Heath SB-1000 and Ameritron AL-80 are pi-L on 160 & 80, pi above
that. SB-200/SB201/SB-220/SB-221, Drake L4 and L7 are pi-network.
Ameritron ALS-600 is a solid state amp with lowpass filter
outputs (half-wave - "double pi").
73,
... Joe, W4TV
> -----Original Message-----
> From: towertalk-bounces@contesting.com
> [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim Brown
> Sent: Wednesday, February 03, 2010 4:04 PM
> To: Tower and HF antenna construction topics.
> Subject: Re: [TowerTalk] Using Stubs to Reject Harmonics
>
>
> On Tue, 2 Feb 2010 13:49:36 -0600, Tim Duffy K3LR wrote:
>
> >Hi Jim:
>
> >I always wanted to test the 1/4 wave "insertion" theory, but
> never got
> >around to it. I would love to hear what the difference is -
> if you can
> >experiment.
>
> Tim,
>
> I haven't done any measurements, but I did do a literature
> search of QST
> product reviews to learn what output circuitry is used by
> power amps that
> you and I are likely to be using. What I learned is that
> MOST, but not
> all, use the pi-L output configuration -- starting from the
> tube, shunt C,
> series L, shunt C, series L. This configuration allows stubs
> to be placed
> at the output of the power amp. Amps that use this
> configuration include
> the original Ten Tec Titan 425, Alpha 374, 76, 77, 87, 91B,
> ACOM 1000 &
> 1010, Ameritron AL-800H, and QRO-2500DX. The AL-82 and
> AL-1200 use a pi-L
> on 160 and 80, but pi network on the other bands.
>
> I can't find reference to the output network of the current
> model Ten Tec
> Titan III, the Alpha 86 or 89, the ACOM 2000, Heath SB-1000
> or SB-220,
> Ameritron ALS-600, or Tokyo High Power products. If I were
> guessing, it
> would be that they follow suit of other products in their
> heritage. The
> Commander HF-1250 and HF-2500 have a pi-network to match the
> tube to 200
> ohms, then a 4:1 toroidal xmfr. From a network point of view
> (that is,
> interaction with stubs), I'd call it a pi.
>
> The Ten Tec Herc II and Centurion, the Kenwood TL-922A all use pi
> networks.
>
> 73,
>
> Jim K9YC
>
>
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