[Antennas] ladder line questions

Mon, 17 Nov 2003 08:17:56 -0500

Dear KZ5V,

Sorry, OM, but you are dead wrong.

The two 50 ohm coax lines would present an impedance at the rig under the
following circumstances:
    1/4 wave long (or odd multiple thereof) and with a 400 ohm termination.

Under any other conditions you would have to know the terminating impedance,
which you do not know without measuring it, and you would then have to
rotate that impedance around the Smith Chart according to the electrical
length of the line.

Go to my website below, click on Amateur Radio Topics and Software
Downloads, and then click on Transmission Lines for Dummies. See Myth #1 and
also Technical Topic "Characteristic Impedance".

Bob Lay (W9DMK) in Dahlgren, VA
http://www.qsl.net/w9dmk
----- Original Message -----
From: "KZ5V" <[email protected]>
To: "George, W5YR" <[email protected]>
Cc: <[email protected]>
Sent: Monday, November 17, 2003 3:53 AM
Subject: Re: [Antennas] ladder line questions

> George,   Thanks...  yup, two 50 ohm coax cables do form a 100 ohm
balenced
> feedline, of sorts.  But also form a 25 ohm impedance load to the
> transmitter.This can be handled with most mfj tuners, if you hook them up
> backwards. But still a bad idea...  Granted there are a lot of ways to
solve
> a problem, but only one best way.  .. and this isnt it.
>   Usually  I agree with you, but this is an exception.
> KZ5V
> ----- Original Message -----
> From: "George, W5YR" <[email protected]>
> To: "Hue Miller" <[email protected]>; <[email protected]>
> Sent: Sunday, November 16, 2003 8:06 PM
> Subject: Re: [Antennas] ladder line questions
>
>
> > Two 50-ohm coaxes form a shielded 100-ohm balanced line.
> >
> > 73/72, George
> > Amateur Radio W5YR -  the Yellow Rose of Texas
> > Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
> > "Starting the 58th year and it just keeps getting better!"
> > [email protected]
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Hue Miller" <[email protected]>
> > To: <[email protected]>
> > Sent: Sunday, November 16, 2003 4:43 PM
> > Subject: Re: [Antennas] ladder line questions
> >
> >
> > >
> > > ----- Original Message -----
> > > From: "HSHK" <[email protected]>
> > >
> > > "....Besides using a 4:1 balun and then running coax, you can
> > > do away with the balun and use balanced coax.
> > >
> > > If you'd like to make some ladder line, the attached pics will
> > > show...
> > >  Bill KA8VIT"
> > >
> > > Bill, attachments don't make it thru the list reflector.  Are the
> > > photos up somewhere else where i could have a look?
> > >
> > > Also- is this correct: the 2 coaxes run this way, as a balanced
> > > coax, 4x the impedance of the single coax?
> > >
> > > And if so- let's say we do this, raising the impedance, let's say
> > > we then want to retain the balanced coax idea ( more for noise
> > > suppression and ground independence ) but want to have the
> > > line impedance the same as for a single coax span. How many
> > > "balanced coax" pairs do we need in parallel? 2 or 4? Just
> > > curious.
> > > Tnx, Hue Miller
> > >
> > > - - -
> > >
> > > Your moderator for this list is:
> > > Larry Wilson KE1HZ [email protected]
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> >
> > Your moderator for this list is:
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> >
> - - -
>
> Your moderator for this list is:
> Larry Wilson KE1HZ [email protected]
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