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Date: Fri, 28 Mar 2014 15:44:53 -0230 (NDT)
From: jcraig@mun.ca
To: rsgb_lf_group@blacksheep.org
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Subject: RE: LF: Polyprop caps [Was VO1NA_OK2BVG]
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Hi Dave and Stefan,

Thank-you for the very helpful information. I hope to get started=20
on the new QRO TX soon.

73
Joe VO1NA

On Fri, 28 Mar 2014, Dave G3WCB. wrote:

> Joe,
>
> Polypropylene caps are recommended for LF work. WIMA MKP types work well.
> FKPs are even better, if you can find them. It's the current through them
> that seems to be the killer, so it's best to make up the desired value wi=
th
> parallel combinations.
>
> 73, Dave G3WCB IO91RM
>
> -----Original Message-----
> From: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org]On Behalf Of Stefan Sch=E4fer
> Sent: 28 March 2014 10:09
> To: rsgb_lf_group@blacksheep.org
> Subject: Re: LF: VO1NA_OK2BVG
>
>
> Hi Joe,
>
> Class E is fascinating and can be high efficient, 98% or so. However the
> output impedance has to be quite exactly 50 Ohm +-j0! A SWR of 1.5 can
> reduce the efficiency significantly so that all the advantages of the
> class E design are lost.
> Thus, i'm using class-D designs. I have 2 PAs for 630m. A small one
> running at 12 VDC,
> https://dl.dropboxusercontent.com/u/19882028/MF/100W-475KHZ-PA.png and
> https://dl.dropboxusercontent.com/u/19882028/MF/DK7FC%20472%20kHz%20PA%20=
15W
> %2B100W.JPG
> and a large one giving 0...1.2 kW, running as a H bridge, switching
> directly at 320V DC.
> The efficiency can easily reach more than 90% too.
> For you, i assume a normal class D using 2 (or 2x2) FETs against ground,
> using a ferrite output transformer may be the best choice. This design
> is used by many active MF stns, i know.
> What power range do you inted to realise?
>
> 73, Stefan/DK7FC
>
> Am 28.03.2014 00:24, schrieb jcraig@mun.ca:
>> Hi Stefan,
>>
>> I have some IRFP140BPF hexfets. Using Alan's G3NYK Class E
>> design spreadsheet for 200 watts at 13.8 Vdd gives 144 and 119 nf
>> for C1 and C2 and 1.14 uH for L.  I have used silver mica for C1 and C2
>> but these are expensive.  What do you use?   I remember mentioned your
>> class e experiments.
>>
>> 73
>> Joe
>>
>> On Wed, 26 Mar 2014, Stefan Sch=E4fer wrote:
>>
>>>
>>> Am 26.03.2014 19:36, schrieb jcraig@mun.ca:
>>>> Perhaps some day I will QRO!
>>>>
>>>> Joe
>>>
>>> Yes, please :-)
>>>
>>> 73, Stefan
>>>
>>>
>
>
>
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