Well the amp is back together. 40 meters will not load without the
additional loading capacitance! The tank must not be right! Oh, one thing
I did notice is that between 10 and 15 meters, you don’t need to move the
tune and load knobs to be resonate on both bands! I bet the 10 and 15 meter
Q is pretty high.
So I'll go back to the Ten-Tec original setup. I'll also add more
capacitance for 160 meters other than what's there. It does tune fine, but
the load cap is almost maxed out at 1900 KHz.
Thanks for all the info!
Jim W7RY
-----Original Message-----
From: Jim W7RY
Sent: Sunday, December 02, 2012 9:52 PM
To: AMPS
Subject: [Amps] Ten-Tec Centurion Load Capacitance
I’m working on a Ten-Tec Centurion for a customer. I noticed that the load
capacitor padders are not hooked to the band switch correctly. The schematic
depicts the way they are actually wired in an actual unit. Which is....
The load cap by itself is 800 pF. They add C13 which is 330 pF on 40 meters,
an additional C19 which is 430 pF on 80 meters, and NO additional loading on
160! This is a standard PI network tank
circuit. Not Pi-L. I would think the load padders would be needed on 80 AND
160. Not on 40.
I know there was some discussion here about using doorknobs instead of
Ten-Tec installed 2KV disks. When I get the amp back together after the
band-switch repair, I’ll see if the load padders drift as
reported. I think I’ll move the padders before I install the tank assembly
back into the amp.
Does anyone have any insight why Ten-Tec did this?
Is there enough loading capacitance in a stock Centurion for 160 meters?
BTW The older SB-220 has an 540 PF load cap in it, the newer SB-220 and the
HL-2200 have a 840 pF load cap. Heath adds a 500 pF mica on 80 meters.
73
Jim W7RY
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