[Amps] New HF amplifier

[Larry Benko]

Jim,

Yes the comments hold true period!  Flux in any core with shorted turns 
will cause extra loss with the exception of a type -0 core which has 
u=1.  I have seen shorted turns on a toroid core causing the toroid to 
heat to the point of cracking.  The shorting contacts on most 
bandswitches were designed for air core inductors where leaving the 
unused part of the coil open can result in bandswitch arcing.  Shorting 
the unused turns in an air core inductor does cause some small loss but 
it is generally deemed to be the preferable choice to having the 
bandswitch arc with the turns open.

For what it's worth you can generally make an inductor for 80 or 160m 
which has higher Q when wound on a low loss toroid vs air.  This 
statement of course needs to be qualified with the requirement that we 
want the amp to be relatively compact in size so that we can't allocate 
a spacious cavern for the output network.

Larry, W0QE


Jim W7RY wrote:
> Do your comments hold true for the L coil?
>
> The tapped L network coil in most amplifiers uses a shorting switch.
>
> 73
> Jim W7RY
>
>
>   
>> -----Original Message-----
>> From: xxw0qe at comcast.net
>> Sent: Mon, 02 Aug 2010 11:05:19 -0600
>> To: amps at contesting.com
>> Subject: Re: [Amps] New HF amplifier
>>
>> What are you using as the basis for this blanket comment?  There is
>> absolutely nothing wrong with tapped toroids.  What causes problems is
>> treating them as is usually done for air core coils which have the
>> unused turns shorted out.  On a toroid you do NOT short out any turns if
>> some of the turns are active.  Otherwise you get significant loss and
>> heating in the toroid.
>>
>> Larry, W0QE
>>
>> Dennis OConnor wrote:
>>     
>>> Tapped toroids show that the designer was too cheap to do the job
>>> right...
>>>
>>> Built cheap, for the cheap! Move along folks, nothing to see here...
>>> Move along...  Keep moving...
>>>
>>>
>>> denny / k8do
>>>
>>>
>>>
>>>
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>
>