What is the recommended ratio for the modulation on the screen of
4-1000s' When I ran 813s as class C plate modulated finals, I always
found it to need adjustment depending on the audio that self modulates
the grid, the amount of drive, and plate loading. The best I had was a
screen winding on the modulation XFMR. Keeping the screen in phase with
the plate modulation was always a bear of a job.
The best I ever did was with a 6146 final using a screen
dropping resistor I placed a 20 uf electrolytic in series with a 10 watt
resistor whose value was chosen to regulate the level of audio the two
piece network was place from screen to ground which reduced the audio on
the screens to about 40 percent when the plate was at 100 percent.
John
WA5BXO
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester
Sent: Sunday, November 30, 2003 12:23 AM
To: amradio@mailman.qth.net
Subject: Re: [AMRadio] Modulation of the screen grid
Since the screen modulatiot impedance is at much higher impedance than
the
plate modulation impedance, you can get by with much lower coupling
capacitance that keeps DC off the screen modulation transformer than 4
uf.
0.5 or 1 uf should be enough.
I once tried a similar circuit to modualte the rf driver stage along
with
the final.
Don K4KYV
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