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[AMPS] HA-10 Warrior Parasitic Supressor Inductor Values

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Subject: [AMPS] HA-10 Warrior Parasitic Supressor Inductor Values
From: Ian White, G3SEK" < (Ian White, G3SEK)
Date: Mon, 3 Sep 2001 17:36:45 +0100
Tom Rauch wrote:
>> > One factor that apparently 
>> >increased the Warrior's VHF instability was so-called
>> >"neutralization". 
>> "So-called" is correct. According to the schematics, it consisted of a
>> feedback capacitor from the output end of the pi-tank, back to the
>> cathode. This will produce feedback of variable amplitude and phase,
>> depending on the settings of the bandswitch and the tuning and loading
>> controls. It's hardly surprising that the amp was more liable to
>> oscillate at some frequency.
>That is NOT correct Ian. Bad enough that Rich says things without 
>being fully aware what is going on! 
>The feedback in the Warrior is from the anode, through a capacitor, 
>through a phase inverting transformer, to the filaments.
>The tuning of the tank has a very minimal effect on phase shift. 
>This is a simple modified bridge system.
>I think you are wrongly confusing it with the system in a Yaesu 
>572B amplifier where feedback is taken AFTER the output tank, 
>which of course WOULD shift phase with tank tuning and 
>destabilize the amplifier at HF with some tank settings.     
Sorry, it appears I was confusing the Warrior with another amp... maybe
the Yaesu, though I don't recall ever seen that schematic.

I agree that a phase inverting transformer, coupled as you describe,
produces a bridge neutralizing arrangement which is pretty much as
broadband as the transformer itself.

>> >Gonset also used neutralization in their 4, 811 amplifier.  
>> I'm not familiar with that schematic: would that be real
>> neutralization, or more of the bogus kind?
>Before you say "bogus", you should look at the system. It works 
>very well in Heath's amp and other amps. It has nothing to do with 
>VHF oscilations, it is to stabilize the amp at upper HF.
I applied the term "bogus" to the system I described, not the one that
is actually in the Heath Warrior.

>Let's not feed people trying to learn misinformation Ian!
Sorry, I was misinformed myself!

73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)

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