If you look closely at the AL1500 it is pi L only on 160 and 80. The L2 coil
is completely shorted out on 40 - 10 meters.
With pi L a much smaller output tune capacitor can be used than with just a
pi network as the impedance at the output of the pi part can be made higher
than 50 ohms which requires less capacitance to tune.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
> On Behalf Of Carl
> Sent: Wednesday, January 26, 2011 11:41 AM
> To: Ulf (SM0NOR)
> Cc: amps@contesting.com; Vic K2VCO
> Subject: Re: [Amps] Pi/L in Ameriton amps?
>
> The designers choice
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "Ulf (SM0NOR)" <ulf@sm0nor.com>
> To: "Carl" <km1h@jeremy.mv.com>
> Cc: "Vic K2VCO" <vic@rakefet.com>; <amps@contesting.com>
> Sent: Wednesday, January 26, 2011 11:32 AM
> Subject: Re: [Amps] Pi/L in Ameriton amps?
>
>
> So, if I interpret this correctly the lower Q of L2 makes the tank less
> sensitive to a wider frequency change? The conclusion of that would thus
> be
> that it is not necessary to tap L2 for each band? How come most
> amplifiers
> do that then?
>
>
> 73's
>
> Ulf (SM0NOR)
> ulf@sm0nor.com
>
>
>
> On 26 jan 2011, at 16.28, Carl wrote:
>
> > It allows a lower tank Q so there is less retuning needed and the L
> takes
> > care of the higher harmonic content. Ameritron has been doing that
> since
> > their beginning.
> >
> > Carl
> > KM1H
> >
> >
> > ----- Original Message -----
> > From: "Vic K2VCO" <vic@rakefet.com>
> > To: <amps@contesting.com>
> > Sent: Wednesday, January 26, 2011 10:06 AM
> > Subject: Re: [Amps] Pi/L in Ameriton amps?
> >
> >
> >> It's common to use a pi-L only on the lower bands and a simple pi on
> the
> >> higher ones. This
> >> may be in order to use a smaller-sized output capacitor. Or perhaps
> >> additional harmonic
> >> suppression is necessary on the lower bands to meet FCC (etc.)
> >> regulations.
> >>
> >> On 1/26/2011 4:35 AM, Ulf (SM0NOR) wrote:
> >>> Yes, you are right.... I was confused because I thought it said
> "pi-l"
> >>> in the specs
> >>> sheet. But it doesn't.
> >>>
> >>> Still my question applies to the bigger amplifiers. For example the
> >>> specifications of
> >>> AL-1500 says "pi-l" but if you check the schematics, the third coil,
> >>> after C2, called
> >>> L4 is only tapped once!
> >>>
> >>>
> >>> 73's
> >>>
> >>> Ulf (SM0NOR) ulf@sm0nor.com
> >>>
> >>>
> >>>
> >>> On 26 jan 2011, at 13.16, Dave M wrote:
> >>>
> >>>>
> >>>> I hate the layout of the supplied schematic , but it is a standard
> Pi
> >>>> network not PiL
> >>>> the second coil is strictly for the higher freqs
> >>>>
> >>>>
> >>>>
> ........................................................................
> ..............................
> >>>>
> >>>>
> >>>>
> >> 73 VE3DV , Dave
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>> From: ulf@sm0nor.com Date: Wed, 26 Jan 2011 13:04:07 +0100 To:
> >>>>> amps@contesting.com
> >>>>> Subject: [Amps] Pi/L in Ameriton amps?
> >>>>>
> >>>>> I'm helping a friend of mine who bought a damaged 811H.
> Transformer
> >>>>> and
> >>>>> tubes where
> >>>>> gone. New transformer is on the way from Ameritron and tubes we
> found
> >>>>> locally. I
> >>>>> think we will have it up and running on no time! Now my question:
> is
> >>>>> it
> >>>>> a pi/l tank
> >>>>> in this amp? The manual says so but the second coil has only two
> >>>>> tappings. Does it
> >>>>> mean that the high bands goes through the same inductance and the
> low
> >>>>> bands go
> >>>>> through the whole coil? What does it do for the intermediate
> >>>>> resistance? I noticed
> >>>>> all Ameritron amps are the same.
> >>
> >>
> >> --
> >> Vic, K2VCO
> >> Fresno CA
> >> http://www.qsl.net/k2vco/
> >> _______________________________________________
> >> Amps mailing list
> >> Amps@contesting.com
> >> http://lists.contesting.com/mailman/listinfo/amps
> >
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