[Amps] New HF amplifier

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Mon, 02 Aug 2010 11:05:19 -0600, Larry Benko <xxw0qe at comcast.net>
wrote:

>
>What are you using as the basis for this blanket comment?  There is 
>absolutely nothing wrong with tapped toroids. 

REPLY:

Air core coils wound with the recommended wire size (ARRL Handbook)
are very reliable, high power toroids much less so. 

I have personally had two output tank toroids arc and burn up even
when the amp was run within specifications. Does that mean all toroids
are bad? No, it means that even when a professional engineer has what
he thinks is a good design, it can still be on the fragile side. 

Had there been air core coils in there, they would still be going
strong, no doubt. 

Don't want to start a flame war. If you like toroids, go for it. Just
beware. High power toroids can run for a long time and suddenly fail.
That's almost unheard of with air core. 

In my homebrew amp, I used #6 solid copper for all coils. It is strong
enough to be self-supporting (no plastic ribs needed, even on large
160 meter coils) and unless it gets hit by a direct lightning strike,
should last forever. 

73, Bill W6WRT