[AMRadio] Old Ham, New AM Enthusiast

[Rob Atkinson]

Driving an amp may be okay at first but after a while it might get
boring.  Most AMers shoot for some kind of plate modulated rig
eventually, but using the Icom as an exciter for an amp can be a great
start.  The one thing you have to be mindful of is most modern
commercially built amps are not made for AM; they are pretty much SSB
CW amps.  Some are better than others, for example the old Henrys and
Alphas.  To get a decent carrier to make one worth your while, you
need at minimum a 1.2 or 1.5 KW amp; not one of those 600 w. jobs.
You need tubes that altogether dissipate at least 1 KW, a plate v.
supply that can handle at least 1/2 A CCS current and a lot of cooling
through the RF deck and plate supply; not your typical quiet amp
cooling (low air volume which is okay for SSB).   Then you can drive
the amp to 250 or 300 w. carrier for 10 or 20 minutes and not have to
watch it constantly while you are transmitting.  I've worked guys
driving single 3-500 and they say they are running 300, one guy even
claimed 400 watts.  His transmissions were very very brief hi hi.
That's no fun.  If you go looking for an amp look for power out spec's
for some kind of continuous duty mode like RTTY and find out if there
is any time limit.  If for example you find a "legal limit" amp but
the mfr says for RTTY you have to drop the power out down to 800 w.
for no more than 10 minutes that's a tip off that something, maybe the
cooling, is going to have to be beefed up for AM.  A FWB rectifier
instead of a voltage doubler in the power supply is good to look for
too.

73

Rob
K5UJ