[NLRS] Homebrew pre-amp design(s), 144, 222, and 432 MHz?

[David Palm]

Thanks for all the good replies on this.  Although I love the idea of trying
to build a preamp--and perhaps I will sometime, for the challenge of
it--several of you recommended the DEMI kits and indeed those are so cost
effective ($25 without the enclosure and connectors, both of which I already
have) that it's pretty much impossible to do better than that.  So likely
that's the way I'll go and save the precious bench time for some other
project (like those W1GHZ transverters that were featured in this month's
QST.)

Thanks and 73,

David W9HQ


On 9/24/09, Dr. Gerald N. Johnson <g369n849j at weather.net> wrote:
>
>
>
> On Thu, 2009-09-24 at 09:07 -0500, David Palm wrote:
> >
> > There are a lot of pre-amp designs floating around out there.  Can
> anybody
> > recommend well-established, works-everytime, homebrew designs for
> pre-amps
> > at 144, 222, and 432 MHz?  I'd like to try my hand at building, but it
> would
> > be helpful to start with something pretty well known.
> >
> > Thanks and 73,
> >
> > David  W9HQ
>
>
> Designs by W5LUA (and WB5LUA earlier) always work well. Classic designs
> by N6CA, Zack Lau (old call KH6CP, now W1VT), and Tommy Henderson,
> WD5AGO both classic and recent work well.
>
> Modern designs with a PHEMT first stage and maybe an MMIC second stage
> are in use in most all the EME stations world wide. They work and have
> good dynamic range. You will see a bias towards using Avago (used to be
> Avantech and before that HP) parts, partly because '5LUA is an
> applications engineer for that factory, but also because the parts work
> well and can be bought from distributors in the US as well as DEMI. By
> the time you find good quality parts, you may find DEMI kits to be quite
> reasonably priced. The NF of a PHEMT preamp is more set by the losses in
> the input circuit than the active device, so just any tuning capacitor
> may not result in the best performance. And it a congested area, you may
> want to consider an input circuit more complex than just the series
> variable and shunt inductor to achieve more out of band rejection.
>
> 73, Jerry, K0CQ
>
>
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