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Re: LF: RF Ferrite - off topic for LF and Micro waves

To: [email protected]
Subject: Re: LF: RF Ferrite - off topic for LF and Micro waves
From: [email protected]
Date: Thu, 14 Sep 2006 08:34:39 EDT
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In a message dated 14/09/2006 08:10:00 GMT Standard Time, [email protected] writes:

The PA uses an MRF 141G Mosfet device rated for 300 Watts out with 14dB gain.  The circuit  itself is quite simple - see the data sheet for teh MRF141G -  and would have been finished a long time ago but for the output transformer.

Andy  G4JNT

Andy.
 
I've used the transformers from the Granberg application note for the MRF151G for comms relays on band 2.  This transformer arrangement appears very efficient and did not need the recommended ferrite sections.  I would suggest you try the 25 ohm coax line transformers but make them just a little larger then Granberg suggests.
Another method is to use two sections of RG58 or its PTFE equivalent in parallel to get the correct 25 Ohm impedance. These are not quite so efficient as the semi rigid but are still OK.
 
I don't have a spare semi rigid transformer, but I'll bring one of the commercial ones produced by Communications Concepts in the USA on Sunday. You may be able to create an easy way to duplicate it.
 
 
 
 
Regards
 
David   'MRF
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