[AMPS] broadband L at output

[Phil Clements]

> Thanks for the advice!!
>
> But seriously does this allow you to use a smaller C at the output?, or
> a lower voltage C at the output. I am curious about this. Since using smaller
> cheaper capacitors is appealing to me since they just not readily available
> here.  I would of thought that the output impedance is higher hence the
> voltage is higher, but i am not sure.

You are correct about the higher voltage. Here is where the savings comes
in:
Let's say you are building an amp with a plate impedance of 2000 ohms.
The value of the load C in a pi network on 160 meters is 2284 pf. To get
this, you will need a variable capacitor (1000-2200 pf) PLUS a fixed capacitor
to pad the variable, AND a dedicated position on the band switch to switch
it in and out. If your C2 load cap is less than 1200 pf, you must repeat this
process for 80 meters also. Now, lets add the 4:1 un un transformer. You
now need only a 1500-2000 pf loading capacitor to cover all bands....no
expensive door knob  or mica padders, and no extra band switch contacts.
This does not impact the cost for the home builder too much, but it represents
a huge savings to the amp manufacturer producing many units. There is
nothing wrong with this method. What is wrong is representing this arrangement
as something superior in harmonic suppression to the Pi network.

> Thanks for your help anyway, beeing hams and cheapskates i wonder why the
> idea has not caught on.

The idea has not caught on because most operators need the additional harmonic
suppression of a Pi-L network, especially in urban areas on the low bands.

> >Subject: Re: [AMPS] broadband L at output
> >Date: Wed, 19 Jan 2000 10:48:16 -0600
> >
> > >
> > > Several companies are starting to use a 4:1 transformer at the output of
> >the
> > > tank circuit. Does this work as well as the conventional PI/L network?
> >What
> > > are the pros and cons of doing this? I am considering using this
> >technique
> > > on my 4cx1500b amp, since it will use a 50 passive grid combined with a
> > > roller in the tank, eliminating a L switch is attractive.
> > >
> > > Pino
> >Beware of the "Snake Oil" salesmen trying to tell you great stories of better
> >IMD and harmonic suppression with the 4:1 coil...pure Bovine Scatology.
> >All the 4:1 transformer does is allow them to use a cheaper loading
> >capacitor.
> >
> >Caveat Emptor!
> >
> >(((73)))
> >Phil, K5PCV




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