[AMRadio] new antenna and matchbox a bust.

Peter Markavage manualman at juno.com
Mon Jan 29 14:43:33 EST 2007

To calculate the impedance of open wire line, you use the formula:
Z(Impedance)= 276 log(2S/D) ohms
where S= center to center distance between the conductors
and D= diameter of conductors

So, what is the impedance of an open wire line that uses to runs of coax
with the outer shields grounded or ungrounded? Since the parallel lines,
and the spacing between them, have some purpose, i.e. to help create the
impedance characteristic for the antenna, it seems to me that the
grounded, and even ungrounded shields, basically isolate each run, and
you might not have really created an effective transmission line or just
some weird transmission line impedance.

Pete, wa2cwa

On Mon, 29 Jan 2007 14:05:59 -0500 Brett gazdzinski
<brett.gazdzinski at verizonbusiness.com> writes:
> > 
> > Ok, I'll bite on a possible solution. Can't for the life of 
> > me understand
> > why you would use RG214 back to the tuner. Two runs??? This 
> > isn't balanced.
> Seems like it would be, why is it not balanced?
> I only use the center conductor of each coax, one for
> each leg of the open wire line.
> I tried it with the shields grounded and ungrounded,
> with no difference. 
> I never tried a loop antenna, I would wonder what 
> sort of pattern one would have.
> What about a triangle?
> No matter what shape I would try, getting the feedline
> close to the house entry point would likely be impossible
> given what I have to work with as supports.
> I also have to stay away from phone lines, power lines 
> out at the street. The current antenna is at right angles
> to the house and lines. That helps with the tvi stuff I think.
> Brett

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