[AMPS] more about the input swamp circuit

[2]

Skipp - Your reply has bogus attribution marks.

>more alpha input circuit talk
>-
>>>The Alpha type circuit provides low swr to the exciter, 
>: Not low enough for transistor radios unless 
>: a tuner is used.  
>-
>Based on all the examples I've seen, the swr is low 
>enough for most radios.  
>- 
>>is also relatively broadband, is low in cost and physical - 
>>mechanical part requirements and easy to install. 
>- 
>: The tradeoff of having no flywheel is not small. - 
>-
>True but it was a relative trade off Alpha felt would 
>work, and it does to a point. 
>- 
>: Two 8874s in parallel have a driving Z of roughly half 
>: of 26-ohms at the negative V peak.  This requires 
>: matching with a Pi-network/flywheel.
>-
>Since this thread started, I tried to locate the magic 
>drive Z value with mixed bag and varied results.  An 
>amps member reported ~95 ohms for a single tube, 
>a W6SAI Radio Handbook says ~160 ohms and now 
>your 2 tube value.   Someone has to have the real value, 
>it's not listed anywhere in plain sight on the Eimac data 
>sheet I just looked up on the web. 
>- 
>The single tube ~95 ohm Z value works with the other 
>circuit values in the Alpha circuit diagram. 
>- 
>>The alternate half cycle is (for the example) pretty much 
>>just the resistor network and some C. So the toroidal rf 
>>xmfr secondary "load" halves. 
>- 
>: What is the swamper resistance?
>- 
>The Alpha 274 (two hole version) has a total parallel 
>swamp R value of 47 ohms as reported on the diagram. 
>The R network value in parallel with the 47.5 ohm dynamic 
>tube Z works out the 23.6 ohms.  The toroid secondary 
>value is reported to be 22.2 ohms.
> -
>: With solid-state radios, sans-tuner, the SWR usually 
>: needs to be 1.2:1 or better to avoid power foldback.  A 
>: swamper/transformer is not capable of that.  
>-
>Without getting into an argument, I will say that many if 
>not most of my common transceivers will drive into swr 
>levels higher than 1.2:1 without a problem. 
>- 
>>It would not provide flywheel, just "better" exciter 
>>matching in the alternate half cycle.  
>- 
>: Exactamente
>- 
>Better matching and the broad band response were 
>the desired results, above a flywheel effect.  I would 
>say the engineering goal was reached with the expected 
>results. 
>-
>skipp 
>
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-  R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.  
end


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