[Amps] GI7B Question - Input Matching

[Joe Subich, W4TV]

> Doesn't the Alpha 76 use the broad band transformer along 
> with a bank of resistors to present the proper load?

Yes, but it is not a good design for solid state rigs. 
The bank of resistors only tempers the impedance swings 
they don't provide the energy storage flywheel of the 
tuned circuit.  Without the flywheel, IMD issues are not 
resolved. 

73, 

   ... Joe, W4TV 
 



> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Roger
> Sent: Sunday, March 14, 2010 9:02 PM
> To: James Colville
> Cc: Amplifier Reflector
> Subject: Re: [Amps] GI7B Question - Input Matching
> 
> 
> 
> 
> James Colville wrote:
> > You need the flywheel effect that a C-L-C tank circuit can 
> provide. A 
> > broad band transformer is not the answer. This was just 
> discussed here 
> > at length not long ago.
> >   
> Doesn't the Alpha 76 use the broad band transformer along 
> with a bank of 
> resistors to present the proper load?
> 
> 73
> 
> Roger (K8RI)
> > 73
> > Jim W7RY
> >
> >
> >
> >
> > On Sun, Mar 14, 2010 at 2:58 PM, ZL2AAA <zl2aaa at paradise.net.nz> 
> > wrote:
> >
> >   
> >> I think you will find it's nearer 35ohms.Morrie
> >> ----- Original Message -----
> >> From: "Lee Buller" <k0wa at swbell.net>
> >> To: <amps at contesting.com>
> >> Sent: Monday, March 15, 2010 9:30 AM
> >> Subject: [Amps] GI7B Question - Input Matching
> >>
> >>
> >>     
> >>> I have been reading about the GI-7B Russian made tube.  It seems 
> >>> that the input impedance of two tubes is around 100 ohms. 
>  Could you 
> >>> not just use
> >>>       
> >> a
> >>     
> >>> 2:1 transformer to make a match from 50 ohms to 100 ohms? 
>  What am I 
> >>> missing here.
> >>>
> >>> Lee - K0WA
> >>>
> >>> Ham Radio Operators:  Kansas QSO Party is August 28-29, 
> 2010.  See 
> >>> www.ksqsoparty.org for details
> >>>
> >>> In our day and age it seems that Common Sense is in short 
> supply.  
> >>> If you don't have any Common Sense - get some Common 
> Sense and use 
> >>> it.  If you can't find any Common Sense, ask for help 
> from somebody 
> >>> who has some Common Sense.  Is Common Sense divine?
> >>>
> >>> Common Sense is the image of the Creator expressing 
> revealed truth 
> >>> in my mind. -  J. Wolf 
> >>> _______________________________________________
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