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Re: [Amps] New HF amplifier

To: Larry Benko <xxw0qe@comcast.net>
Subject: Re: [Amps] New HF amplifier
From: Jim W7RY <w7ry@inbox.com>
Date: Mon, 2 Aug 2010 17:15:44 -0800
List-post: <amps@contesting.com">mailto:amps@contesting.com>
So you're saying Alpha, Ten-Tec, Jim W8ZR, Jerry K8RA and myself are all wrong 
and their designs don't or wont work? 

73 
Jim W7RY 


-----Original Message----- 
From: xxw0qe@comcast.net 
Sent: Mon, 02 Aug 2010 18:54:58 -0600 
To: w7ry@inbox.com 
Subject: Re: [Amps] New HF amplifier 

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@comcast.net Sent: Mon, 02 Aug 2010 
11:05:19 -0600 To: amps@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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