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

[Vic K2VCO]

Right. I said maybe and maybe not. I also included a link to the constant-current curve 
for the 8877 so he can find out for sure.

On 10/20/2013 10:16 PM, Jim W7RY wrote:
> 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
>>
>
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-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/