Date: Tue, 6 Dec 2016 14:22:00 +0000
From: Chris Wilson <chris@chriswilson.tv>
Organization: Gatesgarth Developments
Message-ID: <184658691.20161206142200@chriswilson.tv>
To: mal hamilton <rsgb_lf_group@blacksheep.org>
In-Reply-To: <B00A15B508BA416C9058AE592617412B@malcoHP>
References: <635074543.20161125135600@chriswilson.tv> <B17A095B4EB74117833274924D91D376@malcoHP> <9FCDDE00-7831-485E-9CAF-D15E3522A7B9@gmail.com> <B00A15B508BA416C9058AE592617412B@malcoHP>
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Subject: Re: LF: Re: H Bridge power MOSFET based amps question
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Hello Mal,

On Sunday, November 27, 2016 you replied to my thread.

Thanks for the replies everyone, I will try a low power Class E amp to
learn  more about this class of amplifier. On the cards for 2017 is go
at  an H bridge amp, too, I have much to learn and I thank you for all
for your patient help.


Best regards,
 Chris  2E0ILY                          mailto:chris@chriswilson.tv

 My part time LF grabber is at http://www.chriswilson.tv/grabber.html


> 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