[Amps] The dilemma of Tx tube

[Carl]

----- Original Message ----- 
From: "Jim Thomson" <jim.thom at telus.net>
To: <amps at contesting.com>
Sent: Wednesday, August 01, 2012 8:27 AM
Subject: Re: [Amps] The dilemma of Tx tube


> Date: Wed, 1 Aug 2012 20:37:58 +0930
> From: "Leigh Turner" <invertech at frontierisp.net.au>
> Subject: Re: [Amps] [ham_amplifiers] RE: The dilemma of Tx tube
> choices and lack of decorum (again)
> To: <ham_amplifiers at yahoogroups.com>
> Cc: amps at contesting.com
> Message-ID: <20120801104937.804D723031D at mail.aitel.com.au>
> Content-Type: text/plain; charset="iso-8859-1"
>
>
> Carl, there's nothing at all wrong with posting to both forums in this
> instance as the subject matter here about the problematic dearth of 
> current
> production Tx tubes is equally pertinent to the interests of both; albeit
> perhaps more so to the home brew amp focused ham_amplifiers group.
>
> I'm not sure what you mean by your abstruse and presumably sly derogatory
> reference to "CB style QRO amps"...certainly none of the amps I own, or 
> have
> built, or modified have technical performance that's less than 
> superlative.
> All deploy engineering best practice and would be on par with the finest 
> in
> any technical benchmark performance competition; whether on the lab test
> bench or on-air assessment.
>
> Some of these high performance amps use Russian mil-spec SSB Tx tubes :-)
>
> Cheers,
>
> Leigh
>
> ##  Leigh, PLEASE DON’T  post the same identical posts to both  AMPS @ 
> contesting.com
> and also  the yahoo group.
> It gets  VERY confusing..and real fast.   I had one of my posts  intended 
> for the  yahoo
> group..end up on AMPS  in error.  Although a lot of folks belong to both 
> forums, its
> still a dumb idea..     If you want to post a similar or same topic to 
> both forums, at least
> do it as  two separate  ( and different)  postings, one for each group.
>
> ###  AMPS  @ contesting .com  is a legal limit, table top amp, commercial 
> ham amp type
> of group.   The ham_amplifiers@ yahoogroups,com
> http://groups.yahoo.com/group/ham_amplifiers/  on the other hand, has 
> several  non hams,
> ex broadcast design engineers, 11 m QRO builders, and  loads  and loads of 
> hams
> who build well over the legal limit  amps.  AMPS  @  contesting .com  has 
> no pix, nor
> any file section like the yahoo group does.
>
> ##  although they have similar  amp related issues,  treat them as two 
> separate
> and distinct  groups.   Folks here on AMPS  will be greatly  annoyed when 
> they
> find out their postings  are being reposted to the yahoo group.   Then we 
> have folks like
> Rich measures, who will be arguing with comments made here on 
> AMPS.....over on the
> yahoo forum.   Rich can’t post here... and lots of folks on AMPS cant post 
> on the yahoo forum .
>
> ##  leigh, u might find it amusing, the rest of us don’t.   BTW..although 
> the GS35B  is
> a low cost, big bang for the buck  GG triode.... it has one drawback. 
> Its  an  IMD
> garbage truck on the bands.  It doesn’t even come close to meeting any ITU 
> commerical
> spec for IMD3-5-7-9-11, or any other commercial spec, past or present.  It’s 
> a   dirty
> tube, plane and simple, just measure it.   So is a 4-1000.
>
> Jim   VE7RF


Jim, the 4X1 is not a dirty tube as built. As a Class AB modulator in BCB AM 
service it runs at very low distortion.
A problem is when its driven without an input network or one poorly 
designed/tuned. Another problem is that many if not most 4X1's have been 
beat on hard in commercial service, have low emission, and are being driven 
hard and at very high voltages at times.
Others Ive heard are at the edge of oscillation and you hear the raspiness 
on SSB and CW.

Im sure even the GS-35B can have fairly decent IMD if its operated at or 
less than its full spec. If you read the Russian datasheet it uses 800W as a 
typical output yet the average ham wants to run it at over twice that 
without any thought to what is happening. At the efficiencies quoted by 
several at 2500V then 950-1000W would be the realistic useable power so a 
pair run at 1500W should keep others on the bands happy.

Carl
KM1H



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