At the HAM-Radio meeting 2003 in Friedrichshafen I
have
seen
the Spiderbeam from DF4SA and took one Kit home.
This antenna is a 3 band full size beam for
10/15/20m
and is
very light with only 5.5kg (11 lbs).
The construction is made by four telescopic fiberglass
tubes,
each one 5 meters long, which are hold in the center
by an
aluminium centerpiece.
The individual elements are made by wires which are
supported
by
the fiberglass construction. The antenna consists of:
- 3 elements for 20m
- 3 elements for 15m
- 4 elements for 10m
A single 50 Ohm coax feeds the central multiband
dipol
through
a balun (current balun).
I have installed the antenna twice and obtained
excellent
results with it.
Using a telescopic mast, I installed the antenne 9 to
10 m (30 feet)
above ground.
The SWR curve is very broad and the SWR remains
below
1.4 through
the complete 20m band, and below 1.5 through the full
15m band.
On 10m, the antenna has a small bandwidth and requires
some modification
to correct this.
The signal reports received from 1000 to 5000 km
were
always very strong,
and compared to other local stations, which also
operated
with 3 ele beams,
always in favor of the Spiderbeam!
I was told to have the stongest signal on the band at
that moment.
Contacts to South America and Japan gave real S9
reports,
unfortunately
no local station was qrv to obtain a comparitive report.
My transmit power was 100 W PEP.
---
The F/B ratio on large distance was mostly 3 to 4 S
points
(= 18 to 24 db),
in some cases up to 40 db were reported.
(Measuered by transmitting a constant carrier and
signal
report
from other station).
The installation according to the original
description
is a
somewhat complicated process, as one has to make many
knots with the
rope - and afterwards open them.
Furthermore, all tubes are bent upwards, giving a
strange
look.
Therefore I made some changes.
I built the construction completely flat,
horizontal,
and replaced
all knots by small eye hooks (carabin hooks).
Now the installtion goes much faster and smoother
and
the
optical view is much better.
The flat horizontal construction does not worsen the
electrical characteristics,
however the dimensions of the support ropes has to be
lightly adapted.
There are some electrical modifications in order to
improve
the SWR on the 10m band.
The complete beam
modification,
together with pictures and measured RF data
is described here:
( http://home.tiscalinet.ch/hb9abx )
You find the original description, together with the
specification
at this location:
General judgement:
The Spiderbeam can be recommended as an excellent DX
beam antenna
which can be obtained at a very moderate cost.
The complete kit (version 1) costs about 300 Euros.