[Amps] L-PI amp network

[Steve Bookout]

Thank Jim,

One of my big questions was if I could use GM3SEK's spreadsheet 
calculator.  I'm not too far off from what you came up with and that was 
because we used different numbers here and there.

I've got a brand new 50 ft coil of copper tubing to use up.  In the 
past, I've used solid #4 copper (3/16 inch dia) but too hard to work 
with and it work hardens terribly.   I'm winding it, by hand, on a form 
on a lathe.

Again, thanks for the input.

Steve

On 12/13/2022 9:18 PM, Jim W7RY wrote:
> Here is what I come up with... ~3000 ohms plate load impedance.
>
>
> Oh..... I cant attached to this group!
>
> But you can see it Steve since I copied you directly. The results are 
> highlighted in yellow.
>
> 73, Jim W7RY
>
>
>
> On 12/13/2022 5:23 PM, Steve Bookout wrote:
>> Hello Jim,
>>
>> 4kv.  It's about 4.2 kv, no load.
>>
>> On another point, for the group, 'somewhere, sometime', in more than 
>> one place on the web, I've seen where people recommended using 2.0 as 
>> the 'K' factor, instead of 1.5-1.8, etc.  This was specific to 
>> 8877's.  I used 2.0, as I very, very rarely use a microphone.
>>
>> Just wondering
>>
>> Steve NR4M
>>
>> On 12/13/2022 6:01 PM, Jim W7RY wrote:
>>> What plate voltage are you going to have on the tube of choice Steve?
>>>
>>> Jim W7RY
>>>
>>>
>>> On 12/13/2022 4:36 PM, Steve Bookout wrote:
>>>> Hello all,
>>>>
>>>> (First part is background, so you know a more 'overall' of what I'm 
>>>> doing.)
>>>>
>>>> I've been intending to finish a long-ago-started mono band amp for 
>>>> 10 meters, and I think I regained the enthusiasm I need to complete 
>>>> the project.
>>>>
>>>> I had started out going to use a pair of grounded grid config 
>>>> 4-400's only BECAUSE I HAVE A BUNCH.  That was then, this is now. 
>>>> I've recently found a treasure trove of 8877's and have determined 
>>>> that I have SIX of them!
>>>>
>>>> With the exception of one, all were unknowns, so I 'cooked' them on 
>>>> fil voltage only for a day, and then applied the B+. My test 
>>>> platform as a HB 8877 40 meter amp that I built in the mid 80's. It 
>>>> still uses the same tube.  Peter Dahl 3000 volt 6 KVA transformer, 
>>>> for 4000 volts.   22 watts drives it to 1500 out; ~ 600 ma/.030 grid.
>>>>
>>>> Over the period of about a week, I cycled all of the unknown tubes 
>>>> thru this amp.  They all were similar, taking 22 to 27 watts of 
>>>> drive for the same 1500 watts out;  550 ma to 600ma @.030 ma grid.
>>>>
>>>> That was the background for my real question for the group.
>>>>
>>>> Based upon GM3SEK's PI/PI-L calculator, I'm working with a plate 
>>>> load impedance of ~3000 ohms.  I know from my own experience, and 
>>>> that of others, that it's a pain to get the plate inductor 'right' 
>>>> so that it all works and tunes, as it should and make power with 
>>>> reasonable efficiency.
>>>>
>>>> I have never used an L-Pi, but I basically understand the idea.
>>>>
>>>> IS THERE A RECOMMENDED TOOL OUT THERE, WHICH WILL HELP ME FIGURE 
>>>> OUT MY TWO "L's"?
>>>>
>>>> Using GM3SEK's calculator, I see there is a line, 'Lead inductance 
>>>> (total from tube to tank, but excluding suppressor)', which I have 
>>>> played with.  Adding my 'L' inductance there, say '.6uh', does 
>>>> reduce the inductance associated with PI, and it does raise the 
>>>> value of the C1 capacitor.   ( I am using a 100 pf /15 KV vacuum 
>>>> variable and right now as I write this, I don't remember it's 
>>>> minimum C, but it's in the range of what I think you should see; 
>>>> maybe 5 pf?)  Using this, I was able to come up with about 15 pf, 
>>>> vs 4 pf in a standard PI configuration.
>>>>
>>>> Suggestions on if this would be an accurate way to figure this out? 
>>>>   Or, another/better way?   And, what should I be looking for as 
>>>> maybe a ratio of the 'L' vs the 'L' in the PI network. As I recall, 
>>>> I think I'm looking at about 1.7 uh.
>>>>
>>>> I would appreciate any constructive comments, or even precautionary 
>>>> ones.
>>>>
>>>> 73 de Steve, NR4M
>>>>
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>>>
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