[hpsdr] Penelope T2 orientation - additional info

[Bruce Beford]

> -----Original Message-----
> From: Graham / KE9H [mailto:KE9H at austin.rr.com] 
> Sent: Saturday, November 14, 2009 2:24 PM
> To: Bruce Beford
> Cc: 'n3evl'; hpsdr at lists.openhpsdr.org
> Subject: Re: [hpsdr] Penelope T2 orientation - additional info
> 
> 
> Bruce:
> 
> To the extent that the transformer does not present 75 Ohms 
> to U6, the answer is yes.  It is a 1.5 to 1 impedance ratio 
> transformer, so it will present more like 33 Ohms 
> (differential load) to U6.
> 
> I have not personally looked at the load variation tolerance 
> of U6 run in this configuration.  Penelope seems to be well 
> behaved into loads close to 50 Ohms.  The circuit is very 
> similar to the output stage of the basic FlexRadio-1000.
> 
> --- Graham / KE9H
> 
> ==
> 


Thanks for the reply, Graham. This is what I was thinking as well (33 Ohm
net differential load for U6). 

This means that we are dissipating almost one quarter of our output power in
R4 and R13. (33 ohms + 10 ohms total of R4 and R13 = 43 ohm load for U6)
Since the 10 Ohm combination of R4 and R13 is about 23% of the total load,
about 23% of the available output is disssipated there. Hmmm....



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