Jay in the Mojave wrote:

Hello Tiny:

The Moonraker 4 is a great beam antenna. It was designed around
inexpensive parts, but was very well designed and operated very well.
Having good gain and great rejection.

There are mods out there that install more reflector wires on the quad
reflector. But this will only degrade the Moonraker 4 performance big
time. This being proven with many experiences, and seeing the beams
pattern be distorted from Eznec, a antenna molding program.

The best thing that you can do is use good coax like the LMR-400 and
install the Moonraker 4 on a tower, getting the antenna as high as
possible, with a good rotor, like a HY-Gain 4 or Tailtwister Rotor.

The problem mostly seen with the Moonraker 4 and 6, and PDLII beam
antennas is the use of the Cast Aluminum Hubs that attach the elements
to the boom. Four elements are attached to the Boom using these cheaply
manufactured Cast Aluminum Hubs. After 30 years plus in service these
Cast Aluminum Hubs crack then break after being removed and then
reinstalled again. The best advice is to try to not disturb them.

As the Cast Aluminum Hub is tightened down to compress against the boom
is when the crack and breakage will happen. Even new hubs crack and
break, as I have seen this many times. But when the manufacture was
around supplying replacement hubs there wasn't much of a problem. But
now the manufacture is long gone, these old used hubs have been sold on
E-Bay for 50 dollars for a pair of old unknown condition hubs.

I have had new design hubs made from 6061 T6 Billet Aluminum, but there
not cheap.

I am now rebuilding a Moonraker 6 beam antenna. The Boom has been
replaced with a larger stronger 2 inch diameter Boom, and the boom to
mast Mounting Plate has been replaced and upgraded. The Hubs have been
replaced with the new billet hubs, the over designed truss assembly has
been replaced with a simpler one. The Gamma Matches have been replaced
with a center feed driven element, Hairpin Match, and Balun. The
original elements are the only thing being used from the original antenna.

Photos will come out shortly.

Jay in the Mojave


TINY wrote:

does any one have any good moonraker 4 antenna modifcations and does
swr stay down
or web sites will help.
thanks "Tiny"

Hey Jay, agreed the hubs of the PDLII are fragile. IMHO the tuning of
those ants is another drawback though when done correctly they operate
very well.