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

[Vic K2VCO]

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

-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/