[Amps] feeding the input

[R.Measures]

On May 31, 2004, at 6:06 PM, carl seyersdahl wrote:

> I get the feeling that some may have misunderstood my question about=20=

> the
> resistors.
>   I was referring specifically to the RF negative feedback resistors=20=

> 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=20
> each 10
> ohm resistor on each side of the "filament ckt" of a G-G amp. (572b's)=20=

> VS
> using two ten ohm resistors in series from One .02 cap off the input=20=

> ckt to
> the "fil." or cathode (as the case may be) ...!!!
>    Rich:::  maybe you are the one to answer this one.!!!

=F0  Hello, Carl -- On 160m,  driving both filament leads results in=20
applying equal drive to both ends of the cathode/filament.  However,=20
since 0.02uF represents only c. 5=BDs of XC, this is no big deal.  =
cheerz

>     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=20=

>> that
>> RF return connections should go to pin 1. The QY4-400 ( a 4-400) has=20=

>> 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=20
>> filament
>> returns but says that both screen grid pins should be used to=20
>> equalise the
>> currents.
>>
>> With both QY4-250 and 4-250A's,  I have resistors in both sides. They=20=

>> have
>> series caps (old fashioned molded mica) of 0.01mFd so that I don't=20
>> 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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>
>
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>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org