The grid dissipation is not so much of a factor, since it is inherent in
high u tubes. That's what you pay for high gain. As long as you keep to
class AB1 operation, you shouldn't have grid dissipation problems. The
mishaps happen usually with non ALC controlled transmitter chains, that
can't control the amplitude of the driving signal. It isn't much more
complicated to implement an ALC circuit than installing grid protection
circuits.
as for the other complaints, they are certainly true! But what can
you do? Install a $100 switch? A copper tube tank coil? Use a CCS rated
power transformer? These things will bring up the price at non competitive
levels, something a a manufacturer cannot afford these days.
This is why such a thing, with a little forethought will always be better
when home built than when bought. For a one off you can afford the best you
consider adequate.
Alex 4Z5KS
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Jim Thomson
Sent: Wednesday, March 24, 2010 3:56 AM
To: amps@contesting.com
Subject: [Amps] Good engineering
ORIGINAL MESSAGE:
On Mon, 22 Mar 2010 19:31:09 -0700, "Jim Thomson" <Jim.thom at telus.net>
wrote:
>
>## I wouldn't be holding Command or anybody else up as any kind of
>'standard of engineering excellence.' If these ham amps were built
>right, they would all have individual, adjustable bias for each tube,
>plus mating metering, real bandswitch's and real tank coils, and plate
>xfmrs... and maybe toss in a real tube..... and not something with a floozy
4 watt delicate grid.
REPLY:
Any fool can overbuild a product. Good engineers know when to stop, and good
engineers get paid good money to get it right.
73, Bill W6WRT
## Bill , got any idea what 3 x NEW EIMAC 3CPX-800A7's cost these days?
##That's the tube line up used in the HF-2500E.. really smart. The 12 ga
wireroller inductor,used in the 10 kw palstar ant tuner is a joke, along
with SO-239's,and the mickey mouse balun on the INPUT of the tuner.. which
will explode. Toss in undersized tank coils, bandswitch's, mickey mouse
tune/load padding schemes,t/r relays that hot switch, and you wonder why
the HB amp builder gets into designingand building his own stuff. Ten tec
brags abt the 3.5 kva CCS xfmr used in the centurion,and sez it's good for
7 kw.."IVS" [int voice service], yet it barely does 1.3 kw pep
out....[almost legal limit]. A buddy accidently had his cat fall asleep on
his footswitch for 2 hrs.His 87-A was pumping out a 1.5 kw FM cxr on 29.650
mhz. He had the optional cooling fan.The RF deck had turned into molten
glop ! Alpha tech tells him..... " don't believe the hype"The home builder
has the luxury of using what
ever components he wants.. and can get hishands on. Typ ham amps have cut
every corner there is. 1/4"-3/8"-1/2" cu tubing is cheapat home depot... so
why melt airdux ? Ceramic vac caps are readily available, so I use em
fortune and load. If something is marginal... I re-design it. Who's the
fool ? later... Jim VE7RF
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