High Power HF BA's?

Mark Shaum k9tr at DTNSPEED.NET
Sat Mar 29 18:33:50 EDT 2008

> 1.  Has anyone heard of a conversion of these
>     rigs to a single GI-7B as the sweep tubes
>     become unaffordable or unobtanium?

I have a couple conduction-cooled tetrodes (8072 I think) that are small 
enough to shoehorn one into the final cage of a sweep tube rig and  will run 
well at the usuall 600-800V B+ on hand.  Finding room for a heatsink/fan 
assembly and all the redoing of mechanical layout, neutralization and such 
makes this an imposing task.  I'm not familiar with the GI-7B but any swap 
of finals with something of differing mechanical and electrical 
characteristics is going to be a chore.

> 2.  Has anyone heard of a modification of these
>     so that the final RF amp stage may be used
>     as a SSB amp for an external exciter?
Could be done with a link coil on the grid coils, but that's more switching 
and you lose the ALC function which would be trying to cut gain at some low 
level stage as the finals started to draw significant grid current and start 
to splatter.  S'pose you could wire up an ALC output line to your exciter.

> 3.  Is anyone aware of one in decent cosmetic
>     and operating condition for sale?

Sweep tube rigs, especially Swans, show up at most every hamfest I attend.

Mark K9TR

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