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[VHFcontesting] SSPA Causing Serious Voltage Sag Under Load

To: <222Activity@groups.io>, "'Packrats'" <packrats@mailman.qth.net>, <Moon-Net@groups.io>, <vhfcontesting@contesting.com>
Subject: [VHFcontesting] SSPA Causing Serious Voltage Sag Under Load
From: David R Buckwalter via VHFcontesting <vhfcontesting@contesting.com>
Reply-to: K3SK@buckwalter.co
Date: Wed, 20 Aug 2025 15:42:03 -0400
List-post: <mailto:vhfcontesting@contesting.com>
 

 

I use Eltec server power supplies for my SSPAs and up until now I have not
had an issue.  I recently acquired a Larcan Hi-Hi that is capable of 1500
watts output on 222 MHz.  After making the necessary changes to use the
Larcan I connected for testing to my 50V 3000 watt Eltec power supply.  On
initial key down the amplifier easily puts out 1200+ watts but the supply
voltage drops significantly as does the RF output power.    When running my
other amplifiers I do not have voltage drop and everything works fine.
I have tried this with 3 different power supplies.  My assumption is I am
reaching the current limit of the individual supplies. 

 

If each Eltec is set to the same voltage and current limiting, can I
parallel them?   If so, is it any more complicated than connecting the
outputs together? 

 

 

Dave - K3SK

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