
which must be
tested by law with overload conditions)
2 ALC has its problems and thus not always connected, but
everyone uses
PTT which can be very easily disabled (allow the rig to self
protect) or tx
inhibit, tx enable, or others?
ALC is an analog signal for gradually reducing drive, which
might not be
appropriate for shutdown.
David
G3UNA
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