Message-ID: <B00A15B508BA416C9058AE592617412B@malcoHP>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <635074543.20161125135600@chriswilson.tv> <B17A095B4EB74117833274924D91D376@malcoHP> <9FCDDE00-7831-485E-9CAF-D15E3522A7B9@gmail.com>
In-Reply-To: <9FCDDE00-7831-485E-9CAF-D15E3522A7B9@gmail.com>
Date: Sun, 27 Nov 2016 15:49:25 -0000
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Subject: LF: Re: H Bridge power MOSFET based amps question
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John
I always used SQUARE WAVE to drive my class D es E amps.  The Decca 5501 
modules input is Sine or Sq wave,  the input cct shapes the sine wave to Sq
de mal/g3kev


-----Original Message----- 
From: John Rabson
Sent: Sunday, November 27, 2016 10:28 AM
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: H Bridge power MOSFET based amps question

My experiences with class E single ended amplifiers is similar to that 
reported by Mal. The only caveat I would add is that you should be quite 
sure that you have the right driving waveform. During my early experiments 
with a design based on G3NYK’s spreadsheet I tried a sine wave rather than 
the square wave it should have had. The result was lower efficiency and a 
short life for the FET.

John F5VLF

> On 26 Nov 2016, at 11:35, mal hamilton <g3kevmal@talktalk.net> wrote:
>
> Chris
> The Decca 5501 amp modules use a H bridge class D configuration followed 
> by a series resonant PA circuit and this is  probably one of the most 
> reliable amplifiers about. Use suitable rated FET'S to give the desired RF 
> output.
> Also the protection cct used avoids disaster in the event of an antenna 
> failure short/open cct,
> I have built lots of class D 1Kw push pull amps over the years for LF/MF 
> but they are vunerable to damage with load variations whereas the Decca 
> bridge amps survive. I never had a failure with the Decca, and have been 
> using them for many years.
> Another approach which is worth a consideration is the class E amp single 
> ended, these are very reliable and avoids the crossover switching problems 
> with the push pull system. Setting up procedure is critical but there 
> after very stable,
> Hope these observations help you