Message-ID: <4E36DC88.2050904@iup.uni-heidelberg.de>
Date: Mon, 01 Aug 2011 19:04:08 +0200
From: =?ISO-8859-15?Q?Stefan_Sch=E4fer?= <schaefer@iup.uni-heidelberg.de>
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To: rsgb_lf_group@blacksheep.org
References: <BDEMKFCNLMIILGIFNONNOEHADOAA.victor13@online.nl>
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Subject: Re: LF: RE: frequency doubler and divider
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Hi Victor,

Yes, that should work too. But as Rik says, there must be a 50% duty=20
cycle. And if it's a sine wave, using CMOS gates is not a good idea i=20
think, because there is a wide range where the gate can switch from L to=20
H or H to L. So a comparator must be choosen. And so the sine wave=20
should look clear (no modulation).
Anyway thanks, these are all useful ideas that makes us a bit more=20
creative :-)

73, Stefan/DK7FC

PS: Hmmmm, indeed, not bad that idea! My PA driver has a rectangular=20
output. I will feed that to the optocoupler stage (6N136) to prevent EMC=20
problems in the shack (already works sufficient). Amplified by a BC548=20
and a transformer between + and collector to a core that comes in=20
saturation, one could form a curve at 2x f input that has a sharp rising=20
slope and a lower falling slope. This 2x f signal should be suitable to=20
drive the SG3525. Ah, i'll try all that tomorrow. Hope the PA will be=20
active next weekend :-)


Am 01.08.2011 16:40, schrieb victor13@online.nl:
> Hi Stefan,
>
> wat about a bridge rectifier with a divider? Also broadbanded?
>
> 73
>
> Victor
>
> -----Oorspronkelijk bericht-----
> Van: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org]Namens Stefan Sch=E4fer
> Verzonden: zondag 31 juli 2011 15:06
> Aan: rsgb_lf_group@blacksheep.org
> Onderwerp: LF: frequency doubler and divider
>
>
> LF, VLF,
>
> I just re-invented the wheel ;-) Just by thinking i found one possible
> way how to double and divide a rectangular signal, to achieve an
> accurate 50 % duty cycle :-)
>
> One could take a simple XOR gatter like a CD4070 and a RC circuit. The
> time constant has to be about the half of the period of the wanted
> frequency, e.g. 3.6 us for 137 kHz. The output of the RC circuit
> (voltage across C) and the original signal is fed to one single input o=
f
> the gatter. Then the output frequency will be 2x f input.
>
> All this can be found in the internet as well, of course. But if you
> don't know about that possibility you don't know what to seach in the
> web too. At least i haven't found that method by searching and it also
> wasn't discussed here in the recent time. Furthermore i never saw it on
> a PA design by amateurs i found in the web.
>
> The output signal of the 4070 is then fed to the well known frequency
> divider consisting out of e.g. a CD4013. Then output frequency will be
> the same as on the input but the duty cycle will be accurate 50%!
>
> This is one method to (re-) obtain a suitable drive signal for a H
> bridge PA or class D PA after passing the driver signal through an
> optocoupler or so. I'm sure i will use that method now in several
> circuits, like in the new LF PA that still causes some problems,
> excactly on that matter!
>
> Later i found on the German wiki site:
> http://de.wikipedia.org/wiki/XOR-Gatter#Frequenzverdopplung
>
> 73, Stefan/DK7FC
>
>
>   =20