[Moon] [Moon-Net] 3CX1500 PA 144

[Edward R Cole]

Fausto,

I agree and you will see shift as you increase power because 3CX1500 
changes impedance as more anode current is drawn.  Once I had 
400-600w I found adjusting loading cap and anode cap made more 
output.  It took a lot of playing with the loading cap to find the 
"sweet spot" for best operating.  You have to move up drive in steps 
to get into the proper  tuning.

I found that I needed 55w drive for 1400w.  If I run up to 75w output 
goes to 1800w, but that is above legal limit in US.
My HV is 3700v when output is 1400w so drive and anode current are 
dependent on what your loaded HV runs at.  Lower HV will require 
higher anode current for the same RF level.

I first started with a HVPS that could only provide 2500v at 400ma 
for 600w output.  Only needed about 35w drive.  series of HVPS 
finally reached 4200v unloaded and 3700v at 700ma for 1400w output 
with 55w drive.

I had 3500v at one point and that only gave me 800w.

GL
Ed

At 11:14 PM 8/26/2015, Fausto Coletti wrote:
>I thank everyone for your suggestions,
>
>I did other tests and indeed the power delivered by the driver 
>varies with the input SWR
>of the PA.
>At the moment I'm using for the test an FT225RD as a drivers.
>If I tune the input of the PA for minimum SWR (I can obtain a 1.5 : 
>1), the output power
>of the TX is about 20W for 450W out. HV is 3500V unloaded.
>I think this is the condition of correct tuning , now I try to drive 
>the amplifier with more power
>by using an intermediate driver.
>
>73, Fausto IK4NMF
>_______________________________________________
>Moon-Net posting and subscription instructions are at 
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73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
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