[TenTec] Ig drift on amps
Dr. Gerald N. Johnson
geraldj at storm.weather.net
Sun Feb 8 16:06:42 EST 2009
On Sun, 2009-02-08 at 12:07 -0700, pfizenmayer wrote:
> Looking at Gary's schematic attachment , it looks to me like the output
> network is a PI-L and the padders are at the "midpoint" rather than at the
> 50 ohm point. Dunno ham designs what TT designs a PI-L for at midpoint, but
> some typical ham designs run more like 300 ohms.
>
> 73 de Hank K7HP
>
That certainly complicates figuring the current in the padder because
that design midpoint impedance could be anything between 50 ohms and the
plate load impedance, though some mid value gives better performance
(harmonic reduction) and reduces the size of the loading capacitor
needed.
2 KW at 300 ohms is 775 volts RMS and at 600 ohms is 1095 volts RMS. 220
pf at 2 MHz and 1095 volts carries 3 amps. 6 amps at 4 MHz. May still
just be in the capability of the Cornell-Dubilier metal cased mica
capacitor for voltage, for sure for current.
Otherwise it may be needed to find some old Centralab 850 cylindrical
capacitors or equivalent. RF parts has carried some transmitter parts
like that, also Communication Concepts.
It would take details on the inductances of the two output coils and
would be nice to have the expected values of the load capacitors to
analyze the network for that midpoint impedance. Or maybe with more
work, just the inductance of the output coil.
73, Jerry, K0CQ
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