Re: [Amps] 200-ohm tank and "un-un" in HF amp design?

[Jim W7RY <w7ry@centurytel.net>]

Ummmm... He's using an 8877.

73
Jim W7RY

On 10/20/2013 9:56 PM, Vic K2VCO wrote:
> Don't believe the 1.8.
>
> I found that this is far from the correct value for the 4CX1000A. 
> Maybe it's closer for triodes like 8877s, maybe not.
> See
> <http://www.granta.g4axx.com/Linear_design_notes.php3>
> for an example of how to determine the load impedance from the the 
> constant current curve for the tube. Here's an 8877 datasheet which 
> contains those curves:
> <http://www.g8wrb.org/data/Eimac/3CX1500A7.pdf>
>
> On 10/20/2013 1:37 PM, Jim W7RY wrote:
> > Jim...
> >
> > To figure the plate load impedance:
> >
> > RP = EP / 1.8 X IP
> >
> > 1.8 = K factor for class AB1 (Changes with ZSAC)
> > RP = Plate Resistance
> > EP = Plate Voltage
> > IP = Plate Current
> >
> >
> > 1.8 X .65 Amps = 1.17
> >
> > 1.17/ 4000 = 3418 Ohms plate load impudence.
> >
> > Your actual voltage will more likely be 3800 with a .65amp load which 
> > brings the load down
> > to 3250 Ohms.
> >
> >
> > Better to just switch in some loading padders with your bandswitch.
> >
> > See the last 8 years of the ARRL handbook for the K8RA amplifier 
> > using the 3CX1500D7 tube.
> > There are some great examples there.
> >
> >
> > 73
> > Jim W7RY
> >
> >
> > On 10/20/2013 8:28 AM, Jim Barber wrote:
> > > 1500 watts
> > > 4kV, 625mA
> > > Single 8877 at around 4000 ohms plate impedance in AB2.
> > >
> > > Tnx,
> > > Jim N7CXI
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps