I would respectfully disagree. There are lots of Tube final backups out
there and still some primaries...Smaller markets just don't get the Capital
budgets that larger ones do..Many of the large groups buy the good stuff for
the larger markets and send the junk on down the line to the tail draggers.
I spent a lot of my broadcast career installing the new and moving the junk
down the line for a couple of them... I would be afraid to make the
statement that NO US 50 KW station runs a tube PA ... you may be right, but
I would be a little leary to say it because there are a lot 50KW stations
out there..By the way I
installed the 1st 50 KW AM Broadcast transmitter in the US..1985
...KBMR --1130 Bismarck, ND..A Nautel. S/N 2
number 1 was in Canada.....We went through our share of VMOS FET's keeping
that baby putting out 50KW, but when all the transistors were good, she
would do about 65KW!!! 22 years later it still pops some FETs now and
then, but it's still running except at only 10KW now.....Several years ago
they brought up another 50KW on 710 and due to a license foul ups they had
to drop 1130 back to 10 KW or loose it.
73's
Chuck
W6RD
----- Original Message -----
From: "Rob Atkinson" <ranchorobbo@gmail.com>
To: <tentec@contesting.com>
Sent: Tuesday, October 30, 2007 3:41 PM
Subject: Re: [TenTec] SB-220 Tubes and QSK
Hi Jerry,
It's not about dBs; it's about paying your money and expecting a
certain level of performance and having the product deliver that. You
don't _have_ to run it flat out, but in the case of amps, (as I've
said before) If I pay X thousand dollars for a 1.5 kw amp, I damn well
had better be getting one that can put out 1.5 kw, a.k.a. If I'd
wanted a 1 kw amp, that's what I would have bought.
Now, here we have some poor fella who got a pair of RF Parts 3-500Zs
and he's got some pleasure from the fact that they put out 20% more
goo than his old tubes and you have to pour cold water on him. Don't
you feel great?
I won't get into the other business of how his 20% power increase
helps counter other system losses in feedlines, tank circuits and
ground loss and how it all adds up. You're the engineer; I'm sure you
know it all already.
By the way, no 50 Kw AM broadcast station runs a vacuum tube primary
anymore. They've all been running solid state harris and nautels for
years. some don't even have tube backups. In fact, no u.s. radio
broadcast station of any type runs tubes unless they can't afford a
new tx. The solid state rigs pay for themselves in a few years of
operation. You can get a new solid state 250 w. AM for about what an
Icom Pro III costs. About the size of a flie cabinet drawer, it'll
sit there in a rack and hum along for years. The only problem at the
tx site these days is crack heads pulling up the radials to sell for
scrap copper and yahoos shooting out the tower lamps.
73,
rob / k5uj
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