Hi Chris,
Jon KE9NA said it pretty well.
It sounds like you simply have some bad tubes if indeed you do have adequate
plate voltage and filament voltage (check input taps on transformer).
Be certain that you have loaded heavily enough as this will cause you to
draw grid current before you reach saturation.
There will be a point when you have sufficient drive and the plate is
resonated you will see very little grid current (heavy side of loading) or
much grid current (lightly loaded).
73, Dan Magro
Radiodan W7RF, Portable Clinic
High quality Henry Radio RF Power Amplifiers for LESS!
New, used, unusual, classic radios, accys & RF POWER!
http://www.radiodan.com RFpower@radiodan.com
A trip to our web site is worth the click!
-----Original Message-----
From: KF0FX@aol.com <KF0FX@aol.com>
To: amps@contesting.com <amps@contesting.com>
To: <amps@contesting.com>
Date: Tuesday, June 16, 1998 2:19 AM
Subject: [AMPS] 3-500Z 101
>
>This may seem like a real basic question but keep in mind -- I write
software
>for a living.
>
>As I increase the drive to my SB-221 (2x3-500Z), there is a fairly linear
>relationship between input drive power and output power UNTIL I reach a
magic
>point where the output doesn't increase as fast (gain decreases) and the
grid
>current rises dramatically. Prior to this point, the grid current only
goes
>up slightly with increased RF drive. My question is, why? What causes the
>grid current to go up and what is this telling me? The amplifier has a
gain
>(<500 watts out) of about 15 at 40 & 80 meters. At more than 800 watts,
the
>gain decreases and it is difficult to get more output power.
>
>Comments are appreciated!!
>
>73's
>Chris, KF0FX
>KF0FX@aol.com
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
>
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|