WWVB, 60 kHz was installed and only until recently had a "BIG" parallel
XMSN line running from the transmitter house to the "coil house" where the
vertical antenna was kept matched. It might have been some 1000-feet long
and was made of two conductors, each about 1.5-inches OD. Inside, the
shack looks like something Mr. Tesla (not Musk!) would have been right at
home with. One is forbidden to park a modern vehicle near the "house" as
the RF fields render all electronics "dead". You can park it if I doesn't
stall on the way, but you can't restart it.
Dave - WØLEV
On Wed, Jan 22, 2025 at 10:41 PM Jim Brown <jim@audiosystemsgroup.com>
wrote:
> Again, thanks! I remember reading about that military project, forget
> where. Great example!
>
> The first times I encountered open wire line were either on a tour of
> the Crosley VOA site by our senior EE class (U of Cincy), or maybe at AM
> broadcast stations, where it is widely used and coaxial to feed
> verticals. I've also seen that coaxial open wire line at commercial HF
> communications RX and TX sites north of San Francisco.
>
> 73, Jim K9YC
>
> On 1/22/2025 1:54 PM, David Eckhardt wrote:
> > Jim, far too many hams solidly believe open wire, parallel conductor
> > XMSN lines, radiates just because it isn't shielded. Absolutely wrong
> > if care is taken to keep the currents balanced and the phases opposite.
> > They simply do not understand nor want to take the time to understand
> > the rank basics of a transmission line, coax or open wire, or for that
> > matter, G-line.
> >
> > Nor do they understand that ANY amateur antenna like a dipole is
> > UNBALANCED. Period! Even Uncle most times can not assure that. As you
> > commented, the local environment dictates unbalance between the two
> > sides of a dipole, unless it's in free space..... How many of us
> > absolutely assure homogeneity for a couple of lambda below our
> > antennas? I'll bet none of us hams do, myself included. But I know how
> > to build, measure, and install common mode chokes and use them
> > intelligently. Further, I have never, except for the first three or so
> > years I was licensed, "grounded" (earthed) my station. Three kinds of
> > earth connection: 1) safety (the "green" wire), 2) ESD bleed dump, and
> > 3) lightning remediation (not direct strikes, but for radiated fields
> > from near-by strikes). Also, realize the typical amateur budget does
> > not allow for protection against direct strikes!
> >
> > When Uncle installed the ported coax around the fissile material storage
> > facility on Kirtland AFB in Albuquerque, N.M., he spent millions and
> > millions of your and my tax dollars in preparing the surrounding soil.
> > Even then it wasn't perfect and quite problematic.
> >
> > Yes, I use parallel conductor XMSN line for my HF wires (doublet),
> > exclusively, except for my vertical which is by design, unbalanced.
> > Hams don't get that, either! How many times have I read the question on
> > a number of sites, "Do I need a balun or common mode choke on my
> > vertical"? DDaaaaahhhhh......
> >
> > Dave - WØLEV
> >
> > On Wed, Jan 22, 2025 at 7:35 PM Jim Brown <jim@audiosystemsgroup.com
> > <mailto:jim@audiosystemsgroup.com>> wrote:
> >
> > On 1/22/2025 10:43 AM, K9MA wrote:
> > > The whole point of using coax is to prevent radiation until the
> > RF gets
> > > to the antenna. There's no need to further complicate the issue.
> >
> > There is no more or less radiation from a 2-wire line than from coax.
> > What causes radiation is common mode current, and 2-wire can carry
> just
> > as much common mode as coax of the total antenna system is
> unbalanced.
> > Just as in coax, common mode current in 2-wire line shows up as a
> > difference between current in the two wires, taking both magnitude
> and
> > phase into account.
> >
> > Antennas can be unbalanced by their surroundings, like variable
> height,
> > sloping ground, nearby conductive objects, imbalance in the
> termination
> > of 2-wire line in the shack, including a poorly balanced tuner or
> > matching network.
> >
> > 73, Jim K9YC
> >
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com <mailto:RFI@contesting.com>
> > http://lists.contesting.com/mailman/listinfo/rfi <http://
> > lists.contesting.com/mailman/listinfo/rfi>
> >
> >
> >
> > --
> > *Dave - WØLEV
> > *
> >
> >
>
>
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>
--
*Dave - WØLEV*
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