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Re: [TowerTalk] Using Stubs to Reject Harmonics

To: "'Tower and HF antenna construction topics.'" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Using Stubs to Reject Harmonics
From: "Joe Subich, W4TV" <lists@subich.com>
Reply-to: lists@subich.com, "Tower and HF antenna construction topics." <towertalk@contesting.com>
Date: Wed, 3 Feb 2010 20:43:37 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>

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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