Guys,
Forgive me for being a knuckle head, but because the human voice is
asymmetrical, won't this prevent the screen circuit from properly following
the "modulated" grid, whereby tossing linearity out the window??
Mike(y)
W3SLK
----- Original Message -----
From: Radio WC6W <wc6w@juno.com>
To: <2@vc.net>; <amps@contesting.com>
Sent: Thursday, October 26, 2000 5:03 PM
Subject: [AMPS] Re: G2DAF Amps Circuit
>
>
> On Thu, 26 Oct 2000 12:31:43 -0700 measures <2@vc.net> writes:
> >> If the DAF is built per the original design, with a time constant in
> >>the screen circuit that will allow the screen voltage to follow the
> >>envelope of the SSB signal, then a two-tone test will give valid
> >results.
> >>
> >What time constant? A two tone signal produces constant output in DAF
> >amplifiers, therefore the screen potential can not be following
> >anything.
> >
>
> Hi RIch,
>
> The effective screen resistance of the 4-125A is going to vary quite a
> bit in the DAF as the voltage is going to wander. Let's assume a typical
> value, for the moment, in the range of 10K-15K ohms plus there is an
> additional 27K, if I recall correctly, resistor to ground in some DAF
> implementations. Since there is a .005 uF capacitor in the DAF screen
> circuit, and neglecting the impedance of the charging circuit for the
> moment, the time constant of the screen "supply" is around 25-50 uS
> (considering the two screens plus maybe the resistor). This will be a
> little faster at higher drive levels and somewhat slower a lower drive
> levels
>
> In any case, it is quick enough to follow the envelope of a typical two
> tone test signal or voice generated SSB.
>
> 73,
> Marv WC6W
>
>
>
>
>
>
>
>
>
>
>
>
>
> *
>
> ________________________________________________________________
> YOU'RE PAYING TOO MUCH FOR THE INTERNET!
> Juno now offers FREE Internet Access!
> Try it today - there's no risk! For your FREE software, visit:
> http://dl.www.juno.com/get/tagj.
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
>
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|