Jack Painter wrote:

"Grumpus" wrote

Hi, I'm very curious about the Eavesdropper-T and Eavesdropper-C
dipoles (see Universal-Radio online catalog) for my attic. The
Eavesdropper-T is a trapped dipole center-fed with 100' of 72 ohm
balanced feedline. The Eavesdropper-C is identical except it includes
a coax fitting and does not include a lead-in cable. Both models are
43' long (ideal for my attic space) and include static arrestors. For
the first thirty feet of my attic, there is electrical wiring to the
lights running 3'-4' from the peak of the roof, and for the last ten
feet within a foot of the peak. My questions are will this antenna
mounted at the very peak of the attic:

1. Be safe from lightning strikes?

2. Increase the chances of frying my radios even if electrocution is
not an
issue?

3. Suffer interference from the electrical wiring described above
whether the
lights are on or off?

4. Or interference from the utility lines outside the house which run
both parallel and perpendicular to the proposed antenna 15' to the
side
and 10' below?

5. Need to be grounded? (I believe I have read somewhere that a
balanced
dipole does not need to be grounded in order to deliver an
acceptable
low-noise signal. Is this wrong?)

What I have in mind, especially if I don't need to ground the antenna,
is moving my shack up to the attic and listening to DX on long winter
nights with a jug of corn liquor to keep me warm. Any advice would be
greatly appreciated.

Regards,

Grumpus

Slinky dipole (currently unused)
Radio Shack discone antenna (for scanner)
All in attic of my house

Good morning -

Antenna wiring in your attic is as safe from lighting as any other wiring in
your house. That is, it is subject to electro-magnetic induction from nearby
strikes the same as your home wiring is. So-called static arrestors that are
not rated for several thousand amps and low impedance grounded to a good
lightning protection system...may be useful in limiting some static, but not
the kind from either near or far field lightning energy. If you have nearby
trees that are prone to being struck, recommend you not leave antennas
connected to your radios during storms.

Nearby home wiring should not affect your attic antenna, but the reverse is
not true. You may couple to the wiring if your transmit.

A dipole antenna does not use an RF-transmitter ground for its operation. If
a dipole is not high enough (at least 1/4 wavelength above ground) then
there will be losses to the ground, in this case through your home, when
transmitting. This has no effect on reception.

I would disagree, the same effects that an antenna has for transmission will
also be reflected upon its ability to receive signals. They may not have a great
affect, but it will be there, none the less.

dxAce



Be advised that setting up ops in your attic will limit your ability to
safely operate in the future, should you decide to utilize external
antennas. There is no easy or safe way to properly ground a second story
radio station. Many amatuer operators and hobbyists may run this way, but
disconnecting all outside antenna *outside* the home is a requirement before
thunderstorms in that condition. There is no practical or inexpensive way to
maintain a lightning protection system for connected external antennas when
the radio station is more than a few feet above earth-ground potential.

Best regards,

Jack Painter
Virginia Beach VA