Richard Harrison wrote:
Phil wrote:
"If not, what other homebrew antenna will be fine for the purpose?"

I believe Walter Maxwell, W2DU, while working with RCA`s satellite
program, designed quadrafilar helix antennas to communicate with the
birds. Look at their pattern on page 765 of Kraus` 3rd edition of
"Antennas", then compare with patterns shown on pages 763 and 764. The
advantage is clear.

Best regards, Richard Harrison, KB5WZI

Because one of the very important functions of a TV antenna is to reduce
multi-path interference causing fading and ghosting, directionality is
essential. The quadrifilar helix I'm familiar with is a normal-mode
helix; that is, the maximum radiation or reception is broadside to the
helix, and it has an omnidirectional horizontal pattern when the axis is
vertical. That would be a poor choice for a TV antenna. You might,
though, consider an axial mode helix. That's one which has maximum
radiation or reception in the direction of the helix axis. I don't have
any direct experience with them, but believe they can be made fairly
broadbanded. It might be pretty large and cumbersome, though. You should
be able to find design data on the web for an axial mode helix.

Sorry, I don't have the third edition of Kraus yet. Is there really a
fairly directional quadrifilar helix in it? In the second edition, the
quadrifilar helix is described as a normal mode helix, which is my
experience, and the pattern shown in the book of a conventional normal
mode helix resembles that of a dipole as it should. Quadrifilar helices
are commonly used for GPS receivers, where an omnidirectional pattern is
desirable.

By the way, I finally got a copy of Bailey -- I came across a copy the
other day at Powell's Technical Bookstore, for $15!

Roy Lewallen, W7EL