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Subject: Re: [AMPS] Dentron L Tuned Input

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Subject: Subject: Re: [AMPS] Dentron L Tuned Input
From: (Tom Rauch)
Date: Sat, 8 Jul 2000 05:07:47 -0400
> My memory may be faulty, but I seem to remember someone on the Amp list
> mentioning that a transformer could be used to help the input impediences
> of a ML-2500.  I seem to remember that the tubes were looking for about
> 200 ohms on the input.

When a cathode-driven amplifier uses a tube with a conduction 
angle of less than 360 degrees, there is considerable harmonic 
energy in the cathode circuit.

That makes the amplifier critical for source impedance, including 
harmonics of the drive frequency.

If you don't put a low-pass network between the cathode and 
whatever drives the tube, if that network isn't very close to the tube, 
and if that network doesn't look (from the cathode) like a very low 
impedance at those harmonic frequencies, you can run into all 
sorts of weird problems.

Sometimes with a certain cable length, amplifier style, and exciter 
you can get lucky. Sometimes you don't. 

> The article was from the December 85 issue of CQ magazine starting on page
> 13.  Title:  "The Silver City Kilowatt" by Dean Battishill and Lew McCoy.

I don't know who Dean Battishill is. He might know something 
about RF systems, so there's some hope of technical accuracy if 
he had final authority in the article.

> 73,
> Jim Zellmer, KA0VSL
> >
> > Running a Yaesu FT-847 into the Dentron L with a manual tuner between
> > the
> rig
> > and the amp which is really a pain.
> >
> > Thanks
> > Mike
> Dentron made a "black box" tuned input for their amps. It has a switch on
> the front of it for 160-10m. These are still floating just
> sold on E-Bay three days ago. Henry Radio will sell you a tuned input
> completely assembled and aligned. All you need is a box or build it into
> an amp.
> If you are a builder, look at any ARRL Handbook for details and projects.
> GL!
> Phil, K5PC
> --
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73, Tom W8JI

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