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[Amps] input/output transformer switching

To: amps@contesting.com, amps@contesting.com
Subject: [Amps] input/output transformer switching
From: kg7hf@comcast.net
Date: Wed, 12 Dec 2007 04:37:32 +0000
List-post: <mailto:amps@contesting.com>
Hi everyone,

Thanks for all the replies on the LK500, everyone seemed to converge on the 
same area to check out.  I'm in the process of replacing the parasitic 
suppressor resistors.

While I wait for parts....

Background:   I've mostly finished up my solid state amp based on the MRF141G 
using Motorola app note AR313.  One of my original design goals was 160 - 2 
meter operation & 70cm, but that is another PA strip.  As it seems to be 
turning out, it's basically impossible to make 9:1 and 1:9 input/output 
transformers which work over that broad of a range.   The transformers I have 
work accoring to the app note, but that doesn't give any performance on 160, 
80, and 40 meters.

Solution:  Remove the original matching transformers and replace them with a 
circuit board with two input transformers and two output transformers and some 
relays to switch between them.  The difference between the transformers would 
be the permability of the core material one in/out set would be for lower 
frequency operation, the other for higher frequency operations.    I've drawn 
up a simple schematic showing the switched input and output transformers.  

http://home.comcast.net/~kg7hf/Project2/MRF414G_TEST1.JPG

Does this seem like it would be workable, assumeing lead lengths are all kept 
short?  Is there any way to reduce the number of relays?  I was possibly 
thinking about combining RL2 and RL4 since only half is used on each.

Thanks,
Paul KG7HF
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