[1000mp] Re: amps

[J. Mc Laughlin]

Dear Lou:
    Re: Alpha 99
    I mentioned 1.6:1 VSWR as a means to indicate that the Alpha 99
shuts down if presented with too much reflected power.  The trip point
for shutdown is about 150 watts reflected.  Once I had changed antennas
and receiving band leaving the transmit VFO on another band.  The amp
immediately went to fault mode.
    In short, the Alpha 99 has a protection circuit on everything that
might be a problem.  The up side is that the amp is protected from
"senior moments."  The major downside is that you can not accommodate
antennas with higher VSWR without using a "tuner."  I have expended a
great deal to have antennas not needing a "tuner" (and thus avoiding
their losses and their need to be one more thing to adjust when changing
bands) and yet at the bottom of 40m I am limited by the Alpha 99's VSWR
protection circuit.

    A major plus has been the excellent break-in keying on CW.  Yes, it
takes under 60 watts to drive the Alpha 99 and those watts see a very
low VSWR.  Once you have found the sweet spots of the tuning (the manual
is not effective in explaining how to do this, but it does give you
starting points that have been measured for your amp), retuneing takes
little time/effort.  The amp has no difficulty opperating on
non-traditional bands.  "Converting" the amp to work on the higher bands
involves little more than a snip.
    I do not like the long warm up time nor the lack of a 1 min. cool
off timer after power is cut.

    I regret that my statement about 1.6 VSWR was taken literally.

    It sounds as if you are zeroing in on an amp.  Thanks for sharing
your process.
        73    Mac   N8TT
J. Mc Laughlin  -  Michigan USA
Home:  JCM@Power-Net.Net
Office:  JCM@McLMcL.Com
----- Original Message -----
From: "lhlousek" <lhlousek@nvbell.net>
To: <1000mp@mailman.qth.net>
Sent: Saturday, July 13, 2002 8:53 AM
Subject: [1000mp] Re: amps


> Very interesting and informative amp info again.  Thanks!
>
> I�ve pretty much ruled out the AL-1200 and AL-82 on the basis that
they can take over 100W of drive to reach 1500W
> depending on band.
>
> That leaves the AL-800H and AL-1500.  Also in the running is the Alpha
99.  All get by with between 50 and 60W of drive.
>
> It appears that among the 4 Ameritron 1.5KW amps, only the AL-1200
uses a tube with thoriated tungsten filaments.  The
> 800H is the only one that employs a fast grid current detection to
protect the tube (also has dynamic bias control). The
> AL-1500 is rated for full output only on the traditional bands (80% on
WARC bands).  I assume 10 meters can be enabled
> on the 1500 by a licensed ham although the Ameritron info doesn�t say
so.
>
> It was said the Alpha 99 wouldn�t go above 1.6 SWR.  I assume this is
because the high SWR protection kicked in.  The
> Alpha sense SWR and 6 other parameters to protect the tubes.  Among
the Ameritron amps it appears only the 800H has any
> protection circuitry and it is only for grid current and transformer
temp.  With QSK it is $1100 less than the Alpha.
>
> To me, it seems the only real downside to the 800H compared to the
other amps is that it is rated for only 1kW constant
> carrier instead of the 1.5kW.  I operate 99.9% CW and have no
experience with RTTY .  RTTY may be constant carrier but
> what is the typical TX/RX duty cycle?
>
> Lou W7dzn