[Amps] MRF141g amp kit offered by CCI

[Paul Decker]

Hi Ian, 

I've had similar expierences with Han, although I was trying to get the kit to work from 1.8 to 60 Mhz.  I found it very difficult to bias the kit and to keep oscillation from occuring and very easy to destroy the transistor. 



I think for the price of the kit, it's just as easy to chase down your own parts and to even etch your own circuit board.  The only troublesome parts to find are the balun materials, specifically the coax, but you could purchase those from cci. 



Regards, 

Paul 








Does anyone have experience using this Motorola RF power MOSFET device in the kit AR313 300W offered by Communication Concepts, Inc? 
The appeal is the broadband capability across 10MHz to 150 MHz. 

The idea is to use it on 50 and 70 MHz. 

73, 

Ian ZS6BTE. 

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Message: 2 
Date: Mon, 22 Aug 2011 18:24:49 +0900 
From: "Han Higasa" <higasa at plum.ocn.ne.jp> 
Subject: Re: [Amps] MRF141g amp kit offered by CCI 
To: <amps at contesting.com> 
Message-ID: <3AE8E816FD06482D957B254CE2676CBB at yukikaze2010a> 
Content-Type: text/plain; format=flowed; charset="iso-8859-1"; 
        reply-type=original 

hi Ian 

I have bought one MRF151G kit from CCI and  made 
experiments for long. There are some tips to tell. 

It has too much power even on 2nd and 3rd harmonics 
such as -16dBc (7.5W @300W out). 
You need an absorption type LPF to address these 
high power harmonics. Normal pi-LPFs can burn. 

It is because of high-gain on unnecessary high band 
and it can not be suppressed by feed-back resistors. 

Ballancing two FETs in a gemini package by 
separate gate bias circuits is better to lower these 
harmonics. 

And, maybe it is a fatal defect of the kit - input and 
output board are separated and the FET tend to oscillate. 
You need to short these boards with two pieces of 
cupper ribbon near the FETs. 

It may be the same on MRF141G kit and you need very 
careful experiments to make it work on your desired 
band - GL. 

de Han JE1BMJ.