Date: Fri, 27 Jul 2012 10:28:49 -0400
From: "Roger (K8RI)" <k8ri@rogerhalstead.com>
Subject: Re: [Amps] Overdrive protection
On 7/27/2012 10:11 AM, Jim Hargrave wrote:
> Duh...
> Why not just use the RF PWR adjustment on the front of the transceiver and
> save all that costs and wasted heat dissipated by the attenuator.
>
That is the problem. With the power turned down, the first dit comes
through at full power on some rigs. This approach works just fine in
both of my rigs.
Although the 756 Pro line is notorious for this, mine does not do it,
nor does my FTDX5000MP.
As to ALC I do not use it. The amp has its own internal ALC so the
tiniest Amount of grid current will not only shut it down, but requires
a reset and wait for the tube warmup cycle again. It is protected for
about any thing I can think of.
Other than During a tune-up I've never had it kick out.
73
Roger (K8RI)
## No roger, your amp does NOT have internal ALC, What it has is grid
overcurrent
protection ! Some SS amps will switch in a pad asap, if too much drive
applied... and –or
kick the amp offline. And ditto with tube amps, like tetrodes.
## stick the wrong xcvr on there..like an icom 775, and it will trip all the
time..and be kicking itself
offline as soon as you apply drive, regardless of where u set the power output
control. A buddy here
in town had a 775dsp xcvr... and it put out well over 260 watts for the spike,
regardless of where the
po was was set to...even if set for 20 watts out. It fried his AL-80bx amp
too. 250 watts into a tube amp
= fried bandswitch.
## in any case, I would suggest tweaking the LOAD control such that the¨PO
drops 2%. Tune ur amp
up to say 1550 watts pep out,, THEN increase the loading ( decrease the C of
the load cap), so the
PO drops down to 1500 w pep out. ( 3.7% drop) Or tune up to 1600 pep
out..then tweak load cap
for 1500w pep out. Then its linear..and will absorb most spikes.
## see my other post on how to get rid of the spikes.
## Im surprised alpha has not made a list of lousy xcvrs . “warranty void
if ICOM 775 used” etc.
That would smarten up the xcvr makers real fast. “ warning, do not use the
following xcvrs, due to their
poor IMD. These IMD products will be amplified by your Alpha linear amplifier
to a much greater level”
later........ Jim VE7RF
Jim VE7RF
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