[R-390] Distribution Amplifier

[Jim Brannigan]

Good points.  An attenuator ahead of the amplifiers should help with any
overload problems.  The author includes filters for AM and VHF in the basic
design.

Also, many BA receivers of lesser pedigree than Collins need help above 20
Meters or so.

Jim

> Bob brings up a good point that I think is easily overlooked.
>
> The project has two area in which gain is applied, the distribution
> section, and an optional rf amp ahead of that.  In correspondence
> with the author, I expressed my concern that unknowing builders would
> carelessly include as much gain as they could before the front end of
> their receivers and I suggested some article language cautioning its
> use.
>
> As I'm sure all of us know, most HF receivers seldom need another rf
> stage, not to mention the '390 series.  As Bob points out, IMD and
> other bad things are more likely to happen even without the added
> gain block.  I hope potential builders of the distribution device
> keep that in mind.
>
>                Dennis
>
> > Hi
> >
> > Well don't throw out all the glow in the dark stuff quite yet .....
> >
> > The video amplifiers that form the heart of the ARRL project are
> > pretty darn nice little chips. However they are not rated for IMD and
> > their harmonic distortion numbers begin to climb as you go past about
> > 10 or 12 MHz. That isn't to say they fall apart. Far from it they
> > probably work pretty darn well considering what they are.
> >
> > What they are not is the tuned RF front end on an R-390. I would be
> > very interested to see how they do when attached to a couple hundred
> > feet of wire with the bands open ...
> >
> >  Take Care!
> >
> >   Bob Camp
> >   KB8TQ