[Amps] feeding the input

[wb8jkr at juno.com]

  Since both sides of the filament are at (or should be) the
same RF potential, I don't see where it would make any
difference. Usually there is a capacitor connected acoss
the filament to ensure both sides are the same RF potential.


73,  Mark  WB8JKR


On Mon, 31 May 2004 21:06:57 -0400 "carl seyersdahl"
<carlseye at tampabay.rr.com> writes:
> I get the feeling that some may have misunderstood my question about 
> the
> resistors.
>   I was referring specifically to the RF negative feedback resistors 
> as used
> in the ckts. per Mr. measures's pages.
>   IE; , two caps of .01 mf. each from the pi-net input ckt , to one 
> each 10
> ohm resistor on each side of the "filament ckt" of a G-G amp. 
> (572b's) VS
> using two ten ohm resistors in series from One .02 cap off the input 
> ckt to
> the "fil." or cathode (as the case may be) ...!!!
>    Rich:::  maybe you are the one to answer this one.!!!
>     Please ????
>     carl / kz5ca
> ----- Original Message ----- 
> From: <peter.chadwick at Zarlink.Com>
> To: "carl seyersdahl" <carlseye at tampabay.rr.com>
> Cc: <Amps at contesting.com>; <amps-bounces at contesting.com>
> Sent: Monday, May 31, 2004 6:44 AM
> Subject: Re: [Amps] feeding the input
> 
> 
> >
> >
> >
> >
> > Carl was asking about feedback resistors in cathode/filament 
> circuits.
> >
> > The answer it that it seems to vary. The Mullard data sheet for 
> the
> QY3-125
> > (which is basically a 6151/ 4-125, as opposed to 4D21/4-125  - the
> > difference is that the 6151 doesn't have the metal base shell)) 
> says that
> > RF return connections should go to pin 1. The QY4-400 ( a 4-400) 
> has no
> > restrictions, although it's basically the same sort of device. The
> > QY4-250/6152 also suggests returns to pin 1 on early data sheets.
> >
> > The Philips version of the QY4-250 (QB3.5/750) says nothing about 
> filament
> > returns but says that both screen grid pins should be used to 
> equalise the
> > currents.
> >
> > With both QY4-250 and 4-250A's,  I have resistors in both sides. 
> They have
> > series caps (old fashioned molded mica) of 0.01mFd so that I don't 
> heat
> the
> > resistors with filament current.
> >
> > I guess this probably doesn't help too much - it seems it's 'pays 
> your
> > money and takes your choice' matter.
> >
> > 73
> >
> > Peter G3RZP
> >
> > _______________________________________________
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> > Amps at contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
> 
> 
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> 


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