TopBand: Beverage matching

[Fred Hopengarten]

From:
Fred Hopengarten  K1VR               781/259-0088
Six Willarch Road
Lincoln, MA 01773-5105
permanent e-mail address:  fhopengarten@mba1972.hbs.edu

N1RC and K1VR wrote the 73 article on feeding a Beverage at both ends. 
N1RC, then an undergraduate EE student at MIT, designed the toroids that
I still use. He's still alive and kicking, and offers some thoughts
below. 


--------- Begin forwarded message ----------

From: "Clarke, Bob" <Bob.Clarke@analog.com>
To: Fred Hopengarten <k1vr@juno.com>
Subject: RE: Earl W Cunningham <k6se@juno.com>: Re: TopBand: Beverage 
matching
Date: Thu, 25 Feb 1999 11:40:56 -0500

Ah, fame and fortune. 

You may want to add this as a follow-up post to these guys and give them
my
email address.

Matching Transformer Design 
Bob Clarke, N1RC

I had a couple of goals when designing the transformer. One was wideband
operation.
That's how I came up with the quadrifilar structure. A simple 1:n turns
ratio
had too
much capacitance and wouldn't work on 160M through 40M. The quadrifilar
structure
gave me the right impedance ratio and minimized the number of turns per
each
winding.

In retrospect, I think another benefit of this structure is to reject
out-of-band signals. 
I think (it's been a few years, I'd have to find my notes to be certain
it was
part of the plan) that's why I did
not use an autotransformer. The best way to minimize undesired energy
(i.e., crud from the broadcast band or static bursts, which look like 100
kHz
pulses if memory serves me)
 is to use separate windings - primary and secondary. In an
autotransformer,
there is no isolation, so anything
picked up by the beverage goes straight into the receiver. With separate
primary
and secondary windings, the inefficiency of
the transformer at lower frequencies would provide at least some
attenuation
of a BC band signal and keep it out of the receiver. The same reasoning 
applies to a lightning impulse. And the primary winding goes straight to
ground
at the Beverage.

> ----------
> From: 	Fred Hopengarten[SMTP:k1vr@juno.com]
> Sent: 	Wednesday, February 24, 1999 11:10 PM
> To: 	Clarke, Bob
> Subject: 	Earl W Cunningham <k6se@juno.com>: Re: TopBand:
Beverage
> matching 
> 
> From:
> Fred Hopengarten  K1VR               781/259-0088
> Six Willarch Road
> Lincoln, MA 01773-5105
> permanent e-mail address:  fhopengarten@mba1972.hbs.edu
> 
> All these years later and you are still famous.  You wrote a classic!
> 
> --------- Begin forwarded message ----------
> From: Earl W Cunningham <k6se@juno.com>
> To: nx1g@top.monad.net, topband@contesting.com
> Subject: Re: TopBand: Beverage matching 
> Date: Wed, 24 Feb 1999 19:41:43 EST
> Message-ID: <19990224.164133.4455.0.k6se@juno.com>
> References: <199902241637.LAA06128@contesting.com>
> 
> 
> Craig, NX1G/W1JCC wrote:
> "I think I used the same core quadrafilar wound 3 wires in series for
> primary, 1 wire secondary derived from K1VR article in 73 (remember
that
> mag?)"
--------- End forwarded message ----------

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